具有对称均等负重合量的气动伺服阀零位流动状态分析

分析了具有对称均等负重合量的气动伺服阀在不同供气压力时上游供气节流口和下游排气节流口的流动状态。排气压力为一个标准大气压，供气压力小于0．2374MPa时，零位时的上游两个供气节流口和下游两个排气节流口均为亚音速流动；供气压力等于O．2374MPa时，零位时的上游两个供气节流口为亚音速流动，下游两个排气节流口处于临界流动，即亚音速流动和超音速流动的分界点；供气压力大于0．2374MPa时，零位时的上游两个供气节流口为亚音速流动，下游两个排气节流口为超音速流动，且在零位处的负载压力为供气压力的80．75％。

Flow Characteristics at Neutral Position of Pneumatic Servovalve with Symmetric Even Underlaps

The flow characteristics of control orifices of a pneumatic servovalve with even underlaps under different supply pressure are discussed. The four control orifices of upstream side and down stream side of the pneumatic servovalve at neutral position are subsonic flow when the supply pressure is less than 0.2374MPa. The two control orifices of upstream side of the pneumatic servovalve at neutral position are subsonic flow, but the two control orifices of downstream side are critical flow when the supply pressure is 0.2374MPa. The two control orifices of upstream side of the pneumatic servovalve at neutral position are subsonic flow, but the two control orifices of downstream side are sonic flow when the supply pressure is large than 0.2374MPa, and the pressure of the load ports at x=0 is as much as 80.75% of the supply pressure for a servovalve with symmetric and even underlaps of the spool valve.