Study on the Stability of Spring Valve Considering the Inlet Pipeline

Spring valve is widely used in the control system of unmanned system, and its stability is very important for the precise control and reliable operation of unmanned system. In this paper, a pipe-valve coupling nonlinear dynamic model of liquid medium is established, and the accuracy of the model is verified by using characteristic line method and fourth-order Runge-Kutta. The valve stability is studied through numerical methods from four aspects: inlet flow rate, flow deflection angle, spring pre-compression and inlet pipeline length. From large flow to small flow, the valve spool gradually changes from stable to unstable. In the unstable state, the characteristic frequency of the valve vibration is the acoustic frequency of the inlet pipeline, and the vibration frequency shifts to the high harmonic acoustic characteristic frequency as the flow rate decreases. There is a symmetry around φ = 90° about valve stability characteristics. The motion of the valve tends to be unstable when the flow deflection angle is close to 90°. Small spring precompression and short inlet pipelines increase the stable operating range of the spring valve.