Study On Mixture Formation And Combustion Process Of Spark-Ignition,Heavy Oil Engine

At room temperature, the gasoline mixture is prone to burning and exploding when it encounter fire, and the heavy oil (refer to kerosene or diesel oil) has higher flash point and lower volatilization temperature than the gaseline, it’s easier to store and handle, heavy oil is more accessible. Generally, compression-ignition engine is heavier than spark-ignition engine. In the aviation specific applications, using a spark-ignition engine which is fueled with heavy oil can ensure security, it will not increase the weight of the engine. However, studies on the ignition and flame propagation of heavy-ignition engine are still relatively small, the ignition and flame propagation characteristics of heavy oil mixture (especially heavy non-homogeneous mixture) are in the lack of necessary understanding. Therefore, this paper studied the formation of heavy-oil mixture and combustion processes of the spark-ignition, heavy-oil engine.First, according to the basic structural parameters of the ROTAX914combustion chamber, using AVL FIRE to generate three-dimensional geometric model of the combustion chamber and meshing. Set up mathematical model and determine the initial conditions and boundary conditions. Then verify the validity of the model.Secondly, simulating and analysis of the heavy oil mixture formation processes, and analyze the effects of different injection timing, injection angle and injection mass on the heavy-oil mixture formation processes. Determine of the fuel injection parameters which conducive to ignition and combustion of heavy-oil mixture.Again, study on the ignition and flame propagation characteristics and related factors of the heavy non-homogeneous mixture. The results show that:the fuel injection parameters directly affect the formation of the state of the heavy non-homogeneous mixture, which have an impact on the combustion processes; EGR rate inhibited the growth of the flame kernel; there is an optimum ignition timing so that the ignition delay angle is the least; when the ignition energy reaches a certain value, then increasing the ignition energy has little effect on the growth of the flame kernel, it will reduce the ignition system life, so the ignition energy is not the bigger the better.Finally, the deflagration phenomenon were simulated under non-homogeneous mixture and homogeneous mixture. And analyzing the deflagration and misfire characteristics in different ignition timing, ignition energy, the EGR rate and injection timing conditions. The results show that:the deflagration can be effectively suppressed by the non-homogeneous gas mixture; delaying ignition timing and EGR rate can reduce the deflagration tendency; when the ignition energy is less than the minimum ignition energy required for the engine, it will cause misfire; early injection can reduce the deflagration tendency, but prematurely injection timing can cause misfire.The research results can provide a basis theoretical support for resolving some key issues of the SI, heavy-oil engine, like:atomization of heavy oil, heavy oil ignition and flame propagation, knocking problems, misfire problems.