Large eddy simulation of turbulent combustion processes in propulsion and power systems

Progress toward application of the large eddy simulation (LES) technique to turbulent multiphase combustion processes is presented with emphasis placed on propulsion and power systems. The primary objective is to provide a systematic analysis of the current state-of-the-art and assist in the development of technical performance metrics for model development and validation. Research is currently required to provide both improved multiphase combustion models and improved datasets for validation. Requirements for further model development must be established through detailed analyses of the space–time characteristics of small-scale flame structures and turbulence–chemistry interactions. Concurrently, a refined set of implementation requirements must be established. Steps taken towards these goals are described by first providing a generalized formulation of the filtered conservation equations using an arbitrary filter function that operates on both spatial and temporal scales, with no a priori assumptions made regarding the character of the multiphase fluid elements present in the system. The distinct requirements for LES are listed with a discussion that highlights current progress and unresolved issues. Two case studies are then presented that demonstrate the predictive capabilities of LES when implemented with the appropriate numerics and grid resolution, under highly controlled conditions, and with well-defined boundary conditions. The paper is concluded by highlighting recent findings associated with the International Workshop on Measurement and Computation of Turbulent Nonpremixed Flames.