Numerical Simulation And Analysis On The Effect Of EGR On The Turbo-charging Diesel Engine

Cooled exhaust gas recirculation (EGR) in which a portion of gases leaving the engine are diverted from exhaust through a cooling system, and then remixed with air entering the engine for combustion is the most effective method used to reduce NO_x emission. There is a few model in our country developed for computing the effect of EGR on performance and emissions of a TDi diesel engine. The numerical simulation on the TDi diesel engine has been done to predict the effect of EGR on a heavy-duty DI diesel engine.At first, a common numerical simulation model of a turbo—charging diesel engine is established. The whole system is discretized into many volumes according to the "staggered grid" method. One-dimensional gas dynamic equation has been used to describe the state of gas in any volumes. In simulation, a zero-dimensional combustion model and a NO_x prediction model is used to calculate the combustion in cylinder and NO_x emission respectively. The result of simulation accords with the data of rig.The simulation model of turbo—charging diesel engine is developed. On the basis of the original model, a Venturi mixing valve that combines inlet air and cooled exhaust gas prior to introduction into the cylinder is added to the intake system, and the coefficient of boundary is varied responsing to the change of section geometry of Venturi. The comparison of the EGR rate of simulation and experiment testifies the validity of this method.Modeling the performance such as fuel consumption, exhaust gas temperature, etc. of diesel engine on different EGR rate, it predicts that the effect of EGR on performance of diesel and the degree of effect of different load successfully. The simulation results agree with the experiment data when comparing, and the difference of parameters between the calculation and experiment is controlled in a given range. Calculating the NO_x emission of diesel engine in different EGR rate, it predicts that the effect of EGR on NO_x emission and the degree of EGR effect on NO_X when loading varying. The result is according with experiment data.Modeling the effect of EGR on the combustion process in cylinder, it calculate the pressure VS. crank-angle on different EGR rate. Validating by the experiment, the maximal pressure of the rating point is well according with the experiment.Study the effect of EGR on performance and emission by experiment, validate the calculation result and make up the shortage of simulation. Study the effect of EGR on the emission ,such as HC,CO .