The Research On Performance Of Dynamic Pressure Type Gas-Oil Separator In Aero-engine

Dynamic pressure type oil-air separator is an important component of small aero engine oil system,a device utilizing centrifugal force for separating oil mixture.It has the advantages of simple structure,compact space,relatively high efficiency,etc.Its performance research is one of the frontier problems at home and abroad.The interior of the separator is a three-dimensional strong swirling turbulent flow.There is a gas-liquid two-phase separation phenomenon involving the complicated flow processes such as crushing,spreading and polymerization of the air bubbles.Therefore,it is difficult to study the flow mechanism and performance of the separator.No mathematical model has been proposed to describe the overall separator performance.In this paper,based on the working principle and conditions of the dynamic pressure type oil-air separator,the performance of the separator is systematically studied by combining experimental research,theoretical analysis and numerical simulation.First,an experimental system for measuring the performance of a dynamic pressure type gas-oil separator was designed and built,the experimental models of 4 different structural forms are systematically studied.Through the analysis of the experimental data obtained,the structural form suitable for specific requirements was given.This paper uses volumetric method to distinguish separation performance,and analyzes the influence of the factors such as the cylinder diameter,the length of the cylinder,the inlet inclination angle and the length of the outlet pipe.The results show that the combined structure of the in-line outlet pipe and the tangential outlet pipe can obtain better separation performance;the inlet inclination angle,the length-diameter ratio,the length and diameter of the outlet pipe have the best value for the best performance of the separator.Secondly,the trajectory model of the bubble in the separator was established by theoretical analysis.The influence of the flow rate,tangential velocity and the diameter of the cylinder on the separation performance was analyzed.The results show that the increasing of the tangential velocity of the oil at the inlet helps to improve the separation performance,however,when it increases to a certain extent,the speed of separation performance improvement slows down;When the average axial velocity is smaller,the influence of the increase of flow rate on the centrifugal force is better than the influence on the residence time of the bubble.The separation efficiency increases with the increasing of the flow rate of the oil,however,when the average axial velocity is better,the influence of the flow rate is opposite;The optimal cylinder diameter was determined within a certain flow range.Again,the numerical simulation method was used to study the two-phase flow field in the dynamic pressure type oil-air separator,and the effects of three different flow parameters and six different structural parameters on the performance of the dynamic pressure type oil-air separator were analyzed.The results show that there were many local secondary flow phenomena inside the separator,oil separator flow does not affect the flow structure;the main factors that cause the pressure drop of the separator are the friction loss inside the cylinder,the rotation dissipation and the shrinking structure of the outlet pipe;With the increasing of temperature,the bottom circulation flow of the separator is gradually changed from a single vortex structure to a double vortex structure,and the separation performance is enhanced;with the increase of oil-gas ratio,the bottom circulation flow is gradually split from a double vortex structure to a triple vortex structure,internal rotation is strengthened,the range of gas core columns is reduced,and the separation efficiency is improved significantly;The optimum structural parameters of separator are recommended.Finally,based on dimensional analysis,the separation and resistance prediction model of dynamic pressure type gas-oil separator was established.The multivariable non-linear fitting error was analyzed.The accuracy of the model was verified by comparison with experimental data.The study showed that the separation efficiency and resistance model established in this paper can be used to accurately predict the separation and resistance performance of a dynamic oil-air separator in a certain range.