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

Transient three-dimensional numerical investigations on the side-load physics of an engine encompassing a film-cooled nozzle extension and a regeneratively cooled thrust chamber were performed. The objectives of this study are. to identify the side-load physics and to compute the associated aerodynamic side load. The computational methodology is based on an unstructured-grid pressure-based computational fluid dynamics formulation and a. transient inlet history based on an engine system simulation. Computations simulating engine startup at 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 startups with the nozzle extension attached, computational results show that the dominant side-load physics are the turbine-exhaust-gas-assisted asymmetric Mach disk flow and the subsequent jump of the separation line, which generated the peak side load that decreases as the ambient pressure decreases. For the stub nozzle operating at sea level, the peak side load reduces drastically. The computed side-load physics and the associated peak side load for the sea-level cases agree reasonably well with those of available data from the tests of a similar engine.