液力缓速器低充液率工况扰流柱起效条件判定方法

为揭示低充液率下缓速器工作腔内气相主导的流动规律和降低空转状态下的功率损失，针对某车用液力缓速器构建了带有空损抑制扰流机构的叶轮周期流道模型，通过对低充液率不同转速下液力缓速器扰流机构起效过程流场仿真，分析了不同输入转速和不同充液率工况下的制动转矩、容积率、扰流柱挡片压力差3个关键参数的变化趋势.结果表明，制动转矩在20%充液率前后均有明显的状态变化.18%充液率前各参数单调上升且在18%充液率达到极大值，随后在20%充液率达到极小值，而后继续增大.微观两相流动层面上，20%以下充液率时油液和空气分层明显，而后流动失稳并且在20%以上充液率工况油液和空气流动分层不明显；在充液率大于18%以上时，扰流柱挡片上的压力差值大于所设计预紧力，足以压缩扰流柱挡片进入其腔体内.据此确定了低充液率工况的扰流柱起效判定方法，为扰流机构的设计提供了理论依据. 

Determining Method for Spoilers Operating Condition at Low Oil Charging Ratio in Hydrodynamic Retarder

In order to reveal the flow features dominated by gas phase working at low oil charging ratio and reduce idling power loss in hydrodynamic retarder, the periodic flow passage computational model of some type hydrodynamic retarder was built with spoiler which may suppress idling power loss. And the flow filed simulation was conducted to investigate the action process of spoiler inside cascades at low oil charging ratio operating condition, thus the trends of parameters such as braking torque, oil charging ratio and pressure difference of spoiler baffle were analyzed under the operating condition of different input rotating speeds and oil charging ratios. The results show that, braking torque changes significantly around 20% oil charging ratio, it reaches the maximum value before 18% oil charging ratio, while drops at 20% as local minimum value then raises again; at microscopic view the oil and air inside hydrodynamic retarder work as stratified flow below 20% oil charging ratio, however when oil charging ratio surpasses the 20% stratified flow phenomenon gets unintelligible; the spoiler baffle can be pressed into retarder case when its pressure difference value is larger than designed preload spring force. Based on these the determining method is proposed and the theoretical foundation of spoilers inside a hydrodynamic retarder is provided.