Structural Design And Rainwater Separation Rate Of Automotive Air Intake System Based On Two-Phase Flow

The intake system of an automobile internal combustion engine is generally composed of an intake pipe assembly and an air cleaner assembly.The intake pipe assembly is first exposed to the atmospheric environment,and an air-based flow field environment is formed at the air inlet.After entering the intake manifold assembly,the complex flow field formed by the labyrinth inlet further functions to purify the air and separate impurities.Finally,the air filter assembly completely purifies the air,giving the internal combustion engine a clean,good combustion work environment.Therefore,the intake system is a very important part of the vehicle's power system.Its structural parameters and layout are directly related to the dynamics,economy,reliability and environmental protection of the internal combustion engine.Rainwater separation is one of the important functions of the intake system.If the intake system is flooded,it will reduce the filtration efficiency of the air filter and increase the intake resistance.At the same time,a large amount of fine water mist enters the cylinder of the internal combustion engine through the intake pipe,which may result in insufficient fuel combustion,causing insufficient power and premature failure of the oil in the oil pan.In addition,a large amount of steam containing exhaust gas enters the exhaust aftertreatment system,which easily leads to failure of the post-treatment function,resulting in excessive exhaust emissions.When the water inlet condition is severe,it may even cause the broken rod in the cylinder to cause the engine to be scrapped.Based on the work requirements of the company's product quality improvement,this paper selects the truck product currently equipped with a 6.87-liter displacement 6-cylinder engine as the research object,and studies the air filter discovered during the actual operation of the product under rainy conditions.Firstly,according to the air demand under high engine rated power and idle speed,by optimizing the air flow speed at the high air intake,a grille air intake with a certain shielding function is designed by Pro/e three-dimensional modeling software.An intake manifold assembly having a swirling flow and a labyrinth configuration.Based on the computational fluid dynamics(CFD)theory,the flow field analysis of the intake system was carried out using STAR-CCM+ software,and the visual two-phase flow field of the intake duct was obtained.Based on the air-rainwater two-phase flow theory,the rainwater separation rate of the intake system under three raindrop sizes is calculated and compared with the currently used cyclone inlet scheme.Under the condition that the engine rated power is high and the idle speed is working,and there is no external fluid interference factor,when the angle of the grille at the high inlet of the intake system is 20°~25° and the air flow rate is 2~3m/s,the grid The water inlet rate of the grid intake system is significantly reduced.Finally,the test of the intake system was carried out in the rain shower workshop to determine the final solution of the product,and to some extent solved the problem of water intake of the vehicle intake system under rainy conditions.