Effect of Temperature-Pressure Time History on Auto-Ignition Delay of Air-Fuel Mixture 2018-01-1799
When the compression ratio of the spark ignition engine is set high as a method of improving the fuel efficiency of passenger cars, it is often combined with the direct fuel injection system for knock mitigation. In port injection, there are also situations where the fuel is guided into the cylinder while the vaporization is insufficient, especially at the cold start. If the fuel is introduced into the cylinder in a liquid state, the temperature in the cylinder will change due to sensible heat and latent heat of the fuel during vaporization. Further, if the fuel is unevenly distributed in the cylinder, the effect of the specific heat is added, and the local temperature difference is expanded through the compression process.
In this research, an experiment was conducted using a rapid compression machine for the purpose of discussing the effect of the temperature-pressure time history of fuel on ignition delay time. From the results, it was confirmed that the ignition timing can be advance and retard depending on the temperature-pressure history regardless of the time for the fuel to stay in the cylinder. This indicates that ignition delay can be controlled arbitrarily according to the purpose by manipulating the temperature-pressure history. In addition, zero-dimensional detailed chemical reaction calculation was carried out in order to discuss the effect of the spatial heterogeneity of fuel mixture concentration and temperature on the ignition delay. The results showed that the heterogeneity of the air-fuel mixture essentially shortens the ignition delay time.