Abstract
Recently, a large side load is observed during start-up and shutdown sequences of Japanese LE-7A rocket engine nozzle. The objective of the present paper is to clarify the mechanism producing the large side loads during start-up process. The unsteady 3-D Navier-Stokes equations are solved for start-up process of three types of nozzle contours. That is, truncated perfect (TP) nozzle, 86% compressed truncated perfect (CTP) nozzle and CTP50-R5-L nozzle. The contour of TP nozzle and the contour of 86% CTP nozzle are LE-7 nozzle and the original LE-7A nozzle respectively. Asymmetric flow fields and large side loads are observed for LE-7A and CTP50-R5-L nozzles. There are two flow patterns which cause the large side loads. The first is the simultaneous occurrence of the Free Shock Separation (FSS) and the Restricted Shock Separation (RSS). The second is the oscillation of Mach disk under the RSS condition.
