A priori testing of a two-dimensional unsteady flamelet model for three-feed combustion systems

Abstract

A number of interesting combustion applications involve the mixing of multiple fuel or air streams, such as split-injection and dual-fuel internal combustion engines, which are the main focus of this work, or secondary air in gas turbines. In this study, a two-dimensional flamelet formulation for modeling auto-ignition and combustion in multi-stream configurations is presented and validated using two-dimensional direct numerical simulations (DNS). The DNS simulations were carried out for a multi-stream n-heptane mixture in constant volume isotropic turbulence with finite-rate chemistry according to a reduced chemical mechanism which considers 44 species and 185 reactions. The DNS represents two fuel streams and an oxidizer stream, where the second fuel stream is introduced at a time after the first fuel and oxidizer have started to mix. The resulting data are then used to carry out a priori testing of the two-dimensional flamelet model. The flamelet formulation is found to accurately represent the interaction of the multiple stream mixing and chemistry, thus enabling the accurate prediction of the auto-ignition of each fuel stream.