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  • Institute of Physics (IOP)
  • 2015-2019  (40,845)
  • 2010-2014  (5,853)
  • 1945-1949
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  • 2015-2019  (40,845)
  • 2010-2014  (5,853)
  • 1945-1949
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  • 1
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    Experimental study on performance of BOG compressor (2015)
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    Publication Date: 2015-08-11
    Description: The boil-off gas (BOG) compressor is widely used for recycling the excessive boil-off gas of liquefied natural gas (LNG), and the extra-low suction temperature brings about great challenges to design of the BOG compressor. In this paper, a test system was built to examine the effects of low suction temperature on the compressor performance, in which the lowest temperature reached -178?C by means of a plate-fin heat exchanger with liquefied nitrogen. The test results showed that, as the suction temperature decreased from 20?C to -150?C, the volumetric efficiency of the compressor dropped by 37.0%, and the power consumption decreased by 10.0%. The preheat of the gas by the pipe through the suction flange to suction valve was larger than 20?C as the suction temperature was -150?C, and this value increased with the decreased suction temperature. The pressure loss through the suction valve at lower suction temperature was larger than that at ambient temperature while the volume flow r...
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  • 2
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    Development of High Speed Inverter Rotary Compressor for the Air-conditioning System (2015)
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    Publication Date: 2015-08-11
    Description: In order to meet the various operating loads of an air-conditioning system, an inverter compressor with a wide operational range is necessary. One of the ways to achieve a wide operation range is to drive a small capacity compressor at high speed. Moreover, it is possible to maximize the efficiency in part-load operation condition close to actual operating conditions and to reduce the cost by compact design of a small capacity compressor. In addition, the shortage of maximum capacity, due to the small rated capacity, is covered through high speed operation. However, in general, if the compressor operates at high speed, problems occurs such as reduced efficiency due to friction, increased noise, increased amount of oil discharge and decreased durability of the main components. In order to solve these problems the following have been investigated: optimized dimension parameters of the compression chamber, enhanced shaft design and the structure for the reduction of oil discharge an...
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  • 3
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    New generation of universal modeling for centrifugal compressors calculation (2015)
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    Publication Date: 2015-08-11
    Description: The Universal Modeling method is in constant use from mid - 1990 th . Below is presented the newest 6 th version of the Method. The flow path configuration of 3D impellers is presented in details. It is possible to optimize meridian configuration including hub/shroud curvatures, axial length, leading edge position, etc. The new model of vaned diffuser includes flow non-uniformity coefficient based on CFD calculations. The loss model was built from the results of 37 experiments with compressors stages of different flow rates and loading factors. One common set of empirical coefficients in the loss model guarantees the efficiency definition within an accuracy of 0.86% at the design point and 1.22% along the performance curve. The model verification was made. Four multistage compressors performances with vane and vaneless diffusers were calculated. As the model verification was made, four multistage compressors performances with vane and vaneless diffusers were ca...
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  • 4
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    Carbon and energy saving markets in compressed air (2015)
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    Publication Date: 2015-08-11
    Description: CO 2 reduction and fossil fuel saving represent two of the cornerstones of the environmental commitments of all the countries of the world. The first engagement is of a medium to long term type, and unequivocally calls for a new energetic era. The second delays in time the fossil fuel technologies to favour an energetic transition. In order to sustain the two efforts, new immaterial markets have been established in almost all the countries of the world, whose exchanges (purchases and sales) concern CO 2 emissions and equivalent fossil fuels that have not been emitted or burned. This paper goes deep inside two aspects not yet exploited: specific CO 2 emissions and equivalent fossil fuel burned, as a function of compressed air produced. Reference is made to the current compressor technology, carefully analysing CAGI's (Compressed Air Gas Institute) data and integrating it with the PNUEROP (European Association of manufacturers of compressors, vacuum pu...
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  • 5
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    Numerical Investigation of Different Radial Inlet Forms for Centrifugal Compressor and Influence of the Deflectors Number by Means of Computational Fluid Dynamics Methods with Computational Model Validation (2015)
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    Publication Date: 2015-08-11
    Description: The goal of this work is numerical experiments for five different types of the centrifugal compressor's inlet chambers with the help of CFD-methods and comparison of the computational results with the results of the real experiment which was held in the Nevskiy Lenin Plant in Saint-Petersburg. In the context of one of the chambers the influence of deflectors on its characteristics was investigated. The objects of investigation are 5 inlet chambers of different types which differ from each other by deflectors? existence and by its number. The comparative analyze of the results of numerical and real experiments was held by means of comparison of relative velocity and static pressure coefficient distribution on hub and shroud region, and also by means of loss coefficient values change for all five chambers. As a result of the numerical calculation the quantitative and qualitative departure of CFD- calculations results and real experiment were found out. The investi...
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  • 6
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    An Investigation on the Pin Bearings? Optimization of a Hermetic Reciprocating Compressor (2015)
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    Publication Date: 2015-08-11
    Description: A hermetic reciprocating compressor is the most energy consuming component of the refrigerators. Therefore performance improvement studies of the compressor play an important role to reduce overall energy consumption of the refrigerators. Design of bearings is one of the major study areas influencing reciprocating compressor performance. In this study crank pin and piston pin bearings in hermetic compressor applications are investigated and optimized. The effect of operating conditions, bearing offset between crank pin and piston pin, bearing clearance and bearing location along the shaft on the friction loss were investigated and optimal bearing designs were developed. Efficiency measurements of the compressor showed that the improved crank pin and piston pin bearing designs provide up to 3.8% increase in the COP as a result of reduction in mechanical loss that is significantly influenced by the length of the bearings, bearing location along the shaft and operating c...
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  • 7
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    Trends in high performance compressors for petrochemical and natural gas industry in China (2015)
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    Publication Date: 2015-08-11
    Description: Compressors are the key equipment in the petrochemical and natural gas industry system. The performance and reliability of them are very important for the process system. The application status of petrochemical & natural gas compressors in China is presented in this paper. The present status of design and operating technologies of compressors in China are mentioned in this paper. The turbo, reciprocating and twin screw compressors are discussed. The market demands for different structure compressors in process gas industries are analysed. This paper also introduces the research and developments for high performance compressors in China. The recent research results on efficiency improvement methods, stability improvement, online monitor and fault diagnosis will also be presented in details.
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  • 8
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    Research on the two-phase flow and separation mechanism in the oil-gas cyclone separator (2015)
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    Publication Date: 2015-08-11
    Description: The cyclone separator has attracted increasing attention due to its small size, rapid construction and high separation efficiency. This study investigated its gas-liquid two-phase flow and separation characteristics experimentally and numerically. A numerical model of two- phase flow in the cyclone separator was proposed using the Euler-Lagrange method. The distribution of pressure, tangential and axial velocity in the gas-phase flow field was obtained, and the oil droplet movement was traced. Separation efficiency was also studied experimentally, and the diameter distributions of oil droplets at the inlet and the outlet of the separator were measured by a Malvern laser particle size analyser to verify the simulation model. Based on high-speed photography technology, the oil film distribution and flow pattern on the wall of the cyclone separator were visualised. The variation of oil-gas two-phase flow in the cyclone separator was compared under various inlet flow rates. Based on ...
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  • 9
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    The origin of gas pulsations in rotary PD compressors: ?P or ?U? (2015)
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    Publication Date: 2015-08-11
    Description: This paper is a continuing work from the same authors on the same topic by analogizing the transient shock tube process to the gas pulsation phenomena [1, 2]. It has been demonstrated in the previous theoretical investigation that gas pulsations can be generated either by a sudden velocity change (?U) say from a piston or lobe movement, or by the sudden opening of a pressure difference (?p 4 i) such as during the discharge phase of a rotary PD (Positive Displacement) compressor (screw, scroll or Roots) under UC (Under-Compression) or OC (Over-Compression) conditions. It is further reasoned that the more dominant pulsation source should be from the Ap 41 induced source, but without backing from experiments. This paper is aimed at validating the theoretical predictions through experimental investigation conducted on a Roots blower, a special 100% UC case. This further clarification is important not only to prove the theory, but would pave the way for potent...
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  • 10
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    Performance Comparison of Capacity Control Methods for Reciprocating Compressors (2015)
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    Publication Date: 2015-08-11
    Description: Different capacity control methods are used for adjusting suction flow of reciprocating compressors to meet process need. Compared with recycle or bypass and suction throttling, three capacity control methods of speed control, clearance pockets and suction valve unloading are preferred due to their energy-saving at operating condition of partial load. The paper reviewed state of the art of the current capacity control technologies and their principles. A comprehensive mathematical model was developed to predict thermodynamic and dynamic performance of reciprocating compressors equipped with the capacity control systems of four above-mentioned methods. Comparison of shaft work and mechanical efficiency were conducted for different capacity control methods at the same condition. In addition, their influence on p-v diagram and valve motion were also studied, which is important for reliability and life of the reciprocating compressors. These results were helpful for selection of the ...
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  • 11
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    Design and validation of new cavity profiles for diaphragm stress reduction in a diaphragm compressor (2015)
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    Publication Date: 2015-08-11
    Description: The application of diaphragm compressors is severely limited by the low reliability and short life of diaphragms. The cavity profile has considerable influence on a diaphragm's stress level and therefore on its fatigue life. This experimental and theoretical analysis of the traditional cavity profile (as defined by a single-parameter generatrix) indicated that the short life of diaphragms may be caused by the superposition of peak radial stress and additional stress due to the discharge holes in the central region that occur when the diaphragm clings to the cavity surface. Therefore, two new kinds of cavity profiles are proposed to decrease the diaphragm's radial and total stress. The new cavity profiles based on different generatrices were designed in an attempt to reduce the peak radial stress in the central region. These cavities were manufactured to experimentally validate the designs. Experiments were carried out under various design conditions to investigate the radial stre...
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  • 12
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    Peer review statement (2015)
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    Publication Date: 2015-08-11
    Description: All papers published in this volume of IOP Conference Series: Materials Science and Engineering have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.
