OPTIMIZATION OF MAGNETORHEOLOGICAL FLUID VALVES

In this paper we analyze efficiency of a magnetorheological (MR) fluid valve consisting of a flow channel placed inside a solenoid. The scope of the optimization is to find a proper geometry and dimensions of the flow channel in order to achieve the highest possible inlet pressure ΔP(H) at a given field strength H. We analyze two types of flow channels: spiral channels with different helix angles and packed beds of spherical and cylindrical particles with different aspect ratios, both nonmagnetic and paramagnetic. For the prediction of the valve discharge characteristics in the presence of the magnetic field of an arbitrary orientation, we have used our recent physical models for MR fluid flows through capillaries and porous media. We show that among spiral channels the most efficient is the one having the minimal helix angle, i.e. the densest winding of the spiral. At H=20 kA/m this channel provides the inlet pressure 9 times the pressure in the absence of the field. Comparing the porous beds, we conclude that those made of superparamagnetic material are always more effective than nonmagnetic beds. The shape of the bed particles has also been found to affect the inlet pressure by affecting porosity and tortuosity of the beds. The most effective bed consists of packed cylinders made of magnetically soft steel and having the length-to-diameter ratio of either 0.5 or 5. At H=20 kA/m these beds give the pressure near 40 times the pressure at zero field and thus show a higher effectiveness compared to spiral channels.