Prediction of quarter-wave instability in direct spring operated pressure relief valves with upstream piping by means of CFD and reduced order modelling

This paper focuses on modelling the dynamic instability (flutter/chatter) of gas-service direct spring operated pressure relief valves (DSOPRV) due to the acoustic coupling between the valve body dynamics and the upstream piping. Previous studies have shown through reduced order models that there exists a critical inlet pipe length beyond which self-excited vibrations occur due to the presence of a quarter standing wave in the upstream piping. However, to allow analytical computations and simple design equations, these reduced-order models relied on quasi-steady assumptions for the estimation of the discharge coefficient and the fluid force acting on the valve body. This paper proposes two CFD-based methods for the analysis of the fluid forces and valve stability: firstly, steady-state CFD runs were performed to verify the assumptions of the reduced order models and also to increase their accuracy. Secondly, dynamic CFD simulations using deforming mesh technology were conducted, with which the valve response can be resolved with high fidelity including also transient fluid-structure interactions. Comparing the results of the two approaches verify the use of the reduced-order models for stability predictions.