Oil Free 8 kW High-Speed and High Specific Power Turbogenerator

Abstract

In the paper the authors will present the design and preliminary test results for a high specific power (i.e., kW/kg) fully integrated and completely oil-free gas turbine driven electric generating system that operates with commercially available heavy fuel. The oil-free, high-speed micro-turboalternator system achieves high specific power through operating speeds to 180,000 rpm and the use of compliant foil bearings, high performance compressor and turbine and a permanent magnet alternator. The high operating temperatures and speeds require that oil-free compliant foil bearings be used and that the alternator section be isolated from the turbine engine portion of the system. The selected modular design approach, including compressor and turbine aerodynamic design, system thermal management issues and the corresponding impact on rotor bearing system dynamics, will all be presented. The paper concludes with a presentation of preliminary testing results showing stable full speed operation and peak power generated. Data obtained compares well with design predictions both from a rotordynamic and with regard to the cycle efficiency and performance. Conclusions regarding the ability to scale the technology to even smaller systems will also be presented.