Fabrication of a High Speed Microscale Turbocharger

Abstract

Microscale turbocharger devices have been fabricated and tested. The device, formed by fusion bonding six silicon wafers, consists of a free rotor (with a compressor and turbine) contained within a static structure. A pressure differential across the turbine generates a torque that spins the rotor, producing flow and pressure rise through the compressor. This paper addresses fabrication issues critical to high speed operation of this device, such as journal bearing profile control, nozzle and thrust bearing process control and integration, rotor integration, and rotor imbalance, providing the first discussion of fabrication innovations developed specifically for the turbocharger. Preliminary test results are also included.

Fabrication and high-speed characterization of SU-8 shrouded two-dimensional microimpellers

“…The requirement for the micro centrifugal pump is satisfied at an impeller tip speed of 80 m s −1 or higher. The achieved pressure rise at 300 000 rpm is comparable with that achieved by a silicon microimpeller with a diameter of 8 mm at the same tip speed (about 160 m s −1 ) [6]. The measured adiabatic efficiency varies in the range from 40% to 60%, depending on the rotation speed and flow rate, which roughly satisfies the requirement from the power consumption (figure 1).…”

“…Figure 2 shows two types of two-dimensional microimpellers-an open and a shrouded impeller. The open impeller is used for a MEMS-based gas turbine due to its structural simplicity [2,[6][7][8]. However, the clearance above the top edge of the blades, which causes air leakage, becomes relatively larger for a smaller impeller.…”

“…For MEMS-based gas turbine generators [2,[6][7][8], a silicon microimpeller is used, because silicon has excellent mechanical properties, and can be fabricated precisely by deep reactive ion etching (DRIE). However, DRIE is an expensive process, and silicon is brittle, needing special care for handling.…”

“…Recently, several research groups have been studying microturbomachinery [2][3][4][5][6][7][8][9]. Our group measured the performance of a three-dimensional microimpeller with a diameter of 10 mm at high rotation speed [5].…”