A numerical study of flow field in a flapper-nozzle pilot valve with a moving flapper

As we known that the flapper-nozzle pilot stage is a very vital part in converting the electric signals into hydraulic outputs between the torque motor and main spool in the electro-hydraulic servo-valve. The performance of the flapper-nozzle has a seriously impact on the capability of the entire system. This paper has presented the flow field characteristics in the pilot valve when the flapper is moving, which will reflect the real working conditions. The initial speed is imposed on the flapper which will insure it moving in a way of 2 DOF (Degree of Freedom). Meanwhile, for the reason of saving computational time-consuming, the flapper is substituted by a part of the standard servo-valve. During the simulation, the strategy of overset mesh is utilized to update the moving mesh. Then the simulation results are firstly compared with the experiment result. The results show that the numerical method used in this paper is able to predict the flow field of the flapper-nozzle pilot valve when the flapper is moving. Finally, the translation of the flapper, transient velocity field and the distribution of vorticity are presented. The results also show that the movement of the flapper can make the flow field be a disciplinary and dissymmetry one, the vorticity of the flow field is also more complex but periodicity.