Chemical Kinetics Modeling Tools for Hydrocarbon Scramjet Propulsion System Design

One of the difficulties in reactive flow simulation is the development of reduced models that are capable of predicting the non-equilibrium processes such as ignition and blow-out. Hydrocarbon fuels become viable alternatives to hydrogen at Mach numbers below 10, because of greater fuel densities and endothermic cooling capabilities. However, hydrocarbon fuels show difficulties for flame holding under supersonic conditions due to their long ignition delay times. In present approach, the fuel molecule breaks-down into CH2O and H2 and a detailed CH2O/H2/O2 reaction sub-set consisting of 14 species and around 40 reactions is used for accurate predictions. In Phase I, Combustion Science & Engineering, Inc. has demonstrated this approach for ethylene by implementing the reduced kinetic model in RANS and LES codes to predict combustion stability in WPAFB cavity flameholder experiments. The rate parameters for the fuel decomposition reaction are estimated from ignition delay time measurements. In Phase II, the model reduction strategy will be extended to JP-type fuels. Also, the model reduction procedure will be automated by implementing parameter estimation and optimization algorithms to validate and optimized the reduced kinetic model against detailed model predictions. This reduced kinetic modeling tool will be coupled with CFD codes for commercial applications.