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  • 1
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    Downwind rotor horizontal axis wind turbine noise prediction (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: NASA and industry are currently cooperating in the conduct of extensive experimental and analytical studies to understand and predict the noise of large, horizontal axis wind turbines. This effort consists of (1) obtaining high quality noise data under well controlled and documented test conditions, (2) establishing the annoyance criteria for impulse noise of the type generated by horizontal axis wind turbines with rotors downwind of the support tower, (3) defining the wake characteristics downwind of the axial location of the plane of rotation, (4) comparing predictions with measurements made by use of wake data, and (5) comparing predictions with annoyance criteria. The status of work by Hamilton Standard in the above areas which was done in support of the cooperative NASA and industry studies is briefly summarized.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Lewis Research Center Wind Turbine Dyn.; p 425-430
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Performance and noise of a low pressure ratio variable pitch fan designed for general aviation applications (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A limited study has been conducted to establish the performance and noise characteristics of a low design tip speed (168 m/s, 550 ft/sec) low pressure ratio (1.04) variable pitch fan which was tested in the Langley 30 X 60 tunnel. This fan was designed for minimum noise when installed in the tail mount location of a twin engine aircraft which normally has both nose and tail mounted propulsors. Measurements showed the fan noise to be very close to predictions made during the design of the fan and extremely low in level (65 dBA at 1000 ft) with no acoustic treatment. This is about 8 dB lower than the unshrouded 2 blade propeller normally used in this installation. On the basis of tests conducted during this program, it appears that this level could be further reduced by 2 dBA if optimized acoustic treatments were installed in the fan duct. Even the best of the shrouded propellers tested previously were 7 dB higher in level than the Q-Fan without acoustic treatment. It was found that the cruise performance of this fan was within 5% of the predicted efficiency of 72%. Evaluation of the performance data indicated that disturbances in the inflow to the fan were the probable cause of the reduced performance.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159246
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Acoustic test and analyses of three advanced turboprop models (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Results of acoustic tests of three 62.2 cm (24.5 inch) diameter models of the prop-fan (a small diameter, highly loaded. Multi-bladed variable pitch advanced turboprop) are presented. Results show that there is little difference in the noise produced by unswept and slightly swept designs. However, the model designed for noise reduction produces substantially less noise at test conditions simulating 0.8 Mach number cruise speed or at conditions simulating takeoff and landing. In the near field at cruise conditions the acoustically designed. In the far field at takeoff and landing conditions the acoustically designed model is 5 db quieter than unswept or slightly swept designs. Correlation between noise measurement and theoretical predictions as well as comparisons between measured and predicted acoustic pressure pulses generated by the prop-fan blades are discussed. The general characteristics of the pulses are predicted. Shadowgraph measurements were obtained which showed the location of bow and trailing waves.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159667
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Noise and wake structure measurements in a subsonic tip speed fan (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of an experimental program are reported which show the effect of blade angle, tip speed, fan pressure ratio, and thrust on noise of a model fan of 0.457m (18 inches) diameter operating at subsonic tip speeds at pressure ratios between 1.06 and 1.15. The fan used in this study had 12 blades, 7 stator vanes, and a spacing between the rotor and stator of 1.85 blade chords. This fan was originally designed for aerodynamic testing and was considered a good performer. It was used in the noise test program as it incorporated features found to reduce noise in an earlier analytical parametric study. For a given pressure ratio the fan was shown to exhibit minimum noise at the blade angle and tip speed near that of maximum aerodynamic efficiency. Also, the noise level and spectrum character of this fan showed excellent correlation with scaled data of a similar larger diameter fan. Results of the program confirm the trends shown in the earlier analytical parametric study which showed that fan noise could be reduced for a given thrust and pressure ratio by increasing fan solidity, improving fan aerodynamic design, and operating the fan at an optimum subsonic tip speed. In addition to noise, the blade wake characteristics at the leading edge of the stator were measured in this program. At root and tip sections some difference between predicted and measured wakes was found. However comparisons between predicted and measured wakes at mid span locations was found to be good.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2323
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Noise and wake structure measurements in a subsonic tip speed fan: Tabulation and plots of test data (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Noise and wake structure measurements in a ducted fan were conducted. The tip speed was kept at subsonic levels. The anechoic platform used during the test is described. The following conditions are reported: (1) one third octave band analyses of the fan noise data, (2) narrow band analyses of the fan noise for selected test conditions, (3) narrow band sound power level data for all fan test conditions, and (4) velocity and air angle evaluation of blade wake data.
