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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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10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1949

Design and performance of family of diffusing scrolls with mixed-flow impeller and vaneless diffuser

A family of diffusing scrolls was designed for use with a mixed-flow impeller and a small-diameter vaneless diffuser. The design theory, intended to maintain a uniform pressure around the scroll inlet, permits determination of the position of scroll cross sections of preassigned area by considering the radial variation in fluid density and the effects of friction along the scroll. Inasmuch as the design method leaves the cross-sectional shape undetermined, the effect of certain variations in scroll shape was investigated by studying scrolls having angles of divergence (of the scroll walls downstream of the entrance section) of 24 degrees, 40 degrees, and 80 degrees. A second 80 degree scroll was of asymmetrical construction and a third was plaster-cast instead of sand-cast. Each scroll was tested as a compressor component at actual impeller tip speeds of 700 to 1300 feet per second from full throttle to surge.

Brown, W Byron↗
NASA NTRS1989

Fluctuating pressures in pump diffuser and collector scrolls, part 1

The cracking of scroll liners on the SSME High Pressure Fuel Turbo Pump (HPFTP) on hot gas engine test firings has prompted a study into the nature of pressure fluctuations in centrifugal pump states. The amplitudes of these fluctuations and where they originate in the pump stage are quantified. To accomplish this, a test program was conducted to map the pressure pulsation activity in a centrifugal pump stage. This stage is based on typical commercial (or generic) pump design practice and not the specialized design of the HPFTP. Measurements made in the various elements comprising the stage indicate that pulsation activity is dominated by synchronous related phenomena. Pulsation amplitudes measured in the scroll are low, on the order of 2 to 7 percent of the impeller exit tip speed velocity head. Significant non-sychronous pressure fluctuations occur at low flow, and while of interest to commercial pump designers, have little meaning to the HPFTP experience. Results obtained with the generic components do provide insights into possible pulsation related scroll failures on the HPFTP, and provide a basis for further study.

Sloteman, Donald P.↗
NASA NTRS2000

Conceptual Design Study of a Closed Brayton Cycle Turbogenerator for Space Power Thermal-To-Electric Conversion System

A conceptual design study was completed for a 360 kW Helium-Xenon closed Brayton cycle turbogenerator. The selected configuration is comprised of a single-shaft gas turbine engine coupled directly to a high-speed generator. The engine turbomachinery includes a 2.5:1 pressure ratio compression system with an inlet corrected flow of 0.44 kg/sec. The single centrifugal stage impeller discharges into a scroll via a vaned diffuser. The scroll routes the air into the cold side sector of the recuperator. The hot gas exits a nuclear reactor radiator at 1300 K and enters the turbine via a single-vaned scroll. The hot gases are expanded through the turbine and then diffused before entering the hot side sector of the recuperator. The single shaft design is supported by air bearings. The high efficiency shaft mounted permanent magnet generator produces an output of 370 kW at a speed of 60,000 rpm. The total weight of the turbogenerator is estimated to be only 123 kg (less than 5% of the total power plant) and has a volume of approximately 0.11 cubic meters. This turbogenerator is a key element in achieving the 40 to 45% overall power plant thermal efficiency.

Hansen, Jeff L.↗
NASA NTRS1976

Cold-air performance of a tip turbine designed to drive a lift fan. 1: Baseline performance

Full admission baseline performance was obtained for a 0.4 linear scale of the LF460 lift fan turbine over a range of speeds and pressure ratios without leakage air. These cold-air tests covered a range of speeds from 40 to 140 percent of design equivalent speed and a range of scroll inlet to diffuser exit static pressure ratios from 2.0 to 4.2. Results are presented in terms of specific work, torque, mass flow, efficiency, and total pressure drop.

Haas, J. E.↗
NASA NTRS1977

Cold air performance of a tip turbine designed to drive a lift fan. 2: Partial admission

Partial admission performance was obtained for a 0.4 linear scale version of the LF460 lift fan turbine over a range of speed from 40 to 140 percent of design equivalent speed and a range of scroll inlet total to diffuser exit static pressure ratio from 2.2 to 5.0. The investigation was conducted in two parts, with each part using a different side of the turbine scroll to simulate loss of a gas generator. Each side had an arc of admission of 180. Results are presented in terms of specific work, torque, mass flow, and efficiency.

Haas, J. E.↗
NASA NTRS1978

Cold-air performance of a tip turbine designed to drive a lift fan

Performance was obtained over a range of speeds and pressure ratios for a 0.4 linear scale version of the LF460 lift fan turbine with the rotor radial tip clearance reduced to about 2.5 percent of the rotor blade height. These tests covered a range of speeds from 60 to 140 percent of design equivalent speed and a range of scroll inlet total to diffuser exit static pressure ratios from 2.6 to 4.2. Results are presented in terms of equivalent mass flow, equivalent torque, equivalent specific work, and efficiency.

Haas, J. E.↗
NASA NTRS1978

Cold-air performance of a tip turbine designed to drive a lift fan. 3: Effect of simulated fan leakage on turbine performance

Performance data were obtained experimentally for a 0.4 linear scale version of the LF460 lift fan turbine for a range of scroll inlet total to diffuser exit static pressure ratios at design equivalent speed with simulated fan leakage air. Tests were conducted for full and partial admission operation with three separate combinations of rotor inlet and rotor exit leakage air. Data were compared to the results obtained from previous investigations in which no leakage air was present. Results are presented in terms of mass flow, torque, and efficiency.

Haas, J. E.↗
NASA NTRS1946

Effect of Three Modifications on Performance of Auxiliary-Stage Supercharger for V-1710-93 Engine

Three modifications of the auxiliary-stage supercharger for the V-1710-93 engine were designed and tested as part of an investigation to improve the power output and the altitude performance of the engine. A 12-vane diffuser was substituted for the standard 11-vane diffuser, and a vaneless discharge passage and a modified scroll were designed to increase the flow capacity of the supercharger and thereby to increase the performance at the high volume flows required by the engine. With the 12-vane diffuser installed and the carburetor replaced by an adapter, the equivalent volume flow at the peak efficiency point was increased 25 percent at the lowest speed investigated and 9.5 percent at the highest speed. When the carburetor was used, any increase in equivalent volume flow was masked by choking in the carburetor. A small decrease in the peak adiabatic efficiency resulted from using the 12-vane diffuser. At the high volume flows where the supercharger is required to operate, the performance was improved by the 12-vane diffuser. With the vaneless discharge passage, the surge-free range of the supercharger was increased 35 percent at the lowest tip speed investigated by increasing the maximum air flow. The maximum air flow at high tip speeds was again limited by choking in the carburetor, which masked the effect of the vaneless discharge passage on the maximum air flow. At the high volume flows near the operating point of the supercharger, the performance with the vaneless discharge passage was better than that with the standard 11-vane diffuser. At the low volume flows when the standard 11-vane diffuser gave better performance. The modified scroll gave performance characteristics that were practically the same as those of the standard scroll except at high tip speeds, where the peak performance was improved.

Downing, Richard M.↗