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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Aeroacoustics of contoured plug-nozzle supersonic jet flows

Experimental investigations of the acoustic far-field, the shock associated noise, and the characteristics of the repetitive shock structure of supersonic jet flows issuing from a plug-nozzle having an externally expanded contoured plug with a pointed termination, operated at a range of supercritical pressure ratios of 2.0 to 4.5 are reported. The supersonic jet flow from the contoured plug is shown to be shock-free and virtually wakeless at a pressure ratio of 3.60 (flow Mach number, 1.49). By comparison with the noise characteristics of underexpanded jet flows from an equivalent convergent nozzle, substantial reductions in the total (mixing and the shock associated) noise levels are obtained when the contoured plug nozzle is operated either in the fully-expanded (shock-free) mode or in the over- and the underexpanded modes.

Dosanjh, D. S.↗
NASA NTRS1980

VCE early acoustic test results of General Electric's high-radius ratio coannular plug nozzle

Results of variable cycle engine (VCE) early acoustic engine and model scale tests are presented. A summary of an extensive series of far field acoustic, advanced acoustic, and exhaust plume velocity measurements with a laser velocimeter of inverted velocity and temperature profile, high radius ratio coannular plug nozzles on a YJ101 VCE static engine test vehicle are reviewed. Select model scale simulated flight acoustic measurements for an unsuppressed and a mechanical suppressed coannular plug nozzle are also discussed. The engine acoustic nozzle tests verify previous model scale noise reduction measurements. The engine measurements show 4 to 6 PNdB aft quadrant jet noise reduction and up to 7 PNdB forward quadrant shock noise reduction relative to a fully mixed conical nozzle at the same specific thrust and mixed pressure ratio. The influences of outer nozzle radius ratio, inner stream velocity ratio, and area ratio are discussed. Also, laser velocimeter measurements of mean velocity and turbulent velocity of the YJ101 engine are illustrated. Select model scale static and simulated flight acoustic measurements are shown which corroborate that coannular suppression is maintained in forward speed.

Knott, P. R.↗
NASA NTRS1974

Flight investigation of installation effects on a plug nozzle with a series of boattailed primary shrouds installed on an underwing nacelle

Several variations of a boattailed shroud for a 10 deg conical plug nozzle were tested using an F-106B aircraft for Mach 0.6 to 1.3. The data were obtained so that the tradeoff between boattail and plug size could be studied for an underwing nacelle location. The nozzles were tested with J85-GE-13 turbojet engine, and the data were compared to previous flight results of installed plug nozzles. Boattail area varied from 31 to 66 percent of the nacelle area. The effect of increasing projected boattail area was to increase the gross thrust coefficient in the same way as from isolated data for flight Mach numbers below 0.85. The highest gross thrust coefficient (0.958) was obtained at Mach 0.95 with a long circular arc shroud configuration with a very small amount of secondary air flow.

Head, V. L.↗
NASA NTRS1988

Analysis of supersonic plug nozzle flowfield and heat transfer

A number of problems pertaining to the flowfield in a plug nozzle, designed as a supersonic thruster nozzle, with provision for cooling the plug with a coolant stream admitted parallel to the plug wall surface, were studied. First, an analysis was performed of the inviscid, nonturbulent, gas dynamic interaction between the primary hot stream and the secondary coolant stream. A numerical prediction code for establishing the resulting flowfield with a dividing surface between the two streams, for various combinations of stagnation and static properties of the two streams, was utilized for illustrating the nature of interactions. Secondly, skin friction coefficient, heat transfer coefficient and heat flux to the plug wall were analyzed under smooth flow conditions (without shocks or separation) for various coolant flow conditions. A numerical code was suitably modified and utilized for the determination of heat transfer parameters in a number of cases for which data are available. Thirdly, an analysis was initiated for modeling turbulence processes in transonic shock-boundary layer interaction without the appearance of flow separation.

Murthy, S. N. B.↗
NASA NTRS1973

Effect of nozzle lateral spacing, engine interfairing shape, and angle of attack on the performance of a twin-jet afterbody model with cone plug nozzles

Twin-jet afterbody models were investigated by using two balances to measure separately the thrust minus total axial force and the afterbody drag at Mach numbers from 0 to 1.3. Angle of attack was varied from minus 2 deg to 8.5 deg. Translating shroud cone plug nozzles were tested at dry-power and maximum-afterburning-power settings with a high-pressure air system used to provide jet total-pressure ratios up to 9.0. Two nozzle lateral spacings were studied by using afterbodies with several interfairing shapes. The close- and wide-spaced afterbodies had identical cross-sectional area distributions when similar interfairings were installed on each. The results show that the highest overall performance was obtained with the close-spaced afterbody and basic interfairings. Increasing angle of attack decreased performance for all configurations and conditions investigated.

Berrier, B. L.↗
NASA NTRS1973

Annular truncated plug nozzle flowfield and base pressure characteristics.

The flowfield and base pressure characteristics of an internal-external expansion, truncated plug nozzle are described over the pressure ratio range from 'open' wake to 'closed' wake conditions. The effect of plug length on these characteristics, including the process of wake 'closure' is also presented. An existing method for calculating the flowfield and base pressure, for 'closed' wake operation, is modified to include the internal shock wave generated near the shroud exit. The supersonic portion of the flow is calculated using rotational axisymmetric method of characteristics. The technique of Hartree is employed so that the downstream characteristic point locations can be chosen to fit the developing flowfield. An overexpansion technique is used to detect the internal shock wave in the vicinity of the shroud exit so that its effect on the plug base pressure could be determined. Good agreement between the analytical results and experimental data is obtained for 'closed' wake operations.

Sule, W. P.↗
NASA NTRS1972

Thermal design study of an air-cooled plug-nozzle system for a supersonic cruise aircraft

A heat-transfer design analysis has been made of an air-cooled plug-nozzle system for a supersonic-cruise aircraft engine. The proposed 10deg half-angle conical plug is sting supported from the turbine frame. Plug cooling is accomplished by convection and film cooling. The flight profile studied includes maximum afterburning from takeoff to Mach 2.7 and supersonic cruise at Mach 2.7 with a low afterburner setting. The calculations indicate that, for maximum afterburning, about 2 percent of the engine primary flow, removed after the second stage of the nine-stage compressor, will adequately cool the plug and sting support. Ram air may be used for cooling during supersonic-cruise operations, however. Therefore, the cycle efficiency penalty paid for air cooling the plug and sting support should be low.

Clark, J. S.↗