Design of a High-Efficiency Magnetorheological Valve

A high efficiency design was explored for meso-scale magnetorheological (MR) valves (< 25 mm OD with an annular gap < 1 mm). The objective of this paper is to miniaturize the MR valve while maintaining the maximum performance of the MR effect in the valve. The main design issues in the MR valve involve the magnetic circuit and nonlinear fluid mechanics. The performance of the MR valve is limited by saturation phenomenon in the magnetic circuit and by the finite yield stress of the MR fluid. When field is applied to the magnetic circuit in the MR valve, a semisolid plug (as a result of particle chain formation) forms perpendicular to the flow direction through the valve, and a finite yield stress is developed as a function of field. The resulting plug thickness is used to control flow rate through, and pressure drop across, the MR valve. The nondimensional plug thickness is evaluated as a basis for evaluating valve efficiency. Design parameters of the MR valve are studied and an optimal performance was designed using steel (Permalloy) material in the magnetic circuit. A maximum magnetic flux density at the gap was achieved in the optimized valve design based on a constraint on the outer diameter limitation. Valve performance was verified with simulation. A flow mode bypass damper system was fabricated and was used to experimentally validate valve performance.