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  • 13
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    The development of a control system for a small high speed steam microturbine generator system (2015)
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    Publication Date: 2015-08-11
    Description: Steam is a widely used energy source. In many situations steam is generated at high pressures and then reduced in pressure through control valves before reaching point of use. An opportunity was identified to convert some of the energy at the point of pressure reduction into electricity. To take advantage of a market identified for small scale systems, a microturbine generator was designed based on a small high speed turbo machine. This machine was packaged with the necessary control valves and systems to allow connection of the machine to the grid. Traditional machines vary the speed of the generator to match the grid frequency. This was not possible due to the high speed of this machine. The characteristics of the rotating unit had to be understood to allow a control that allowed export of energy at the right frequency to the grid under the widest possible range of steam conditions. A further goal of the control system was to maximise the efficiency of generation under all cond...
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  • 14
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    The Characteristics and Causes of Push-off During Screw Rotor Manufacture, and its Compensation by Multi-axis Machine Path Calculations (2015)
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    Publication Date: 2015-08-11
    Description: When grinding helical components, errors occur at the beginning and end of the contact path between the component and grinding wheel. This is due to the forces on the component changing as the grinding wheel comes into and out-of full contact with the component. In addition, shaft bending may add depth changes which vary along the length. This may result in an interrupted contact line and increased noise from the rotors. Using on-board scanning, software has been developed to calculate a compensated grinding path, which includes the adjustments of head angle, work rotation and infeed. This grinding path compensates not only lead errors, but also reduces the profile errors as well. The program has been tested in rotor production and the results are shown.
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  • 15
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    A thermal model for analysis of hermetic reciprocating compressors under the on-off cycling operating condition (2015)
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    Publication Date: 2015-08-11
    Description: The on-off cycling operating condition of compressors is very common in low capacity refrigeration systems, being characterized by alternate periods in which the compressor is either operating (on) or idle (off). Thermal interactions between the compressor components affect its performance during the operating period and establish the initial condition for the compressor start up from idle condition. This paper presents a numerical model to predict the temperature field of hermetic reciprocating compressors under on-off cycling conditions. The model adopts a lumped formulation for control volumes formed in the fluid solution domain and the finite volume method to solve heat conduction in the solid components. Some required heat transfer coefficients were experimentally adjusted. Predictions for temperature were compared to measurements and good agreement was observed, especially for the thermal transient during the period in which the compressor is off.
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  • 16
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    Study on Design of Rotor Profile for the Twin Screw Vacuum Pump with Single Thread Tooth (2015)
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    Publication Date: 2015-08-11
    Description: The trapezoidal profile is always used as part of tooth profile in the screw vacuum pump. However, interferential phenomenon occurs when using trapezoidal tooth profile. The arc is added to the trapezoidal profile to obtain the self-conjugate curve. The geometric characters of new profiles are compared with the old ones from view point of area of leakage triangle, length of contacting line, area utility coefficient, and etc. The rotor with the selfconjugate curve has characteristics of the small axial leakage area. Radial leakage from the carryover was within the same volume and would not influence the mass flow rate of the vacuum pump. High ultimate vacuum can be reached by utilizing this profile.
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  • 17
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    Prediction of uncertainty of 10-coefficient compressor maps for extreme operating conditions (2015)
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    Publication Date: 2015-08-11
    Description: Empirical compressor maps are a simple and reliable approach for heating and cooling system designers to estimate compressor refrigerant mass flow rate and power consumption quickly. These maps were used for a long time since most compressor manufacturers build the maps with extensive test matrices, leading to good accuracy. However, the situation changes when engineers extrapolate the maps to investigate the compressor's performance under extreme operating conditions such as for cold climate heat pump applications or under conditions with system faults. Engineers are not confident on the exact uncertainty of the extrapolation, and often claim that the inaccuracy of their studies is a result of high extrapolation uncertainty. This paper presents a method to estimate the extrapolation uncertainty due to the structure of the test matrix that trains the manufacturer maps and helps the investigators to understand if the extrapolation is the main cause of their inaccuracy. To verify t...
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  • 18
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    Simulation of erosion by a particulate airflow through a ventilator (2015)
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    Publication Date: 2015-08-11
    Description: Particulate flows are a serious problem in air ventilation systems, leading to erosion of rotor blades and aerodynamic performance degradation. This paper presents the numerical results of sand particle trajectories and erosion patterns in an axial ventilator and the subsequent blade deterioration. The flow field was solved separately by using the code CFX- TASCflow. The Lagrangian approach for the solid particles tracking implemented in our inhouse code considers particle and eddy interaction, particle size distribution, particle rebounds and near walls effects. The assessment of erosion wear is based on the impact frequency and local values of erosion rate. Particle trajectories and erosion simulation revealed distinctive zones of impacts with high rates of erosion mainly on the blade pressure side, whereas the suction side is eroded around the leading edge.
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  • 19
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    Influence of liquid in clearances on the operational behaviour of twin screw expanders (2015)
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    Publication Date: 2015-08-11
    Description: A lot of effort has been expended on understanding the influences of an injected auxiliary liquid on a twin screw expander's performance. Sealed clearances improve performance on the one hand, but involve considerable frictional losses on the other hand. This paper contributes to an evaluation of these opposing effects with regard to the efficiency of screw expanders. First, thermodynamic analyses using the multi-chamber model-based simulation tool KaSim , developed at the Chair of Fluidics, are presented for a test screw expander in order to show the maximum potential of clearance sealing. This analysis involves thermodynamic simulations for sealed and unsealed clearances and leads to an order of priorities for different clearance types. Second, hydraulic losses within front and housing clearances are calculated, applying an analytical model of incompressible one-phase clearance flow. Subsequently dry and wet screw expanders are evaluated while both clearance sealing and f...
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  • 20
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    Design Evolution: From Rolling Piston to Revolving Vane to Cross-Vane Expander-compressor unit (2015)
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    Publication Date: 2015-08-11
    Description: In this paper the design evolution from rolling piston compressor (RP) to revolving vane compressor (RV) and finally to cross-vane expander-compressor unit (CVEC) is presented and discussed. The details in the design philosophy which initiated this evolution will be presented and discussed. It is estimated that more than 90% of the room air-conditioners uses RP in its compressor. This is because of its advantages: it has the few parts, it is simple geometrically and it is reliable. However, it is with no weaknesses. RP's weaknesses lie in three parts: too many rubbing surfaces with high relative rubbing velocity with each other which give rise to high frictional losses; components (eccentric and roller) are not rotating at their centres and resulted in unnecessary inherent vibration; vane tip is constantly rubbing against the roller making it a weakest part in design. To overcome RP's weaknesses, RV is introduced. As compared to RP, RV has fewer rubb...
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  • 21
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    Centrifugal compressor surge detecting method based on wavelet analysis of unsteady pressure fluctuations in typical stages (2015)
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    Publication Date: 2015-08-11
    Description: Centrifugal compressors are complex energy equipment. Automotive control and protection system should meet the requirements: of operation reliability and durability. In turbocompressors there are at least two dangerous areas: surge and rotating stall. Antisurge protecting systems usually use parametric or feature methods. As a rule industrial system are parametric. The main disadvantages of anti-surge parametric systems are difficulties in mass flow measurements in natural gas pipeline compressor. The principal idea of feature method is based on the experimental fact: as a rule just before the onset of surge rotating or precursor stall established in compressor. In this case the problem consists in detecting of unsteady pressure or velocity fluctuations characteristic signals. Wavelet analysis is the best method for detecting onset of rotating stall in spite of high level of spurious signals (rotating wakes, turbulence, etc.). This method is compatible with state of the art DSP s...
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  • 22
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    Structural and torsional vibration analysis of a dry screw compressor (2015)
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    Publication Date: 2015-08-11
    Description: This paper investigates torsional vibration and pulsating noise in a dry screw compressor. The compressor is designed at Gardner Denver (GD) and is oil free and use for mounting on highway trucks. They are driven using a Power Take-Off (PTO) transmission and gear box on a truck. Torque peak fluctuation and noise measurements are done and their sources are investigated and reported in this work. To accurately predict the torsional response (frequency and relative angular deflection and torque amplitude), the Holzer method is used. It is shown that the first torsional frequency is manifested as sidebands in the gear train meshing frequencies and this can lead to noise that is the result of amplitude modulation. Sensitivity analysis of the drive train identifies the weakest link in the drive train that limits the first torsional frequency to a low value. Finally, the significance of higher mode shapes on inter-lobe clearance distribution of the rotors is investigated.
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  • 23
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    Investigation of three lobes roots blower with special ejector (2015)
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    Publication Date: 2015-08-11
    Description: A volumetric Roots type blower with spur three or two lobes rotors has a high performance at a small unit size and is used mainly at the pressure ratio in the range of 1,4 - 1,6. A significant limitation of this parameter is due to the nature of the compressor working process, in particular a rapid, almost instantaneous increase in the pressure in the working chamber because of back flow. This leads to a decrease in performance and efficiency, and increase of the compressor noise level. One of the ways to overcome this drawback is the use of bypassing of part of compressed and cooled gas at injection through the ejector into the working chamber that is simultaneously disconnected from both discharge and suction. Due to this, the pressure increase process becomes more gradual as related to the rotor angle of rotation, and additional suction of portions of gas from the suction line by ejection effect becomes possible, which increases the efficiency and performance of the compressor...
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  • 24
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    Observation of Oil Flow Characteristics in Rolling Piston Rotary Compressor for Reducing Oil Circulation Rate (2015)
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    Publication Date: 2015-08-11
    Description: The oil circulation rate (OCR) of the rolling piston rotary compressor is a significant factor which affects the performance of refrigeration system. The increase of oil discharge causes decreasing of the heat transfer efficiency in the heat exchanger, pressure drop and lack of oil in lubricate part in compressor. In this study, the internal flow of compressor was visualized to figure out the oil droplet flow characteristics. The experiments and Computational Fluid Dynamics (CFD) simulations were conducted in various frequency of compressor to observe the effect of operation frequency on oil droplet flow characteristics for reducing OCR. In situ, measurement of oil droplet diameter and velocity were conducted by using high speed image visualization and Particle Image Velocimetry (PIV). The flow paths were dominated by copper wire parts driving the motor which was inserted in compressor. In order to verify the reliability of CFD simulation, the tendency of oil flow characteristics...
