A Method for Estimating Jet Entrainment Effects on Nozzle-afterbody Drag PDF Download
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Author: R. C. Bauer Publisher: ISBN: Category : Airplanes Languages : en Pages : 30
Book Description
A highly simplified analysis was used to derive an expression for estimating the induced afterbody drag caused by the turbulent jet-mixing process. The approach estimates the induced velocity produced by the jet-mixing process and uses small perturbation concepts to estimate the resulting pressure change on the afterbody surface from which the induced afterbody drag coefficient is obtained. The theoretical induced afterbody drag (entrainment drag) is combined with the maximum jet plume diameter blockage condition to form a correlation method that accounts for the effect of jet area ratio, exit angle, total temperature, molecular weight and ratio of specific heats for a given external stream Mach number, Reynolds number, and afterbody geometry. For verification, the correlation method was used to predict the drag of an H2 and C2H4 jet from the measured drag of an N2 jet and to predict the drag of a hot jet from the measured drag of a cold jet for both the 15- and 25-deg AGARD afterbody configurations in the Mach number range from 0.6 to 1.5. The average accuracy of the correlation method is better than 10% for both afterbody configurations and is 40 to 50 % more accurate than a correlation method based only on the blockage parameter. A brief numerical study indicates that the major parameter which correlates the jet entrainment effect is the product of the jet gas constant and total temperature. (Author).
Author: R. C. Bauer Publisher: ISBN: Category : Airplanes Languages : en Pages : 30
Book Description
A highly simplified analysis was used to derive an expression for estimating the induced afterbody drag caused by the turbulent jet-mixing process. The approach estimates the induced velocity produced by the jet-mixing process and uses small perturbation concepts to estimate the resulting pressure change on the afterbody surface from which the induced afterbody drag coefficient is obtained. The theoretical induced afterbody drag (entrainment drag) is combined with the maximum jet plume diameter blockage condition to form a correlation method that accounts for the effect of jet area ratio, exit angle, total temperature, molecular weight and ratio of specific heats for a given external stream Mach number, Reynolds number, and afterbody geometry. For verification, the correlation method was used to predict the drag of an H2 and C2H4 jet from the measured drag of an N2 jet and to predict the drag of a hot jet from the measured drag of a cold jet for both the 15- and 25-deg AGARD afterbody configurations in the Mach number range from 0.6 to 1.5. The average accuracy of the correlation method is better than 10% for both afterbody configurations and is 40 to 50 % more accurate than a correlation method based only on the blockage parameter. A brief numerical study indicates that the major parameter which correlates the jet entrainment effect is the product of the jet gas constant and total temperature. (Author).
Author: W. L. Peters Publisher: ISBN: Category : Airplanes Languages : en Pages : 50
Book Description
The objective of this investigation was to isolate those parameters defined as jet mixing effects on afterbody drag in an effort to develop a method of correcting or simulating the effects of jet temperature in wind tunnel experiments. Data used in the investigation were obtained from experiments conducted in the AEDC Aerodynamic Wind Tunnel (1T) with a strut-mounted model at free-stream Mach numbers from 0.6 to 1.2. Integrated afterbody pressure drag coefficient data were acquired for three nozzle area ratios (1.0, 1.24, and 2.96) using various unheated jet exhaust gas compositions that allowed a variation in gas constant from 55 to 767 ft/lbf/lbm-deg R. Jet mixing effects on afterbody drag coefficient produced by varying jet gas constant and nozzle area ratio at nozzle design pressure ratio, and the drag effects resulting from variations in nozzle pressure ratio at certain overexpanded jet conditions were observed to be similar functions of mass flux ratio. A simple experimental method has been proposed to allow corrections of afterbody drag coefficient data obtained in the wind tunnel (using an ambient temperature air jet) for the effects of jet gas constant. By inference, a similar drag correction can be obtained for the combined effect of gas constant and temperature, assuming their product defines the effects on drag produced by variations in either property. (Author).
Author: Publisher: ISBN: Category : Aeronautics Languages : en Pages : 1460
Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: C. E. Robinson Publisher: ISBN: Category : Aerodynamics, Transonic Languages : en Pages : 98
Book Description
Results of an experimental and analytical research investigation on nozzle/afterbody drag are presented. Experimental afterbody (and boattail) drag coefficients and pressure distributions are discussed for an isolated, strut-mounted nozzle/afterbody model for the Mach number range from 0.6 to 1.5. Some data are also given for free-stream unit Reynolds numbers from one million to approximately four million per foot. The experimental data were obtained for the basic model with an air-cooled and a water-cooled Ethylene/air combustor to provide hot-jet duplication as well as cold-jet simulation. The temperature of the nozzle exhaust gas was varied from 530R (burner-off) to approximately 2500R for several nozzle pressure ratios from jet-off to those corresponding to a moderately under-expanded exhaust plum. The initial series of experiments was conducted with the air-cooled combustors, and the effect of jet temperature on afterbody drag was somewhat masked by the effects of the secondary airflow from the cooling air. The general trend, however, shows a decreasing afterbody drag with increasing exhaust gas temperature and with decreasing secondary airflow at a fixed nozzle pressure ratio. (Modified author abstract).
Author: R. C. Bauer
Author: R. C. Bauer
Author: W. L. Peters
Author: Frederick C. Guyton
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Author: Richard G. Wilmoth
Author: C. E. Robinson
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Author: Earl A. Price (Jr.)