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  • 1
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    Design of a high-speed digital processing element for parallel simulation (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A prototype of a custom designed computer to be used as a processing element in a multiprocessor based jet engine simulator is described. The purpose of the custom design was to give the computer the speed and versatility required to simulate a jet engine in real time. Real time simulations are needed for closed loop testing of digital electronic engine controls. The prototype computer has a microcycle time of 133 nanoseconds. This speed was achieved by: prefetching the next instruction while the current one is executing, transporting data using high speed data busses, and using state of the art components such as a very large scale integration (VLSI) multiplier. Included are discussions of processing element requirements, design philosophy, the architecture of the custom designed processing element, the comprehensive instruction set, the diagnostic support software, and the development status of the custom design.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: NASA-TM-83373 , E-1641 , NAS 1.15:83373
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    An automated procedure for calculating system matrices from perturbation data generated by an EAI Pacer and 100 hybrid computer system (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Techniques are presented for determining the elements of the A, B, C, and D state variable matrices for systems simulated on an EAI Pacer 100 hybrid computer. An automated procedure systematically generates disturbance data necessary to linearize the simulation model and stores these data on a floppy disk. A separate digital program verifies this data, calculates the elements of the system matrices, and prints these matrices appropriately labeled. The partial derivatives forming the elements of the state variable matrices are approximated by finite difference calculations.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-TM-73869 , E-9465
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Performance of a J85-13 compressor with clean and distorted inlet flow (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results presented are of a series of experimental tests in which a J85-13 turbojet engine was subjected to both distorted and undistorted inlet total pressure conditions. A distinctive feature of the data base obtained is that it includes compressor interstage information not previously recorded for a J85-13 engine. Each of the eight compressor stages was instrumented to obtain the characteristics of the individual stages for undistorted inlet conditions, and these data are documented in the report along with the undistorted compressor overall performance. Also included in the report is the overall performance of the compressor exposed to 14 different distorted-inlet conditions - 10 circumferential patterns and 4 radial patterns. The distortion patterns were introduced using screens that spoiled from 8 to 50 percent of the compressor face area; the distortion screen density, or the area blocked by the screen wire per unit area of screen, varied from 26 to 69 percent.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-3304 , E-8311
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    A generalized memory test algorithm (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A general algorithm for testing digital computer memory is presented. The test checks that (1) every bit can be cleared and set in each memory work, and (2) bits are not erroneously cleared and/or set elsewhere in memory at the same time. The algorithm can be applied to any size memory block and any size memory word. It is concise and efficient, requiring the very few cycles through memory. For example, a test of 16-bit-word-size memory requries only 384 cycles through memory. Approximately 15 seconds were required to test a 32K block of such memory, using a microcomputer having a cycle time of 133 nanoseconds.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-TM-82874 , E-1250 , NAS 1.15:82874
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Frequency response of an axial-flow compressor exposed to inlet pressure perturbations (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Experimental results of a series of engine tests designed to obtain the stage dynamics of an eight-stage axial-flow compressor over the frequency range of 0.5 to 200 hertz are presented. The total pressure at the compressor face was varied by means of a secondary air jet system installed in the engine inlet and positioned to oppose the primary airflow. Total-pressure probes located at each compressor stage were used to obtain the frequency response of each compressor-stage total pressure to the average compressor-inlet total pressure. The engine operating conditions were chosen to illustrate the effects of changing the rotor speed, changing the exhaust nozzle area, and isolating the compressor discharge pressure perturbations from the fuel control and hence, the fuel flow.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-TM-X-3012 , E-7709
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Application of a hybrid computer to sweep frequency data processing (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A hybrid computer program is presented which can process as many as 10 channels of sweep frequency data simultaneously. The program needs only the sine sweep signal used to drive the system, and its correponding quadrature component, to process the data. It can handle a maximum frequency range of 0.5 to 500 hertz. Magnitude and phase are calculated at logarithmically spaced points covering the frequency range of interest. When the sweep is completed, these results are stored in digital form. Thus, a tabular listing and/or a plot of any processed data channel or the transfer function relating any two of them is immediately available.
    Keywords: COMPUTERS
    Type: NASA-TM-X-2753 , E-7232
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Analytical prediction of the performance and stability of a J85-13 compressor with distorted inlet flow (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The parallel compressor concept was studied using a compressor model based on the overall clean-inlet performance map obtained from experimental tests in an altitude chamber using a General Electric J85-13 turbojet engine. The model, which includes a static-pressure balance calculation at compressor discharge, was exercised at conditions corresponding to 10 different screen-induced distortion patterns included in the experimental data base. The spoiled area of these patterns ranged from 30 deg to 180 deg, and the distortion screen density, or the area blocked by the screen wire per unit area of screen, varied from 26 to 69 percent. The study indicates that at the higher corrected speeds, the analytical surge lines obtained are good representations of the corresponding experimental surge lines and are independent of distortion angle or distortion angle or distortion level.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-3515 , E-8887
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Turbomachinery CFD on parallel computers (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The role of multistage turbomachinery simulation in the development of propulsion system models is discussed. Particularly, the need for simulations with higher fidelity and faster turnaround time is highlighted. It is shown how such fast simulations can be used in engineering-oriented environments. The use of parallel processing to achieve the required turnaround times is discussed. Current work by several researchers in this area is summarized. Parallel turbomachinery CFD research at the NASA Lewis Research Center is then highlighted. These efforts are focused on implementing the average-passage turbomachinery model on MIMD, distributed memory parallel computers. Performance results are given for inviscid, single blade row and viscous, multistage applications on several parallel computers, including networked workstations.
    Keywords: COMPUTER SYSTEMS
    Type: Computing Systems in Engineering (ISSN 0956-0521); 3; 6; p. 613-623.
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Simulating a small turboshaft engine in real-time multiprocessor simulator (RTMPS) environment (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A Real-Time Multiprocessor Simulator (RTMPS) has been developed at NASA Lewis Research Center. The RTMPS uses parallel microprocessors to achieve computing speeds needed for real-time engine simulation. This report describes the use of the RTMPS system to simulate a small turboshaft engine. The process of programming the engine equations and distributing them over one, two, and four processors is discussed. Steady-state and transient results from the RTMPS simulation are compared with results from a main-frame-based simulation. Processor execution times and the associated execution time savings for the two and four processor cases are presented using actual data obtained from the RTMPS system. Included is a discussion of why the minimum achievable calculation time for the turboshaft engine model was attained using four processors. Finally, future enhancements to the RTMPS system are discussed including the development of a generalized partitioning algorithm to automatically distribute the system equations among the processors in optimum fashion.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-87216 , E-2876 , NAS 1.15:87216 , SCS Multiconference; Jan 23, 1986 - Jan 25, 1986; San Diego, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Partitioning and packing mathematical simulation models for calculation on parallel computers (1986)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The development of multiprocessor simulations from a serial set of ordinary differential equations describing a physical system is described. Degrees of parallelism (i.e., coupling between the equations) and their impact on parallel processing are discussed. The problem of identifying computational parallelism within sets of closely coupled equations that require the exchange of current values of variables is described. A technique is presented for identifying this parallelism and for partitioning the equations for parallel solution on a multiprocessor. An algorithm which packs the equations into a minimum number of processors is also described. The results of the packing algorithm when applied to a turbojet engine model are presented in terms of processor utilization.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-TM-87170 , E-2808 , NAS 1.15:87170 , 1986 International Conference on Parallel Processing; Aug 19, 1986 - Aug 22, 1986; St. Charles, IL; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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