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    Numerical investigation of a centrifugal compressor with circumferential grooves in vane diffuser (2015)
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    Publication Date: 2015-08-11
    Description: Enhancing stall and surge margin has a great importance for the development of turbo compressors. The application of casing treatment is an effective measure to expand the stall margin and stable operation range. Numerical investigations were conducted to predict the performance of a low flow rate centrifugal compressor with circumferential groove casing treatment in vane diffuser. Numerical cases with different radial location, radial width and axial depth of a circumferential single groove and different numbers of circumferential grooves were carried out to compare the results. The CFD analyses results show that the centrifugal compressor with circumferential grooves in diffuser can extend stable range by about 9% while the efficiency over the whole operating range decreases by 0.2 to 1.7%. The evaluation based on stall margin improvement showed the optimal position for the groove to be located was indicated to exist near the leading edge of the diffuser, and a combination of p...
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    Systematic parametric design/calculation of the piston rod unit (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-08-11
    Description: In this article a modern and economic method for the strength calculation of the piston rod unit and its components under different operating conditions will be presented. Herefore the commercial FEA - Software will be linked with the company-owned calculation tools. The parametric user input will be followed by an automatic Pre- and Postprocessing. Afterwards the strength calculation is processed on all critical points of the piston rod connection, assisted by an extra module, based on general standards and special codes for reciprocating compressors. In this process most arrangements of the piston rod unit as well as the special geometries of the single-components (piston, piston rod and piston nut) can be considered easily. In this article the modeling of the notches, especially on the piston rod, piston as well as the piston nut will be covered in detail.
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    Thermal modelling and analysis of an oil-free linear compressor (2015)
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    Publication Date: 2015-08-11
    Description: Gas superheating in the suction system may significantly reduce the volumetric and isentropic efficiencies of small reciprocating compressors adopted for household refrigeration. This paper reports a thermal modelling approach developed to predict superheating in an oil- free linear compressor. A simulation code based on the finite volume method was adopted to solve heat conduction in the solid components and gas flow inside the compressor shell. In order to reduce the computational cost, the compression cycle inside the cylinder was modelled with a transient lumped formulation, but in a coupled manner with the remainder of the solution domain. Comparisons between numerical and experimental results of temperature showed discrepancies in some solid components and in the gas path along the discharge system. However, the model was able to predict suction gas superheating in good agreement with measurements. A sensitivity analysis of the temperature distribution with respect to two d...
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    Numerical analysis of the turbulent fluid flow through valves. Geometrical aspects influence at different positions (2015)
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    Publication Date: 2015-08-11
    Description: The aim of this paper is to carry out a group of numerical experiments over the fluid flow through a valve reed, using the CFD&HT code TermoFluids, an unstructured and parallel object-oriented CFD code for accurate and reliable solving of industrial flows. Turbulent flow and its solution is a very complex problem due to there is a non-lineal interaction between viscous and inertial effects further complicated by their rotational nature, together with the three-dimensionality inherent in these types of flow and the non-steady state solutions. In this work, different meshes, geometrical conditions and LES turbulence models (WALE, VMS, QR and SIGMA) are tested and results compared. On the other hand, the fluid flow boundary conditions are obtained by means of the numerical simulation model of hermetic reciprocating compressors tool, NEST-compressor code. The numerical results presented are based on a specific geometry, where the valve gap opening percentage is 11% of hole diamet...
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    TCO optimization during design phase - assessment of bearing concepts by calculation and simulation (2015)
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    Publication Date: 2015-08-11
    Description: Energy efficiency has been a key issue for screw machines for many years. This article describes a new analytical procedure for determining rolling bearing friction and the use of the procedure for designing compressor bearing supports. Further analytical options for a calculative assessment of the overall efficiency of bearing support alternatives are presented in the design phase based on parameter analyses performed by the BearinX ? calculation software, which includes the new friction calculation by means of a mechanical, tribological model.
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    Experimental performance of a piston expander in a small- scale organic Rankine cycle (2015)
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    Publication Date: 2015-08-11
    Description: Volumetric expanders are suitable for more and more applications in the field of micro- and small-scale power system as waster heat recovery or solar energy. This paper present an experimental study carried out on a swatch-plate piston expander. The expander was integrated into an ORC test-bench using R245fa. The performances are evaluated in term of isentropic efficiency and filling factor. The maximum efficiency and power reached are respectively 53% and 2 kW. Inside cylinder pressure measurements allow to compute mechanical efficiency and drown P-V diagram. A semi-empirical simulation model is then proposed, calibrated and used to analyse the different sources of losses.
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    Calculation procedures for oil free scroll compressors based on mathematical modelling of working process (2015)
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    Publication Date: 2015-08-11
    Description: Basic propositions of calculation procedures for oil free scroll compressors characteristics are presented. It is shown that mathematical modelling of working process in a scroll compressor makes it possible to take into account such factors influencing the working process as heat and mass exchange, mechanical interaction in working chambers, leakage through slots, etc. The basic mathematical model may be supplemented by taking into account external heat exchange, elastic deformation of scrolls, inlet and outlet losses, etc. To evaluate the influence of procedure on scroll compressor characteristics calculations accuracy different calculations were carried out. Internal adiabatic efficiency was chosen as a comparative parameter which evaluates the perfection of internal thermodynamic and gas-dynamic compressor processes. Calculated characteristics are compared with experimental values obtained for the compressor pilot sample.
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    A thermal network model for induction motors of hermetic reciprocating compressors (2015)
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    Publication Date: 2015-08-11
    Description: This paper describes a simulation model for small reciprocating compressors with emphasis on the electrical motor modelling. Heat transfer is solved through algebraic equations derived from lumped thermal energy balances applied to the compressor components. Thermal conductances between the motor components are characterized via a thermal network model. The single-phase induction motor is modelled via an equivalent circuit, allowing predictions for the motor performance and distributed losses. The predicted temperature distribution is used to evaluate the stator and rotor windings resistances. The thermal and electric models are solved in a coupled manner with a model for the compression cycle. Predictions of temperature distribution, motor efficiency, as well as isentropic and volumetric efficiencies, are compared with experimental data at different operating conditions. The model is then applied to analyse the motor temperature as a function of input voltage and stator wire dia...
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    The Benefits of Installing Remote IO to a Two Stage Oil Free Screw Compressor Package in an Upstream Oil and Gas Application (2015)
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    Publication Date: 2015-08-11
    Description: A two stage oil free screw compressor package was recently delivered to a major blue chip oil and gas giant for use on one of their oil platforms located in the North Atlantic. During initial design it became clear that the amount of instrumentation required on the package would be substantial. As a result of this an elegant solution was required that would move non-critical inputs and outs (IO) from the control panel to the package itself. This paper first describes the problems caused by the substantial amount of instrumentation required on the package. This description includes how the instrumentation is classed as critical and non-critical and what signals must still be sent over a hard wire and why. As the final location of the package is in an extremely hazardous environment, a highly corrosive marine environment, and the compressor itself is compressing highly combustible hydrocarbon gas, the protection methods employed by the instruments to prevent explosion is then...
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    9th International Conference on Compressors and their Systems (2015)
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    Publication Date: 2015-08-11
    Description: The 9th International Conference on Compressors and their Systems will be held in London from 5th ? 9th September 2015, and as its Chairman, it is my pleasure to welcome you. This series of conferences started in 1999 organised by the Fluid Machinery Group of the Institution of Mechanical Engineers (IMechE) but since 2009 it has been managed by City University London in conjunction with the IMechE and the Institute of Refrigeration, both of which have been very proactive in promoting it. The Organising committee is grateful for their support and continued encouragement. This year, after rigorous reviewing, we have accepted over 80 technical papers for publication, the highest number in the conference history. On behalf of the organising committee I would like to thank the reviewers for their hard work and assistance. In addition to the main technical sessions, this year we have introduced a third day, specifically for Industry, to consider technology, b...
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    Sponsors and partners (2015)
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    Publication Date: 2015-08-11
    Description: A list of sponsors and partners is available in the PDF.
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    Study of torque matching of revolving vane compressor and expander (2015)
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    Publication Date: 2015-08-11
    Description: An investigation was carried out to find the most optimum configuration, particularly the torque matching characteristics, of an integrated Revolving Vane compressor- expander. To carry out the study, a mathematical model of the integrated compressor-expander was developed. An open cycle air refrigeration system was adopted. The controlled parameter was the angle shift between the compressor and the expander. The observed parameters were the peak torque requirement and the bearing load. The results show that when properly matched, the peak torque can be reduced by more than 65% while the bearing loads can be reduced by up to 25%, depending on operating conditions. Unfortunately, the optimum angle shifts for peak torque do not always coincide with those for bearing load. When the pressure and inertial components of the torques are comparable or when the inertial component is dominant, the optimum angle shifts for peak torque and bearing load are around 180? and 330?, respectively....
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    Compressor-fan unitary structure for air conditioning system (2015)
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    Publication Date: 2015-08-11
    Description: An extremely compact, therefore space saving unitary structure of short axial length is produced by radial integration of a revolving piston rotary compressor and an impeller of a centrifugal fan. The unitary structure employs single motor to run as the compressor so the airflow fan and eliminates duality of motors, related power supply and control elements. Novel revolving piston rotary compressor which provides possibility for such integration comprises the following: a suction gas delivery system which provides cooling of the motor and supplies refrigerant into the suction chamber under higher pressure (supercharged); a modified discharge system and lubricating oil supply system. Axial passages formed in the stationary crankshaft are used to supply discharge gas to a condenser, to return vaporized cooling agent from the evaporator to the suction cavity of the compressor, to pass a lubricant and to accommodate wiring supplying power to the unitary structure driver -external rot...
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    Performance Testing of Jefferson Lab 12 GeV Helium Screw Compressors (2015)
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    Publication Date: 2015-08-11
    Description: Oil injected screw compressors have essentially superseded all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, reliability, minimal vibration, and capability of handling helium's high heat of compression. At the present state of compressor system designs for helium refrigeration systems, typically two-thirds of the lost input power is due to the compression system. It is important to understand the isothermal and volumetric efficiencies of these machines to help properly design the compression system to match the refrigeration process. It is also important to identify those primary compressor skid exergetic loss mechanisms which may be reduced, thereby offering the possibility of significantly reducing the input power to helium refrigeration processes which are extremely energy intensive. This paper summarizes the results collected during the commissioning of the new compressor system for Jefferson Lab's (JLab's) 12 GeV ...
