A study of NOx emission reduction by using EGR and Miller cycle on heavy two-stroke diesel engine 2019-01-0945
In this paper, the influences of EGR and Miller cycle of heavy two-stroke diesel engine on NOx emission were investigated. In the IMO Tier Three emission regulations, the NOx emission was tightly restricted so that single emission reduction technology cannot meet the requirements very well. There is no doubt that EGR is the most effective way on reducing NOx emission, but the fuel consumption increasing at the same time. In consideration of emission reduction with economical efficiency, EGR and Miller cycle were used together in the simulation. Their performance of in-cylinder pressure, in-cylinder temperature, mass in chamber, emission (NOx and soot) and fuel consumption were simulated on single-cylinder 3D model. In model constructing, the wet condition was considered (take the difference between real using environment and experiment environment in to consideration). And comparing with the experimental data, the error of the basic model is in the acceptable range. The simulation result shows the "trade-off" relationship between NOx and soot under EGR, and also the performance of reducing NOx in different load. Then using Miller cycle (achieve by delay the closing timing of exhaust valve with intake boosting) to optimize the fuel consumption base on the EGR results. Finally, the combustion conditions under different EGR ratio and different Miller cycle condition was reflected by in-cylinder pressure, the contours of in-cylinder temperatures and the generating area of NOx, and according to the simulation results of EGR and Miller cycle, The optimum scheme was giving out to satisfy the IMO Tier Three with better fuel economy performance.
Zhijie Zhu, Xingyu Liang, Yuesen Wang, Bo Liu
State Key Laboratory of Engines, China Shipbuilding Power Engineering Institute