The present paper deals with the numerical study of high pressure LOx/H2 orLOx/hydrocarbon combustion for propulsion systems. The present research effortis driven by the continued interest in achieving low cost, reliable access tospace and more recently, by the renewed interest in hypersonic transportationsystems capable of reducing time-to-destination. Moreover, combustion at highpressure has been assumed as a key issue to achieve better propulsiveperformance and lower environmental impact, as long as the replacement ofhydrogen with a hydrocarbon, to reduce the costs related to ground operationsand increase flexibility. The current work provides a model for the numericalsimulation of high- pressure turbulent combustion employing detailed chemistrydescription, embedded in a RANS equations solver with a Low Reynolds numberk-omega turbulence model. The model used to study such a combustion phenomenonis an extension of the standard flamelet-progress-variable (FPV) turbulentcombustion model combined with a Reynolds Averaged Navier-Stokes equationSolver (RANS). In the FPV model, all of the thermo-chemical quantities areevaluated by evolving the mixture fraction Z and a progress variable C. Whenusing a turbulence model in conjunction with FPV model, a probability densityfunction (PDF) is required to evaluate statistical averages of chemicalquantities. The choice of such PDF must be a compromise between computationalcosts and accuracy level. State- of-the-art FPV models are built presuming thefunctional shape of the joint PDF of Z and C in order to evaluateFavre-averages of thermodynamic quantities. The model here proposed evaluatesthe most probable joint distribution of Z and C without any assumption on theirbehavior.
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