Design of a 50-watt air supplied turbogenerator

This thesis presents the design of a high-pressure-ratio, low-flow turbogenerator with 50 W electrical power output, designed to operate from a 5-bar air supply. The research shows that a MEMS-based silicon turbine in combination with a micro-machined generator can meet the design objectives of the turbogenerator. The turbogenerator architecture comprises a single-stage radial inflow turbine and a direct coupled cylindrical permanent-magnet synchronous generator. To address its key design trade-offs and fundamental engineering challenges, the design space is first explored in terms of the key design variables: device diameter and rotor shaft speed. To guide the selection of the two variables, a simplified model for the scaling of turbine and generator power is developed. Next, the integrated turbine and generator design is analyzed and designed in detail. The minimum manufacturable turbine blade span is identified as the key challenge imposed by the low flow requirement. Furthermore, the small scale of the blades results in high rotational speeds. Since the turbine and generator are integrated, the high speed makes the generator design challenging because of manufacturing tolerances, material stress limitations and losses. Thus, the design trade-off is between generator complexity and turbine blade manufacturability. The analysis shows that the viable low-flow 50 W turbogenerator design space is narrowly constrained by the minimum blade span and the 5-bar pressure supply, demanding MEMS fabrication for the short turbine blades. A single-stage MEMS radial turbine is designed in detail, and assessed for performance and manufacturability. The rotor speed at design conditions is 450,000 rpm with a rotor radius of 5 mm, a rotor blade span of 200 um, and a blade tip clearance of 20 um.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Jovanovic, Stevan, S.M. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Zoltán S. Spakovszky.

• Aeronautics and Astronautics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/45262

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/45262