The Simulation Research Of Multiple Injection Strategy For DI Diesel Engine

In order to meet increasingly stringent emissions regulations, must optimize combustion, and fuel injection optimizing is an important way of diesel engine combustion optimization. This paper studies the influence of injection rate on diesel engine combustion and emissions.Using commercial CFD simulation software Fire, this paper analyzes the combustion process , NO and Soot formation of the original diesel engine from the point of macro and micro respectively. NO mainly generated in the reverse extrusion gap between piston and the cylinder head and the region away from the wall of the exposure combustion chamber pit in the slow burning and main burning phase . Soot mainly generated near the wall of the exposure combustion chamber pit in the main burning phase .In the slow burning phase and after burning phase generated less. It has diffirent effects on the emissions even diffirent injection timing changes in the same margin.This paper simulates cases for different pilot spray or post spray single parameter and analyzes the result of simulation,then gets that Pre-main injection interval angle has less effect on NO and Soot mass. Duration of pre-injection spray directly determine the kinetic energy and spatial distribution in the combustion chamber, affect the premixed combustion and diffusion combustion ratio indirectly. The more fuel the pre-fuel injection spray, the worse power gets, pre-injection should be controlled below 10%; Besides the post-injection fuel quantity makes greater dynamic impact, post-injection single parameter just has less effect on Soot mass.This paper selects the pilot injection and post injection parameters firstly, and then using orthogonal experiment ,designs 36 cases . Through simulate and compare the results , finds a better fuel injection rate in a shorter time.Results is useful for understanding the diesel engine cylinder combustion and NO and Soot generation process deeply.The research method can quickly optimize the injection rate of a condition and so determine the fuel injection Map map of full conditions, provide a guarantee for the high-pressure common rail diesel technology and the promotion of electronic control.