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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Peak axial-velocity decay with single- and multi-element nozzles

Jet peak-velocity decay data were obtained for a variety of circular and noncircular single-element and multi-element nozzles for application to externally-blown-flap (EBF) STOL aircraft. These data permit a rational approach, in terms of element type and element spacing, to nozzles designed to promote mixing of the jet exhaust with the surrounding air. Rapid mixing and the resulting lower axial jet velocity decreases the noise caused by the interaction of jet impingement on the flap assembly of EBF STOL aircraft. Empirical relationships are presented that permit the prediction of peak axial-velocity decay curves for a wide spectrum of mixer-type nozzles. The data are useful also in the design of ejector-type noise suppressors and for the suppression of VTOL downwash velocities caused by vertically oriented exhaust nozzles.

Vonglahn, U. H.↗
NASA NTRS1972

Forward flight effects on mixer nozzle design and noise considerations for STOL externally blown flap systems

Experimental data of the peak axial-velocity decay in a moving airstream are presented for several types of nozzles. The nozzles include a six-tube mixer nozzle of a type considered for reduction of jet-flap interaction noise for externally-blown-flap STOL aircraft. The effect of secondary flow on the core flow velocity decay of a bypass nozzle is also discussed. Tentative correlation equations are suggested for the configurations evaluated. Recommendations for minimizing forward velocity effects on velocity decay and jet-flap interaction noise are made.

Vonglahn, U. H.↗
NASA NTRS1972

Peak axial-velocity decay with single- and multi-element nozzles.

Jet peak-velocity decay data were obtained for a variety of circular and noncircular single-element and multi-element nozzles for application to externally-blown-flap STOL aircraft. These data permit a rational approach, in terms of element type and element spacing, to nozzles designed to promote mixing of the jet exhaust with the surrounding air. Rapid mixing and the resulting lower axial jet velocity decreases the noise caused by the interaction of jet impingement on the flap assembly of EBF STOL aircraft. Empirical relationships are presented that permit the prediction of peak axial-velocity decay curves for a wide spectrum of mixer-type nozzles. The data are useful also in the design of ejector-type noise suppressors and for the suppression of VTOL downwash velocities caused by vertically oriented exhaust nozzles.

Von Glahn, U. H.↗
NASA NTRS1972

Forward flight effects on mixer nozzle design and noise considerations for STOL externally blown flap systems.

Experimental data of the peak axial-velocity decay in a moving airstream are presented for several types of nozzles. The nozzles include a six-tube mixer nozzle of a type considered for reduction of jet-flap interaction noise for externally-blown-flap STOL aircraft. The effect of secondary flow on the core flow velocity decay of a bypass nozzle is also discussed. Tentative correlation equations are suggested for the configurations evaluated. Recommendations for minimizing forward velocity effects on velocity decay and jet-flap interaction noise are made.

Vonglahn, U. H.↗
NASA NTRS1973

Small-scale noise tests of a slot nozzle with V-gutter target thrust reverser

The noise generated by a 2.26- by 11.43-cm slot nozzle with a V-gutter reverser, as well as some aerodynamic data on flow, thrust-reversal efficiency, and nozzle jet velocity decay were studied. The experimental data are scaled up to sizes suitable for reversing the wing flow of a 45/400-kg augmentor-wing-type STOL airplane, yielding perceived noise levels well above the 95-PNdb design goal on the 152-m sideline. The reverser, in addition to being noisier than the nozzle alone, also had a more uniform directional distribution and more high frequency noise. The maximum overall sound pressure level and the effective sound power level both varied with the sixth power of nozzle jet velocity. Preliminary experiments indicated possible sideline noise reduction by shielding.

Stone, J. R.↗
NASA NTRS1973

Analysis and testing of two-dimensional slot nozzle ejectors with variable area mixing sections

Finite difference computer techniques have been used to calculate the detailed performance of air to air two-dimensional ejectors with symmetric variable area mixing sections and coaxial coverging primary nozzles. The analysis of the primary nozzle assumed correct expansion of the flow and is suitable for subsonic and slightly supersonic velocity levels. The variation of the mixing section channel walls is assumed to be gradual so that the static pressure can be assumed uniform on planes perpendicular to the axis. A test program was run to provide two-dimensional ejector test data for verification of the computer analysis. A primary converging nozzle with a discharge geometry of 0.125 inch x 8.0 inch was supplied with 600 SCFM of air at about 35 psia and 180 F. This nozzle was combined with two mixing section geometries with throat sizes of 1.25 inch x 8.0 inch and 1.875 inch x 8.0 inch and was tested at a total of 11 operating points.

