Demonstration and Characterization of a Multi-Stage Silicon Microturbine

This paper presents the experimental testing and characterization of a microscale radial outflow turbine with four concentric stages. The device is a five layer structure composed of shallow and deep reactive ion etched silicon wafers and an ultrasonically drilled Pyrex glass wafer that are assembled using anodic and fusion bonding techniques. They enclose a 4mm diameter rotor that was spun up to 330,000 rpm and produced roughly 0.1W of mechanical power from each stage totaling 0.38W with 0.75 atm differential pressure across the microturbine. Modeling of the turbine based on a mean line analysis with loss correlations extracted from CFD suggests a turbine isentropic efficiency of 35% and Re=266 at the maximum speed. The pressure distribution across the blades rows was measured and showed close agreement with the calculation results. Using the model, the microturbine is predicted to produce 3.2 watts with an isentropic efficiency of 63% at a rotor speed of 1.1 million rpm.