Abstract
The research of oil/air two-phase flow and heat transfer is the fundamental work of the design of lubrication and heat transfer in aero-engine bearing chamber. The determination of impact state criterion of the moving oil droplets with the wall and the analysis of oil droplet deposition characteristics are important components. In this paper, the numerical analysis model of the impact between the moving oil droplet and the wall is established by using the finite volume method, and the simulation of oil droplet impingement on the wall is carried out. Then the effects of oil droplet diameter, impact velocity, and incident angle on the characteristic parameters of impact state are discussed. The characteristic parameters include the maximum spreading length, the maximum spreading width, and the number of splashing oil droplets. Lastly the calculation results are verified through comparing with the experimental results in the literature. The results show as follows: (1) The maximum spreading width of oil droplet firstly increases and then slows down with the incident angle and the oil droplet diameter increasing; (2) when the oil droplet diameter becomes small, the influence of the incident angle on the maximum spreading length of oil droplet is obvious and vice versa; (3) with the impact velocity and diameter of oil droplet increasing, the maximum spreading width of oil droplet increases firstly and then slows down, and the maximum spreading length increased gradually; (4) the number of splashing oil droplets increases with the incident angle and impact velocity increasing; and (5) compared with the experimental data in literature, the critical dimensionless splashing coefficient K c proposed in this paper can better distinguish the impact state of oil droplet.
Highlights
Lubrication oil is supplied to roller or ball bearings via an under-race lubrication method and sheds into aero-engine bearing chamber in the form of oil droplets
Gorse et al [17] carried out an experimental study on the oil droplet generation by roller bearing in a wide range of engine conditions, the results revealed that the pressure across the bearing and the structure of the bearing support had strong influence on the generation of oil droplets
The deposition characteristics of oil droplet are calculated under different operating
Summary
Lubrication oil is supplied to roller or ball bearings via an under-race lubrication method and sheds into aero-engine bearing chamber in the form of oil droplets. Mundo et al [2] observed the impact phenomenon of alcohol, water, and solid wall through experimental research, analyzed the influence of physical parameter of solution, impact parameter and droplet diameter on the collision, and introduced the characteristic parameter as the criterion for judging whether the droplet splashes or not. Carried out an experimental study on the impact between the droplet and the inclined wall, found the phenomenon of spread, rebound, and splash appeared after the impact between the droplet and the solid surface, and analyzed the influence of the incident angle and impact velocity of the droplet on the spreading characteristics and rebound rate of the liquid film. Chen et al [19] established the oil droplet movement model in the air fluid by Lagrangian method, and analyzed the deposition characteristics of the moving oil droplet after colliding with the bearing chamber wall. The quantitative analysis of the number of splashing secondary oil droplets could provide the initial condition for further research on coalescence and breakup of the secondary oil droplet in the bearing chamber
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