Scramjet Performance Computed for a JP-7-Fueled Generic X-51 Vehicle
Yunseok Choi, Michael F. Yost, Evan W. Lerner, James F. Driscoll
Abstract
Ways to improve the performance of a dual-mode scramjet engine within a generic X-51 hypersonic vehicle were computed using the MASIV reduced-order model. Two new aspects are that the finite-rate chemistry of a hydrocarbon (JP-7) fuel was added for the first time, and certain tradeoffs were quantified that arise due to the short vehicle length (4.6 m), which narrows the operating ranges of ram and scram modes. A goal was to maximize the operating range of the ram mode, which is limited by unstart, as well as the range of the scram mode, which is limited by incomplete fuel burn. Four parameters were varied: fuel–air equivalence ratio, Mach number, fuel injector diameter, and number of fuel injectors. Results indicate that achieving an acceptable design is complicated by the mixing–reaction–strain out tradeoff. A solution was achieved by directing the fuel to two sets of wall injectors having small diameters for ram mode and larger diameters for scram mode. Results demonstrate the need to include finite-rate chemistry to properly compute the heat release profile and interactions between the inlet, isolator, combustor, and thermal choking.