摘要：The EGR (exhaust gas recirculation) technique can greatly reduce the NOx emission of diesel engines, especially when an EGR co.ler is employed. Numerical simulations are applied to study the flow field and temperature distributions inside the EGR co.ler. Three different models of EGR co.ler are investigated, among which model A is a traditional one, and models B and C are improved by adding a helical baffle in the co.ling area. In models B and C the entry directions of co.ling water are different, which mostly influences the flow resistance. The results show that the improved structures not only lengthen the flow path of the co.ling water, but also enhance the heat exchange rate between the co.l and hot media. In co.clusion we suggest that the improved structures are more powerful than the traditional one.