U型节流阀流场特性的数值和试验研究

Experimental and numerical investigation of flow field characteristics in a U-shaped throttle valve

液压控制阀的调压精度和工作稳定性依赖于流道内部流场特性的深入研究。基于Schnerr-Sauer空化模型和标准k-ε湍流模型,开展了双U型节流阀内空化流场仿真计算。搭建了可视化试验台,通过高速相机捕捉了透明节流阀内的空化形态流场。通过对双U型节流阀内部流场特性及影响因素的试验和数值分析可知:节流口为主要压降区,由收缩流变为扩散流,是空化发生的主要区域。节流槽出口处的空泡群狭长型,且与出口截面呈一定角度、稳定存在。随着进出口压差的减小,双U型节流阀节流口空化强度进一步缩小,且向节流口萎缩。随着开度的增大,空泡团由团状逐渐收缩为细长状,空化区域及空化强度均呈现先增强再减弱的趋势。此外,一级槽的深度也是影响双U型节流阀内部空化流场的重要因素。一级槽深度减小时,节流槽内阻力增加,压力恢复加快,空化区域及空化强度亦逐渐减弱。随着一级槽深度值减小,高速流范围变小,空化面积亦减小。合理控制双U型节流槽深度,可以有效抑制空化发生程度。

The control accuracy and stability of the hydraulic control valve depend on the in-depth study of the flow field characteristics in a throttle valve.Based on the Schnerr-Sauer cavitation model and the standard k-εturbulence model,the cavitation flow in a U-shaped throttle valve was obtained numerically.A visualization test rig was built,the cavitation flow in the transparent throttle valve was captured by a high-speed camera.The flow field characteristics of oil flow through the orifice of the U-shaped throttle valve and its influencing factors were studied by combining experimental and numerical methods,and the conclusions are as follows:the main pressure drop happens at the throttle orifice,and the flow changes from the contraction flow to the diffusion flow.The throttle orifice is the main area where cavitation occurs.The cavitation bubbles are stable and locate at the outlet of the throttle groove with a certain angle,whose shape are long and narrow.With the decreasing pressure difference,the cavitation intensity in the U-shaped throttle valve is reduced,and the cavitation bubble is shrunk towards the orifice.With the opening degree increasing,the cavitation flow gradually changes from a mass to a slender shape,and the cavitation intensity increases firstly and then decreases gradually.Furthermore,the depth of the first groove is one of the main factors which affects the cavitation flow in the U-shaped throttle valve.When the groove depth decreases,the resistance in the notch increases.The pressure recovery would be speed up,and the cavitation area and the cavitation intensity will also be weakening.With decreasing depth of the groove,the range of high-speed flow becomes smaller,and the cavitation area also decreases.The decreasing groove depth is an effective method to inhibit the occurrence of cavitation.