Numerical simulation and experimental research on flow force and pressure stability in a nozzle-flapper servo valve

Jian Kang, Zhaohui Yuan, Muhammad Tariq Sadiq

Research output: Contribution to journalArticlepeer-review


In the nozzle flapper servo valve, the transient flow force on the flapper is the fundamental reason that affects the pressure stability. The pressure pulsation in the pilot stage causes forced vibration of the flapper, and its deviation will directly influence the control pressure difference, which will make the pressure appear unstable. In order to grasp the principle and characteristics of transient flow force and its influence on pressure stability, a mathematical model of flapper displacement and control pressure is derived. For collecting the dynamic changes of the transient flow force and recording the motion behavior of the flapper, a three-dimensional model of the pilot-stage is established. Numerical simulations of turbulence phenomenon analysis are conducted with a variation of flapper displacement ranging from 5 µm to 20 µm. It can be concluded that the change trend of the flapper displacement is similar to the steady-state flow force and the transient flow force pulsation amplitude. Under the same structural parameters, the pulsating frequency of the flow force remains basically constant. The fluctuation of the flow force of the pilot stage will cause the pressure of the servo valve control cavity to vibrate to a certain extent, which is a factor that cannot be ignored that affects the output stability of the servo valve.

Original languageEnglish
Article number1404
Pages (from-to)1-19
Number of pages19
Issue number11
Publication statusPublished - 3 Nov 2020

Bibliographical note

Funding Information:
study was supported by the Special Research Project of Civil Aircraft (MJ-2016-S-54).


  • Mathematical model
  • Numerical simulation
  • Pressure stability
  • Servo valve
  • Transient flow force


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