3-Dimensional Numerical Simulation and Research on Internal Flow about Different EGR Rates in Venturi Tube of EGR System for a Turbocharged Diesel Engine

Exhaust gas recirculation technology is one of the main methods to reduce engine emissions. The pressure of the intake pipe of turbocharged direct-injection diesel engine is high, and it is difficult to realize EGR technology. The application of Venturi tube can easily solve this problem. In this paper, the working principle of guide-injection Venturi tube is introduced, the EGR system and structure of a turbocharged diesel engine using the guide-injection Venturi tube are studied. According to the working principle of EGR system of turbocharged diesel engine, the model of guide-injection Venturi tube is established, the calculation grid is divided, and it is carried out by using Computational Fluid Dynamics method that the three-dimensional numerical simulation of the internal flow of Venturi tube under different EGR rates injection. The flow field state, velocity field, pressure field and exhaust gas concentration parameters of the mixture formed by air and EGR exhaust gas in Venturi tube are analyzed. The calculation results show that the EGR rate has a great impact on the initial pressure recovery effect before the compression section of the Venturi tube. The greater the EGR rate ejection amount, the worse the pressure recovery effect. In order to meet the requirement of large EGR rate, the Venturi diffuser angle should be reduced while keeping the length of the diffuser section unchanged. The diameter of the throat of the mixing section and the diameter of the EGR ejection port can be appropriately increased, the number of ejection ports can also be appropriately increased. This paper also proves that the Venturi tube of the ejector EGR system can overcome the pressure deficit between the exhaust pipe and the intake pipe of the turbocharged direct-injection diesel engine, which verifies the feasibility of the EGR Technology of the turbocharged direct-injection diesel engine through the Venturi tube.