Design, fabrication and characterization of an axial-flow turbine for flow sensing

This paper presents a novel micro-power conversion device that combines an axial flow turbine with an axial-flux electromagnetic generator. The device has a sandwich structure, consisting of a top silicon stator, a polymer rotor and a bottom silicon stator. Axial gas flow through the device causes rotation, while permanent magnets embedded in the rotor induce output voltage in planar coils on the stators. Compared to radial flow devices the axial-flow design is more compact and can operate at lower pressure ratios. Details of the device design and fabrication process are given, and preliminary results are presented for the variation of output voltage, rotation speed, and pressure ratio with flow rate for nitrogen gas. The test results show operation over a wide dynamic range.