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At least 721 records · Page 40

Exhaust emissions survey of a turbofan engine for flame holder swirl type augmentors at simulated altitude flight conditions

Emissions of carbon dioxide, total oxides of nitrogen, unburned hydrocarbons, and carbon monoxide from an F100 afterburning two spool turbofan engine at simulated flight conditions are reported. Tests were run at Mach 0.8 at altitudes of 10.97 and 13.71 km (36,000 and 45,000 ft), and at Mach 1.2 at 13.71 km (45,000 ft). Emission measurements were made from intermediate power (nonafterburning) through maximum afterburning, using a single point gas sample probe traversed across the horizontal diameter of the exhaust nozzle. The data show that emissions vary with flight speed, altitude, power level, and radial position across the nozzle. Carbon monoxide emissions were low for intermediate and partial afterburning power. Unburned hydrocarbons were near zero for most of the simulated flight conditions. At maximum afterburning, there were regions of NOx deficiency in regions of high CO. The results suggest that the low NOx levels observed in the tests are a result of interaction with high CO in the thermal converter. CO2 emissions were proportional to local fuel air ratio for all test conditions.

Moss, J. E., Jr.↗

Performance of a 2D-CD nonaxisymmetric exhaust nozzle on a turbojet engine at altitude

Baseline thrust and cooling data obtained with a 2D-CD versatile research exhaust nozzle mounted on a turbojet engine in an altitude chamber are presented. The tests covered a range of nozzle pressure ratios, nozzle pressure ratios, nozzle throat areas, and internal expansion area ratios. The thrust data obtained show good agreement with theory and scale model results after correcting the data for leakage and bypass cooling flows. Additional work is needed to improve predictability of cooling performance.

Straight, D. M.↗

Axisymmetric and non-axisymmetric exhaust jet induced effects on a V/STOL vehicle design. Part 3: Experimental technique

The jet induced effects of several exhaust nozzle configurations (axisymmetric, and vectoring/modulating varients) on the aeropropulsive performance of a twin engine V/STOL fighter design was determined. A 1/8 scale model was tested in an 11 ft transonic tunnel at static conditions and over a range of Mach Numbers from 0.4 to 1.4. The experimental aspects of the static and wind-on programs are discussed. Jet effects test techniques in general, fow through balance calibrations and tare force corrections, ASME nozzle thrust and mass flow calibrations, test problems and solutions are emphasized.

Schnell, W. C.↗

Exhaust gas measurements in a propane fueled swirl stabilized combustor

Exhaust gas temperature, velocity, and composition are measured and combustor efficiencies are calculated in a lean premixed swirl stabilized laboratory combustor. The radial profiles of the data between the co- and the counter swirl cases show significant differences. Co-swirl cases show evidence of poor turbulent mixing across the combustor in comparison to the counter-swirl cases. NO sub x levels are low in the combustor but substantial amounts of CO are present. Combustion efficiencies are low and surprisingly constant with varying outer swirl in contradiction to previous results under a slightly different inner swirl condition. This difference in the efficiency trends is expected to be a result of the high sensitivity of the combustor to changes in the inner swirl. Combustor operation is found to be the same for propane and methane fuels. A mechanism is proposed to explain the combustor operation and a few important characteristics determining combustor efficiency are identified.

Aanad, M. S.↗

Effect of vacuum exhaust pressure on the performance of MHD ducts at high B-field

The effect of area ratio variation on the performance of a supersonic Hall MHD duct showed that for a given combustion pressure there exists an area ratio below which the power generating region of the duct is shock free and the power output increases linearly with the square of the magnetic field. For area ratios greater than this, a shock forms in the power generating region which moves upstream with increasing magnetic field strength resulting in a less rapid raise in the power output. The shock can be moved downstream by either increasing the combustion pressure or decreasing the exhaust pressure. The influence of these effects upon duct performance is presented in this paper.