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    Gas dynamic design of the pipe line compressor with 90% efficiency. Model test approval (2015)
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    Publication Date: 2015-08-11
    Description: Gas dynamic design of the pipe line compressor 32 MW was made for PAO SMPO (Sumy, Ukraine). The technical specification requires compressor efficiency of 90%. The customer offered favorable scheme - single-stage design with console impeller and axial inlet. The authors used the standard optimization methodology of 2D impellers. The original methodology of internal scroll profiling was used to minimize efficiency losses. Radically improved 5th version of the Universal modeling method computer programs was used for precise calculation of expected performances. The customer fulfilled model tests in a 1:2 scale. Tests confirmed the calculated parameters at the design point (maximum efficiency of 90%) and in the whole range of flow rates. As far as the authors know none of compressors have achieved such efficiency. The principles and methods of gas-dynamic design are presented below. The data of the 32 MW compressor presented by the customer in their report at the 16 th Inte...
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    Keeping Your Compressor Healthy: Developing the Right Lubricant Formulation is the Key (2015)
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    Publication Date: 2015-08-11
    Description: Selecting the correct compressor lubricant is crucial to the duration of the compressor and the refrigerant systems? useful life. However, developing an optimized lubricant for a refrigeration system requires a multitude of screenings and tests. The compatibility and stability of the lubricant with the refrigerant and compressor components needs to be examined at various accelerated conditions. The lubricant and refrigerant working viscosity must be determined at various refrigerant concentrations, temperatures and pressures as the diluted refrigerant in the lubricant has a significant effect on the viscosity. The correct lubricant formulation needs to be investigated for optimal performance. A compressor lubricant can provide many benefits to a refrigeration system such as bearing durability, sealing, and increased efficiency. Sometimes it is necessary to formulate the lubricant in order to optimize system performance. Specifically, this study investigated anti-wear properties o...
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    Optimization of the axial compressor flow passage to reduce the circumferential distortion (2015)
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    Publication Date: 2015-08-11
    Description: This work is motivated by the necessity to reduce the effects of the flow circumferential distortion in the flow passage of the aircraft gas turbine engine (GTE). In previous research, the authors have proposed the approaches to decrease of the flow circumferential distortion arising from the mid-support racks of GTE compressor and having a negative impact on the blade rows, located upstream. In particular, the idea of introducing the circumferentially non-uniform blade pitch and profile stagger angle of guide vanes located in front of the support was contributed in order to redistribute the flow and decrease the dynamic stresses in the rotor wheel of the same stage. During the research presented in this paper, another principal of reduction of the flow circumferential distortion was chosen. Firstly, the variants of upgrading the existing support racks were found. Secondly, the new design of support was offered. Both the first and the second version of the support design variatio...
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    Modelling of fluid flow and heat transfer in a reciprocating compressor (2015)
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    Publication Date: 2015-08-11
    Description: Efficiency of reciprocating compressor is strongly dependent on several parameters. The most important are valve behaviour and heat transfer. Valves affect the flow through the suction and discharge line. Heat flow from the walls to working fluid increases the work of the cycle. Understanding of these phenomena inside the compressor is a necessary step in the development process. Commercial CFD tools offer wide range of opportunities how to simulate the flow inside the reciprocating compressor nowadays, however they are too demanding in terms of computational time and mesh creation. Several approaches using various correlation equation exist to describe the heat transfer inside the cylinder, however none of them was validated by measurements due to the complicated settings. The goal of this paper is to show a comparison between these correlations using in-house code based on energy balance through the cycle.
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    Parallel operation of NH3 screw compressors - the optimum way (2015)
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    Publication Date: 2015-08-11
    Description: The use of more smaller industrial NH3 screw compressors operating in parallel seems to offer the optimum way when it comes to fulfilling maximum part load efficiency, increased redundancy and other highly requested features in the industrial refrigeration industry today. Parallel operation in an optimum way can be selected to secure continuous operation and can in most applications be configured to ensure lower overall operating economy. New compressors are developed to meet requirements for flexibility in operation and are controlled in an intelligent way. The intelligent control system keeps focus on all external demands, but yet striving to offer always the lowest possible absorbed power, including in future scenarios with connection to smart grid.
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    Compressor Lubrication -the key to Performance (2015)
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    Publication Date: 2015-08-11
    Description: Today, Low Global Warming Potential Refrigerants are being evaluated, optimized and applied. Higher-pressure refrigerants, refrigerant blends, and new chemical families of refrigerants are candidates. Compressor designs and system components are being evaluated to deliver the desired capacity, efficiency and reliable performance for intended applications. Once the Refrigerant family is chosen based on Environmental and Heat transfer properties, System Chemistry between the Refrigerant and Lubricant families are scrutinized for optimum miscibility and solubility. These directly affect the Phase separation between the 2 liquid phases and reduction of viscosity. Over the entire Operating Envelope, the ?oil return? and ?viscosity reduction? problems are assessed. Compatibility aspects between chemicals (Refrigerants, Lubricants) and materials of construction (metallic, polymeric, elastomeric) are verified to avoid failures in use. System Components, compressor bearings, expansi...
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    Compressor map prediction tool (2015)
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    Publication Date: 2015-08-11
    Description: Shell Global Solutions uses an in-house developed system for remote condition monitoring of centrifugal compressors. It requires field process data collected during operation to calculate and assess the machine's performance. Performance is assessed by comparing live results of polytropic head and efficiency versus design compressor curves provided by the Manufacturer. Typically, these design curves are given for specific suction conditions. The further these conditions on site deviate from those prescribed at design, the less accurate the health assessment of the compressor becomes. To address this specified problem, a compressor map prediction tool is proposed. The original performance curves of polytropic head against volumetric flow for varying rotational speeds are used as an input to define a range of Mach numbers within which the non-dimensional invariant performance curve of head and volume flow coefficient is generated. The new performance curves of polytropic head vs. f...
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    Analysis of the screw compressor rotors? non-uniform thermal field effect on transmission error (2015)
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    Publication Date: 2015-08-11
    Description: The vibrational state of the screw compressor is largely dependent on the gearing of the rotors and on the possibility of angular backlash in the gears. The presence of the latter leads to a transmission error and is caused by the need for the downward bias of the actual profile in relation to the theoretical. The loss of contact between rotors and, as a consequence, the current value of the quantity, characterizing the transmission error, is affected by a large number of different factors. In particular, a major influence on the amount of possible movement in the gearing will be exerted by thermal deformations of the rotor and the housing parts in the working mode of the machine. The present work is devoted to the analysis of the thermal state in the operation of the screw oil-flooded compressor and its impact on the transmission error and the possibility of losing contact between them during the operating cycle.
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    Performance Measurements of a Low Specific Speed TurboClaw? Compressor (2015)
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    Publication Date: 2015-08-11
    Description: Low specific speed compressors have been historically based on positive displacement machines. Attempts to bring advantages of turbomachinery such as oil free, low parts counts, low cost of manufacture, and reliability to low flow rate applications have not been sparse, but the principle difficulty has always been that the conventional turbomachine design operates at ultra-high speed to deliver low volume flow rates. This is synonymous with low efficiency due to higher losses (windage, surface finish, and tip clearances). The innovative TurboClaw? design is a low specific speed turbomachinery with forward swept impeller geometry. It owes its high efficiency and operational stability to careful design of its nearly tangential forward swept blading and diffuser geometry.
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    Sample of CFD optimization of a centrifugal compressor stage (2015)
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    Publication Date: 2015-08-11
    Description: Industrial centrifugal compressor stage is a complicated object for gas dynamic design when the goal is to achieve maximum efficiency. The Authors analyzed results of CFD performance modeling (NUMECA Fine Turbo calculations). Performance prediction in a whole was modest or poor in all known cases. Maximum efficiency prediction was quite satisfactory to the contrary. Flow structure in stator elements was in a good agreement with known data. The intermediate type stage ?3D impeller + vaneless diffuser+ return channel? was designed with principles well proven for stages with 2D impellers. CFD calculations of vaneless diffuser candidates demonstrated flow separation in VLD with constant width. The candidate with symmetrically tampered inlet part b 3 / b 2 = 0,73 appeared to be the best. Flow separation takes place in the crossover with standard configuration. The alternative variant was developed and numerically tested. The obtained experience ...
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    Update on single-screw expander geometry model integrated into an open-source simulation tool (2015)
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    Publication Date: 2015-08-11
    Description: In this paper, a mechanistic steady-state model of a single-screw expander is described with emphasis on the geometric description. Insights into the calculation of the main parameters and the definition of the groove profile are provided. Additionally, the adopted chamber model is discussed. The model has been implemented by means of the open-source software PDSim (Positive Displacement SIMulation), written in the Python language, and the solution algorithm is described. The single-screw expander model is validated with a set of steady-state measurement points collected from a 11 kWe organic Rankine cycle test-rig with SES36 and R245fa as working fluid. The overall performance and behavior of the expander are also further analyzed.
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    Low-order models of a single-screw expander for organic Rankine cycle applications (2015)
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    Publication Date: 2015-08-11
    Description: Screw-type volumetric expanders have been demonstrated to be a suitable technology for organic Rankine cycle (ORC) systems because of higher overall effectiveness and good part-load behaviour over other positive displacement machines. An 11 kWe single-screw expander (SSE) adapted from an air compressor has been tested in an ORC test-rig operating with R245fa as working fluid. A total of 60 steady-steady points have been obtained at four different rotational speeds of the expander in the range between 2000 rpm and 3300 rpm. The maximum electrical power output and overall isentropic effectiveness measured were 7.3 kW and 51.9%, respectively. In this paper, a comparison between two low-order models is proposed in terms of accuracy of the predictions, the robustness of the model and the computational time. The first model is the Pacejka equation-based model and the second is a semi-empirical model derived from a well-known scroll expander model and modified to include the geometric a...
