Simulation study on spray combustion mechanism of diesel-gasoline blend fuels

In order to reveal the spray combustion mechanism of blend fuels, a combustion model was established using EDC model based on previous experimental research. The simulation results show that under lower co-flow temperature, the auto-ignition of n-heptane (represent diesel) occurred earlier than gasoline (represent gasoline), as a result of the combined effect of slower vaporization rate and lower activation energy required for the initial dehydrogenation reaction. On the contrary, under high co-flow temperature condition, iso-octane began to ignite before n-heptane, because the chemical reaction of both n-heptane and iso-octane occurs rapidly due to the rapider vaporization so that the auto-ignition delay is most determined by the vaporization and diffusion rate of fuel. The simultaneous auto-ignition temperature “Ts” was defined in previous work to represent the co-flow temperature, at which diesel and gasoline ignited spontaneously. Further simulation research results show that, the increment of injection pressure and background pressure will increase Ts, and the impact of injection pressure on Ts is much less than that of background pressure.