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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

High tip speed fan inlet noise reduction using treated inlet splitters and accelerating inlets (quiet engine program fan C scale model)

A series of inlet suppression tests were run on a supersonic tip speed fan which employed an acoustically treated cowl wall, treated splitters and elevated average throat Mach numbers in various combinations. Results show appreciable fan noise reductions at high fan speeds; 15-18 PNdB. On the basis of inlet total pressure recovery loss per PNdb of noise reduction, an inlet with no splitters produced the most efficient design. However, greater reduction in noise was achieved with one splitter in the inlet. It was also noted that moderate increases in inlet Mach number increased noise in the acoustically treated inlets and that Mach numbers in excess of 0.65 were required before net noise reduction was realized.

Kazin, S. B.↗
NASA NTRS1973

Acoustic testing of a supersonic tip speed fan with acoustic treatment and rotor casting slots. Quiet engine program scale model fan C

Acoustic tests were conducted on a high tip speed (1550 ft/sec, 472.44 m/sec) single stage fan with varying amounts of wall acoustic treatment and with circumferential slots over the rotor blade tips. The slots were also tested with acoustic treatment placed behind the slots. The wall treatment results show that the inlet treatment is more effective at high fan speeds and aft duct treatment is more effective at low fan speeds. Maximum PNL's on a 200-foot (60.96 m) sideline show the untreated slots to have increased the rear radiated noise at approach. However, when the treatment was added to the slots inlet radiated noise was decreased, resulting in little change relative to the solid casing on an EPNL basis.

Kazin, S. B.↗
NASA NTRS1974

Conceptual design studies of a V/STOL civil lift fan transport including effect of size and fan pressure ratio

Conceptual design studies of V/STOL Lift Fan Commercial short-haul transport aircraft for the 1980-85 time period were studied to determine their technical and economic feasibility. The remote lift fan configurations with a variation in fan pressure ratio from 1.2 to 1.5 were investigated. Also studied were variation in stage length from 200 nautical miles to 800 nautical miles and cruise Mach numbers of 0.75 and 0.85. These results indicate a four engine configuration was feasible. The 95 PNdb noise footprint would be approximately 45 acres and the DOC's would be about 60% greater than conventional transports.

Source record↗
NASA NTRS2002

New Fan Engine Noise-Reduction Concept Using Trailing Edge Blowing of Fan Blades Demonstrated

A major source of noise in commercial turbofan engines is the interaction of the fan blade wakes with the fan exit vanes (stators). These wakes can be greatly reduced by filling them with air blown out of the blade trailing edge. Extensive testing of this concept has demonstrated significant noise reductions. These tests were conducted on a low-speed, 4- ft-diameter fan using hollow blades at NASA Glenn Research Center's Aeroacoustic Propulsion Laboratory (AAPL).

Heidelberg, Laurence J.↗
NASA NTRS1973

Conceptual design studies of candidate V/STOL lift fan commercial short haul transport for 1980 - 1985 V/STOL lift fan study

Conceptual designs of V/STOL lift fan commercial short haul transport aircraft for the 1980-85 time period were studied to determine their technical and economic feasibility. The engine concepts included both integral and remote fans. The scope of the study included definition of the hover control concept for each propulsion system, aircraft design, aircraft mass properties, cruise performance, noise and ride qualities evaluation. Economic evaluating was also studied on a basis of direct operating costs and route structure.

Eldridge, W. M.↗
NASA NTRS1977

Single-stage, low-noise, advanced technology fan. Volume 4: Fan aerodynamics. Section 1: Results and analysis

Test results at design speed show fan total pressure ratio, weight flow, and adiabatic efficiency to be 2.2, 2.9, and 1.8% lower than design goal values. The hybrid acoustic inlet (which utilizes a high throat Mach number and acoustic wall treatment for noise suppression) demonstrated total pressure recoveries of 98.9% and 98.2% at takeoff and approach. Exhaust duct pressure losses differed between the hardwall duct and treated duct with splitter by about 0.6% to 2.0% in terms of fan exit average total pressure (depending on operating condition). When the measured results were used to estimate pressure losses, a cruise sfc penalty of 0.68%, due to the acoustically treated duct, was projected.

