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  • 1
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    Quiet engine test results (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: The acoustic and aerodynamic test results obtained with the two quiet engines are given in this presentation. Some of the test results reviewed include the performance of the untreated or baseline quiet engines. In addition, test results are shown for various degrees and areas of engine acoustic treatment. Finally, the results obtained on a flight-type, acoustically treated nacelle added to one of the quiet engines is examined.
    Keywords: AIRCRAFT
    Type: Aircraft Engine Noise Reduction; p 183-214
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Radially leaned outlet guide vanes for fan source noise reduction (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Two quiet engine program half scale fans one with a subsonic and the other with a supersonic fan tip speed at takeoff were run with 30 degree leaned and radial outlet guide vanes. Acoustic data at takeoff fan speed on the subsonic tip speed fan showed decreases in 200-foot sideline noise of from 1 to 2 PNdb. The supersonic tip speed fan a takeoff fan speed, however, showed noise increases of up 3 PNdb and a decrease in fan efficiency. At approach fan speed, the subsonic tip speed fan showed a noise decrease of 2.3 PNdb at the 200-foot sideline maximum angle and an increase in efficiency. The supersonic tip speed fan showed noise increase of 3.5 PNdb and no change in efficiency. The decrease in fan efficiency and the nature of the noise increase largely high frequency broadband noise lead to the speculation that an aerodynamic problem occurred.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-134486 , R73AEG176
    Format: application/pdf
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  • 3
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    Acoustic testing of a 1.5 pressure ratio low tip speed fan with casing tip bleed (QEP Fan B scale model) (1971)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A scale model of the bypass flow region of a 1.5 pressure ratio, single stage, low tip speed fan was tested with a rotor tip casing bleed slot to determine its effects on noise generation. The bleed slot was located 1/2 inch (1.3 cm) upstream of the rotor leading edge and was configured to be a continuous opening around the circumference. The bleed manifold system was operated over a range of bleed rates corresponding to as much as 6% of the fan flow at approach thrust and 4.25% of the fan flow at takeoff thrust. Acoustic results indicate that a bleed rate of 4% of the fan flow reduces the fan maximum approach 200 foot (61.0 m) sideline PNL 0.5 PNdB and the corresponding takeoff thrust noise 1.1 PNdB below the level with zero bleed. However, comparison of the standard casing (no bleed slot) and the slotted bleed casing with zero bleed shows that the bleed slot itself caused a noise increase.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-120822
    Format: application/pdf
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  • 4
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    Acoustic testing of a 1.5 pressure ratio, low tip speed fan (QEP fan B scale model) (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A scale model (0.484 scale factor) of a single stage fan designed for a 1.5 pressure ratio and 1160 ft/sec tip speed was tested to determine its noise characteristics. The fan had 26 blades and 60 outlet guide vanes, with vanes spaced two rotor blade aerodynamic chords from the blades. The effects of speed, exhaust nozzle area and fan frame acoustic treatment on the scale model's noise characteristics were investigated.
    Keywords: AERODYNAMICS
    Type: NASA-CR-120789
    Format: application/pdf
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  • 5
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    Single stage, low noise advanced technology fan. Volume 3: Acoustic design (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The acoustic design for a half-scale fan vehicle, which would have application on an advanced transport aircraft, is described. The single stage advanced technology fan was designed to a pressure ratio of 1.8 at a tip speed of 503 m/sec (1,650 ft/sec). The two basic approaches taken in the acoustic design were: (1) minimization of noise at the source, and (2) suppression of the generated noise in the inlet and bypass exhaust duct. Suppression of the generated noise is accomplished in the inlet through use of the hybrid concept (wall acoustic treatment plus airflow acceleration suppression) and in the exhaust duct with extensive acoustic treatment including a splitter. The goal of the design was attainment of twenty effective perceived noise decibels (20 EPNdB) below current Federal Air Regulation noise standards for a full-scale fan at the takeoff, cutback, and approach conditions. Predicted unsuppressed and suppressed fore and aft maximum perceived noise levels indicate that the cutback condition is the most critical with respect to the goal, which is probably unattainable for that condition. This is also true for aft radiated noise in the approach condition.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-134803 , R76AEG259-VOL-3
    Format: application/pdf
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  • 6
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    Acoustic results of supersonic tip speed fan blade modification (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A supersonic tip speed single stage fan was modified with the intent of reducing multiple pure tone (MPT) or buzz saw noise. There were three modifications to the blades from the original design. The modifications to the blade resulted in an increase in cascade throat area causing the shock to start at a lower corrected fan speed. The acoustic results without acoustically absorbing liners showed substantial reduction in multiple pure tone levels. However, an increase in the blade passing frequency noise at takeoff fan speed accompanied the MPT reduction. The net result however, was a reduction in the maximum 1000-foot (304.8 m) altitude level flyover PNL. For the case with acoustic treatment in the inlet outer wall, the takeoff noise increased relative to an acoustically treated baseline. This was largely due to the increased blade passing frequency noise which was not effectively reduced by the liner.
    Keywords: AIRCRAFT
    Type: NASA-CR-121233 , R73AEG07
    Format: application/pdf
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  • 7
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    Acoustic and aerodynamic testing of a scale model variable pitch fan (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A fully reversible pitch scale model fan with variable pitch rotor blades was tested to determine its aerodynamic and acoustic characteristics. The single-stage fan has a design tip speed of 1160 ft/sec (353.568 m/sec) at a bypass pressure ratio of 1.5. Three operating lines were investigated. Test results show that the blade pitch for minimum noise also resulted in the highest efficiency for all three operating lines at all thrust levels. The minimum perceived noise on a 200-ft (60.96 m) sideline was obtained with the nominal nozzle. At 44% of takeoff thrust, the PNL reduction between blade pitch and minimum noise blade pitch is 1.8 PNdB for the nominal nozzle and decreases with increasing thrust. The small nozzle (6% undersized) has the highest efficiency at all part thrust conditions for the minimum noise blade pitch setting; although, the noise is about 1.0 PNdB higher for the small nozzle at the minimum noise blade pitch position.
    Keywords: AIRCRAFT
    Type: NASA-CR-121232 , R73AEG196
    Format: application/pdf
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  • 8
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    LF336 lift fan modification and acoustic test program (1971)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Investigating lift fan noise reduction by configuration modifications in LF336/A
    Keywords: AIRCRAFT
    Type: NASA-CR-1934
    Format: application/pdf
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  • 9
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    Acoustic testing of a 1.5 pressure ratio low tip speed fan with a serrated rotor (QEP fan B scale model) (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: 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.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-120846
    Format: application/pdf
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  • 10
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    NASA/GE quiet engine C acoustic test results (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The acoustic investigation and evaluation of the C propulsion turbofan engine are discussed. The engine was built as a part of the Quiet Engine Program. The objectives of the program are as follows: (1) to determine the noise levels produced turbofan bypass engines, (2) to demonstrate the technology and innovations which will reduce the production and radiation of noise in turbofan engines, and (3) to acquire experimental acoustic and aerodynamic data for high bypass turbofan engines to provide a better understanding of noise production mechanisms. The goals of the program called for a turbofan engine 15 to 20 PNdB quieter than currently available engines in the same thrust class.
    Keywords: PROPULSION SYSTEMS
    Type: NASA-CR-121176 , R73AEG364
    Format: application/pdf
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