Characterization of Flow Field Structure and Species Composition in a Shear Coaxial Rocket GH2/GO2 Injector: Modeling of Wall Heat Losses

A LES combustion model for the prediction of wall-heat transfer in rocket engines and confined combustors is developed. The model employs a flamelet-formulation, in which wall heat-loss effects are introduced by including a source term in the unsteady flamelet equations. This source term is modeled as convective heat-loss process, which evolves on a time-scale that is slow compared to the characteristic chemical scales. This time-scale is modeled by employing a Nusselt-number relation. The thermochemical composition of the non-adiabatic flamelet structure is then obtained from the solution of the unsteady flamelet equations, and is parameterized in terms of mixture fraction, temperature, and scalar dissipation rate. The model is applied in LES of a uni-element rocket injector that was experimentally investigated by Pal et al. [Third Int. Workshop on Rocket Comb. Modeling, Paris, France, March, 13-15, 2006]. Comparisons with adiabatic modeling results show that the consideration of wall-heat losses results in a significant reduction in the temperature in the recirculation zone and a 25 % reduction in the OH mass fraction at the combustor exit. © 2011 by D.J. Lee, S. Thakur, J. Wright, M. Ihme, and W. Shyy