Shi Weijie

New approach of suppressing cavitation in water hydraulic components

Cavitation frequently appears in high pressure water hydraulic components and leads to serious hydraulic erosions and horrible hydrodynamic noises. In this paper, a novel approach of suppressing cavitation was proposed, inducing the outlet pressure back to the orifice to improve the pressure distribution of throttle valves. In order to realize this approach, an optimized throttle valve chamber structure was designed. After that, the anticavitation performance of the valve was investigated. A theoretical cavitation cloud model was built based on bubble dynamics. In order to solve the mathematic cavitation model, the velocity field and pressure distribution of the novel throttle valve were simulated through Computational Fluid Dynamics(CFD). Combining the simulation results, the mathematic cavitation cloud model was solved through numerical calculations. Moreover, new indexes estimating cavitation intensity were proposed scientifically to investigate cavitation phenomenon. Then, the comparison of the novel throttle valve (with an innovative valve chamber) and traditional throttle valve in anticavitation performance was conducted under different conditions. Finally, the experiment about anticavitation performance was completed on the test rig. The calculation and experiment results indicated that the approach, inducing the outlet pressure back to the orifice, was effective in suppressing cavitation.

Simulation research of grease-releasing mechanism for oil-retaining bearing

Focusing on oil-retaining bearing worked in water environment, simulation analysis of the whole oil-retaining bearing is carried out to investigate the grease-releasing mechanism of sintered metal-powder bearing, and the overflow process is simulated by way of water displacing oil. The result shows that threshold pressure gradient exists while oil flows, and the value of gradient has a complicated relationship with extent of porosity, but it is well correlated with permeability of bearing. The overflow speed of grease is dependent on porosity, the temperature of flow field, pressure, and the overflow speed rises while one of above-mentioned factors increases.