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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

An investigation of compressor noise by use of a spinning mode synthesizer.

Use of the Spinning Mode Synthesizer (SMS) as a tool for studying the properties of such complex waves as those generated by fan engines. This has greatly reduced the amount of trial and error techniques used for optimizing duct liners. The SMS was designed by using simple transducer theory and properly controlling the phasing to each of 8 loudspeakers. It provides a means for making in-duct measurements of the radial, axial, and circumferential modal distributions. Results are presented which show that the device is of value for investigation of the highly complex nature of compressor radiated noise.

Oslac, M. J.↗
NASA NTRS1973

Gated compressor, distortionless signal limiter

Comparator/multiplier arrangement is capable of limiting input power to voice coil so that desired maximum current level is never exceeded. Overall test system consists of signal source which produces frequency spectrum required for acoustic test, gated compressor circuit, and power amplifier feeding transducer.

Woodbury, R. C.↗
NASA NTRS1973

Design and flight testing of a nullable compressor face rake

A compressor face rake with an internal valve arrangement to permit nulling was designed, constructed, and tested in the laboratory and in flight at the NASA Flight Research Center. When actuated by the pilot in flight, the nullable rake allowed the transducer zero shifts to be determined and then subsequently removed during data reduction. Design details, the fabrication technique, the principle of operation, brief descriptions of associated digital zero-correction programs and the qualification tests, and test results are included. Sample flight data show that the zero shifts were large and unpredictable but could be measured in flight with the rake. The rake functioned reliably and as expected during 25 hours of operation under flight environmental conditions and temperatures from 230 K (-46 F) to greater than 430 K (314 F). The rake was nulled approximately 1000 times. The in-flight zero-shift measurement technique, as well as the rake design, was successful and should be useful in future applications, particularly where accurate measurements of both steady-state and dynamic pressures are required under adverse environmental conditions.

Holzman, J. K.↗
NASA NTRS1973

Backswept impeller and vane island diffuser and shroud for NASA advanced-concepts compressor test rig

A centrifugal impeller based on an existing backswept design was defined. In addition, a vaned diffuser was designed to match this impeller and also to be compatible with an existing 6:1 compressor test rig. The mechanical integrity of this design was verified by analysis. Hardware was procured and inspected to insure conformity with design tolerances. An overspeed test was successfully conducted on one of the impellers fabricated under this program.

Perrone, G. L.↗
NASA NTRS1973

Preliminary design of a mini-Brayton Compressor-Alternator-Turbine (CAT)

The preliminary design of a mini-Brayton compressor-alternator-turbine system is discussed. The program design goals are listed. The optimum system characteristics over the entire range of power output were determined by performing a wide-range parametric study. The ability to develop the required components to the degree necessary within the limitations of present technology is evaluated. The sensitivity of the system to various individual design parameters was analyzed.

Source record↗
NASA NTRS1974

Boundary layers in centrifugal compressors

The utility of boundary-layer theory in the design of centrifugal compressors is demonstrated. Boundary-layer development in the diffuser entry region is shown to be important to stage efficiency. The result of an earnest attempt to analyze this boundary layer with the best tools available is displayed. Acceptable prediction accuracy was not achieved. The inaccuracy of boundary-layer analysis in this case would result in stage efficiency prediction as much as four points low. Fluid dynamic reasons for analysis failure are discussed with support from flow data. Empirical correlations used today to circumnavigate the weakness of the theory are illustrated.

Dean, R. C., Jr.↗
NASA NTRS1974

Self-energized plasma compressor

The self-energized plasma compressor is described which compresses plasma discharged from a coaxial plasma generator. The device includes a helically shaped coil which is coaxially aligned with the center axis of the coaxial plasma generator. The plasma generator creates a current through the helical coil which, in turn, generates a time varying magnetic field that creates a force which acts radially upon the plasma. The coaxial plasma generator and helical coil move the plasma under high pressure and temperature to the narrow end of the coil. Positioned adjacent to the narrow end of the coil are beads which are engaged by the plasma to be accelerated to hypervelocities for simulating meteoroids.

Shriver, E. L.↗
NASA NTRS1975

Particle flow within a transonic compressor rotor passage with application to laser-Doppler velocimetry

A theoretical analysis was conducted of the dynamic behavior of micron size particles moving in the three-dimensional flow field of a rotating transonic axial-flow air compressor rotor. The particle velocity lag and angular deviation relative to the gas were determined as functions of particle diameter, mass density and radial position. Particle size and density were varied over ranges selected to correspond to typical laser-Doppler velocimeter (LDV) flow field mapping applications. It was found that the particles move essentially on gas stream surfaces and that particle tracking is relatively insensitive to the rotor radial coordinate. Velocity lag and angular deviation increased whenever particle size or mass density increased, and particle tracking was more sensitive to a change in particle diameter than to a corresponding change in mass density. Results indicated that velocity and angular deviations generally less than 1 percent and 1 degree could be achieved with 1 gm/cc tracer particles with diameters of 1 micron or less.

Maxwell, B. R.↗
NASA NTRS1974

Fracture mechanics analysis of a high-pressure hydrogen facility compressor

The investigation and analysis of a high-pressure hydrogen facility compressor is chronicled, and a life prediction based on fracture mechanics is presented. Crack growth rates in SA 105 Gr II steel are developed for the condition of sustained loading, using a hypothesis of hydrogen embrittlement associated with plastic zone reverse yielding. The resultant formula is compared with test data obtained from laboratory specimens.

