Flow And Heat Transfer Analysis In Bearing Chamber And Improvement Of Scavenge Structure

As the interface between the oil and the sealing device,a complex oil and gas two-phase flow and heat transfer process occurs in the bearing cavity,and the flow state and heat transfer capability of the oil seriously affect the stability and reliability of the working of the bearing cavity.To master the flow and heat transfer characteristics of the two-phase flow field in the cavity is an important basis for the design and improvement of the bearing cavity structure.In this paper,an aero-engine test part model is used as the research object,and the method of CFD(Computational Fluid Dynamics)is adopted to study the flow and heat exchange in the cavity and improve the scavenge structure.First,the two-phase flow and heat transfer characteristics in the bearing cavity were analyzed under different speed and oil supply conditions.The results show that the increase of rotational speed and oil supply quantity makes the circumferential distribution of slip oil more uniform and strengthens the wall heat transfer,while the increase of rotational speed leads to the decrease of axial distribution uniformity and the decrease of oil return efficiency;the increase of oil supply quantity brings the increase of slip oil accumulation in the oil return port.Secondly,the effects of oil droplet diameter,impact speed and angle on its spreading and heat transfer characteristics were investigated,based on which,the upper and lower wall structures of the oil return port were improved for the problem of oil accumulation.The results show that increasing the oil droplet diameter,impact speed and angle,and reducing the wall contact angle can improve the spreading coefficient and wall heat transfer capacity;the local heat transfer coefficient at the front edge of the oil film is higher than other locations;the "concave" upstream wall surface can effectively improve the oil film flow rate and reduce the accumulation;the "concave" downstream wall surface can quickly attenuate the heat transfer property.The "concave" downstream wall surface can quickly attenuate the oil droplet momentum and reduce the circumferential climbing distance.Finally,the improved scavenge wall surface is applied to the bearing cavity,and a bearing cavity model with concave wall return port is established to investigate the effect of the return port depth and width on the flow heat transfer and oil return efficiency in the cavity.The results show that increasing the depth and width of the scavenge can increase the oil return efficiency0.73～10.68%.The comprehensive performance of the scavenge structure with h=2/9R-w=2/3R is the best.