Abstract
In diesel engines, ignition delay is determined as the period between fuel injection and ignition. The ignition delay affects the initial combustion and the following combustion process. In this study, the gas fuel (propane, methane or hydrogen) mixed with air was induced into the cylinder and the light oil was injected as ignition source. Here, the ignition delay in this kind of engine was focused as a basic study. Even in the dual fuel like this engine, the ignition delay time is predicted by changing the value of the constant, A in Livengood-Wu equation while the others constants is the same in an ordinary diesel engine. Ignition delay becomes long in air/methane or air/propane mixture because the temperature at injection timing of light oil decreases. In air/hydrogen mixture, the ratio of specific heats increases slightly, however, the mole fraction of oxygen decreases due to decrease of the mass of air. Therefore, the ignition delay in air/hydrogen mixture is a little longer than that in just air. When the light oil is injected near at top dead center, slight heat release appears due to the self-ignition of gas fuel and the cycle-to-cycle variations of the ignition delay and the following combustion increase.
