CFD analysis of a check valve from SAFRAN Helicopter Engines using a Lattice-Boltzmann solution

Abstract

Unsteady Computational Fluid Dynamics (CFD) solvers with accurate turbulence modelling are increasingly required to solve real industrial problematics where most applications include complex moving parts, highly turbulent flows and transient phenomena. Most of these industrial requirements are out of reach for the traditional CFD solutions based on steady state or unsteady Reynolds-Averaged Navier-Stokes (RANS) turbulence approaches and with limited capabilities to deal with moving parts and Fluid-Structure Interaction (FSI). XFlow is the innovative CFD software developed by Next Limit Dynamics to deal with this increasing demand on new industrial applications. XFlow features a particle-based discretization approach that uses a state-of-the-art Lattice-Boltzmann Method (LBM) to discretize the continuous Boltzmann equation, a time evolution equation for statistical probability distribution functions that describe accurately the behavior of a fluid. This proprietary particle-based kinetic solver implements at collision operator a Large Eddy Simulation (LES) turbulence model fully coupled with a generalized law of the wall (WMLES) in order to solve the transient turbulent effects usually observed on industrial applications. The aim of the work presented in this paper is to demonstrate the capability of the XFlow approach to predict costly instability issues of the Check Valves (CV) integrated inside the fuel circuit in helicopter engines. The results of XFlow will be compared to the experimental measurements provided by SAFRAN Helicopter Engines on one of their CV designs during real working conditions. The CV dynamics will be modelled in XFlow as a rigid body with one degree of freedom along the axis aligned with the flow direction. A spring effort is modelled with a pre-load force and a stiffness. With these two parameters, XFlow computes dynamically the valve position according to the dynamic movement equation based on the hydraulic and spring forces applied on. As preliminary step, different fixed flow-rate boundary conditions will be applied at the inlet of the CV in order to validate the global valve characteristics with the incompressible solver. The CV oscillations are studied considering acoustics with an additional bulk viscosity term inside the flow equations. An increasing inlet volumetric flow law is applied to compute the dynamic response of the valve and to predict the frequency and the flow-rate range at which instabilities appear. This simulation shows a good agreement; the experimental instability range is well predicted as the eigen frequency.