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    Computation of Flow in Screw Compressors (2015)
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    Publication Date: 2015-08-11
    Description: A CFD model enabling accurate and computationally affordable simulation of unsteady flow in screw compressors has been developed. This paper focuses on computational aspects, including real-gas CFD using hybrid structured/unstructured moving grids, and specifics of grid generation for moving rotors and their communication with the discharge plenum.
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    Analytical Grid Generation for accurate representation of clearances in CFD for Screw Machines (2015)
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    Publication Date: 2015-08-11
    Description: One of the major factors affecting the performance prediction of twin screw compressors by use of computational fluid dynamics (CFD) is the accuracy with which the leakage gaps are captured by the discretization methods. The accuracy of mapping leakage flows can be improved by increasing the number of grid points on the profile. However, this method faces limitations when it comes to the complex deforming domains of a twin screw compressor because the computational time increases tremendously. In order to address this problem, an analytical grid distribution procedure is formulated that can independently refine the region of high importance for leakage flows in the interlobe space. This paper describes the procedure of analytical grid generation with the refined mesh in the interlobe area and presents a test case to show the influence of the mesh refinement in that area on the performance prediction. It is shown that by using this method, the flow domains in the vicinity of the i...
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    Modeling of an Oil-Free Carbon Dioxide Compressor Using Sanderson-Rocker Arm Motion (S-RAM) Mechanism (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-08-11
    Description: A simulation model to predict the performance of a prototype CO 2 compressor is presented. This prototype compressor employs the Sanderson-Rocker Arm Motion (S-RAM) mechanism, which converts the rotary motion of the shaft into a linear reciprocating motion of the cylinders. The piston stroke can be variable by changing the incline angle between the connecting rod and compressor main shaft centerline. The compressor model is mainly composed of two main sub-models simulating the kinematics of the drive mechanism and the compression process. A valve sub-model is included in the compression process model.
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    Numerical simulation of a twin screw expander for performance prediction (2015)
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    Publication Date: 2015-08-11
    Description: With the increasing use of twin screw expanders in waste heat recovery applications, the performance prediction of these machines plays an important role. This paper presents a mathematical model for calculating the performance of a twin screw expander. From the mass and energy conservation laws, differential equations are derived which are then solved together with the appropriate Equation of State in the instantaneous control volumes. Different flow processes that occur inside the screw expander such as filling (accompanied by a substantial pressure loss) and leakage flows through the clearances are accounted for in the model. The mathematical model employs all geometrical parameters such as chamber volume, suction and leakage areas. With R245fa as working fluid, the Aungier Redlich-Kwong Equation of State has been used in order to include real gas effects. To calculate the mass flow rates through the leakage paths formed inside the screw expander, flow coefficients are conside...
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    Multi-objective optimization for impeller shroud contour, the width of vane diffuser and the number of blades of the centrifugal compressor stage based on the CFD calculation (2015)
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    Publication Date: 2015-08-11
    Description: The study presents the results of multi-objective optimization for a high flow centrifugal compressor stage with impeller pressure ratio ?=1.3 and conditional flow rate coefficient ?=0.108. The compressor stage includes an impeller with 3D backswept blades, a vane diffuser and an axial inlet. The goal of optimization is to increase polytropic efficiency and polytropic head ratio of the basic design. The CFD method is used to estimate compressor efficiency at rated duty. CAE optimization is applied based on the parametric optimization of impeller shroud contour and number of blades of the impeller and diffuser versus the original design. Parameterization of geometrics is also used to the width-ratio of vane diffuser in the range of b 3 /D 2 = 0.08-0.097. The study considers 52 cases of the optimization of impeller shroud contour and the number of blades in the search for the improved design. The optimization procedure uses the automatic generated computation grid...
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    A parametric optimization procedure for the suction system of reciprocating compressors (2015)
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    Publication Date: 2015-08-11
    Description: The design of the suction system of compressors is of fundamental importance for efficiency and reliability. This paper reports a method developed to optimize the suction system of a reciprocating compressor, by using the genetic algorithm NSGA-II. The isentropic and volumetric efficiencies are used as objective functions, while the bending fatigue stress is used as a constraint to meet valve reliability. A simulation model of the compression cycle was coupled to the optimization procedure, with correlations for flow and force effective areas in terms of geometric parameters of the suction valve. Valve dynamics was numerically solved via the finite element method. The proposed optimization procedure was applied to a reciprocating compressor adopted for household refrigeration, identifying suction system geometries more efficient than the original design.
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    Experimental performance evaluation of heat pump-based steam supply system (2015)
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    Publication Date: 2015-08-11
    Description: Heat pumps have become increasingly important as a technology to reduce primary energy consumption and greenhouse effect gas emission. They are presently used mainly on residential air-conditioning and domestic hot water and are expected to spread to industrial heating processes. In 2011, Kobe Steel, Ltd. developed and commercialized two heat pump- based steam supply systems; the high efficiency steam supply system with a steam temperature of 120?C (SGH120) and the system which enables a steam temperature of 165?C (sGh165). For promoting the spread of these industrial heat pumps and enhancing the reliability of them, we investigate experimentally steam generation rate, energy efficiency and controlled performance of the SGH165 under various operating conditions on the assumption of actual different industrial processes, and evaluate technical possibilities for better performance.
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    Optimisation of two-stage screw expanders for waste heat recovery applications (2015)
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    Publication Date: 2015-08-11
    Description: It has previously been shown that the use of two-phase screw expanders in power generation cycles can achieve an increase in the utilisation of available energy from a low temperature heat source when compared with more conventional single-phase turbines. However, screw expander efficiencies are more sensitive to expansion volume ratio than turbines, and this increases as the expander inlet vapour dryness fraction decreases. For singlestage screw machines with low inlet dryness, this can lead to under expansion of the working fluid and low isentropic efficiency for the expansion process. The performance of the cycle can potentially be improved by using a two-stage expander, consisting of a low pressure machine and a smaller high pressure machine connected in series. By expanding the working fluid over two stages, the built-in volume ratios of the two machines can be selected to provide a better match with the overall expansion process, thereby increasing efficiency for particular...
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    Experimental investigation on materials and lubricants for sliding-vane air compressors (2015)
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    Publication Date: 2015-08-11
    Description: Positive-displacement compressors and, among them, sliding-vane rotary machines are widely used in the compressed air sector. As in many other industrial fields, the efficient utilization of energy has become a major goal also in this sector. The aim of the present activity is the experimental investigation on the influence of two vanes materials (cast iron and aluminium with anodized surface) and of four commercial lubricants (characterized by different formulations and additives concentrations) on the performance of a mid-capacity sliding-vane rotary compressor in a number of operating pressures. The performance is identified by both the volume flow rate and the absorbed mechanical power, evaluated according to the international standard ISO 5167 and ISO 1217. The campaign indicates that the considered lubricants do not affect appreciably the volumetric flow rate. On the other hand, the specific lubricants determine a variation of about 1% of the mechanical power for both mater...
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    Development of a Gas Dynamic and Thermodynamic Simulation Model of the Lontra Blade Compressor? (2015)
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    Publication Date: 2015-08-11
    Description: The Lontra Blade Compressor ? is a patented double acting, internally compressing, positive displacement rotary compressor of innovative design. The Blade Compressor is in production for waste-water treatment, and will soon be launched for a range of applications at higher pressure ratios. In order to aid the design and development process, a thermodynamic and gas dynamic simulation program has been written in house. The software has been successfully used to optimise geometries and running conditions of current designs, and is also being used to evaluate future designs for different applications and markets. The simulation code has three main elements. A positive displacement chamber model, a leakage model and a gas dynamic model to simulate gas flow through ports and to track pressure waves in the inlet and outlet pipes. All three of these models are interlinked in order to track mass and energy flows within the system. A correlation study has been c...
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    A Fault Alarm and Diagnosis Method Based on Sensitive Parameters and Support Vector Machine (2015)
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    Publication Date: 2015-08-11
    Description: Study on the extraction of fault feature and the diagnostic technique of reciprocating compressor is one of the hot research topics in the field of reciprocating machinery fault diagnosis at present. A large number of feature extraction and classification methods have been widely applied in the related research, but the practical fault alarm and the accuracy of diagnosis have not been effectively improved. Developing feature extraction and classification methods to meet the requirements of typical fault alarm and automatic diagnosis in practical engineering is urgent task. The typical mechanical faults of reciprocating compressor are presented in the paper, and the existing data of online monitoring system is used to extract fault feature parameters within 15 types in total; the inner sensitive connection between faults and the feature parameters has been made clear by using the distance evaluation technique, also sensitive characteristic parameters of different faults have been ...
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    Lost water and nitrogen resources due to EU consumer food waste (2015)
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    Publication Date: 2015-08-12
    Description: The European Parliament recently called for urgent measures to halve food waste in the EU, where consumers are responsible for a major part of total waste along the food supply chain. Due to a lack of data on national food waste statistics, uncertainty in (consumer) waste quantities (and the resulting associated quantities of natural resources) is very high, but has never been previously assessed in studies for the EU. Here we quantify: (1) EU consumer food waste, and (2) associated natural resources required for its production, in term of water and nitrogen, as well as estimating the uncertainty of these values. Total EU consumer food waste averages 123 (min 55?max 190) kg/capita annually (kg/cap/yr), i.e. 16% (min 7?max 24%) of all food reaching consumers. Almost 80%, i.e. 97 (min 45?max 153) kg/cap/yr is avoidable food waste, which is edible food not consumed. We have calculated the water and nitrogen (N) resources associated with avoidable food waste. The associated blue wate...
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    Change points of global temperature (2015)
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    Publication Date: 2015-08-04
    Description: We aim to address the question of whether or not there is a significant recent ?hiatus?, ?pause? or ?slowdown? of global temperature rise. Using a statistical technique known as change point (CP) analysis we identify the changes in four global temperature records and estimate the rates of temperature rise before and after these changes occur. For each record the results indicate that three CPs are enough to accurately capture the variability in the data with no evidence of any detectable change in the global warming trend since ?1970. We conclude that the term ?hiatus? or ?pause? cannot be statistically justified.
