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| Analysis of internal friction and viscosity-temperature effect on vaporization and properties of sealing liquid film |
| (School of Engery and Power Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013， China) |
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Abstract Due to the factors of high water temperature in the sealed medium and internal friction heat generation in the lubricating film, the waterlubricated mechanical seals often cause vaporization of liquid film and affect sealing performance. To investigate the influence of viscositytemperature effect and internal friction effect on the vaporization and sealing performances of liquid film,a computational model of liquid film vaporization was established,and the relationship between saturation temperature and pressure of water, the viscositytemperature effect and the fluid internal friction effect were taken into account. The results show that the two effects mainly affect the properties of lubricating film and sealing performance through the change of medium viscosity. For the sealing medium with high temperature, the temperature change of the lubricating film mainly depends on the temperature rise caused by the internal friction heat and the temperature drop caused by the normal temperature pumping flow. The viscosity temperature effect reflects the temperature change in the viscosity change, and it also causes the changes in internal frictional heat, pumping effect and dynamic pressure effect to affect film pressure, film temperature and phase transition. The two effects have obvious influence on film pressure and film temperature at high speed. When the rotational speed is lower than 5 000 r·min-1, with the increasing of speed, the liquid phase vaporization is significantly suppressed, and the vaporization degree is decreased rapidly. When the rotational speed is higher than 5 000 r·min-1, the internal friction heat heating, the increase of vaporization in diffusion gap and the carrying and diffusion of highspeed flow on the vapor bubble caused by the high rotational speed can increase the degree of vaporization, while the result of ignoring two effects is significantly deviated. The internal friction effect decreases the opening force and increases the leakage, while the viscositytemperature effect increases the opening force and decreases the leakage.
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Received: 10 October 2019
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