Transient Three -Dimensional Side Load Analysis of a Film Cooled Nozzle

Transient t hree -dimensional numerical investigations on the side load physics for a n engine en comp assing a film cooled nozzle extension and a regeneratively cooled thrust chamber , were performed. The objectives of this study are t o identify the side load physics and to compute the associated aerodynamic side load using an anchored computational meth odology. The computational methodology is based on an unstructured -grid, pressure based computational fluid dynamics and heat transfer formulation, and a transient inlet history based on an engine system simulation. Computations simulating engine startup a t ambient pressures corresponding to sea level and three high altitudes were performed . In addition, computations for both engine startup and shutdown transients for a stub nozzle operating at sea level were also performed. For engine startup s with the no zzle extension attached , computational result s show the dominant side load physics are the turbine exhaust gas film coolant induced asymmetric Mach disk flow and the subsequent jump of the shock foot or the jump of the separation line which generated the p eak side load. That peak side load decreases rapidly and progressively as the ambient pressure decreases with the increasing altitudes . For the stub nozzle operating at sea level, t he peak side load reduces drastically and comes from the simultaneous free -shock separation to partial restricted shock transition and the shock breathing a t the nozzle lip during startup, whereas the magnitude of the side load during shut down is almost negligible . The computed side load characteristics for the sea level cases agree re asonably well with those of available data from the tests of a similar engine.