Current compression ignition strategies which can achieve high thermal efficiency and ultra-low emissions such as dual-fuel PCI combustion and gasoline direct injection compression ignition have utilized stratified fuel mixture to optimize combustion processes. Thus this paper investigated the more detailed relation between equivalence ratio distribution and history of heat release rate. The results concluded that richer mixtures closer to stoichiometric ratio increase heat release rate because the ignition timing of the mixture is less dependent on equivalence ratio so that the mixtures tend to ignite simultaneously, and the advanced ignition of the richer mixture increases ambient temperature while inducing the ignition of surrounding leaner mixture.
