Hybrid Double-Divergent Nozzle as a Novel Alternative for Future Rocket Engines

Abstract

The efficiency of a rocket engine is dependent on altitude adaptability of its nozzle. In this context, double-divergent nozzles (DDNs) have drawn immense interest. The DDNs explored till now comprise of two nozzles of the same contour such as double conical and dual bell. In such DDNs, although the issue of altitude compensation may be partially addressed, the losses associated with the particular type of nozzle contour may get aggravated. This work proposes a novel concept of a hybrid double-divergent rocket nozzle (HDDN) as an alternative to mitigate certain undesirable characteristics of fluid flow through the nozzle. Two types of HDDNs, having extensions of planar minimum length nozzle and planar thrust-optimized parabolic, have been studied. A planar double conical nozzle is taken as reference. The flow analysis is performed using commercially available software ANSYS Fluent for various nozzle pressure ratios. The realizable turbulence model is used for closing the Reynolds-averaged Navier–Stokes equations. The side loads, moments, coefficient of thrust (), and thrust-to-weight ratio have been investigated. At the highest nozzle pressure ratio, the conical thrust-optimized parabolic HDDN exhibits an increase of by 4% and an increase of thrust-to-weight ratio by about 18% vis-à-vis the reference design.