A direct solution for flowrate and force along a cone-seated poppet valve for laminar flow conditions

Abstract

A new set of equations is developed, giving insight into the flow and pressure distribution across poppet valves with large cone-shaped seats. The equations apply for laminar flow, which appears when the length of the seat is much greater than the valve opening gap, and are a useful design tool for applications where a linear pressure/flow characteristic could be a distinct control advantage. The momentum equation is also applied to determine the static forces on the conical spool and it is confirmed that, for small chamfered-type seats, momentum forces can still play a decisive role on the total force. However, as the length of the seat increases to a cone type the dominant role is then played by the pressure forces acting on the seat, producing a much more predictable valve characteristic. The new equations allow accurate design of the seat length to minimize this static force variation. In order to validate the equations developed, a three-dimensional computational fluid dynamics (CFD) analysis of the flow along the valve seat has been performed and a test rig was designed to check experimentally the pressure distribution and flow along such a valve. Very good agreement has been obtained between experimental, CFD and theoretical pressure/flow results.