Vroman, G. A.↗
NASA NTRS1975

Interim prediction method for fan and compressor source noise

A method is presented for interim use in assessing the noise generated by fans and compressors in turbojet and turbofan engines. One-third octave band sound pressure levels consisting of broadband, discrete tone, and combination-tone noise components are predicted. Spectral distributions and directivity variations are specified. The method is based on that developed by other investigators with modifications derived from an analysis of full-scale, single-stage fan data. Comparisons of predicted and measured noise performance are presented, and requirements for improving the method are discussed.

Heidmann, M. F.↗
NASA NTRS1975

Experience with integrally-cast compressor and turbine components for a small, low-cost, expendable-type turbojet engine

Experiences with integrally-cast compressor and turbine components during fabrication and testing of four engine assemblies of a small (29 cm (11 1/2 in.) maximum diameter) experimental turbojet engine design for an expendable application are discussed. Various operations such as metal removal, welding, and re-shaping of these components were performed in preparation of full-scale engine tests. Engines with these components were operated for a total of 157 hours at engine speeds as high as 38,000 rpm and at turbine inlet temperatures as high as 1256 K (1800 F).

Dengler, R. P.↗
NASA NTRS1975

Experience with integrally-cast compressor and turbine components for a small, low-cost, expendable-type turbojet engine

A discussion regarding experiences with integrally-cast compressor and turbine components during fabrication and testing of four engine assemblies of a small (29 cm (11-1/2 in.) maximum diameter) experimental turbojet engine design for an expendable application is presented. Various operations such as metal removal, welding, and re-shaping of these components are performed in preparation of full-scale engine tests. Engines with these components have been operated for a total of 157 hours at engine speeds as high as 38,000 rpm and at turbine inlet temperatures as high as 1256 K (1800 F).

Dengler, R. P.↗
NASA NTRS1976

Effects of multi-element acoustic treatment on compressor inlet noise

An analytic and experimental study was conducted with the objective of developing both a basic understanding of axially segmented inlet acoustic treatment liners, and design procedures for enhancing the suppression of compressor inlet radiated noise. Anechoic chamber measurements demonstrated that the multielement treatment produced significantly more low frequency suppression than uniform treatment. Further, in-duct spinning mode patterns generated by the rotating vehicle were successfully measured and used as input to an analytical prediction procedure, providing significant improvement in inlet suppression predictions. The study indicated that phased inlet liners can be designed to provide increased noise suppression compared to uniform treatment.

Kraft, R. E.↗
NASA NTRS1977

Analytical and experimental studies of acoustic performance of segmented liners in a compressor inlet

The performance of axially segmented (phased) acoustic treatment liners in the inlet of a compressor was investigated. Topics discussed include: (1) the validation of a theoretical procedure to predict propagation and suppression characteristics of duct liners; (2) the in-duct measurement of spinning modes; (3) investigation of phased treatment designs; (4) high Mach inlet acoustic tests; and (5) an experimental investigation of inlet turbulence. The analytical prediction for the multi-segmented treatment was found to provide the correct order of magnitude of suppression and was generally within 50% of that determined experimentally. Refinements required to improve the correlation are identified. Suppression due to high subsonic Mach number flow effects was found to become significant above an average throat Mach number of 0.65 to 0.7 and 20 PNdB was achieved with an average throat Mach number in the range of 0.80 to 0.85. For the measured turbulence in the inlet, including the axial and circumferential turbulence intensities and the axial integral length scale, data are presented with and without an inlet screen showing that the screen reduced the turbulence intensities and that the BPF noise was reduced as a consequence.

Motsinger, R. E.↗
NASA NTRS1978

Simplified data compressor

Image data are compressed for transmission by simple, economical circuitry. Compressor handles data in blocks of 64 samples. Mean from previous line is subtracted, and pseudo-random sequence of positive and negative 1's multiplies samples of each block. Hadamard transform applied to blocks yields 64 transform coefficients. Each coefficient is compared with approximation to corresponding coefficient of previous line, and difference is quantized. Values are transmitted or stored. Procedure is reversed to reproduce image.

Rice, R. F.↗
NASA NTRS1977

Experimental clean combustor program: Turbulence characteristics of compressor discharge flows

The results of turbulence measurements at the entrance to the diffuser duct of a large gas turbine are presented. Hot film and hot wire measurements were conducted over a compressor discharge temperature range of 450K to 608K. It was found that the turbulent intensity at the I.D. and midspan locations increases gradually from 6 + or - 1 percent at idle to 7 + or - 1 percent at approach; the turbulent intensity at the O.D. location increases from 7.5 + or - 0.5 percent at idle to 15 + or - 0.5 percent at approach. The energy in the velocity waves is uniformly distributed over a 0.1 to 5 kHz bandwidth, and the cut-off frequency is not a strong function of the engine operation. The axial length of the Fourier components within this bandwidth varies from 0.021 to 1.05m. The turbulence near the diffuser O.D. is of sufficient amplitude and scale to affect the flow to the front end sections of the burner.

Follansbee, P. S.↗
NASA NTRS1978

Investigation of the jet-wake flow of a highly loaded centrifugal compressor impeller

Investigations, aimed at developing a better understanding of the complex flow field in high performance centrifugal compressors were performed. Newly developed measuring techniques for unsteady static and total pressures as well as flow directions, and a digital data analysis system for fluctuating signals were thoroughly tested. The loss-affected mixing process of the distorted impeller discharge flow was investigated in detail, in the absolute and relative system, at impeller tip speeds up to 380 m/s. A theoretical analysis proved good coincidence of the test results with the DEAN-SENOO theory, which was extended to compressible flows.

Eckardt, D.↗