Sullivan, T. J.↗
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 NTRS1973

Acoustic testing of a 1.5 pressure ratio low tip speed fan with a serrated rotor (QEP fan B scale model)

A scale model of the bypass flow region of a 1.5 pressure ratio, single stage, low tip speed fan was tested with a serrated rotor leading edge to determine its effects on noise generation. The serrated rotor was produced by cutting teeth into the leading edge of the nominal rotor blades. The effects of speed and exhaust nozzle area on the scale models noise characteristics were investigated with both the nominal rotor and serrated rotor. Acoustic results indicate the serrations reduced front quadrant PNL's at takeoff power. In particular, the 200 foot (61.0 m) sideline noise was reduced from 3 to 4 PNdb at 40 deg for nominal and large nozzle operation. However, the rear quadrant maximum sideline PNL's were increased 1.5 to 3 PNdb at approach thust and up to 2 PNdb at takeoff thust with these serrated rotor blades. The configuration with the serrated rotor produced the lowest maximum 200 foot (61.0 m) sideline PNL for any given thust when the large nozzle (116% of design area) was employed.

Kazin, S. B.↗
NASA NTRS1972

Evaluation of range and distortion tolerance for high Mach number transonic fan stages. Task 2: Performance of a 1500-foot-per-second tip speed transonic fan stage with variable geometry inlet guide vanes and stator

A 0.5 hub/tip radius ratio compressor stage consisting of a 1500 ft/sec tip speed rotor, a variable camber inlet guide vane and a variable stagger stator was designed and tested with undistorted inlet flow, flow with tip radial distortion, and flow with 90 degrees, one-per-rev, circumferential distortion. At the design speed and design IGV and stator setting the design stage pressure ratio was achieved at a weight within 1% of the design flow. Analytical results on rotor tip shock structure, deviation angle and part-span shroud losses at different operating conditions are presented. The variable geometry blading enabled efficient operation with adequate stall margin at the design condition and at 70% speed. Closing the inlet guide vanes to 40 degrees changed the speed-versus-weight flow relationship along the stall line and thus provided the flexibility of operation at off-design conditions. Inlet flow distortion caused considerable losses in peak efficiency, efficiency on a constant throttle line through design pressure ratio at design speed, stall pressure ratio, and stall margin at the 0 degrees IGV setting and high rotative speeds. The use of the 40 degrees inlet guide vane setting enabled partial recovery of the stall margin over the standard constant throttle line.

Bilwakesh, K. R.↗
NASA NTRSDate not supplied

Quiet Spacecraft Cabin Ventilation Fan Development: Motivation and Context

It is important to control acoustical noise aboard crewed space vehicles and space habitats to provide a satisfactory environment for voice communications, alarm audibility, and restful sleep, and to minimize the risk for hearing loss and annoyance. As with most noise control efforts, it is best to control the noise at the source, and for spaceflight vehicles these are typically the fans associated with the Environmental Control and Life Support (ECLS) system. These include air ventilation fans, such as the main air conditioning fan (the ‘cabin fan’), intermodule ventilation (IMV) fans, air revitalization fans (for removal of carbon dioxide and trace contaminates), and thermal cooling fans. Thermal cooling pumps that circulate cooling fluid are another significant noise source in spaceflight vehicles, but these are outside of the scope of this paper. Throughout the history of crewed spaceflight, there have been issues with noise from ECLS ventilation fans. In the Apollo Command Module (CM) the crew would turn off the CM cabin fan once in orbit and use the backup suit-loop fan for ventilation because noise from the cabin fan interfered with communications and was an annoyance. On the Space Shuttle the ventilation system underwent significant redesign, including the addition of ventilation system mufflers, with resulting noise levels that were still too-high for long-duration missions. In the early years of International Space Station (ISS) operations, acoustical noise was one of the top two habitability issues, resulting in significant noise controls (along with significant cost and crew-time impacts) being implemented on-orbit on many fans, with significant noise reductions realized only after replacing noisy fans with fans of a quieter design, funded by the ISS Program. And, with the spaceflight vehicles and habitats currently being developed, there are again concerns with noise levels from ventilation fans. In the Orion vehicle, additional duct mufflers needed to be added to address the cabin fan noise. The Gateway’s Habitation and Logistics Outpost (HALO) module and low-Earth orbit (LEO) Freeflyer habitats are currently working to solve this problem. This will also be an issue for lunar and Mars spaceflight vehicles, space suits, and surface habitats. In an effort to address this problem, NASA is working to leverage the technology developed in its Aeronautics Research Mission Directorate (ARMD), specifically at the Glenn Research Center (GRC), to design highly efficient and quiet fans for reducing community noise levels from civilian aircraft. This technology was created over decades of research and development, and was proven to be effective at reducing aircraft noise levels. The current collaboration across NASA Centers, including HQ, GRC, and the Johnson Space Center (JSC) in this area is the first effort at re-purposing these tools, i.e. design codes and techniques, developed for high Reynolds number fans to spaceflight vehicle and habitat, low Reynolds number, fans. This paper will discuss the need for transfer of aeronautics fan design technology to spaceflight use. This paper will also discuss the potential benefits from this, which are significant, including 1) volume and mass savings from noise controls that are no longer as large or needed at all, 2) reduced system pressure loss from mufflers and silencers (that don’t need to be as restrictive) for better ventilation, 3) reduced power draw because of the reduced system pressure loss and the highly efficient fan design, and 4) satisfying spaceflight vehicle acoustic requirements to provide a safe and habitable acoustic environment for astronaut crewmembers. All of these benefits will be crucial for the successful development and operations of future spaceflight vehicles, space suits, and habitats.

