Analysis of oil shedding and ligaments formation on bearing rotary elements

For designing efficient lubrication system of an aeroengine bearing chamber, sufficient knowledge on oil/air two-phase flow characteristics is required. When analyzing bearing chamber two-phase flow, the essential prerequisite is quantifying the oil ligaments, which are detached from bearing rotary elements and shed into the bearing chamber. Related investigations are mainly targeted at liquid shedding on the rotating disk as opposed to the bearing rotary elements. Moreover, the research based on bearing rotary elements is conducted by experiment. Due to the limited operating conditions, experimental studies cannot guide engineering applications. To overcome these limitations, a theoretical model is established in this paper, for revealing the mechanism of oil shedding from bearing rotary elements and quantifying the shedding ligaments. The theoretical model is validated against experimental results from classical studies. In addition, the correlation for shedding ligaments number based on aeroengine bearing structural and operational parameters is obtained via theoretical analysis. The analytical results demonstrate that oil shedding and ligaments formation appear at the edge of bearing inner race outer-periphery. The number of shedding ligaments increases with the rise of shaft rotational speed while decreases with the growth of oil viscosity.     

Synchronous chirp mode extraction: A promising tool for fault diagnosis of rolling element bearings under varying speed conditions

As critical components in modern aerospace productions, rolling element bearings(REBs) generally work under varying speed conditions, which brings great challenges to their operating health monitoring. Some novel time–frequency decomposition(TFD) algorithms are established recently to extract nonlinear features from the non-stationary signals effectively, which are promising for realizing fault diagnosis of REBs under varying speed conditions. However, numerous personal experiences must be incor...     

基于有限元--离散元耦合的粒子阻尼减振研究

在侧挂构型发射任务中，中心承力筒与卫星直接连接，其动力学特性对卫星的振动响应有直接影响。首先分析中心承力筒的模态特性，据此完成粒子阻尼器的结构参数设计。随后，使用有限元--离散元耦合仿真方法，确定了阻尼器填充粒子的最佳直径和阻尼器最佳安装位置。仿真结果表明，该方案下星箭界面减振效果可达40%。最后，使用最优粒子阻尼参数开展水平激励实验。实验结果表明，与未安装粒子阻尼器相比，中心承力筒+粒子阻尼器组合体的减振效果可达35%以上，与仿真结果一致。     

Pressure performance for a thin-walled ring and turbulent-jet orifice modeled elastic squeeze film damper

This paper explores an analytical model for Elastic Ring Squeeze Film Damper (ERSFD) with thin-walled ring and turbulent-jet orifices, and uncovers its Oil Film Pressure Performance (OFPP). Firstly, the ring deformation is addressed by using the Fourier series expansion approach and the orifice outflow rate is characterized with the Prandtl boundary layer theory. Secondly, applying finite difference scheme, the influence of elastic ring flexibility, orifice diameter, and attitude angle on the OFPP is analyzed. Finally, Outer chamber pressure was measured experimentally at different rotor speeds. The results indicate that the outer chamber pressure coats an individual load-carrying region and spreads symmetrically pertaining to the attitude angle. Its amplitude drops as the elastic ring flexibility decreases but boosts with the reduction of the orifice diameter. For inner chamber pressure, the orifice diameter effects a similar trend to the outer cavity, but exhibits more stable distribution regarding the attitude angle. Minimizing the elastic ring flexibility causes an increase in amplitude. The model is validated by the test results giving that the outer chamber pressure shifts synchronously and periodically with the variation of the attitude angle, while the pressure amplitude increases slightly at higher rotor speeds.