Research On Two-phase Flow Characteristics Of Oil-gas In Aero-engine Bearing Chamber

As the power unit of an aircraft,the bearing chamber plays an important role in the high-speed rotating working stage.An in-depth study of the two-phase flow and heat transfer characteristics of oil-gas in the bearing chamber will help improve the working performance and stable operation of aero engines.In this paper,a simplified model of a certain type of aero-engine bearing chamber is used as the research object.A 4109-type aviation lubricant is selected,take its physical and chemical properties as reference,and a VOF multiphase flow model,a RNG k-?turbulence model,and numerical simulation of two-phase flow in bearing chamber by sliding grid technique.The VOF multiphase flow model was used to capture the two-phase interface of oil and gas,and the effects of rotor speed and oil supply amount on the air velocity and lubricant distribution in the bearing chamber were analyzed.At the same time,the heat transfer in the bearing cavity is analyzed numerically,and the influence of the rotating speed and oil supply on the temperature field in the bearing chamber is investigated.In view of the above work,the main conclusions of this paper are as follows:（1）Affected by the distribution of lubricating oil and the movement of the gas phase,the temperature field of the bearing chamber in the circumferential direction shows that the temperature of the upper part is higher than the temperature of the lower part;In the axial direction,the temperature near the inlet side of lubricating oil is lower than that of the air inlet side.（2）The extent of lubricating oil temperature rise is proportional to the contact area between the lubricating oil and the outer wall surface.It is pointed out that to improve the fluid-solid heat transfer ability,increasing the contact area between the oil phase and the outer wall surface is an effective way.（3）The distribution characteristics of lubricating oil in the circumferential direction are:the rotation speed is increased,the accumulation position will be more upward,the residence time is increased,and the heat transfer between fluid and solid is strengthened.With the increase of oil supply,the volume of lubricating oil in the bearing chamber increases,so the lubricating oil is more likely to accumulate,and the position of oil phase accumulation and accumulation is closer to the oil return port,and the residence time in the bearing chamber is reduced,so that the unit volume of lubricating oil Less heat absorption.（4）As the speed of the bearing increases,the temperature rise increases when the lubricant leaves the bearing chamber,and the heat per unit mass of lubricant takes away more.Through the analysis of the data,the relationship between the Nusselt number and the Reynolds number of the bearingrotor（Re _U）is fitted:Nu～Re _U^0.391.The change of oil supply amount has little effect on the wall heat transfer coefficient.The analysis results indicate that a higher fuel supply is more suitable for applications with high speed or high air intake.Through the numerical simulation analysis of the flow field and heat transfer characteristics in the bearing chamber,some reference is provided for solving the characteristics of oil and gas movement and structural optimization in the bearing chamber.