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    Crop failure rates in a geoengineered climate: impact of climate change and marine cloud brightening (2015)
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    Publication Date: 2015-08-04
    Description: The impact of geoengineering on crops has to date been studied by examining mean yields. We present the first work focusing on the rate of crop failures under a geoengineered climate. We investigate the impact of a future climate and a potential geoengineering scheme on the number of crop failures in two regions, Northeastern China and West Africa. Climate change associated with a doubling of atmospheric carbon dioxide increases the number of crop failures in Northeastern China while reducing the number of crop failures in West Africa. In both regions marine cloud brightening is likely to reduce the number crop failures, although it is more effective at reducing mild crop failure than severe crop failure. We find that water stress, rather than heat stress, is the main cause of crop failure in current, future and geoengineered climates. This demonstrates the importance of irrigation and breeding for tolerance to water stress as adaptation methods in all futures. Analysis of global...
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    A simple scaling approach to produce climate scenarios of local precipitation extremes for the Netherlands (2015)
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    Publication Date: 2015-08-04
    Description: Scenarios of future changes in small scale precipitation extremes for the Netherlands are presented. These scenarios are based on a new approach whereby changes in precipitation extremes are set proportional to the change in water vapor amount near the surface as measured by the 2m dew point temperature. This simple scaling framework allows the integration of information derived from: (i) observations, (ii) a new unprecedentedly large 16 member ensemble of simulations with the regional climate model RACMO2 driven by EC-Earth, and (iii) short term integrations with a non-hydrostatic model Harmonie. Scaling constants are based on subjective weighting (expert judgement) of the three different information sources taking also into account previously published work. In all scenarios local precipitation extremes increase with warming, yet with broad uncertainty ranges expressing incomplete knowledge of how convective clouds and the atmospheric mesoscale circulation will react to climate...
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    Satellite observation of tropical forest seasonality: spatial patterns of carbon exchange in Amazonia (2015)
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    Publication Date: 2015-08-04
    Description: Determining the seasonality of terrestrial carbon exchange with the atmosphere remains a challenge in tropical forests because of the heterogeneity of ecosystem and climate. The magnitude and spatial variability of this flux are unknown, particularly in Amazonia where empirical upscaling approaches from spatially sparse in situ measurements and simulations from process-based models have been challenged in recent scientific literature. Here, we use satellite proxy observations of canopy structure, skin temperature, water content, and optical properties over a period of 10 years (2000?2009) to constrain and quantify the spatial pattern and seasonality of carbon exchange of Amazonian forests. We identify nine regions through an optimized cluster approach with distinct leaf phenology synchronized with either water or light availability and corresponding seasonal cycles of gross primary production (GPP), covering more than 600 million ha of remaining old growth forests of Amazo...
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    Gradient nanostructured surface of a Cu plate processed by incremental frictional sliding (2015)
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    Publication Date: 2015-08-08
    Description: The flat surface of a Cu plate was processed by incremental frictional sliding at liquid nitrogen temperature. The surface treatment results in a hardened gradient surface layer as thick as 1 mm in the Cu plate, which contains a nanostructured layer on the top with a boundary spacing of the order of 100 nm. The boundary spacing increases with increasing distance from the surface, and is accompanied with a decrease in hardness from 2179?31MPa in the topmost surface layer to 568?10 MPa in the undeformed matrix.
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    Cube texture formation during the early stages of recrystallization of Al-1%wt.Mn and AA1050 aluminium alloys (2015)
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    Publication Date: 2015-08-08
    Description: The cube texture formation during primary recrystallization was analysed in plane strain deformed samples of a commercial AA1050 alloy and an Al-1%wt.Mn model alloy single crystal of the Goss{110} orientation. The textures were measured with the use of X-ray diffraction and scanning electron microscopy equipped with an electron backscattered diffraction facility. After recrystallization of the Al-1%wt.Mn single crystal, the texture of the recrystallized grains was dominated by four variants of the S{123} orientation. The cube grains were only sporadically detected by the SEM/EBSD system. Nevertheless, an increased density of poles corresponding to the cube orientation was observed. The latter was connected with the superposition of four variants of the S{123} orientation. This indicates that the cube texture after the recrystallization was a ?compromise texture?. In the case of the recrystallized AA1050 alloy, the strong cube texture r...
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    Phase decomposition and nano structure evolution of metastable nanocrystalline Cu-Co solid solutions during thermal treatment (2015)
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    Publication Date: 2015-08-08
    Description: Nanocrystalline and ultrafine-grained Cu 100-x Co x (x = 26 and 76) solid solutions have been prepared by severe plastic deformation (SPD) of elemental powder mixtures. For both concentrations a supersaturated solid solution fcc phase was identified after the deformation process with grain sizes of less than 50 nm for Co rich solutions and around 100 nm for Cu rich solutions. Additionally, synthesis of nanocrystalline materials in the Cu-Co alloy system by electrodeposition has been conducted. Microstructural characterization by scanning and transmission electron microscopy, differential scanning calorimetry, and microhardness measurements are used to investigate the structural evolution, the thermal stability and mechanical properties of the different nanocrystalline Cu-Co alloy materials during isothermal and non-isothermal annealing. In this study it is shown that the phase decomposition of the metastable Cu-Co solid solutions has a significant influence on ...
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    Microstructure and hardness development in a copper-nickel diffusion gradient model system (2015)
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    Publication Date: 2015-08-08
    Description: Cu has been electrolytically coated with Ni and subsequently deformed by rotary swaging up to a strain of e=2 to create a chemical gradient at the interface of the two elements. The extend of this chemical intermixing has been investigated through Energy Dispersive X- ray (EDX) spectroscopy in the Scanning and Transmission Electron Microscope (SEM and TEM). The depth, in which intermixing takes place, is about 1pm from the interface. Because of the uniform deformation, the structure does not get elongated but rather uniformly reduced in size. Microindentation hardness measurement shows a hardness increase from 120 to 135kp/mm 2 in the Cu phase with increasing strain. After annealing at 200?C for up to 4h the hardness first decreases, but raises above the value for the highly strained sample. The experimental findings are discussed with emphasis on surface mechanical alloying as a process of both scientific and technological interest.
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    Distributions of energy storage rate and microstructural evolution in the area of plastic strain localization during uniaxial tension of austenitic steel (2015)
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    Publication Date: 2015-08-08
    Description: The presented work is devoted to an experimental determination of the energy storage rate in the area of strain localization. The experimental procedure involves two complementary techniques: i.e. infrared thermography (IRT) and visible light imaging. The results of experiments have shown that during the evolution of plastic strain localization the energy storage rate in some areas of the deformed specimen drops to zero. To interpret the decrease of the energy storage rate in terms of micro-mechanisms, microstructural observations using Transmission Electron Microscopy (TEM) and Electron Back Scattered Diffraction (EBSC) were performed. On the basis of microstructural studies it is believed that a 0 value of energy storage rate corresponds to the state in which only two dominant components of the texture appear, creating conditions for crystallographic shear banding.
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    Crystallographic aspects of nucleation and growth during primary recrystallization in stable single crystals of Al and Al-1%Mn alloy (2015)
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    Publication Date: 2015-08-08
    Description: The early stages of recrystallization have been characterized in stable, single crystals of Al and an Al-1%wt. Mn alloy to rigorously quantify the orientation relations between nuclei and simple deformation structures. Goss{110} and brass{110} oriented samples were deformed in a channel-die to develop a homogeneous structure composed of two sets of symmetrical microbands and then lightly annealed. SEM/EBSD analyses demonstrate a strong relation between as-deformed orientations and the limited number of recrystallized grain orientations. The misorientation angles across the recrystallization front are mostly grouped in the ranges of 25-55? around axes located near, but not at, the normals of all four {111} planes. In some cases the orientation of the growing grain transforms through the formation of a first generation twin with the twinning plane normal lying near the rotation axis. The intensity of new grain nucleation in near-surface areas is significantly ...
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    Recovery by triple junction motion in heavily deformed metals (2015)
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    Publication Date: 2015-08-08
    Description: A number of processes may occur during recovery, which reduce the stored energy and coarsen the structure, paving the way for the nucleation of recrystallization. In this review, recovery is discussed based on the initial deformed structure. Recovery in samples deformed to low-to-medium strains is briefly considered, whereas recovery in samples deformed to much higher strains is discussed in more detail. An example is Al, where a new and important recovery mechanism is triple junction motion, which can remove thin lamellae and consequently increase the thickness of neighbouring lamellae. This recovery mechanism therefore coarsens the structure and causes a gradual transition from a lamellar to a near equiaxed structure preceding recrystallization. This mechanism is discussed in conjunction with structural pinning, which stabilizes the coarsening microstructure, thereby balancing the forces controlling the rate of recovery by triple junction motion. Operation of triple junction mo...
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    Peer review statement (2015)
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    Publication Date: 2015-08-08
    Description: All papers published in this volume of IOP Conference Series: Materials Science and Engineering have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.
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    Characterization of boundary roughness of two cube grains in partly recrystallized copper (2015)
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    Publication Date: 2015-08-08
    Description: Protrusions and retrusions typically form on recrystallizing boundaries and thus the boundaries often appear rough. Characterization of the boundary roughness is necessary in order to evaluate the effects of protrusions and retrusions on boundary migration. In the current work, a variable termed area integral invariant is employed to provide quantitative information of individual protrusions/retrusions on boundaries surrounding two selected recrystallizing grains in partly recrystallized copper as well as of the overall roughness of the boundaries.
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    Microstructure and mechanical properties of ARB processed Mg-3% Gd alloy (2015)
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    Publication Date: 2015-08-08
    Description: Mg alloys have various advantages. However, the low formability due to the poor ductility of Mg alloys limits their engineering applications. In this study, an Mg-3% Gd alloys was chosen to explore processing approaches for improving its strength and ductility combination. The alloy was processed by accumulative roll-bonding (ARB) at 400 ?C to 4 cycles followed by annealing at various temperatures. The microstructures after annealing were characterized by the electron backscatter diffraction technique and the mechanical properties were measured by a tensile test. It was found that the alloy has a good combination of strength and ductility after 2 cycle ARB processing followed by annealing at 290?C for 1h. The strength is 2.3 times higher than that of the fully annealed coarse grained alloy, and the elongation is comparable with that of fully annealed coarse grained counterpart. The good mechanical properties were related to the fine-sized heterogeneous microstructures and weakene...
