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  • 11
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2013-08-31
    Description: Aspects of dc to dc conversion were studied in terms of a class of switching voltage regulators from a stability viewpoint. Background concepts of nonlinear system theory were considered, including the problem of obtaining suitable realizations for a class of positive operators. It is shown that the state evolution equations for a power conversion network are in general of bilinear form, and that the theory of lie groups and lie algebras is useful in analyzing such systems. The feedback stabilization of a class of bilinear systems whose state space is a manifold is also discussed.
    Keywords: ELECTRONIC EQUIPMENT
    Type: NASA-CR-120830
    Format: application/pdf
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  • 12
    Publication Date: 2013-08-31
    Description: A backswept impeller with design mass flow rate of 1.033 kg/sec was tested with both a vaned diffuser and a vaneless diffuser to establish stage and impeller characteristics. Design stage pressure ratio of 5.9:1 was attained at a flow slightly lower than the design value. Flow range at design speed was 6 percent of choking flow. Impeller axial tip clearance at design speed was varied to determine effect on stage and impeller performance.
    Keywords: AERODYNAMICS
    Type: E-9074 , NASA-TM-X-3552
    Format: application/pdf
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  • 13
    Publication Date: 2011-08-19
    Description: Computer program (MERNEW3D) developed that prepares bulk of input data set required for Denton three-dimensional inviscid turbomachine-blade-row analysis code. Denton input generated from minimum of geometry and flow-variable information by using cubic spline curve fits for interpolation and extrapolation. Curve-fitting procedures taken from previously developed and widely used NASA computer program (MERIDL), which performs meridional streamsurface analysis.
    Keywords: MACHINERY
    Type: LEW-14061 , NASA Tech Briefs (ISSN 0145-319X); 9; 3; P. 154
    Format: text
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  • 14
    Publication Date: 2019-07-13
    Description: A centrifugal impeller which was initially designed for a pressure ratio of approximately 5.5 and a mass flow rate of 0.959 kg/sec was tested with a vaneless diffuser for a range of design point impeller area ratios from 2.322 to 2.945. The impeller area ratio was changed by successively cutting back the impeller exit axial width from an initial value of 7.57 mm to a final value of 5.97 mm. In all, four separate area ratios were tested. For each area ratio a series of impeller exit axial clearances was also tested. Test results are based on impeller exit surveys of total pressure, total temperature, and flow angle at a radius 1.115 times the impeller exit radius. Results of the tests at design speed, peak efficiency, and an exit tip clearance of 8 percent of exit blade height show that the impeller equivalent pressure recovery coefficient peaked at a design point area ratio of approximately 2.748 while the impeller aerodynamic efficiency peaked at a lower value of area ratio of approximately 2.55. The variation of impeller efficiency with clearance showed expected trends with a loss of approximately 0.4 points in impeller efficiency for each percent increase in exit axial tip clearance for all impellers tested.
    Keywords: AERODYNAMICS
    Type: NASA-TM-87237 , E-2190 , NAS 1.15:87237 , USAAVSCOM-TR-85-C-21 , TR-85-C-21 , International Gas Turbine Conference and Exhibition; 8-12 Jun. 1986; Dusseldorf; Germany
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  • 15
    Publication Date: 2019-07-13
    Description: An experimental investigation of the three dimensional flow field through a low aspect ratio, transonic, axial flow fan rotor has been conducted using an advanced laser anemometer (LA) system. Laser velocimeter measurements of the rotor flow field at the design operating speed and over a range of through flow conditions are compared to analytical solutions. The numerical technique used herein yields the solution to the full, three dimensional, unsteady Euler equations using an explicit time marching, finite volume approach. The numerical analysis, when coupled with a simplified boundary layer calculation, generally yields good agreement with the experimental data. The test rotor has an aspect ratio of 1.56, a design total pressure ratio of 1.629 and a tip relative Mach number of 1.38. The high spatial resolution of the LA data matrix (9 radial by 30 axial by 50 blade to blade) permits details of the transonic flow field such as shock location, turning distribution and blade loading levels to be investigated and compared to analytical results.
