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  • 1
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    Energy Efficient Engine Exhaust Mixer Model Technology (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An exhaust mixer test program was conducted to define the technology required for the Energy Efficient Engine Program. The model configurations of 1/10 scale were tested in two phases. A parametric study of mixer design options, the impact of residual low pressure turbine swirl, and integration of the mixer with the structural pylon of the nacelle were investigated. The improvement of the mixer itself was also studied. Nozzle performance characteristics were obtained along with exit profiles and oil smear photographs. The sensitivity of nozzle performance to tailpipe length, lobe number, mixer penetration, and mixer modifications like scalloping and cutbacks were established. Residual turbine swirl was found detrimental to exhaust system performance and the low pressure turbine system for Energy Efficient Engine was designed so that no swirl would enter the mixer. The impact of mixer/plug gap was also established, along with importance of scalloping, cutbacks, hoods, and plug angles on high penetration mixers.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-165459 , NAS 1.26:165459 , PWA-5594-164
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Variable cycle engines for advanced supersonic transports (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Variable Cycle Engines being studied for advanced commercial supersonic transports show potential for significant environmental and economic improvements relative to 1st generation SST engines. The two most promising concepts are: a Variable Stream Control Engine and a Variable Cycle Engine with a rear flow-control valve. Each concept utilizes variable components and separate burners to provide independent temperature and velocity control for two coannular flow streams. Unique fuel control techniques are combined with cycle characteristics that provide low fuel consumption, similar to a turbojet engine, for supersonic operation. This is accomplished while retaining the good subsonic performance features of a turbofan engine. A two-stream coannular nozzle shows potential to reduce jet noise to below FAR Part 36 without suppressors. Advanced burner concepts have the potential for significant reductions in exhaust emissions. In total, these unique engine concepts have the potential for significant overall improvements to the environmental and economic characteristics of advanced supersonic transports.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: SAE PAPER 751086 , National Aerospace Engineering and Manufacturing Meeting; Nov 17, 1975 - Nov 20, 1975; Culver City, CA
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Jet noise characteristics of unsuppressed duct burning turbofan exhaust system (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Recent aero-acoustic tests of model coannular nozzles have shown that less noise is generated if the higher-velocity jet is exhausted from the outer annular passage rather than from the primary nozzle. These findings are of particular significance to a duct-burning turbofan (DBTF) engine being studied for application to an advanced supersonic transport. Unlike conventional turbofan engines that have peak velocities from the primary nozzle, it is possible to design a DBTF engine to have a fan velocity higher than that of the primary flow. Results are presented for a NASA-sponsored model test program that covers a range of fan to primary-area ratios from 0.75 to 1.2, and a range of fan to primary-velocity ratios from 0.4 to 2.8. Correlations are given that relate radiated sound power to fan velocity, fan to primary-velocity ratio, and fan to primary-area ratio. Corresponding exhaust-plume velocity-traverse data are presented which suggest that the observed noise benefits may be due to the more rapid decay of the annular flow because of shear stresses on the inner surface that result from the lower-velocity primary flow.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-149 , Aerospace Sciences Meeting; Jan 26, 1976 - Jan 28, 1976; Washington, DC
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Flight effects on the aero/acoustic characteristics of inverted profile coannular nozzles (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effect of simulated flight speed on the acoustic and aerodynamic characteristics of coannular nozzles is examined. The noise and aerodynamic performance of the coannular nozzle exhaust systems over a large range of operating flight conditions is presented. The jet noise levels of the coannular nozzles are discussed. The impact of fan to primary nozzle area ratio and the presence of an ejector on flight effects are investigated. The impact of flight speed on the individual components of the coannular jet noise was ascertained.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-162419 , PWA-5501
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Aero-acoustic tests of duct-burning turbofan exhaust nozzles (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The acoustic and aerodynamic characteristics of several exhaust systems suitable for duct burning turbofan engines are evaluated. Scale models representing unsuppressed coannular exhaust systems are examined statically under varying exhaust conditions. Ejectors with both hardwall and acoustically treated inserts are investigated.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-162254 , PWA-5296
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Experimental evaluation of exhaust mixers for an Energy Efficient Engine (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Static scale model tests were conducted to evaluate exhaust system mixers for a high bypass ratio engine as part of the NASA sponsored Energy Efficient program. Gross thrust coefficients were measured for a series of mixer configurations which included variations in the number of mixer lobes, tailpipe length, mixer penetration, and length. All of these parameters have a significant impact on exhaust system performance. In addition, flow visualization pictures and pressure/temperature traverses were obtained for selected configurations. Parametric performance trends are discussed and the results considered relative to the Energy Efficient Engine program goals.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 80-1088 , Joint Propulsion Conference; Jun 30, 1980 - Jul 02, 1980; Hartford, CT
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Aero-acoustic performance characteristics of duct burning turbofan exhaust nozzles (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A recent experimental investigation has identified the aero/acoustic characteristics of exhaust nozzles for duct heating turbofan engines over a range of simulated flow conditions. Jet noise and performance levels are summarized for a series of coannular nozzles representing both acoustically suppressed and unsuppressed designs operating in a static environment. The basic coannular nozzles were found to provide inherent noise suppression. Multi-element suppressor nozzles provided additional noise suppression, but with appreciable thrust loss. The impact of these results on the advanced supersonic transport studies is also presented, indicating potentially large reductions in take-off gross weight or community noise footprints.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-148 , Aerospace Sciences Meeting; Jan 26, 1976 - Jan 28, 1976; Washington, DC
    Format: text
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    NASA TECHNICAL REPORTS
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