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    Effect of initial grain size on inhomogeneous plastic deformation and twinning behavior in high manganese austenitic steel with a polycrystalline microstructure (2015)
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    Publication Date: 2015-08-08
    Description: The grain size effect on the deformation twinning in a high manganese austenitic steel which is so-called TWIP (twining induced plastic deformation) steel was studied in order to understand how to control deformation twinning. The 31wt%Mn-3%Al-3% Si steel was cold rolled and annealed at various temperatures to obtain fully recrystallized structures with different mean grain sizes. These annealed sheets were examined by room temperature tensile tests at a strain rate of 10 -4 /s. The coarse grained sample (grain size: 49.6?m) showed many deformation twins and the deformation twinning was preferentially found in the grains in which the tensile axis is parallel near to [111]. On the other hand, the sample with finer grains (1.8 ?m) had few grains with twinning even after the tensile deformation. The electron back scattering diffraction (EB SD) measurements clarified the relationship between the anisotropy of deformation twinning and that of inhomogeneous plastic deformation...
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    Investigation of SIBM driven recrystallization in alpha Zirconium based on EBSD data and Monte Carlo modeling (2015)
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    Publication Date: 2015-08-08
    Description: The work focuses on the influence of moderate plastic deformation on subsequent partial recrystallization of hexagonal zirconium (Zr702). In the considered case, strain induced boundary migration (SIBM) is assumed to be the dominating recrystallization mechanism. This hypothesis is analyzed and tested in detail using experimental EBSD-OIM data and Monte Carlo computer simulations. An EBSD investigation is performed on zirconium samples, which were channel-die compressed in two perpendicular directions: normal direction (ND) and transverse direction (TD) of the initial material sheet. The maximal applied strain was below 17%. Then, samples were briefly annealed in order to achieve a partly recrystallized state. Obtained EBSD data were analyzed in terms of texture evolution associated with a microstructural characterization, including: kernel average misorientation (KAM), grain orientation spread (GOS), twinning, grain size distributions, description of grain boundary regions. In p...
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    Phase dependent restoration mechanisms of TC8 titanium alloy during hot compression in the two phase region (2015)
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    Publication Date: 2015-08-08
    Description: The TC8 titanium alloy was isothermally compressed at 1133 K and 1213 K in the (?+?) two phase region. The microstructural evolution and restoration mechanism in the ? and ? phases were characterized by optical microscopy and transmission electron microscopy. The results show a significant effect of phase content on the microstructural evolution and restoration mechanism. The grain refinement occurs in the ? phase at both temperatures, but in the ? phase only at the higher temperature of 1213 K. This difference in microstructural evolution is attributed to the different temperature dependence of restoration mechanisms in the two phases. A significant increase in the volume fraction of ? phase makes the restoration mechanism in the ? phase change from dynamic recovery (DRV) to dynamic recrystallization (DRX), which subsequently induces the ? grain refinement.
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    Uncovering the true nature of deformation microstructures using 3D analysis methods (2015)
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    Publication Date: 2015-08-08
    Description: Three-dimensional electron backscatter diffraction (3D EBSD) has emerged as a powerful technique for generating 3D crystallographic information in reasonably large volumes of a microstructure. The technique uses a focused ion beam (FIB) as a high precision serial sectioning device for generating consecutive ion milled surfaces of a material, with each milled surface subsequently mapped by EBSD. The successive EBSD maps are combined using a suitable post-processing method to generate a crystallographic volume of the microstructure. The first part of this paper shows the usefulness of 3D EBSD for understanding the origin of various structural features associated with the plastic deformation of metals. The second part describes a new method for automatically identifying the various types of low and high angle boundaries found in deformed and annealed metals, particularly those associated with grains exhibiting subtle and gradual variations in orientation. We have adapted a 2D image ...
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    Structural coarsening during annealing of an aluminum plate heavily deformed using ECAE (2015)
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    Publication Date: 2015-08-08
    Description: The microstructure and softening behaviour have been investigated in an aluminum plate heavily deformed by equal channel angular extrusion and subsequently annealed at 170 ?C. It is found that at this temperature the microstructure evolves by coarsening with no apparent signs of recrystallization even after 2 h of annealing. Both coarsening and softening are rapid within first 10 minutes of annealing followed by a slower evolution with increasing annealing duration. Evidence of triple junction (TJ) motion during coarsening is obtained by inspecting the microstructure in one region using the electron backscatter diffraction technique both before and after annealing for 10 minutes. The fraction of fast-migrating TJs is found to strongly depend of the type of boundaries composing a junction. The greatest fraction of fast- migrating TJs is in the group, where all boundaries forming a junction are high angle boundaries. The fraction of fast-migrating TJs is significantly lower for jun...
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    Dynamic recrystallization of Zr-1Sn-0.3Nb alloy during hot compression (2015)
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    Publication Date: 2015-08-08
    Description: In this paper, using a hot-rolled and recrystallized Zr-1Sn-0.3Nb alloy sheet, five strain levels (10, 20, 30, 45 and 60%) of uniaxial compression experiments were performed at 700 o C with a strain rate of 0.001s -1 using a Gleeble 1500D thermal simulator. The morphologies, distributions and misorientations of the grain boundaries at different strains were characterized by an electron backscatter diffraction (EBSD) technique. The EBSD maps indicated that dynamic recrystallization occurred during the high-temperature deformation. The processes, namely, grain boundary bulging, strain induced subboundaries around the bulged grain boundaries and their transformation from low misorientation to high misorientation, were considered as the formation mechanisms of recrystallized grains. At the early stage of deformation, low angle boundaries (LABs) formed in grains, the original grain boundaries become serrated, and LABs formed around the serrated boundaries. With incr...
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    Preferred lattice misorientations in rolled aluminium: tracking experiments and crystal plasticity simulations (2015)
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    Publication Date: 2015-08-08
    Description: The microstructural heterogeneities developed in the grains of hot deformed Al have been quantified by applying the microtexture tracking technique to hot plane strain compressed Al-0.1%Mn. By successive EBSD measurements over the same (internal) surface at different strains, a large data set of lattice orientation and disorientation development has been obtained in over 150 grains up to strains of 1.2. Simultaneously, high resolution finite element simulations have been carried out to large strains with the same grain orientations; both experiments and simulations focus on the orientation distributions developed within individual grains. It is shown that 15-20% of the grains undergo orientation splitting, usually when the orientation is both symmetrical with respect to the loading and divergent in terms of potential lattice rotations. An analysis of the reorientation velocity field predicted for hot PSC provides a first order indication of the particular grain orientations expec...
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    Effects of interface roughness on the annealing behaviour of laminated Ti-Al composite deformed by hot rolling (2015)
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    Publication Date: 2015-08-08
    Description: A laminated Ti-Al composite has been fabricated by hot compaction and hot rolling of alternate layers of commercial purity Ti and Al sheets with a thickness of 200 ?m. The hot compaction temperature was 500?C and in a following step the composite has been reduced 50% in thickness by hot rolling. The fully consolidated composite has been annealed at 300?C and 500?C for different length of time. As a result of the differences in crystal structure and mechanical properties between Ti and Al protrusions and retrusions formed at the interface. A heterogeneous interface has thereby been created. The heterogeneity affected the recovery kinetics of the aluminium phase which at 300?C was faster near the interface than in the middle of the Al layer. This effect of a heterogeneous interface is of relevance when optimizing the thermomechanical processing of the composite to obtain high strength and formability for application.
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    Is the ozone climate penalty robust in Europe? (2015)
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    Publication Date: 2015-08-18
    Description: Ozone air pollution is identified as one of the main threats bearing upon human health and ecosystems, with 25 000 deaths in 2005 attributed to surface ozone in Europe (IIASA 2013 TSAP Report #10). In addition, there is a concern that climate change could negate ozone pollution mitigation strategies, making them insufficient over the long run and jeopardising chances to meet the long term objective set by the European Union Directive of 2008 ( Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 ) (60 ppbv, daily maximum). This effect has been termed the ozone climate penalty. One way of assessing this climate penalty is by driving chemistry-transport models with future climate projections while holding the ozone precursor emissions constant (although the climate penalty may also be influenced by changes in emission of precursors). Here we present an analysis of the robustness of the climate penalty in Europe across time periods and scenar...
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    Facing unprecedented drying of the Central Andes? Precipitation variability over the period AD 1000–2100 (2015)
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    Publication Date: 2015-08-18
    Description: Projected future trends in water availability are associated with large uncertainties in many regions of the globe. In mountain areas with complex topography, climate models have often limited capabilities to adequately simulate the precipitation variability on small spatial scales. Also, their validation is hampered by typically very low station density. In the Central Andes of South America, a semi-arid high-mountain region with strong seasonality, zonal wind in the upper troposphere is a good proxy for interannual precipitation variability. Here, we combine instrumental measurements, reanalysis and paleoclimate data, and a 57-member ensemble of CMIP5 model simulations to assess changes in Central Andes precipitation over the period AD 1000–2100. This new database allows us to put future projections of precipitation into a previously missing multi-centennial and pre-industrial context. Our results confirm the relationship between regional summer precipitation and 200 hPa zonal ...
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    Net exchanges of methane and carbon dioxide on the Qinghai-Tibetan Plateau from 1979 to 2100 (2015)
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    Publication Date: 2015-08-21
    Description: Methane (CH 4 ) is a potent greenhouse gas (GHG) that affects the global climate system. Knowledge about land–atmospheric CH 4 exchanges on the Qinghai-Tibetan Plateau (QTP) is insufficient. Using a coupled biogeochemistry model, this study analyzes the net exchanges of CH 4 and CO 2 over the QTP for the period of 1979–2100. Our simulations show that the region currently acts as a net CH 4 source with 0.95 Tg CH 4 y −1 emissions and 0.19 Tg CH 4 y −1 soil uptake, and a photosynthesis C sink of 14.1 Tg C y −1 . By accounting for the net CH 4 emission and the net CO 2 sequestration since 1979, the region was found to be initially a warming source until the 2010s with a positive instantaneous radiative forcing peak in the 1990s. In response to future climate change projected by multiple global climate models (GCMs) under four representative concentration pathway (RCP...
