A Parametric Investigation of the Annular Jet Concept for Obtaining Afterbody Drag Data at Transonic Mach Numbers.

摘要

A parametric experimental program was conducted at free-stream Mach numbers of 0.6, 0.9, and 1.2 to investigate the plume simulation characteristics of annular jets. Plume simulation evaluation was based upon comparisons of afterbody pressure drag from integration of afterbody pressure measurements. Data were obtained on a 15-deg boattail afterbody attached to a strut-supported cylindrical centerbody. Geometric variables covered a range of sting-to-nozzle exit diameter ratios from 0 to 0.95 and nozzle area ratios from 1.0 to 1.5. High pressure air at ambient temperature was utilized for the exhaust gas. The results indicate that matching of the exhaust plume maximum diameter provides a reasonable afterbody drag correlation, accounting for effects of annular jet, nozzle exit-to-throat area ratio, and nozzle pressure ratio for conditions where drag follows the classical trend indicative of a plume shape dependence. Plume diameter correlation was not successful, for the pressure ratios of this investigation, for annular jet configurations having sting-to-nozzle exit diameter ratios of 0.95 at all Mach numbers and 0.866 at Mach number 1.2. There were no significant differences in the trends with angle of attack between the annular and conventional jet configurations over the angle-of-attack range from -2 to 6 deg. (Author)