In order to improve the inadequacy of the current research on oil droplet size distribution in aero-engine bearing chamber, the influence of oil droplet size distribution with the oil droplets coalescence and breakup is analyzed by using the computational fluid dynamics-population balance model (CFD-PBM). The Euler–Euler equation and population balance equation are solved in Fluent software. The distribution of the gas phase velocity field and the volume fraction of different oil droplet diameter at different time are obtained in the bearing chamber. Then, the influence of different initial oil droplet diameter, air, and oil mass flow on oil droplet size distribution is discussed. The result of numerical analysis is compared with the experiment in the literature to verify the feasibility and validity. The main results provide the following conclusions. At the initial stage, the coalescence of oil droplets plays a dominant role. Then, the breakup of larger diameter oil droplet appears. Finally, the oil droplet size distribution tends to be stable. The coalescence and breakup of oil droplet increases with the initial diameter of oil droplet and the air mass flow increasing, and the oil droplet size distribution changes significantly. With the oil mass flow increasing, the coalescence and breakup of oil droplet has little change and the variation of oil droplet size distribution is not obvious.

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 $Kc$ proposed in this paper can better distinguish the impact state of oil droplet.

为了研究强脉冲激光在镁合金中诱导冲击波的衰减,采用Nd:Glass脉冲激光(1054 nm,23 ns)对AZ31B变形镁合金试样表面进行冲击,并利用响应快、测量范围大的PVDF压电膜传感器以及示波器实时测量了强脉冲激光在镁合金靶中诱导激光冲击波的相对压力.根据冲击波每次在靶材背面反射时,所经过距离的不同得到激光冲击波在镁合金中的衰减规律.结果表明,在激光能量为5J的强脉冲激光作用下,镁合金中冲击波衰减的平均速度为5.83×103 m/s,与镁合金中应力波纵波的传播速度相符;强脉冲激光诱导冲击波在镁合金中是以指数规律衰减的.试验所得分析结果对激光冲击强化镁合金的应用具有重要意义.

MATEC Web of Conferences, open access proceedings in Materials science, Engineering and Chemistry

The dynamic pressure oil-air separator plays a vital role in aero-engine lubrication systems, as its performance directly determines overall reliability and efficiency. To enhance lubrication performance, it is essential to understand the internal flow characteristics within the separator. In this study, a Mixture multiphase flow model was employed to numerically investigate the oil-air two-phase flow field inside the separator. The effects of inlet velocity and initial oil-air ratio on the distributions of air phase, tangential velocity, and axial velocity were systematically analyzed to elucidate the correlation between flow field structure and separation performance. Numerical results indicate that the tangential velocity distribution conforms to a Rankine vortex structure: a forced vortex exists in the central region, while a free vortex forms near the wall. Axial velocity is negative near the central axis, indicating air motion toward the outlet, and positive near the wall, representing oil motion toward the bottom. At an initial oil-air ratio of 7:3, increasing the inlet velocity from 3.5 to 4.5 m/s stabilizes the internal swirling flow and mitigates air accumulation at the bottom, raising separation efficiency from 90.7% to a maximum of 93.9%. Moreover, a higher initial oil-air ratio facilitates a stable, continuous oil film along the wall, suppressing turbulent interphase mixing. Consequently, at 4.0 m/s, increasing the ratio from 7:3 to 8:2 further enhances efficiency from 92.5% to 93.3%. Numerical predictions agree well with experimental data, with a maximum error of 6%.