Dynamic Thermal Neutron Radiography for Filling Process Analysis and CFD Model Validation of Visco-Dampers

The visco-damper is a crucial engine accessory from an operation- as well as vehicle-safety point of view. The service life of this damping product is determined by the degradation of the silicone oil applied to it. The thermal and mechanical degradation of the oil starts not at the first operation of the damper, but at the manufacturing stage when the oil is filled into the damper’s gap at high pressure. Finite volume method-based computational fluid dynamic calculations provide an opportunity to optimize the filling process by minimizing the oil degradation. A three-dimensional, transient, non-Newtonian, multiphase, coupled fluid dynamic and heat transfer simulation model was developed to analyse the filling process and to investigate the effect of the slide bearing’s cut-off position on the filling process. Dynamic thermal neutron radiography was employed to visualize the filling of a test damper for model validation from viscous and fluid dynamic aspects. Distinct properties of neutrons compared to the more commonly applied X-rays were proven to be an effective tool for real-time monitoring of the silicone oil’s front propagation in the damper’s gap and for quantifying the characteristics of the filling process. Visual matching and comparison of propagation times and oil front velocity profiles were used to validate the simulation results.