Modeling high-pressure mixing and combustion processes in liquid rocket engines

Modeling high-pressure mixing and combustion processes in liquid rocket engines involves a variety of challenges that include all of the classical closure problems and a unique set of problems imposed by the introduction of thermodynamic nonidealities and transport anomalies. The complicating factors of chemical kinetics, highly nonlinear source terms, and subgrid-scale velocity and scalar-mixing interactions must all be considered. The situation becomes more complex with increasing pressure because of an inherent increase in the flow Reynolds number and difficulties that arise when fluid states approach the critical condition. This paper 1) outlines the fundamental difficulties associated with modeling mixing and combustion processes at near-critical conditions, 2) outlines the theoretical and numerical framework developed to handle these difficulties, and 3) presents the results of simulations that lend insight into the intricate nature of the problem. Case studies focus on model performance and accuracy requirements, Lagrangian-Eulerian treatments of transcritical spray dynamics, and pure Eulerian treatments of trans-critical and supercritical mixing and combustion processes.