Numerical study of wall heat transfer inside a combustion chamber under conventional diesel combustions and low temperature combustion conditions

摘要

The engine simulations using computational fluid dynamics (CFD) commercial code ANSYS-Forte is employed to study the effects of in-cylinder combustion on heat transfer through the combustion chamber walls. In this numerical study, three different combustion regimes are explored and compared. A conventional diesel combustion (CDC) and low temperature combustion (LTC) with early and late injection conditions are investigated. To simulate the velocity field in the computational domain, the renormalization group (RNG) k-ε turbulence model Is chosen. Also, a detailed chemistry CHEMKIN Pro package is implemented in a combustion model to calculate the reaction mechanism for the engine simulations. To obtain predicted heat flux results from three different combustion regimes, the available heat transfer wall model including temperature wall function and gas density variation is applied. To model validation, the simulated results is validated against experimental data from N14 engines which are operated with three different engine conditions. The predicted in-cylinder pressure and apparent heat release rate for three different modes of combustion performs reasonably well agreement with available experimental data. Three different points of interest on a piston surface are also investigated. The predicted heat fluxes through the walls provide the similar global trends for three combustion regimes. The magnitudes of simulated heat flux for a conventional diesel combustion (CDC) regime are in the normal range of typical measured values of diesel combustions and are the highest among all three combustion regimes, while the heat flux results of low temperature combustion with late injections are the lowest.