Large Eddy Simulations of Turbulent Reacting Flows in an Opposed-Piston Two Stroke Engine

The two-phase filtered mass density function (FMDF) subgrid-scale model has been used for large eddy simulation (LES) of turbulent spray combustion in a generic single cylinder, opposed-piston, two-stroke engine configuration. The LES/FMDF is implemented via an efficient, hybrid numerical method in which the filtered compressible Navier-Stokes equations are solved with a high-order, multi-block, compact differencing scheme, and the spray and FMDF are implemented with stochastic Lagrangian methods. The reliability and consistency of the numerical methods are established for the engine configuration by comparing the Eulerian and Lagrangian components of the LES/FMDF. The effects of various operating conditions like boost pressure, heat transfer model, fuel spray temperature, nozzle diameter, injection pressure, and injector configuration on the flow field, heat loss and the evolution of spray and combustion are studied.