Three Dimensional Simulation of Time-Dependent Scramjet Isolator/Combustor Flowfields Implemented on Parallel Architectures

Abstract

The development of a parallel Navier-Stokes solver for computing time-dependent,three-dimensional reacting flowfields within scramjet (supersonic combusting ramjet)engines is presented in this work. The algorithm combines low-diffusion upwinding methods, timeaccurate implicit integration techniques, and domain decomposition strategies to yield an effective approach for large-scale simulations. The algorithm is mapped to a distributed memoryIBM SP-2 architecture and a shared memory Compaq ES-40 architecture using the MPI-1 message-passingstandard. Two and three-dimensional simulations of time-dependent hydrogen fuel injection into a modelscramjet isolator / combustor configuration at two equivalence ratios are performed. Thesesimulations are used to gain knowledge of engine operability, inlet performance, isolatorperformance, fuel air mixing, flame holding, mode transition, and engine unstart.Results for an injection at a ratio of 0.29 show qualitative agreement withexperiment for the two-dimensional case, but revealed a slow progression towardengine unstart for the three-dimensional case. Injection at an equivalence ratio of 0.61resulted in engine unstart for both two-dimensional and three-dimensional cases.Engine unstart for the three-dimensional case occurs as a response to the formation and growthof large pockets of reversed flow along the combustor side wall. These structuresdevelop at an incipient pressure above 154 kPa and result in significant blockage of the core flow,additional compression, and chemical reaction within the boundary layer. All of these factors promotea much more rapid unstart as compared with the two-dimensional case.