Performance Characteristics of a Micro Air Grinder Operated by a Two-Stages Axial-Type Turbine

Abstract

Performance characteristics are experimentally studied with various nozzles, stators and rotors on a partially admitted small axial-type turbine, which could be applied to a driver of micro air grinders. When air tools adopt axial-type turbines as a driver, they could operate without friction and abrasion because the turbine rotor does not make contact with the casing. In order to maintain these merits on a small axial-type turbine without reducing power, performance characteristics are examined through measuring the specific output power with eight different stators and three different rotors and nozzles. The tested turbine consists of two-stages and its mean radius of flow passage is 9.2mm. The experimental results show that the output power improvement on the first stage is significant comparing with that on the second stage because partially admitted flow is fully diffused in the second stage. Meanwhile, the output power is increased to 16-22% by changing the nozzle blade angle from 60° to 70° because the first stage performance is directly affected by the flow spouted from the nozzle. These results indicate that blade angles greatly influence the performance of a micro turbine operating in partial admission. When an appropriate stator and rotor that are designed in accordance with the flow spouted from the nozzle are installed in the rotating part, the output power is increased up to 38% depending on the blade angle.