Simulation Study On Heavy-duty Diesel Engine Using Miller Cycle And Its Working Process

During recent years, our living environment has been being devastated seriously especial by the haze crisis which is becoming more and more heavy and it also threatens our safety. As is known to us, the major cause of haze is our car emissions. So not only China’s, global countries’ limits to car emissions are more and more strict, which requires scientists on internal-combustion engine to try their best to decrease emissions of our vehicles while keeping the economic and power performance. The most dangerous and largest in amount one must be NOX among vehicle emissions.With the rapid development of computer technology, numerical simulation analysis and computation of internal-combustion engine are making great progress and used widely.This can not only shorten the developing and designing circle of diesel engine, but also cut down the cost, which has profound meaning to developing and designing internal-combustion engine and predicting the emissions.Software GT-Power is used in this essay to simulate and analyze the intermediate speed heavy-duty diesel engine’s working process and miller cycle is also applied to the engine, and also the emissions will be predicted. After observing the structure of the diesel engine, the physical model is established in the software; The parameters — length and diameter of all pipes、structure sizes of the real engine、injection parameters、injection system、intake and exhaust phase and so on are obtained after referring to relevant data and measuring the real engine, and then select appropriate combustion model after analysis to improve the physical model. Simulate the working process of the diesel engine on the work condition of all rotating speeds and 50% load, using the established model and make a contrast between the results of simulation and experiment. The contrast shows that the errors are all lower than 5%, among the limits which prove that the performance parameters of the diesel engine obtained by the simulation can match with the experiment data well. That proves the model can be used to conduct the calculation coming. Two kinds of miller cycle plans are carried on the turbo-charged diesel engine to conduct the simulation calculation and after comparing the results, the better plan is selected that is changing cam timing miller cycle. What’s more, the optimized early intake valve closing angles are chose on 1000/rpm, 25%、50%、75% and 100% work conditions which are 40、30 、 40 and 30 ° CA respectively. On the basis on it, the research on the effects of compression ratio 、 injection timing and injection pressure on the performances of the engine is conducted, and the reasons are illustrated. Finally, the optimized parameters of them are selected. On all kinds of loads, the optimized compression ratios are 15.4、14.9、15.9 and 14.9,respectively; The optimized injection timings are-10、-8、-8 and-12°CA,respectively; The optimized injection pressures are 110 、 150 、 130 and 130 MPa,respectively. It gives the diesel engine an optimized plan, which has great feasibility, to try its best to decrease NOX emission while keeping certain power and economic performance.