Modelling the steady-state analysis of a jet pipe electrohydraulic servo valve

Abstract

In this paper, an attempt has been made to simulate the steady-state operation of a jet pipe electrohydraulic servo valve using the finite element (FE) method. The jet pipe electrohydraulic servo valve is a mechatronic component, used for precise flow control applications in gas turbine engines. It has two assemblies: a first-stage torque motor assembly and a second-stage valve assembly. Between the first and the second stage, there is a mechanical feedback spring assembly to stabilize the valve operation. Each assembly has various delicate and precise components interacting with fluid flows. In the present paper, the structural components were modelled with general-purpose finite elements, e.g. shell, beam, and solid elements, while the fluid cavities were modelled with special-purpose hydrostatic fluid elements. The fluid flows from one fluid cavity to another fluid cavity were modelled with fluid links. The simulation was carried out in a commercially available FE code, ABAQUS, interfaced with user subroutines to form a closed-loop system. The FE simulation clearly showed the dynamics of the jet pipe and spool displacement in achieving the equilibrium position when the applied torque and restoring torques balance, known as steady state. The pressure and flow variations during torque balance are presented. The effect of the feedback loop from the second-stage spool movement to the first-stage jet pipe is seen in the FE results obtained. The theoretical aspects of pressure recovery and flow modelling are presented and used in FE simulation.