Mechanism Model Research And Numerical Simulation On Dynamic Pressure Type Gas-oil Separator

Dynamic pressure type lubricant-air separator is a degassing apparatus of lubricantsystem in aeroengine. it separates the gas from lube due to the centrifugal force produced by aswirling motion of the incoming gas and lube mixture. It has a simple and compact structurewithout inner swirling part and high separation efficiency. However the flow in separator isvery complex especially when it involves three-dimensional turbulent flow with strong vortex,two-phase hydrodynamics, bubble breakup and bubble coalescence mechanism, so it is achallenge for experimental measurement and numerical simulation. So far the complexphenomena taking place in separator are not fully understood, and the methods to predict theperformance is unavailable yet,The main way to design separator is based on experience. Inthis thesis, the distributing and separating characteristics of two-phase field are researchedthrough mechanism model and CFD simulation, which provides a reference for the design.The following two parts are the main work in this dissertation.1.First, the mechanism models are built for each part of the separator according to thefluid phenomenon, which includes inlet model, vortex shape model,the lube velocitypredicting model and bubble trajectory model. Then the method to calculate the seperator sizeis provided conbining to such models mentioned above.finally,the built bubble trajectorymodel is used to study the separating performance of the separator, in which the main task isto study how the variables like tangential velocity, diameter of the separator and rate of flowmake an influence on the separating efficiency. The solution shows that the higher tangentialvelocity is, the better separating performance the separator can have and based on the rate offlow, the suitable diameter is decided.2.First, the suitable turbulence model is chosen based on the inner field nature of theseparator which is obtained by simulation through CFD software Fluent. Then the solution fortwo-phase fluid field inner the separator obtained by mixture model shows that the locationwhere has the maximum pressure can make a difference to separating efficiency. Soimprovement like lowering the pressure around oil outlet has been made to increase theseparating efficiency. At last, the bubble trajectory is simulated by DPM model for the part oilregion below the inlet, in order to research how the turbulence dispersion, bubble diameter,tangential velocity, rate of flow and the length ratio can affect the gas carry-under, which provides a reference to the design of separator.