Effect of injection timing on the combustion and emissionformation of a DI heavy duty diesel engine

Direct injection diesel engines are well established today as the main solution for relevant non-road heavy duty vehicles such as marine, train and etc. At the same time, emission legislation (mainly for NOx and particulate matter) becomes stricter, reducing their limit to extremely low values. The numerical part of the research project performed at AVL Germany is concentrating on the development of a numerical procedure for the simulation of the gas exchange, the mixture formation, the combustion process and the pollutant formation in large common-rail diesel engines. As the target engine is a new generation engine and it is under development, another heavy duty diesel engine is used for validation of the present numerical method. The results of CFD model is in a very good agreement with the experimental results and could be used in this new engine development process with acceptable level of reliability and confidence. This work examines the effect of advanced injection timing on the combustion and emissions characteristics of DI diesel engine. The engine has standard injection timing of 17 BTDC. The numerical tests were conducted at five different injection timings (15, 16, 18 and 19 CA BTDC). By advancing of injection timing, the pressure in the cylinder increases and due to heat release increase in premix step, the amount of total NOx will be increased. Moreover, because of trade-off trend of soot and NOx, the amount of soot will be decreased. The retarding injection timing causes a large amount of fuel being ignited near the top dead center in which makes a rise in pressure and soot.

کلیدواژه ها:

Diesel engine ، Heavy duty ، Low emission ، Combustion modeling ، Spray modeling