| With the tightening of emission legislation, the development of key technologies for diesel engines such as fuel system technology, EGR technology and electronic control technology have been improved to a great extent.The study of this paper was based on 12 L heavy diesel engine developed. This engine was developed and applied with the external EGR and without SCR system. The engine met the CN IV emission. This system was designed by three-dimensional tool, which simulating 3D model of EGR system to choose the optimal option, and selecting trials to determine the optimal configuration. For the optimal EGR system, aspects as the pipe, the mixer configuration and the valve were paid special attention. The intake air schemes from the 123 cylinder mixing part and the 6th cylinder. Considering the uniformity, pressure loss and disposal, the opposite direction of fresh air with holes was chosen as the EGR outlet. Finally, the butterfly valve with low pressure loss and high flow quality was selected.Validation results of simulation and bench-test showed that when the EGR outlet is bevel connection, engine obtained the ideal overall performance. The cool-butterfly valve could reduce the fuel consumption with no influence of NOx and PM emission covering the middle-low load area of full speed and high load of middle-low speed.Enough EGR ratio is the key goal of matching turbo charger for EGR engine. Matching of high charging ration system, variable flow charging system and turbo charger for EGR engine were introduced in this paper, which was the theory basis of the EGR-turbocharger engine. Considering of the cost, waste gate valve and EGR were chosen to study.The transient control of the EGR diesel became much more complex due to the EGR system. The influence of fuel system and EGR calibration strategy to emission and economy was studied and validated in this paper. The results showed that due to the delay of the supply of the fresh air, combustion worsen leaded to the bad soot emission in the transient state. Through the transient correction of the rail pressure and EGR valve, the soot emission would be decreased.The optimal improving scheme was achieved by EGR optimal design and calculating simulation. Meanwhile, transient correction was demonstrated to testify its necessary to emission. The results showed that China IV emission could be satisfied by EGR combined with turbo charger and fuel combustion system. |
PDF Full Text Request