This thesis presents the development process of a micro turbopump system, as part of a micro steam turbine power-plant-on-a-chip, which implements the Rankine thermal cycle for micro power generation using silicon microtechnology. The device consists of a four-stage radial planar type turbine with radial outward flow and a spiral groove viscous pump, supported on gas-lubricated bearings.; Analytical models were developed for component design: (1) a model based on mean line analysis with loss correlations extracted from CFD for the turbine; (2) a flow resistance model for the thrust bearing; (3) models based on lubrication theory for the pump and seal. They were integrated to enable the microsystem design while satisfying rotor operation balance conditions.; The complete device is composed of five wafers: one glass wafer, one silicon-on-insulator (SOI) wafer, and three silicon wafers. The silicon wafers are micromachined by shallow and deep reactive ion etching while the glass wafer is ultrasonically drilled. The anodically bonded glass and SOI wafer stack and fusion bonded silicon wafer stack are manually assembled with mechanical alignment for testing with the 4 mm diameter rotor inserted between them. The pressure difference across the turbine drives the rotor and draws water through the viscous pump, which is located on the back side of the rotor. A spiral groove seal surrounds the pump to prevent the pumped water from flooding and impeding the rotor operation. Hydrostatic thrust bearing and journal bearings are employed for the axial and lateral balance of the rotor, respectively.; The turbine was tested using compressed air and spun up to 330,000 rpm, which corresponds to 70m/s in tip speed and produced roughly 0.1 W of mechanical power from each stage totaling 0.38W with 0.75 atm of differential pressure across the microturbine. Modeling of the turbine suggests a turbine isentropic efficiency of 35% and Re=266 at the maximum speed achieved. The pressure distribution across the blade 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. The pump performance chart was completely characterized for speeds up to 20,000 rpm. The pump model predicted 7.2% of maximum efficiency over the range of operating speeds.; This work proves the concept and provides the design basis of the rotating subsystem of a micro Rankine power generation system. The technology developed herein will also contribute to the development of other types of microscale turbomachinery-based systems, such as gas turbines, coolers, and pumps.
展开▼
