Coupling of in situ adaptive tabulation and dynamic adaptive chemistry: An effective method for solving combustion in engine simulations

Abstract

Using detailed mechanisms to include chemical kinetics in computational fluid dynamics simulations is required for many combustion applications, yet the resulting computational cost is often extremely prohibitive. In order to reduce the resources dedicated to this stage, we investigated the coupling of the dynamic adaptive chemistry (DAC) reduction scheme with the in situ adaptive tabulation (ISAT) algorithm. This paper describes the tabulation of dynamic adaptive chemistry (TDAC) method which takes advantage of both ISAT and DAC to reduce the impact of the mesh and the oxidation mechanism on the computational cost, particularly for unsteady applications like internal combustion engines. In the context of homogeneous charge compression ignition (HCCI), we performed simulations on simplified 2D cases using various n-heptane mechanisms and on a real case mesh using a detailed 857-species iso-octane mechanism. Compared to the direct integration of the combustion reactions, results are in very good agreements and a speed-up factor above 300 is obtained. This is significantly better than what was reported for ISAT and DAC which illustrates the synergy of the two methods. In addition, an experimental validation has also been performed with low load HCCI data. Accordingly, the TDAC method is a significant improvement for the computation of the combustion chemistry in engine simulations and allows the use of detailed mechanisms with practical case meshes in simulations that are inconceivable using direct integration.