Simulation Of Combustion Of Diesel Engine Burning DME

Dimethyl ether(DME) is one kind of the new type and the clean alternative fuels for diesel engine. The research about DME is universal used on diesel engine is processing. So studying the burning characteristics of DME is propitious to manufacture and optimize DME engine. In this paper, a Quasi-dimensional combustion model for DME engine is developed on the base of diesel's Quasi-dimensional combustion model and DME engine's experimental investigation. This model is based upon drop vaporizing combustion model and includes fuel spray, mass entrainment, fuel evaporation, heat transfer, ignition and combustion, etc. The calculation zone is divided as the time of spray in cylinder. This model considers the vaporizing peculiarity of DME in cylinder. It adopts an assumed injection process as a sine law which is close to the actual injection process. The start of combustion of fuel zones is determined by an ignition delay model, the combustion is assumed to proceed at equivalence ratio and the combustion process of every fine zone don't affect each other. Whole model is divided as three parts: compressing, burning and expanding and compiles the computing program by VB. The model is proved through the comparing the calculating pressure curve with the actual testing. In most working states, the simulation predicted results agree with the experimental data. The variety of the graph is same both. It proves the model works well.It gets across to judge operation capability of engine by thermal efficiency, noise, asperity and emission. Generally speaking, thermal efficiency conflicts with noise and emission. So it needs to consider various factors and adjust the parameters of engine for improving the capability of engine. It changes parameters of the injection system to find the factors which affect the performances of DME engine. The parameters include injection advance, injection duration and overall circulating section of injector. Thestudying indicates that it can improve performance of DME engine by advancing injection, shortening injection duration, accretion overall circulating section of injector and provides some advices for optimizing the DME engine.At last, this paper analyses amply the main contaminations of diesel engine: smoking and NOx whose principle bring out and how to control. It analyses the reasons about DME engine which has no smoking and lower NOx by linking the DME's physics and chemistry character with the simulation results. Contained vast oxygen of DME molecule, burned no macromolecule compound and formed well fuel spray are the reason of no smoking. The lower temperature of cylinder is the main reason of lower NOx.