Simulation of fluid-structure interaction and impact force on a reed valve

Abstract

The cyclic impact force between a reed valve and the seat plate is the main reason of the valve failure in many thermo-technical devices as compressors, engines, etc. According to experimental observations the latter is due to fatigue and usually occurs in the leading part of the valve ‘neck’. In this work, a complex numerical analysis is presented aimed to studying the external forces and internal stresses suffered by the valve. In particular, the impact force between the valve and the seat is studied. The numerical analysis relies on the coupled synergy of two different simulation concepts. In order to do so, two codes are used: (1) first, the in-house Computational Fluid Dynamics (CFD) code presented in [1] is employed to simulate the Fluid-Structure Interaction (FSI) between gas and valve, extracting reference data for valve displacement and external gas pressures; (2) second, the analysis of the internal structure stresses, together with the impact forces with the plate is implemented in a Computational Solid Dynamics (CSD) code developed in FreeFEM++ [2]. The impact force representation is based on the formulation presented in [3] where a conserving algorithm for frictionless dynamic contact/impact is developed. Due to the importance of obtaining an adequate impact force, an exhaustive study is carried out on its characterization in terms of numerical parameters, such as the penalty stiffness. Under this framework, the valve displacement and impact velocities are verified. Hence, impact forces are analysed in different scenarios, obtaining interesting observations about stresses distribution, with a particular focus on the points where failure is experienced.