    Keywords: AERODYNAMICS
    Type: NASA-TM-83739 , E-2150 , NAS 1.15:83739 , USAAVSCOM-TR-83-C-16 , Ann. Intern. Gas Turbine Conf.; 3-7 Jun. 1984; Amsterdam; Netherlands
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  • 16
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-07-13
    Description: An investigation is conducted concerning the state equations which arise in the description of power processing systems. Attention is given to the role played by Lie groups and Lie algebras in the characterization of the dynamical features of the systems. The bilinear equations used for the representation of the network characteristics are discussed along with the nature of the solutions for the equations. The application of the described approaches is illustrated with the aid of a number of network examples.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Annual Allerton Conference on Circuit and System Theory; October 3-5, 1973; Monticello, IL
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  • 17
    Publication Date: 2019-07-13
    Description: A low speed centrifugal compressor facility recently built by the NASA Lewis Research Center is described. The purpose of this facility is to obtain detailed flow field measurements for computational fluid dynamic code assessment and flow physics modeling in support of Army and NASA efforts to advance small gas turbine engine technology. The facility is heavily instrumented with pressure and temperature probes, both in the stationary and rotating frames of reference, and has provisions for flow visualization and laser velocimetry. The facility will accommodate rotational speeds to 2400 rpm and is rated at pressures to 1.25 atm. The initial compressor stage being tested is geometrically and dynamically representative of modern high-performance centrifugal compressor stages with the exception of Mach number levels. Preliminary experimental investigations of inlet and exit flow uniformly and measurement repeatability are presented. These results demonstrate the high quality of the data which may be expected from this facility. The significance of synergism between computational fluid dynamic analysis and experimentation throughout the development of the low speed centrifugal compressor facility is demonstrated.
    Keywords: AERODYNAMICS
    Type: NASA-TM-103710 , E-5938 , NAS 1.15:103710 , AVSCOM-TR-91-C-003 , AD-A242473 , International Gas Turbine and Aeroengine Congress and Exposition; 3-6 Jun. 1991; Orlando, FL; United States
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  • 18
    Publication Date: 2019-07-13
    Description: An experimental and computational investigation of the NASA Low-Speed Centrifugal Compressor (LSCC) flow field has been conducted using laser anemometry and Dawes' 3D viscous code. The experimental configuration consists of a backswept impeller followed by a vaneless diffuser. Measurements of the three-dimensional velocity field were acquired at several measurement planes through the compressor. The measurements describe both the throughflow and secondary velocity field along each measurement plane and in several cases provide details of the flow within the blade boundary layers. The experimental and computational results provide a clear understanding of the development of the throughflow momentum wake which is characteristic of centrifugal compressors.
    Keywords: AERODYNAMICS
    Type: NASA-TM-106421 , E-8258 , NAS 1.15:106421 , ARL-TR-331 , eeting of the AGARD Propulsion and Energetics Panel, Technology Requirements for Small Gas Turbine Engines; 4-6 October 1993; Montreal, Ontario; Canada
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  • 19
    Publication Date: 2019-07-13
    Description: A centrifugal compressor facility being built by the NASA Lewis Research Center is described; its purpose is to obtain benchmark experimental data for internal flow code verification and modeling. The facility will be heavily instrumented with standard pressure and temperature probes and have provisions for flow visualization and laser Doppler velocimetry. The facility will accommodate rotational speeds to 2400 rpm and will be rated at pressures to 1.25 atm. The initial compressor stage for testing is geometrically and dynamically representative of modern high-performance stages with the exception of Mach number levels. Design exit tip speed for the initial stage is 500 ft/sec with a pressure ratio of 1.17. The rotor exit backsweep is 55 deg from radial.
    Keywords: AERODYNAMICS
    Type: NASA-TM-83398 , E-1675 , NAS 1.15:83398 , Joint Propulsion Conf. and Tech. Display; 27-29 Jun. 1983; Seattle
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  • 20
    Publication Date: 2019-07-13
    Description: The work in power processing is reported. Input-output models, and Lie groups in control theory are discussed along with the methods of analysis for time invariant electrical networks.
    Keywords: MATHEMATICAL AND COMPUTER SCIENCES (GENERAL)
    Type: NASA-CR-134708
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