气动真空发生器系统背压与抽吸性能关系分析

对气动系统中常用的真空发生器样机,采用有限体积法对其内部流场进行数值计算,分析了背压不同时内部压力分布和吸入流速改变情况。以此为基础,测量系统背压升高时吸入流量变化量,绘制了背压与吸入流量关系曲线,提出了通过判断系统背压防止逆流现象的方法。在真空发生器系统的设计和应用中,需要在理论计算的基础上,根据试验得出系统正常工作的背压范围,防止逆流现象,保证系统工作。

Relationship between Back Pressure and Suction Ability of Pneumatic Ejector System

Pneumatic ejector is an important vacuum source for agricultural automation. During the application of pneumatic ejector, the increasing back pressure may cause the suction ability to get worse intensely and the normal operation of the system will be greatly influenced. Regarding the ejectors used in pneumatic systems, the air flow was analyzed with finite volume method based on ejector inner mechanical structural parameters. The changes of pressure distribution and suction flow velocity were studied when the back pressure was variable. Based on the theoretical analysis, an experimental apparatus was set up and the suction mass flow rate was measured as the back pressure increased. The relationship between back pressure and suction mass flow rate was obtained. Judging from both of theoretical analysis and experimental result, the suction flow rate characteristics remained unchanged at first and then got worse intensely as the back pressure increased. A method was proposed to prevent reverse flow by estimating back pressure, which was an effective complementary approach for ejector systematic design. When designing a pneumatic ejector system, the back pressure range where the ejector worked normally should be derived both from theoretical calculation and experimental test. Reverse flow could be prevented if the back pressure was controlled within normal range, thus the optimum performance would be achieved.