A CFD study on the unsteady forces on a hydraulic poppet valve

Poppet valves are widely used in industrial hydraulics, notably in pressure relief valves. These valves tend to self-oscillate even under steady-state conditions, often referred to as valve chatter. For developing reliable mathematical models for this phenomenon it is important to estimate the unsteady flow forces, especially damping. This paper presents a CFD-based analysis of valve dynamics; unsteady axisymmetric simulations including deforming mesh were performed for two inlet boundary conditions. In the first case the inlet pressure was stepwise changed and the damping coefficient was estimated with the help of the resulting free oscillations. In the second case an ODE was embedded to the solver modelling the pressure dynamics of the hydraulic system, whose capacity destabilizes the relief valve’s operation giving rise to limit cycle oscillations. A qualitative and quantitative description of the variation of flow forces during the oscillation cycle is presented.