Effect of Ramp Geometry on Single Expansion Ramp Nozzle Performance Characteristics

Abstract

In high-speed flight regimes, the drag plays a significant role in determining the overall performance of the aerospace vehicle. One proposed solution is to integrate a single expansion ramp nozzle (SERN) at the aft of the vehicle to mitigate the drag effects. This work investigates the effects of nozzle geometry on flow and performance characteristics of SERN with a thrust-optimized parabolic and minimum-length nozzle ramp contours, which have not been explored with regard to these aspects. A computational study is carried out on these two ramp contours using compressible Reynolds Averaged Navier–Stokes equations over a range of nozzle pressure ratio (NPR). In the tested range of NPR, the restricted shock separation is found to be the chief mode of flow separation in SERN, along with the change in the size of recirculation zone and separation bubble. At NPR 3, the thrust-optimized parabolic ramp contour shows an increment of thrust coefficient by 29.2% over the minimum-length nozzle; whereas at NPR 3.5, the minimum-length nozzle demonstrates an increment of thrust coefficient by 56.3% over the thrust-optimized parabolic at 0-deg M cowl angle. Further, in the tested range of NPR, the minimum-length nozzle shows an improved lift coefficient at 5 deg cowl angle.