Smith, J. M.↗

Aerodynamic interactions with turbulent jet exhaust plumes

The importance of aerodynamic interactions associated with external flow-field effects on turbulent jet exhaust plume structure is discussed. A viscous/inviscid prediction technique is presented which combines the overlaid mixing and inviscid plume components of the JANNAF Standardized Plume Flow-Field (SPF) model with inviscid external flow and boundary-layer analyses for treating nozzle afterbodies at subsonic/transonic speeds. Validation of the technique via comparisons between predictions and experiment for cold-air jet plumes is presented. Predicted spatial temperature distributions for hot, nonafterburning plumes are presented and compared to results obtained from more simplified prediction techniques in order to assess the importance of the aerodynamic interactions associated with external boundary layers and pressure gradients. It is demonstrated that these interactions play a significant role in determining the near-field turbulent mixing and inviscid plume shock structure. The implication of these results to plume radiation predictions is discussed.

Wilmoth, R. G.↗

Transonic, Axisymmetric Flow Over Nozzle Afterbodies With Supersonic Jet Exhausts

Predictions require less computation than Navier-Stokes solutions. RAXJET computer program predicts transonic, axisymmetric flow over nozzle afterbodies with supersonic jet exhausts and includes effects of boundarylayer displacement, separation, jet entrainment, and inviscid jet plume blockage. RAXJET written in FORTRAN IV.

Wilmoth, R. G.↗

Meteorological assessment of SRM exhaust products' environmental impact

The environmental impact of solid rocket motor (SRM) exhaust products discharged into the free air stream upon the launching of space vehicles that depend upon SRM boosters to obtain large thrust was assessed. The emission of Al2O3 to the troposphere from the SRMs in each Shuttle launch is considered. The Al2O3 appears as particles suitable for heterogeneous nucleation of hydrochloric acid which under frequently occurring atmospheric conditions may form a highly acidic rain capable of damaging property and crops and of impacting upon the health of human and animal populations. The cloud processes leading to the formation of acid rain and the concentration of the acid that then reaches the ground, and the atmospheric situations that lead to the production of cloud and rain at and near a launch site, and the prediction of weather conditions that may permit or prohibit a launch operation are studied.

Dingle, A. N.↗

User's manual for the REEDM (Rocket Exhaust Effluent Diffusion Model) computer program

The REEDM computer program predicts concentrations, dosages, and depositions downwind from normal and abnormal launches of rocket vehicles at NASA's Kennedy Space Center. The atmospheric dispersion models, cloud-rise models, and other formulas used in the REEDM model are described mathematically Vehicle and source parameters, other pertinent physical properties of the rocket exhaust cloud, and meteorological layering techniques are presented as well as user's instructions for REEDM. Worked example problems are included.

Bjorklund, J. R.↗

Program listing for the REEDM (Rocket Exhaust Effluent Diffusion Model) computer program

The program listing for the REEDM Computer Program is provided. A mathematical description of the atmospheric dispersion models, cloud-rise models, and other formulas used in the REEDM model; vehicle and source parameters, other pertinent physical properties of the rocket exhaust cloud and meteorological layering techniques; user's instructions for the REEDM computer program; and worked example problems are contained in NASA CR-3646.

Bjorklund, J. R.↗

Characterization of a high-pressure diesel fuel injection system as a control technology option to improve engine performance and reduce exhaust emissions

Test results from a high pressure electronically controlled fuel injection system are compared with a commercial mechanical injection system on a single cylinder, diesel test engine using an inlet boost pressure of 2.6:1. The electronic fuel injection system achieved high pressure by means of a fluid intensifier with peak injection pressures of 47 to 69 MPa. Reduced exhaust emissions were demonstrated with an increasing rate of injection followed by a fast cutoff of injection. The reduction in emissions is more responsive to the rate of injection and injection timing than to high peak injection pressure.