Gilbert, G. B.↗
NASA NTRS1973

Site alteration effects from rocket exhaust impingment during a simulated Viking Mars landing. Part 1: Nozzle development and physical site alternation

A potential interference problem for the Viking '75 scientific investigation of the Martian surface resulting from retrorocket exhaust plume impingement of the surface was investigated experimentally and analytically. It was discovered that the conventional bell nozzle originally planned for the Viking Lander retrorockets would produce an unacceptably large amount of physical disturbance to the landing site. An experimental program was subsequently undertaken to find and/or develop a nozzle configuration which would significantly reduce the site alteration. A multiple nozzle configuration, consisting of 18 small bell nozzles, was shown to produce a level of disturbance that was considered by the Viking Lander Science Teams to be acceptable on the basis of results from full-scale tests on simulated Martian soils.

Romine, G. L.↗
NASA NTRS1973

Flight investigation of acoustic and thrust characteristics of several exhaust nozzles installed on underwing nacelles on an F106 airplane

To determine flyover noise and thrust and to investigate whether flight velocity significantly affects the noise of exhaust nozzles, a series of flight tests was conducted on three different exhaust nozzles of a type suitable for supersonic transport aircraft. The tests were conducted using an F-106B aircraft modified to carry two underwing nacelles, each containing a calibrated turbojet engine. A flyover altitude of 91 meters (300 ft) and a Mach number of 0.4 provided acoustic data that were repeatable to within + or -1.5 PNdB. Flyover results showed that an auxiliary inlet ejector nozzle was the quietest of the nozzles tested; flight velocity appeared to reduce its noise.

Burley, R. R.↗
NASA NTRS1973

Velocity decay and acoustic characteristics of various nozzle geometries with forward velocity

Utilizing a static test stand, 6- by 9-foot wind tunnel and 13-inch circular free jet, aerodynamic and acoustic data were obtained with a convergent circular nozzle, bypass nozzle, 6-tube mixer nozzle, and velocity decay surveys with and without forward velocity. The acoustic data include total sound power, directivity and frequency spectra obtained statically and with forward velocity. The relation of aerodynamic and acoustic measurements statically and in forward flight for the various nozzle configurations are discussed.

Vonglahn, U. H.↗
NASA NTRS1974

Vented vectoring-nozzle for STOL and V/STOL aircraft

Vented vectoring-nozzle has superior thrust coefficient and is lighter in weight because it does not require completely enclosed elbow duct ordinarily used to deflect nozzle flow. Improved nozzle has primary nozzle and three-sided elbow deflector.

Esker, D. W.↗
NASA NTRS1974

The computation of steady nozzle flow by a time-dependent method

The steady flow in two-dimensional and axisymmetric nozzles was computed using a time-dependent method. In this method the interior mesh points were computed using the MacCormack finite-difference scheme, while a characteristic scheme was used to calculate the boundary mesh points. No explicit artificial viscosity term was included. The fluid was assumed to be a perfect gas. This method was used to compute the flow in a 45 deg - 15 deg conical, converging-diverging nozzle, a 15 deg conical, converging nozzle, and a 10 deg conical, plug nozzle. Good agreement between the numerical solution and experimental data was found. In contrast to previous time-dependent methods, the computational times were less than one minute on a CDC 6600 computer.

Cline, M. C.↗
NASA NTRS1974

Jet noise from co-axial nozzles over a wide range of geometric and flow parameters

Free field pure jet noise data were taken for a large range of coaxial nozzle configurations. The core nozzles were circular (1 to 4 in. diameter) and plug types. The fan to core area ratio varied from 0.7 to 43.5, while the velocity ratio typically varied from 0 to 1. For most cases the two nozzles were coplanar but large axial extensions of either nozzle were also tested. Correlation of the data resulted in a simple procedure for estimating ambient temperature subsonic coaxial jet noise spectra over a wide range of geometric and flow parameters.

Olsen, W.↗
NASA NTRS1974

Reynolds number effects on boattail drag of exhaust nozzles from wind tunnel and flight tests

A family of nacelle mounted high angle boattail nozzles was tested to investigate Reynolds number effects on drag. The nozzles were flown on a modified F-106B and mounted on scale models of a F-106 in a wind tunnel. A 19- to 1-range of Reynolds number was covered as a result of the large size differences between models and by flying over a range of altitude. In flight, the nozzles were mounted behind J-85 turbojet engines. Jet boundary simulators and a powered turbojet engine simulator were used on the wind tunnel models. Data were taken at Mach numbers of 0.6 and 0.9. Boattail drag was found to be affected by boattail number. The effect is a complex relationship dependent upon boundary layer thickness and nozzle boattail shape. As Reynolds number was increased from the lowest values obtained with scale models, boattail drag first increased to a maximum at the lowest flight Reynolds number and then decreased.

