Modelling internal combustion engines with dynamic staggered mesh refinement

Abstract

Modelling internal combustion engines (ICEs) with multidimensional computational fluid dynamics (CFD) is challenging due to the fuel spray, combustion chemistry and moving piston involved. To accurately simulate ICEs as well as to maintain acceptable computational cost, dynamic mesh refinement techniques could be applied. Although modelling ICEs with staggered mesh is ubiquitous in the engine combustion community, the dynamic refinement of staggered mesh in the context of multidimensional engine simulations is not reported in the literatures due to the numerical difficulties in the momentum solution at the gird fine-coarse interface and to deal with moving boundaries. To address these difficulties, we propose a dynamic refinement scheme to cell-by-cell refine the staggered mesh on-the-fly based on the fuel evaporation and thermochemical state in the multidimensional dynamic staggered mesh and it is able to handle the complexity caused by the moving boundaries in engine simulations and momentum solution at the fine-coarse interface in the dynamic mesh. This mesh refinement scheme is then implemented in the widely-used ICEs simulation codes for engine simulations with fuel sprays. A wide variety of computational examples including shock wave, compression, constant volume fuel spray, constant volume fuel spray combustion are first employed to test the scheme and finally, compression ignition combustion engine simulations are conducted with the proposed methodology.