Mcfadden, J. J.↗

Thrust performance of a variable-geometry, divergent exhaust nozzle on a turbojet engine at altitude

A variable geometry, low aspect ratio, nonaxisymmetric, two dimensional, convergent-divergent exhaust nozzle was tested at simulated altitude on a turbojet engine to obtain baseline axial, dry thrust performance over wide ranges of operating nozzle pressure ratios, throat areas, and internal expansion area ratios. The thrust data showed good agreement with theory and scale model test results after the data were corrected for seal leakage and coolant losses. Wall static pressure profile data were also obtained and compared with one dimensional theory and scale model data. The pressure data indicate greater three dimensional flow effects in the full scale tests than with models. The leakage and coolant penalties were substantial, and the method to determine them is included.

Straight, D. M.↗

Some observations on the aerodynamics of an airfoil with a jet exhausting from the lower surface

A preliminary investigation was carried out to study the aerodynamics of an 18% symmetrical airfoil with a rectangular jet exhausting from the lower surface. Static pressures on the airfoil surface and total pressures in the near wake were measured at jet momentum coefficients ranging from 0 to 2. Results from these measurements were used to study the effects of a jet-cross flow interaction on the aerodynamics of an airfoil. These results were also compared with those obtained from a two-dimensional inviscid theoretical model. Measurements indicate positive and negative pressure regions in front of and behind the jet respectively. The intensity of the pressure in these regions increases with increasing jet strength. Upper surface pressures also decrease due to an effective angle of attack induced by the jet-cross flow interaction. The pressure variations on the upper and lower surfaces induce a positive sectional lift coefficient on the airfoil. The magnitude of the lift coefficient for a given momentum coefficient decreases with decreasing aspect ratio of the nozzle.

Leopold, D.↗

Measurement of acoustic modes and wall impedance in a turbofan exhaust duct

Acoustic measurements made with in-duct modal probes show how individual acoustic modes, as generated by fan/stator interaction, interact with a well-characterized liner. This measured attenuation provides a critical test for predicted attenuation as developed from the theoretical analysis of sound propagation in annular ducts with treatment and sheared flow. The primary investigations took place in the exhaust duct of a model fan mounted in an anechoic chamber. The results presented include induct attenuation, sound power attenuation as measured in the far field, and in-situ acoustic impedance measurements of the treated wall sections. Good theory/experiment agreement was found; the differences of treatment suppression between theory and measured values differed at most by 2.7 dB.

Fiske, G. H.↗

Sound propagation in segmented exhaust ducts - Theoretical predictions and comparison with measurements

Suppressions due to acoustic treatment in the annular exhaust duct of a model fan have been theoretically predicted and compared with measurements. The predictions are based on the modal analysis of sound propagation in a straight annular flow duct with segmented treatment. Measured values of the mode distribution of the fan noise source (fan-stator interaction source only) and the acoustic impedance of the treatment in the duct were used as input to the prediction program. The predicted suppressions (under the assumption of uniform flow in the duct) compared well with the measured in-duct suppression for all test conditions. The measurements were made in an anechoic chamber and the interaction modes generated in the fan spanned a cut-off ratio range from nearly one to seven.

Joshi, M. C.↗

Velocity and temperature characteristics of two-stream, coplanar jet exhaust plumes

The subsonic jet exhaust velocity and temperature characteristics of model scale, two stream coplanar nozzles were obtained experimentally. The data obtained included the effects of fan to primary stream velocity and temperature ratios on the jet axial and radial flow characteristics. Empirical parameters were developed to correlate the measured data. The resultant equations were shown to be extensions of a previously published single stream jet velocity and temperature correlation.

Vonglahn, U. H.↗

A temperature correlation for the radiation resistance of a thick-walled circular duct exhausting a hot gas

It is often useful to know the radiation impedance of an unflanged but thick-walled circular duct exhausting a hot gas into relatively cold surroundings. The reactive component is shown to be insensitive to temperature, but the resistive component is shown to be temperature dependent. A temperature correlation is developed permitting prediction of the radiation resistance from a knowledge of the temperature difference between the ambient air and the gas flowing from the duct, and a physical basis for this correlation is presented.

Mahan, J. R.↗