Membrane Geometry
Finite Element simulation (implemented in Comsol Multiphysics 5.6, detailed setup in Section \ref{802803} shows that the maximum magnetic flux density occurs at the annular region at the edge of the iron core. The magnetic field generated by the coil at the plane of the air channel is shown in Figure \ref{270853}(A). To investigate the impact of MRE membrane geometry on valve performance, four different MRE membrane geometries (shown in Figure \ref{270853}(B)) were fabricated and tested based on the simulated magnetic field. All four geometries cover the annular region with the strongest magnetic field. The simulated magnetic fields with different MRE geometries are shown in Figure \ref{270853}(C). The FE simulation shows that the "Full" and "Parallel line" provides the strongest magnetic field strength within the air channel. The larger magnetic flux density indicates that the MRE membrane can more effectively regulate the airflow given the same amount of electric current. To validate the simulation, four samples with different MRE geometries were fabricated and tested.
Experimental validation is performed with a constant input pressure of 20 kPa, while the detailed schematics are shown in Figure \ref{270853}(D). The experimental results are shown in Figure \ref{270853}(E). The valve with "Full" geometry shows the best performance, which successfully shuts down the 20 kPa incoming flow with a minimum electric current of 2.25 A. The valve with "center" geometry is able to shut down the 20kPa incoming flow only when the electric current reached 3 A. Based on these results, the MRE geometry chosen for fabricating the MRE valves is the "Full" geometry, due to its optimal performance and ease of fabrication.