Christopher S. Allen↗
NASA NTRS2013

The Effect of Bypass Nozzle Exit Area on Fan Aerodynamic Performance and Noise in a Model Turbofan Simulator

The design of effective new technologies to reduce aircraft propulsion noise is dependent on identifying and understanding the noise sources and noise generation mechanisms in the modern turbofan engine, as well as determining their contribution to the overall aircraft noise signature. Therefore, a comprehensive aeroacoustic wind tunnel test program was conducted called the Fan Broadband Source Diagnostic Test as part of the NASA Quiet Aircraft Technology program. The test was performed in the anechoic NASA Glenn 9- by 15-Foot Low Speed Wind Tunnel using a 1/5 scale model turbofan simulator which represented a current generation, medium pressure ratio, high bypass turbofan aircraft engine. The investigation focused on simulating in model scale only the bypass section of the turbofan engine. The test objectives were to: identify the noise sources within the model and determine their noise level; investigate several component design technologies by determining their impact on the aerodynamic and acoustic performance of the fan stage; and conduct detailed flow diagnostics within the fan flow field to characterize the physics of the noise generation mechanisms in a turbofan model. This report discusses results obtained for one aspect of the Source Diagnostic Test that investigated the effect of the bypass or fan nozzle exit area on the bypass stage aerodynamic performance, specifically the fan and outlet guide vanes or stators, as well as the farfield acoustic noise level. The aerodynamic performance, farfield acoustics, and Laser Doppler Velocimeter flow diagnostic results are presented for the fan and four different fixed-area bypass nozzle configurations. The nozzles simulated fixed engine operating lines and encompassed the fan stage operating envelope from near stall to cruise. One nozzle was selected as a baseline reference, representing the nozzle area which would achieve the design point operating conditions and fan stage performance. The total area change from the smallest to the largest nozzle was 12.9 percent of the baseline nozzle area. The results will show that there are significant changes in aerodynamic performance and farfield acoustics as the fan nozzle area is increased. The weight flow through the fan model increased between 7 and 9 percent, the fan and stage pressure dropped between 8 and 10 percent, and the adiabatic efficiency increased between 2 and 3 percent--the magnitude of the change dependent on the fan speed. Results from force balance measurements of fan and outlet guide vane thrust will show that as the nozzle exit area is increased the combined thrust of the fan and outlet guide vanes together also increases, between 2 and 3.5 percent, mainly due to the increase in lift from the outlet guide vanes. In terms of farfield acoustics, the overall sound power level produced by the fan stage dropped nearly linearly between 1 dB at takeoff condition and 3.5 dB at approach condition, mainly due to a decrease in the broadband noise levels. Finally, fan swirl angle survey and Laser Doppler Velocimeter mean velocity and turbulence data obtained in the fan wake will show that the swirl angles and turbulence levels within the wake decrease as the fan nozzle area increases, which helps to explain the drop in the fan broadband noise at all fan speeds.

Hughes, Christopher E.↗