Wilcox, F. A.↗
NASA NTRS1974

Parametric study of relaminarization of turbulent boundary layers on nozzle walls

By means of comparisons between theoretical predictions and experimental data, the accuracy of a boundary procedure to predict the effect of large streamwise accelerations upon initially turbulent boundary layers is assessed. The boundary layer procedure is based upon simultaneous solution of the boundary layer partial differential equations and the integral turbulence kinetic energy equation. The results of the present investigation show the ability of the procedure to accurately predict properties of boundary layers subjected to large streamwise accelerations. The procedure is used to conduct a parametric study of the effect of free stream turbulence, heat transfer, Reynolds number, acceleration, and Mach number on boundary layers in supersonic nozzles to assist in the design of a quiet tunnel. Results of the investigation show that, even in the presence of moderate free-stream turbulence levels, the boundary layer in the approach section of the quiet tunnel nozzle relaminarizes and becomes thin enough to be removed by a small slot in the nozzle wall. Furthermore, the calculations indicate that it should be possible to maintain a laminar boundary layer for the entire length of the supersonic portion of the quiet tunnel nozzle.

Kreskovsky, J. P.↗
NASA NTRS1974

Flow in a discrete slotted nozzle with massive injection

An experimental investigation has been conducted to determine the effect of massive wall injection on the flow characteristics in a slotted nozzle. Some of the experiments were performed on a water table with a slotted-nozzle test section. This has 45 deg and 15 deg half angles of convergence and divergence, respectively, throat radius of 2.5 inches, and throat width of 3 inches. The hydraulic analogy was employed to qualitatively extend the results to a compressible gas flow through the nozzle. Experimental results from the water table include contours of constant Froude and Mach number with and without injection. Photographic results are also presented for the injection through slots of CO2 and Freon-12 into a main-stream air flow in a convergent-divergent nozzle in a wind tunnel. Schlieren photographs were used to visualize the flow, and qualititative agreement between the results from the gas tunnel and water table is good.

Perkins, H. C.↗
NASA NTRS1974

Cold-flow performance of several variations of a ram-air-cooled plug nozzle for supersonic-cruise aircraft

Experimental data were obtained with a 21.59 cm (8.5 in.) diameter cold-flow model in a static altitude facility to determine the thrust and pumping characteristics of several variations of a ram-air-cooled plug nozzle. Tests were conducted over a range of nozzle pressure ratios simulating supersonic cruise and takeoff conditions. Primary throat area was also varied to simulate afterburner on and off. Effect of plug size, outer shroud length, primary nozzle geometry, and varying amounts of secondary flow were investigated. At a supersonic cruise pressure ratio of 27, nozzle efficiencies were 99.7 percent for the best configurations.

Harrington, D. E.↗
NASA NTRS1974

Jet noise from coaxial nozzles over a wide range of geometric and flow parameters

Free field pure jet noise data were taken for a large range of coaxial nozzle configurations. The core nozzles were circular (1 to 4 in. diam.) and plug types. The fan to core area ratio varied from 0.7 to 43.5, while the velocity ratio typically varied from 0 to 1. For most cases the two nozzles were coplanar but large axial extensions of either nozzle were also tested. Correlation of the data resulted in a simple procedure for estimating ambient temperature subsonic coaxial jet noise spectra over a wide range of geometric and flow parameters.

Olsen, W.↗
NASA NTRS1973

Noise tests of a high-aspect-ratio slot nozzle with various V-gutter target thrust reversers

The results of experiments on the noise generated by a 1.33 x 91.4 cm slot nozzle with various V-gutter reversers are presented. The experiments were conducted with near-ambient temperature jets at nozzle pressure ratios of 1.25 to 3.0, yielding jet velocities of about 190 to 400 m/sec. At pressure ratios of 2 or less, the reversers, in addition to being noisier than the nozzle alone, also had a more uniform directional distribution and more high-frequency noise. At pressure ratios above 2, the nozzle alone generated enough shock noise that the levels were about the same as for the reversers. The maximum overall sound pressure level and the effective overall sound power level both varied with the sixth power of jet velocity over the range tested.

Stone, J. R.↗