Effects of geometric parameters on internal performance and flowfield of single expansion ramp nozzles

3-D Navier-Stokes calculations were carried out to investigate the effects of geometric parameters on internal performance and flowfield of single expansion ramp nozzles (SERNs). The results show that, in general, the nozzle sidewall extension has a beneficial effect on nozzle thrust. However, excessive large wetted surface area of sidewall results in great friction loss, which is already prevailing over the pressure gain by sidewall extension. The partial sidewalls perform slightly better than full sidewalls, and the axial thrust ratio C_fa is 2% larger than short sidewalls. Moreover, the extended sidewall reduces the pitch thrust vector angle δ_p effectively at the design point. The long curved ramp obtains higher C_fa and smaller δ_p than the short curved ramp, and the C_fa reaches 0.983 at design point, which is comparable with the conventional axisymmetric and two-dimensional convergent-divergent (2DCD) nozzles. Under the conditions of relatively high nozzle pressure ratios (NPRs), large throat aspect ratio reduces the spanwise expansion losses effectively, with higher C_fa and smaller δ_p, and the margin increases with increasing NPR.