Study Of Reducing Turbocharged Internal Combustion Engine Emission Using EGR Technology

With the development of global automobile industry, the pollution caused by automobile exhaust gas has become more and more serious, especially NOx pollution. During these years, the government recognizes the problem and legislates to limit the exhaust emission. As the main power source of vehicle, the question how to purify NOx emission for diesel engine has become one of the hotspots. Now, technology of EGR is known as the effective method to purify NOx emission, which is available for diesel engine.The external EGR and internal EGR of the turbocharged engine are introduced in this article. The mechanism of nitrogen oxides formation and how the EGR can reduce the NOx emission are studied, and we have done the test experiments of the external EGR on a turbocharged diesel engine, The main contents includes:(1) EGR is an effective method to reduce NOx emission. But at higher load the mean pressure of exhaust pipe is lower than that of intake pipe, common EGR system can not work effectively. A new EGR system with Venturi pipe has been designed based on a diesel engine, this EGR system can reduce the pressure of intake pipe, and it is easy to introduce the exhaust gas into the intake pipe, and made the pressure of mixture of intake air and EGR gas come back to the original inlet pressure. The flow characteristic of venture pipe has been investigated and the EGR rate has been found out at different operating conditions to suit the Tier 2 emission regulation. This paper also shows the relationships between EGR rate and NOx, smoke and fuel consumption. The EGR rate range which NOx smoke and fuel consumption can all accepted has been found out. The effect of cooled EGR is also described in this paper. The result shows that cooled the recalculating exhaust gas can reduce the NOx emission more effectively. This research can be applied widely.(2) New cam profiles by changing the cam's phase angle in order to achieve the internal EGR are studied, and we can reduce the engine's HC and NOx emission by decreasing the overlap angle of the engine.At last, the internal EGR of a turbocharged engine is studied.