下游泵送螺旋槽密封空化试验及性能分析

基于自主设计的可视化试验装置及膜温和膜厚测量方法,对下游泵送螺旋槽密封空化特征及性能参数进行试验研究.探讨了油压和转速对不同螺旋槽密封液膜中空穴发生位置、空穴分布及空穴边界的影响,拟合了不同螺旋槽密封空穴边界的试验关系式,并对不同空化模型的理论泄漏量和膜厚与相应试验值进行了对比分析.结果表明:内槽型和中槽型密封的空穴均发生在螺旋槽内,但两者的空穴区形状明显不同;油压的增加有助于抑制液膜中空穴的发生,而转速的增加反之;尤其是内槽型,油压对其空穴发生影响更为显著;在低转速或高油压时,Reynolds和JFO两空化模型均可用于预测泄漏量和膜厚;在高转速或低油压时,JFO空化模型预测值更准确,而Reynolds空化模型预测值偏大.

Cavitation Experiment and Performance Analysis of Downstream Pumping Spiral Groove Seals

Cavitation characteristic of downstream pumping spiral groove seals were investigated experimentally based on a self-designed visualization experimental device and accurate measurement methods for film thickness and film temperature. Effects of rotating speed and oil pressure on the location of cavitation occurrence, cavitation distribution and cavitation boundary were discussed, and theoretical leakage and film thickness calculated respectively from Reynolds and JFO cavitation models were compared with corresponding test values. The results show that the cavitation of both the inner groove and middle groove type seals occurs in spiral grooves, but the cavitation shape is not the same with each other. For the two seals, the liquid film rupture boundaries all locate the helical boundary of back flow side as well as distinct liquid film reformation boundaries exist between the complete liquid film field and the cavitation field along the direction of increased circumference angle, relative to the liquid film rupture boundary. The increasing of oil pressure helps to inhibit the cavitation occurrence, while the increasing of rotating speed is opposite. Especially for the inner groove type seals, effect of oil pressure is more obvious on the cavitation occurrence. Both Reynolds and JFO cavitation models can be used to accurately predict the leakage and film thickness under the situation of lower rotating speed or higher oil pressure, namely, without cavitation or smaller cavitation area. While JFO cavitation model can be more suitable to predict the parameters than Reynolds cavitation model by which the values predicted are rather large under the circumstance of higher rotating speed or lower oil pressure, with larger cavitation area.