Solving Combustion Chemistry in Engine Simulations

Abstract

Models suited for the prediction of chemical effects in spark‐ignition (SI) and compression‐ignition (CI) engines are presented. Starting from one‐step global kinetics, the role of chemistry for the understanding of ignition phenomena is illustrated. However, as only detailed elementary kinetics provide a reliable basis for predictions, methods for the reduction of large chemical mechanisms and their tabulation are outlined. An example for the systematic reduction by using steady‐state analysis is presented. This leads to a relatively small number of global steps, each of which governs a rate‐determining time scale of the entire chain process. For SI engines, effects of chemistry are discussed for spark models, turbulent flame propagation, and knock models. For the case of CI engines, the direct integration model, the characteristic time model, and the representative interactive flamelet (RIF) model and their use in engine simulations are presented.

On the effect of injection timing on the ignition of lean PRF/air/EGR mixtures under direct dual fuel stratification conditions

“…Despite the presence of the reactivity inhomogeneity in Case 2, however, an excessive HRR occurs due to a very short combustion duration similar to the 0-D ignition. This is mainly because the ignition delay decreases exponentially with increasing pressure dur- ing the compression stroke [67] , which eventually removes the differences in the ignition delays of local fuel/air mixtures in Case 2. As such, the RCCI combustion is more likely to occur by the spontaneous ignition mode of combustion rather than the deflagration mode as in the conventional HCCI combustion [39] .…”