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ACTA AERONAUTICAET ASTRONAUTICA SINICA ›› 2015, Vol. 36 ›› Issue (11): 3724-3733.doi: 10.7527/S1000-6893.2015.0032

• Material Engineering and Mechanical Manufacturing • Previous Articles     Next Articles

Neutral flow state analysis of pneumatic servovalves with symmetric underlaps

YIN Yaobao, LI Changming   

  1. College of Mechanical Engineering, Tongji University, Shanghai 200092, China
  • Received:2014-10-23 Revised:2015-01-24 Online:2015-11-15 Published:2015-02-11
  • Supported by:

    National Natural Science Foundation of China (51175378,51475332)

Abstract:

In view of lacking a theoretical basis for null characteristics design of pneumatic servovalves (PSV) with symmetric underlaps, their slide valve stage mathematical model is established according to gas mass flow formula of single orifice. Influencing factors of the neutral flow states of the upstream and downstream orifices are analyzed adopting hypothesis verification method. It shows that at different ratios of supply and exhaust pressure, PSVs of uneven coefficient less than 0.5283 have three combinations of neutral flow state, which are both upstream and downstream orifices in subsonic state, in sonic state, and the upstream orifice in sonic flow while the downstream one in subsonic flow; and PSVs of uneven coefficient no less than 0.5283 have two combinations of neutral flow state, respectively, both the upstream and downstream orifices in subsonic flow, and the upstream orifice in subsonic state while the downstream one in sonic state. So the uneven coefficient of underlaps and the ratio of supply and exhaust pressure jointly determine the neutral gas flow state. Three valves with uneven coefficient of 0.5,1,2 are verified by calculations and experiments. The theoretical analysis is in good agreement with experimental results.

Key words: pneumatic, servovalve, symmetric underlaps, neutral gas flow state, uneven coefficient, ratio of supply and exhaust pressure

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