Numerical Simulation Study On Separation Performance Of Oil-air Separator For Engine

Energy conservation and emission reduction have become a common theme ofthe automotive industry in the world today, the strict emission regulations require tocontinuously improve the automotive crankcase ventilation system performance.Oil-gas separator is a necessary functional component of the crankcase ventilationsystem in a plastic valve chamber cover, which has an important impact on thestability and security of the engine work. Therefore, the design and performanceresearch of the oil-gas separator is one of the most important part in the design anddevelopment process of the plastic valve chamber cover.Due to the short development cycle and low cost advantage of computernumerical simulation technology, it is widely used in engineering. In this paper,computational fluid dynamics numerical simulation method is used in the study. Thesimulation of two-phase flow field of the labyrinth oil-gas separator in the plasticvalve chamber cover is performed by using CFD software FLUENT. The result offlow field distribution law and oil droplet trajectory can provide theoretical supportfor the subsequent design and development.This paper first introduced the numerical simulation theory of gas-liquidtwo-phase flow, including the calculation method of the single-phase flow simulation,the mesh model generation, the numerical model and calculation method of gas-liquidtwo-phase flow. Then the two-phase flow numerical model and the boundaryconditions, which are applicable to the study object in this paper is determined.In the calculation of the two-phase flow field in oil-gas separator, the continuousphase gas flow field is calculated first to get the distribution of the pressure andvelocity field and pressure difference between the import and export of the separator.Afterwards discrete phase of oil droplets particles are added to the continuous phaseflow field, discrete phase model and stochastic tracking model are used to simulatethe trajectory of the oil droplet particles, and the oil-gas separation efficiency iscalculated. In order to study the oil-gas separator performance under variousconditions, the piston leakage amount, the oil content in the gas mixture and thediameter of the oil droplets are changed during the calculation of the separation efficiency, so as to analyze the influence of these variables on the separationperformance.It shows the distribution law of continuous phase flow field of oil-gas separatorthrough a series of simulation. By analyzing we get the air motion characteristics inthe flow field and the main sources of pressure loss. In the simulation results of thetwo-phase flow field, the separation efficiency of droplets in different particlediameters are obtained, and the influence and reasons of the piston leakage amountand the oil content in the gas mixture on the separation efficiency are also illustrated.The paper also shows the flow characteristics of the particles in different diametersaccording to the trajectory of the oil droplets. The calculation results give basis andreference for the oil-gas separator performance improvement.