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    Can improved agricultural water use efficiency save India’s groundwater? (2015)
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    Publication Date: 2015-08-21
    Description: Irrigated agriculture is placing increasing pressure on finite freshwater resources, especially in developing countries, where water extraction is often unregulated, un-priced and even subsidized. To shift agriculture to a more sustainable use of water without harming the food security and livelihoods of hundreds of millions of smallholders, substantial improvements of water use efficiency will be required. Here, we use detailed hydroclimatic and agricultural data to estimate the potential for the widespread adoption of efficient irrigation technologies to halt the depletion of India’s groundwater resources. Even though we find substantial technical potential for reversing water table declines, we show that the impacts are highly sensitive to assumptions about farmers’ water use decisions. For example, we find that widespread adoption of proven technologies that include drip and sprinkler irrigation has the potential to reduce the amount of excessive extraction of groundwater by ...
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    Torsional Vibration Analysis of Reciprocating Compressor Trains driven by Induction Motors (2015)
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    Publication Date: 2015-08-11
    Description: The dynamic study of electric motor driven compressors, for Oil&Gas (O&G) applications, are traditionally performed in two steps separating the mechanical and the electrical systems. The packager conducts a Torsional Vibration Analysis (TVA) modeling the mechanical system with a lumped parameter scheme, without taking into account the electrical part. The electric motor supplier later performs a source current pulsation analysis on the electric motor system, based on the TVA results. The mechanical and the electrical systems are actually linked by the electromagnetic effect. The effect of the motor air-gap on TVA has only recently been taken into account by adding a spring and a damper between motor and ground in the model. This model is more accurate than the traditional one, but is applicable only to the steady-state condition and still fails to consider the reciprocal effects between the two parts of the system. In this paper the torsional natural frequencies calculate...
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    Rotor clearance design and evaluation for an oil injected twin screw compressor (2015)
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    Publication Date: 2015-08-11
    Description: Designing twin screw compressors to safely operate at higher than normal temperatures poses a challenge as the compressor must accommodate larger peak thermal distortions while ideally maintaining efficiency at nominal operating conditions. This paper will present a case study of an oil injected compressor tested at elevated discharge temperatures with original and revised clearances. The local thermal distortions occurring within the compressor during operation were estimated using a procedure developed by the authors - thermodynamic results from a chamber model were used to approximate component temperature distributions that are then used to predict possible thermal distortions and the resulting affect on clearance gaps. The original and revised clearance designs are evaluated and performance penalties incurred due to the modifications are discussed.
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    Reviewers 2015 (2015)
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    Publication Date: 2015-08-11
    Description: A list of reviewers is available in the PDF.
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    The impact of component performance on the overall cycle performance of small-scale low temperature organic Rankine cycles (2015)
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    Publication Date: 2015-08-11
    Description: Low temperature organic Rankine cycles offer a promising technology for the generation of power from low temperature heat sources. Small-scale systems (?10kW) are of significant interest, however there is a current lack of commercially viable expanders. For a potential expander to be economically viable for small-scale applications it is reasonable to assume that the same expander must have the ability to be implemented within a number of different ORC applications. It is therefore important to design and optimise the cycle considering the component performance, most notably the expander, both at different thermodynamic conditions, and using alternative organic fluids. This paper demonstrates a novel modelling methodology that combines a previously generated turbine performance map with cycle analysis to establish at what heat source conditions optimal system performance can be achieved using an existing turbine design. The results obtained show that the same turbine can be effec...
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    Modelling, sizing and testing a scroll expander for a waste heat recovery application on a gasoline engine (2015)
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    Publication Date: 2015-08-11
    Description: Waste heat recovery technologies in a mobile application emerge every time energy becomes a valuable resource. It has been the case in the 70s with oil crisis and it is starting to regain some interests now due to the continuously rising price of oil and due to the restrictive standards imposed by the different governments. This paper deals with the recovery on the exhaust gases of an internal combustion engine by using a Rankine system. The study focuses on the expander, which is one of the most important components of the system. The use of a scroll expander operating with steam is currently investigated through simulation and experimentation. This paper presents the modelling of a scroll expander. The model is a detailed model including various losses such as leakage, friction or under or over expansion. This model has been used to design and size a tailor-made scroll expander. This was necessary due to the small amount of expanders on the market and also to have a machine tha...
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    Reciprocating and Screw Compressor semi-empirical models for establishing minimum energy performance standards (2015)
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    Publication Date: 2015-08-11
    Description: The efficiency bar for a Minimum Equipment Performance Standard (MEPS) generally aims to minimize energy consumption and life cycle cost of a given chiller type and size category serving a typical load profile. Compressor type has a significant chiller performance impact. Performance of screw and reciprocating compressors is expressed in terms of pressure ratio and speed for a given refrigerant and suction density. Isentropic efficiency for a screw compressor is strongly affected by under- and over-compression (UOC) processes. The theoretical simple physical UOC model involves a compressor-specific (but sometimes unknown) volume index parameter and the real gas properties of the refrigerant used. Isentropic efficiency is estimated by the UOC model and a bi-cubic, used to account for flow, friction and electrical losses. The unknown volume index, a smoothing parameter (to flatten the UOC model peak) and bi-cubic coefficients are identified by curve fitting to minimize an appropria...
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    Numerical and Experimental Investigation of Pressure Losses at Suction of a Twin Screw Compressor (2015)
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    Publication Date: 2015-08-11
    Description: Rotary twin screw machines are used in the wide range of industrial applications and are capable of handling single and multiphase fluids as compressors, expanders and pumps. Concentration of liquid in the inlet flow can influence the performance of the machine significantly. Characteristics of the multiphase flow at the suction of a screw compressor depend on the local flow velocities and concentration. Local flow velocity measurements inside the screw compressors are difficult to obtain. However other flow properties such as local pressures are easier to attain. It is therefore useful to carry out experiments with local pressure variations in the suction which can be used to validate the 3D numerical Computational Fluid Dynamic (CFD) models that could help in studying the single and multiphase flow behaviour in screw compressors. This paper presents experimental efforts to measure the local pressure losses inside the suction plenum of the screw compressor. Pressure variat...
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    A miniature Rotary Compressor with a 1:10 compression ratio (2015)
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    Publication Date: 2015-08-11
    Description: Micro compressors have applications in medical devices, robotics and ?nanosatellites?. The problem of active cooling for photo detectors in ?nano-satellites? becomes more important because the majority of space missions target Earth observation, and passive cooling does not provide the required temperatures to achieve the desired SNR levels. Reciprocating compressors used in cryocoolers cause vibrations. VERT Rotors has built an ultralow-vibration rotary compressor with 40mm-long screws, and our prototype delivered 1:10 compression ratio. This ?nano? compressor is a non-conventional conical type consisting of an Inner conical screw rotor revolving inside an Outer screw rotor.
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    Analysis of the gas-dynamic performance of a vaned diffuser with given velocity distribution along the vane's surfaces (2015)
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    Publication Date: 2015-08-11
    Description: Extension of the effective range of vaned diffusers is one of the promising ways to improve the centrifugal compressor's stages which are used in numerous fields of industry. The new method of profiling of the diffuser vanes has been developed using Stratford's results and boundary layer theory by Loytsanskiy. The developed method is based on the solution of the inverse task of gas-dynamic using given velocity distribution along the vane's surface. Comparison of the results of numerical simulations for different diffusers has shown that the performance of the diffuser designed with the resulting velocity distribution are better. Influence of the vane profile, number of the vanes, diffuser outlet diameter and the diffuser width on diffuser characteristics has been investigated. The results of the simulations have been used to formulate recommendations on the design of high-effectiveness vaned diffusers for centrifugal stages of different types.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    CFD simulation of a screw compressor including leakage flows and rotor heating (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-08-11
    Description: Computational Fluid Dynamics (CFD) simulations have promising potential to become an important part in the development process of positive displacement (PD) machines. CFD delivers deep insights into the flow and thermodynamic behaviour of PD machines. However, the numerical simulation of such machines is more complex compared to dynamic pumps like turbines or fans. The fluid transport in size-changing chambers with very small clearances between the rotors, and between rotors and casing, demands complex meshes that change with each time step. Additionally, the losses due to leakage flows and the heat transfer to the rotors need high-quality meshes so that automatic remeshing is almost impossible. In this paper, setup steps and results for the simulation of a dry screw compressor are shown. The rotating parts are meshed with TwinMesh, a special hexahedral meshing program for gear pumps, gerotors, lobe pumps and screw compressors. In particular, these meshes include axial and ...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 99
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    3D Transient CFD Simulation of Scroll Compressors with the Tip Seal (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-08-11
    Description: A new template simulation tool is developed for scroll compressors/expanders capable of modelling tip seal leakages. This scroll template generates a high quality 3D multiblock structured mesh from user-input stationary and orbiting scroll surfaces. The mesh movement is then automatically calculated to account for every position of the orbiting scroll, maintaining good grid quality and smooth movement throughout the whole revolution. A state- of-the-art efficient CFD solver is used to solve Navier-Stokes equations, capable of simulation with both real gas and ideal gas. A case study is presented for a generic scroll compressor with refrigerant R410A. The case was run with and without the tip seal volumes. Comparisons are made to show the impact of tip seals on the compressor performance.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 100
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    A Diagnosis method of the small end fault on reciprocating compressor connecting rod (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-08-11
    Description: The connecting rod is the key moving part of a reciprocating compressor, of which the stress state is extremely complicate and the wear fault of the small end is always a bottleneck problem in the field of fault monitoring and diagnosing. This paper is aimed to present a new method to diagnose the above wear fault. Firstly, a contact model of a clearance in the revolute joint of the small end of a connecting rod bearing (SECRB) was established and a multi-body simulation tool was utilized to simulate the slider-crank mechanism with a clearance, from which the dynamic influence of wear gap in SECRB of a slider-crank mechanism was obtained. Based on the study above, we extracted the characteristics of the wear fault of SECRB and then proposed a brand new approach to monitoring and diagnosing this wear fault by analyzing the angle domain of vibration signals. The availability was verified by conducting an experiment on a reciprocating compressor. And the experimental results show th...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
    Location Call Number Expected Availability
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