Flow Field Simulation And Structure Optimization Of Heavy Vehicle Intake System

Recently,with the increase of automobile amount in China,the environmental pollution caused by automobile exhaust has become more and more serious,especially the pollution caused by particulate matter from heavy vehicles.In order to limit the emission of particulate matter in automobile exhaust,the state has also issued relevant emission regulations which put forward higher requirements for the emission limits of particulate matter in automobile exhaust.In order to make the emission of particulate matter in automobile exhaust meet the requirements,it is an effective way to start with the automobile intake system.While the high intake port and air filter are important components of the intake system and have an important impact on the performance of the engine,which can provide clean and sufficient air for the engine to fully burn the fuel in the engine,reduce the emission of particulate matter in the exhaust gas,reduce the wear of engine cylinders and extend the life of the engine.Although the current intake system has higher filtration efficiency,its pressure drop is also larger,thereby increasing the power loss of the engine.Therefore,the structure of the main components of the intake system needs to be optimized to reduce the pressure drop of the intake system.In this study,the high intake port and air filter of heavy truck were studied by numerical simulation method.For high intake port,the accuracy of Reynolds stress model and Discrete-Phase stochastic trajectory model to simulate the flow field and the raindrop separation efficiency are verified through experiments.Then,the two-phase flow of high intake port was simulated and the effects of grille angle,flashing and flashing structure on high intake port flow field and raindrop separation efficiency were analyzed.While for air filter,according to the existing problems of air filter,a new type of air filter was proposed,and the structure parameters of it designed.Also,the accuracy of the flow field simulation of air filter using k-εmodel and porous media model was verified by experiments.On one hand,based on the k-εmodel and the porous medium model,the flow field of the new type of air filter was simulated,and the influence of cone structure parameters on the flow field of new type of air filter was analyzed.On the other,based on response surface methodology,the cone structure parameters of new type of air filter were optimized with pressure drop as optimization objective,and the optimal cone structure parameters and operation parameters were obtained.The results show that:(1)The experimental results were compared with the simulation values.The error between the two models is less than 12.16%,which shows that it is feasible to simulate flow field of the high intake port and raindrop separation efficiency by using k-εmodel and DPM model.(2)With the decrease of the grille angle,both the pressure drop of the high intake port and the uniformity of the flow field increase.With the addition of flashing structure,the pressure drop of the high intake port increases,but the uniformity of the flow field decreases.The improved high intake port can not only reduce the pressure drop of the high intake port,but also improve the flow field uniformity of the high intake port.The efficiency of raindrop separation increases with the decrease of the grille angle.When the grille angle is less than 25~o,if the grille angle continues to decrease,the increasing speed of raindrop separation efficiency will slow down,while the pressure drop will rise in a straight line.When the grille angle is greater than 30~o,if the grille angle continues to increase,the pressure drop of the high intake port will decrease a lot,and the raindrop separation efficiency of the high intake port will also drop sharply.With the addition of flashing structure,the separation efficiency of raindrops is increased by about 20%.The separation efficiency of raindrops between optimized high intake port and original high intake port is:high intake port A>high intake port D>high intake port B>high intake port C.The separation efficiency of raindrops under different rainfall intensities can reach more than 85%,which is as follows:heavy rain>medium rain>light rain.While the separation efficiency of the high intake port for raindrops with different particle sizes can reach more than 82%,which with larger particle sizes is higher than that with smaller particle sizes.(3)The error between the experimental results and the simulated values is less than 11.32%,which shows that it is feasible to simulate the flow field of the air filter by using k-εmodel and porous medium model.(4)Compared with ordinary air filter,cone structure can not only reduce the pressure drop of air filter by 20%,but also improve the uniformity of flow field of it.It is also found that with the increase of the cone height,the flow field uniformity of the air filter becomes worse and the pressure drop is not uniform.With the increase of cone top radius,the flow field uniformity of air filter becomes worse,and the pressure drop decreases first and then increases.With the increase of cone fold height,the flow field uniformity of air filter becomes worse,and the pressure drop increases.(5)Through the analysis of response surface methodology,it can be seen that the cone height h,cone top radius r,cone fold height b1 and inlet wind speed v all have influence on pressure drop,and the significant effect is:v>b1>r>h.There are optimum structural parameters and operating conditions to minimize the pressure drop of the new type of air filter.And within the parameters range of this study,there are optimum structural parameters and operating conditions to optimize the pressure loss of the new air filter,which is 1998.95Pa.The optimum structural parameters h=300mm,r=40mm,b1=30mm,and the optimum operating parameters v=17.66m/s.