Computational Study of Fluid Flow in Multi-Stage Pinch Mode MR Valves

Abstract:
Magnetorheological (MR) fluids are well-known representatives of smart materials. While in the presence of magnetic field the material develops a yield stress. The technology has been used in the automotive industry in semi-active vehicle suspension applications using MR fluid-based controlled dampers. The vehicle dampers utilize MR valves operating in one of the four fundamental modes, i.e., the flow mode. In the essence, the (existing) conventional flow-mode valves energize the MR fluid by magnetic flux perpendicular to the fluid flow path. In the study the authors explore opportunities for extending the dynamic range of controlled MR valves operating in pinch mode. By convention, a pinch mode valve would feature a single constant cross-section area flow channel with magnetic poles located in it over which non-uniform magnetic field is induced. The single pole-gap pair is a so-called valve stage assembly. Here, the authors examine ways of extending the dynamic range of pinch mode valves by employing a number of valve stages in series in the channel. The authors examine various scenarios based on variations of the number of stages in the channel and the number of solenoids in the valve assembly. To accomplish this, the authors propose a magnetostatic model of the MR pinch mode valve that is one-way coupled with a CFD (computational fluid dynamics) model of the flow channel, and then execute a parametric study to estimate the pinch valve output changes with respect to the number of stages and the solenoids in the valve. The results are then presented in the form of plots of averaged pressure drop vs volumetric flow rate, respectively, at various levels of ampere turns (or coil current). To summarize, the obtained results reveal improvements in the pinch mode valve dynamic range, however, challenges in reducing the magnetic flux leakage between the neighbouring poles are evident at the same time.