Structure Design And Heat Transfer Performance Optimization Of EGR Cooler For National Six Diesel Engine

Nowadays,the problem of environmental pollution is very serious in the world.All the countries are looking for new energy to replace traditional energy.In the field of automobile,people are trying to find ways to reduce pollutant emissions.With the continuous development of the times,people generally praise diesel engine,because diesel engine has such huge advantages as high thermal efficiency,high power,high torque and good reliability,And the diesel engine has good economy and power performance.Due to many advantages of diesel engine,modern technology diesel engine is gradually becoming the main vehicle power in various countries.Now the trend of vehicle power diesel has become the consensus of the international automotive industry.With the implementation of the higher emission standard of the sixth national standard,EGR cooler has been widely used in diesel engine to achieve the combustion process of high efficiency and low emission.In this thesis,the structure design and heat transfer performance analysis and optimization of EGR cooler for a diesel engine are carried out according to the national six emission standards.Firstly,the types of EGR cooler and the basic theory of heat transfer equation are briefly introduced.The outlet temperature of coolant is calculated,the average temperature difference is calculated,the heat transfer area and total heat transfer coefficient are calculated,and the calculation parameters are obtained.Then,the three-dimensional model of pitted tubular EGR cooler is established in CATIA software,Next,the simulation analysis of the pitting tubular EGR cooler is carried out.Similarly,the mathematical model of heat transfer,fluid flow,turbulence model and ideal gas law are introduced.Then the surface heat transfer coefficient is calculated by using temperature field.Then the model is imported into mesh module of ANSYS software for mesh generation.Finally,the finite element pre-processing and solution setting are carried out in ANSYS fluent software,The temperature field,pressure field and heat transfer efficiency of the EGR cooler are analyzed by simulation.Then change the structure of EGR cooler,change the pit tube structure into the inner fin structure,and then analyze according to the above method,carry out three-dimensional modeling in CATIA software,divide the mesh in mesh module of ANSYS software,preprocess the finite element model in ANSYS FLUENT software,and then carry out solution setting and simulation analysis,The simulation results of temperature field of inner fin EGR cooler are obtained.After that,the temperature field and heat transfer efficiency of the pitting tube EGR cooler and the inner fin EGR cooler are compared and analyzed.Through the comparison,it is concluded that the indexes of the inner fin EGR cooler model are better than the pitting tube EGR cooler.Therefore,the structure of the inner fin EGR cooler is optimized.In order to further meet the design requirements and reduce the gas side pressure difference as far as possible,the fin ripple amplitude is optimized.The 3D modeling of CATIA software,mesh generation in ANSYS software and preprocessing of finite element model in ANSYS FLUENT software are also carried out,The simulation results show that the heat transfer efficiency is 86.43%when the ripple amplitude A = 0.9 mm.Finally,the experimental verification was carried out,and the sample manufacturing and heat transfer performance test were carried out.The measured heat transfer efficiency was88.55%.After analysis,we can see that the experimental and simulation data are in good agreement,and the designed EGR cooler has high heat transfer efficiency,and has a certain design margin.It is feasible through simulation and experimental verification.