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  • 1
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    The Research of PID Control in a Large Scale Helium Refrigerator (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-12-19
    Description: In the development of a helium refrigerator, the control of load temperature stability is an important requirement. We usually use multistage control strategies to achieve the precise control of it. Each level has its strict control logic. PID controllers are the core control module in the process. Therefore, a research of its principle and parameters’ setting occupies an important position in the development work. This paper detailed describes the PID control principle used in a large scale helium refrigerator of 10kW@20K, as well as several improvements on PID parameters’ setting, by using simulations and experiments in combination. The temperature is eventually controlled more precise.
    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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  • 2
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    Alleviating coking in ethanol steam reforming by co-loading binary oxides Ni-M (M=Ag, Cu, Mn) on peony-like ceria (2011)
    Institute of Physics (IOP)
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    Publication Date: 2011-06-23
    Description: Previously, hydrothermally prepared mesoporous peony-like ceria (PCO) material was shown to exhibit superior catalytic properties for CO oxidation and ethanol reforming. Ni supported PCO had been shown to have high activity for ethanol steam reforming at low temperature. In this work, Ag, Cu and Mn is co-loaded with Ni on PCO catalysts by impregnation method. The catalysts were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and a combined thermogravimetry, differential scanning calorimetry, and mass spectrometry (TG-DSC-MS). It was found that all the catalysts gave 100% ethanol conversion above ca. 300°C and exhibited similar H 2 yield. It is found that the severe coking problem for the Ni-loaded PCO catalyst was alleviated significantly if Ag, Cu or Mn is co-loaded. Among them, the addition of Mn is the most effective in reducing carbon formation.
    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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  • 3
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    Numerical analysis and experiment research on fluid orbital performance of vane type propellant management device (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-01-16
    Description: Vane type propellant management device (PMD) is one of the key components of the vane-type surface tension tank (STT), and its fluid orbital performance directly determines the STT's success or failure. In present paper, numerical analysis and microgravity experiment study on fluid orbital performance of a vane type PMD were carried out. By using two-phase flow model of volume of fluid (VOF), fluid flow characteristics in the tank with the vane type PMD were numerically calculated, and the rules of fluid transfer and distribution were gotten. A abbreviate model test system of the vane type PMD is established and microgravity drop tower tests were performed, then fluid management and transmission rules of the vane type PMD were obtained under microgravity environment. The analysis and tests results show that the vane type PMD has good and initiative fluid orbital management ability and meets the demands of fluid orbital extrusion in the vane type STT. The results offer valuable g...
    Print ISSN: 1757-8981
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 4
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    Investigation on cavitation for hump characteristics of a pump turbine in pump mode (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-01-16
    Description: In order to get the accurate hump characteristic curve of a pump turbine in pump mode, three dimensional steady simulations were carried out using SST k-ω turbulence model with cavitation model and without cavitation model under different operation condition points with 19 mm guide vanes opening. A refinement grids were generated to adapt the turbulence model. The results obtained with cavitation model show a better agreement with experiments. The detailed analysis was undertaken to find out the relationship between the cavitation and hump region. It is concluded that the hump characteristic is related with cavitation.
    Print ISSN: 1757-8981
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 5
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    Structural and magnetic properties of Pr 0.3 Tb 0.7 Fe 1.9-x Mn x Ribbons (2015)
    Institute of Physics (IOP)
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    Publication Date: 2015-12-11
    Description: The structural and magnetic properties of Pr 0.3 Tb 0.7 Fe 1.9-x Mn x ribbons have been investigated using X-ray diffraction, vibrating sample magnetometry and the standard strain gauge technique. According to the XRD spectra, all ribbons of Pr 0.3 Tb 0.7 Fe 19-x Mn x demonstratea pure Laves phase, which benefits from the melt-spun technology. The Curie temperature of the Pr 0.3 Tb 0.7 Fe 1.9-x Mn x alloys decreases gradually from 366°C for x=0.1 to 328°C for x=0.3. Meanwhile, magnetostriction at room temperature demonstrates a maximum at x=0.1.
