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  • 1
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    In:  Other Sources
    Publication Date: 2019-06-28
    Description: Electrohydraulic servo controls moving elements of airflow valve. Position of moving element and attached piston is monitored by linear variable-differential transformer (LVDT). Single-stage servo valve lets fluid into and out of piston volume in response to feedback signals from the LVDT.
    Keywords: MECHANICS
    Type: LEW-13730 , NASA Tech Briefs (ISSN 0145-319X); 6; 3; P. 295
    Format: text
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  • 2
    Publication Date: 2019-06-27
    Description: An airflow valve and its electrohydraulic actuation servosystem are described. The servosystem uses a high-power, single-stage servovalve to obtain a dynamic response beyond that of systems designed with conventional two-stage servovalves. The electrohydraulic servosystem is analyzed and the limitations imposed on system performance by such nonlinearities as signal saturations and power limitations are discussed. Descriptions of the mechanical design concepts and developmental considerations are included. Dynamic data, in the form of sweep-frequency test results, are presented and comparison with analytical results obtained with an analog computer model is made.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-TP-1678 , E-252
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-28
    Description: A four cylinder Stirling engine, transient engine simulation computer program is presented. The program is intended for controls analysis. The associated engine model was simplified to shorten computer calculation time. The model includes engine mechanical drive dynamics and vehicle load effects. The computer program also includes subroutines that allow: (1) acceleration of the engine by addition of hydrogen to the system, and (2) braking of the engine by short circuiting of the working spaces. Subroutines to calculate degraded engine performance (e.g., due to piston ring and piston rod leakage) are provided. Input data required to run the program are described and flow charts are provided. The program is modular to allow easy modification of individual routines. Examples of steady state and transient results are presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-82774 , E-1103 , DOE/NASA/51040-37 , NAS 1.15:82774
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-28
    Description: A technique for extracting the in-stall pumping characteristics for an axial flow compressor operating in an engine system environment is developed. The technique utilzes a Hybrid computer simulation of the compressor momentum equation in which actual transient data are used to provide all terms but the desired compressor characteristic. The compressor force characteristic as a function of corrected flow and speed results from the computation. The critical problem of data filtering is addressed. Results for a compressor operating in a turbofan engine are presented and comparison is made with the conventional compressor map. The relationship of the compressor surge charcteristic with its rotating stall characteristic is explored. Initial interpretation of the measured results is presented. Previously announced in STAR as N84-22566
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 84-1206
    Format: text
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  • 5
    Publication Date: 2019-06-28
    Description: A computer program for simulating the steady state and transient performance of a four cylinder Stirling engine is presented. The thermodynamic model includes both continuity and energy equations and linear momentum terms (flow resistance). Each working space between the pistons is broken into seven control volumes. Drive dynamics and vehicle load effects are included. The model contains 70 state variables. Also included in the model are piston rod seal leakage effects. The computer program includes a model of a hydrogen supply system, from which hydrogen may be added to the system to accelerate the engine. Flow charts are provided.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-83053 , E-1348 , NAS 1.15:83053 , DOE/NASA/52040-44
    Format: application/pdf
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  • 6
    Publication Date: 2019-07-13
    Description: A technique for extracting the in-stall pumping characteristics for an axial flow compressor operating in an engine system environment is developed. The technique utilizes a Hybrid computer simulation of the compressor momentum equation into which actual transient data are used to provide all terms but the desired compressor characteristic. The compressor force characteristic as a function of corrected flow and speed result from the computation. The critical problem of data filtering is addressed. Results for a compressor operating in a turbofan engine are presented and comparison is made with the conventional compressor map. The relationship of the compressor surge characteristic with its rotating stall characteristic is explored. Initial interpretation of the measured results is presented.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-83639 , E-2082 , NAS 1.15:83639 , Joint Propulsion Conf.; Jun 11, 1983 - Jun 13, 1983
    Format: application/pdf
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  • 7
    Publication Date: 2019-07-13
    Description: A four working space, double acting piston, Stirling engine simulation is being developed for controls studies. The development method is to construct two simulations, one for detailed fluid behavior, and a second model with simple fluid behaviour but containing the four working space aspects and engine inertias, validate these models separately, then upgrade the four working space model by incorporating the detailed fluid behaviour model for all four working spaces. The single working space (SWS) model contains the detailed fluid dynamics. It has seven control volumes in which continuity, energy, and pressure loss effects are simulated. Comparison of the SWS model with experimental data shows reasonable agreement in net power versus speed characteristics for various mean pressure levels in the working space. The four working space (FWS) model was built to observe the behaviour of the whole engine. The drive dynamics and vehicle inertia effects are simulated. To reduce calculation time, only three volumes are used in each working space and the gas temperature are fixed (no energy equation). Comparison of the FWS model predicted power with experimental data shows reasonable agreement. Since all four working spaces are simulated, the unique capabilities of the model are exercised to look at working fluid supply transients, short circuit transients, and piston ring leakage effects.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-81569 , DOE/NASA/1040-17 , E-534 , Intersoc. Energy Conversion Eng. Conf.; Aug 18, 1980 - Aug 22, 1980; Seattle
    Format: application/pdf
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  • 8
    Publication Date: 2019-07-13
    Description: A four working space, double acting piston, Stirling engine simulation was developed for controls studies. Two simulations, one for detailed fluid behavior, and a second model with simple fluid behavior but containing the four working space aspects and engine inertias, validate these models separately, then upgrade the four working space model by incorporating the detailed fluid behavior model for all four working spaces. The single working space model contains the detailed fluid dynamics. The four working space (FWS) model was built to observe the behavior of the whole engine. The drive dynamics and vehicle inertia effects are simulated. The capabilities of the model are exercised to look at working fluid supply transients, short circuit transients, and piston ring leakage effects.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-81648 , E-9356-7 , DOE/NASA/51040-21 , Automotive Technol. Develop. Contractor Coordination Meeting; Nov 11, 1980 - Nov 13, 1980; Dearborn, MI; United States
    Format: application/pdf
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