    Keywords: FLUID MECHANICS
    Type: NASA-CR-132259
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Prop-fan data support study (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Updated parametric prop-fan data packages are presented and the rationale used in developing the new prop-fan data is detailed. These data represent Hamilton Standard's projections of prop-fan characteristics for aircraft that are expected to be in-service in the 1985 to 1990 time frame. The basic prop-fan configuration was designed for efficient cruise operation at 0.8 Mach number and 10,668M altitude. The design blade tip speed is 244 mps and the design power loading is 301 KW/M squared.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-152141
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Evaluation of wind tunnel performance testings of an advanced 45 deg swept 8-bladed propeller at Mach numbers from 0.45 to 0.85 (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The increased emphasis of fuel conservation in the world and the rapid increase in the cost of jet fuel has stimulated a series of studies of both conventional and unconventional propulsion systems for commercial aircraft. The results of these studies indicate that a fuel saving of 15 to 30 percent may be realized by the use of an advanced high-speed turboprop (Prop-Fan) compared to aircraft equipped with high bypass turbofan engines of equivalent technology. The Prop-Fan propulsion system is being investigated as part of the NASA Aircraft Energy Efficient Program. This effort includes the wind tunnel testing of a series of 8 and 10-blade Prop-Fan models incorporate swept blades. Test results indicate efficiency levels near the goal of 80 percent at Mach 0.8 cruise and an altitude of 10.67 km (35,000 ft). Each successive swept model has shown improved efficiency relative to the straight blade model. The fourth model, with 45 deg swept blades reported herein, shows a net efficiency of 78.2 at the design point with a power loading of 301 kW/sq meter and a tip speed of 243.8 m/sec (800 ft/sec.).
    Keywords: AERODYNAMICS
    Type: NASA-CR-3505
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Progress report on propeller aircraft flyover noise research (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Initial results of a program to investigate the sources of noise in unshrouded propellers under forward flight conditions are reported. Tests were conducted using a three-blade full-scale instrumented propeller mounted on a twin-engine aircraft. Measurements included (1) far-field noise at fixed ground stations and at two aircraft wing tip locations, (2) blade surface pressures at seven locations on one of the propeller blades, (3) atmospheric turbulence encountered by the aircraft in flight, and (4) aircraft operating conditions. The results confirm that significantly lower levels of propeller noise are produced in forward flight than at static conditions. It is tentatively concluded that propeller noise generation in flight may be dominated by steady loading at blade passage frequency, but at higher frequencies unsteady loading due to interaction with natural atmospheric turbulence may be the dominant mechanism of noise generation. Under static conditions the total noise signature appears to be the result of interaction of the propeller with persistent turbulent eddies passing through the propeller disk.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: SAE PAPER 760454 , Business Aircraft Meeting; Apr 06, 1976 - Apr 09, 1976; Wichita, Kan.
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Analytical parametric investigation of low pressure ratio fan noise (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of an analytical study are reported which shows the effect of various physical and operating parameters on noise produced by low pressure ratio propulsive fans operating at subsonic top speeds. Acoustical duct lining effects are included in the study. The concepts used to develop the noise theory used in the study, as well as the correlation between the theory and model test results are also presented. It is shown that good correlation has been established between theory and experiment. Using the theory, it is shown that good aerodynamic design, maximum acceptable fan solidity, low tip speed operation and use of few blades and vanes leads to the lowest noise levels. Typical results of the study indicate that a fan operating at 1.2 fan pressure ratio and 700 ft/second tip speed with 12 blades and 7 vanes and including modest acoustic treatment on the duct wall would produce levels allowing a 100,000 lb. STOL aircraft to meet a noise level objective of 95 PNdB at 500 ft at takeoff.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2188 , HSER-5990
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Results of initial prop-fan model acoustic testing. Volume 2 - Appendices B thru F (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Acoustic measurements on prop-fan model propulsion system - Vol. 2, appendices
    Keywords: PHYSICS, GENERAL
    Type: NASA-CR-111842-2 , HSER-5787-VOL-2
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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