    Print ISSN: 1757-8981
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  • 6
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    Investigation on pressure fluctuation in a Francis turbine with improvement measures (2014)
    Institute of Physics (IOP)
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    Publication Date: 2014-12-11
    Description: For a prototype turbine operating under part load conditions, the turbine output power is fluctuating strongly. The test for the prototype turbine at site shows that the main reason is the resonance between the draft tube vortex frequency and the generator natural frequency. In order to reduce the fluctuation of power output, different measures are investigated with using CFD methods. To keep the turbine unchanged, four kinds of draft tubes are examined, including the original draft, the draft tube with extending runner cone, the draft tube with damping gates and the draft tube with flow deflectors. The results are analyzed and compared in order to examine the effects on pressure fluctuation and formation of vortex rope of draft tube. It is found that adding flow deflector is the most effective to change the frequency of the draft tube vortex rope and reduce the amplitude of pressure fluctuation.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 7
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    Dynamic Performances of the Herringbone-Grooved Gas Bearing (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-10-02
    Description: Aiming at studying the dynamic performances of herringbone-grooved gas bearings, a model is built to analysis the relationship between herringbone-grooved gas bearings parameters and its performances such as friction torque, stiffness, stamping, etc. In this model, the hydrodynamic effect of compressible fluid and the shunting effect of herringbone groove are taken into account, and the partial derivative method which based on local integral finite difference method is used to calculate the modal at the same time. The result shows that when the average gap and the length-diameter ratio are decreasing, the rotate speed and eccentricity ratio will be increasing and the hydrodynamic effect of the gas bearing will be enhanced. Increasing groove angle, decreasing width-ridge ratio or aggrandizing length-groove ratio can improve its load capacity. The parameters such as rotate speed and eccentricity ratio are the most important factors which affect the dynamic characteristics of herri...
    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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  • 8
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    A method of measuring iron content in Chinese fir leaf and root tissues by using an automatic chemical analyzer (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-12-20
    Description: This paper discusses a new method for determining the iron content in Chinese fir leaves and roots using a SmartChem200 automatic chemical analyzer. With a pH value of 4-5, Fe 3 + was reduced to Fe 2 + by hydroxylamine hydrochloride, and Fe 2 + and 1,10-phenanthrolinemonohydrate generated an orange complex. The iron content was calculated based on the absorbance measured at a wavelength of 510 nm. The absorbance is directly proportional to the Fe 2 + content within a certain concentration range of Fe 2 +. The absorbance had a good linear relationship with the Fe 2 + content in the range of 0.01 mgL −1 to 5 mgL −1 ; the linear regression equation of the standard curve was Y=0.0632*X-0.00002, and the correlation coefficient was 1.0000. The method is convenient and rapid, and the experimental results were reliable.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 9
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    A new hybrid DC circuit breaker topology (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-10-31
    Description: Being advantageous for long-distance power transmission and new energy connection, DC system has wide range of applications in many scenarios. As the capacity of DC power grids increases, the fault current is more difficult to interrupt. And the DC circuit breaker which is very important for protecting DC grid attracts more and more attention of researchers. In this paper, a new hybrid DC circuit breaker topology based on the technique of thyristor forced current zero is proposed. The breaker is able to interrupt the fault current in several milliseconds, and the mechanical switch can be cut off at zero current. In addition, no extra power supply and control devices are needed, the pre-charging capacitor can obtain energy from DC grid directly. Therefore, the control process is simpler and the reliability is greatly improved. The operating principle of the proposed circuit breaker is analyzed in detail, and then the simulation is carried out in PSCAD/EMTDC which verifies the cor...
    Print ISSN: 1755-1307
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    Topics: Geography , Geosciences , Physics
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  • 10
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    Dynamics of a single droplet with different viscosity impact onto a stainless-steel surface (2018)
    Institute of Physics (IOP)
    Details
    Publication Date: 2018-10-31
    Description: The phenomena of droplet-surface interaction have important applications in many industrial fields. In different scenarios, the viscosity of the liquid droplet that impacts on the solid surface is usually different, and the viscosity of the droplet has a great impact on the results of the droplet impingement. In this paper, the phenomena of single droplets with different viscosity (deionized water, 50% glycerol/water solution, 99% glycerol/water solution) and different Weber number ( We ) in the range of 147.6-939.4 impacting on a flat stainless-steel plate were recorded by a high-speed camera at 4,000 fps, and the spreading behaviour of droplets with different properties were observed. The effect of droplet viscosity and Weber number on the droplet spread on the solid surface is quantitatively analysed, and the results demonstrate that the increase in Weber number has a promoting effect on the maximum spreading diameter, whereas the increase in viscosity has the opposite e...
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    Topics: Geography , Geosciences , Physics
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