Demonstration of a MEMS-based turbocharger on a single rotor

A MEMS-based turbocharger with a novel configuration was developed and demonstrated. The compressor and turbine are installed on the same plane of the rotor. The advantages of this configuration include structural simplicity and good rotor balance. For the fabrication, we developed a special deep RIE condition to realize spike-free, uniform etching. And, we found a low wafer warp condition of five times of the anodic bonding. The device rotated at 50 000 rpm. The tip speed of the compressor approached 25 m s^-1 and it is only a twentieth of the aimed tip speed. The device could not pass the natural frequency of the rotor. From the test results, we found some issues to be solved for high speed rotation. Concerning fabrication, the accurate manufacturing of bearing orifices, and a flat, uniform etched surface are required for the thrust bearing. A straight journal bearing wall is required for the hydrostatic journal bearing. Concerning bearing design, the journal bearing does not have sufficient stiffness or load capacity to support the centrifugal force of the rotor because of the remarkably short bearing length.