Investigation Of Flow, Heat Transfer And Structure Optimization Of U Type Shell-and-tube EGR Cooler

In recent years,the rapid development of automobile industry make the vehicle emission pollution has become one of the main source of environmental pollution.With the increasingly serious energy crisis and pollution problems,auto emission regulations become more and more stringent.Technology of exhaust gas recirculation(EGR)can effectively reduce the internal combustion engine NOx emissions,as well as impact the internal combustion engine power performance,fuel economy and particulate emissions of different level.The performance of EGR cooler heat transfer play a vital role in EGR system.Thermal stress caused by uneven distribution of temperature is an important reason lead to structural failure of the EGR cooler.Therefore,based on a 2.0 L diesel engine EGR system of cooler as the research object,on the heat transfer and flow structure optimization has important engineering application value.This article is based on a new U type tube shell-and-tube EGR cooler,established this EGR cooler 3 d model,and based on this model,the threaded tube thread pitch,tube slot and tube width these three threaded tube key structure parameters set five variable levels respectively,and analyzes these several variables' effect on mesh number and the heat transfer surface.Then in the finite element analysis software ANSYS simulation analysis platform is established,and different model were used for the simulation calculation.The basic model of temperature field,pressure field and velocity field were analyzed,and the results with the experimental bench and the simulation calculation were compared.The deviation of simulation and experimental comparison between the data of temperature is 1.56% and the data of pressure drop is 3.56%,which in the range of allowable engineering calculation.Verify the feasibility of the simulation.Also explores the thread pitch,tube slot and tube width impact on cooler heat transfer and pressure drop characteristics.The thread pitch,tube slot and tube width gradually decrease influence on cooler heat transfer characteristics.Then,the structure of EGR cooler shell side and tube side were optimized respectively.In the shell side to join the bow baffle and in tube side to interpolate twisted tape,to strengthen heat transfer.Explores the influence of baffle plate number on the cooler interior temperature field,pressure field and velocity field,and the effect of heat and pressure drop brought by baffle plate number change are analyzed,and appropriate to join the shell side of the baffle plate can improve the temperature within the dense area.As for insert twisted tape,the length,width and pitch these three key structure parameters of twisted tape changed,and the level of each parameter set five variable,and carries on the simulation of these models,compared the heat and pressure drop characteristics of before and after the change,shows the significant effect of twisted tape.When inserted into the prototype twisted tape under the maximum gas flow,the outlet temperature decreased 34.87?,in thermal efficiency increased by 7.98%,the outlet pressure drop decreased 0.054 kPa pressure drop resistance reduced by 0.32%.Finally,respectively discusses the twisted tape between the length,width and pitch of the effects of exchange heat and pressure drop characteristics.The twisted tape length,pitch and width gradually decrease influence on cooler heat transfer characteristics.In this paper,the research contents can be for the future analysis on heat and pressure drop characteristics of the automobile EGR cooler and provide the certain reference value for cooler design and production,and this simulation method can be used for other type coolers' simulation calculation.The established testing system to verify the simulation method is feasible.