Development and Testing of a Novel Centrifugal Gas Turbine Design: Combustor Development and Load Testing

A novel centrifugal gas turbine design was developed and prototype tested. The research effort consisted of the design, development, and full prototype testing of a 50 HP centrifugal gas turbine. The novelty of the centrifugal gas turbine concept is that it is based on a radial flow gas turbine consisting of a centrifugal compressor and impulse turbine mounted on the same side of a rotating wheel. The radial flow-vaned combustor is mounted on the wheel’s stationary shroud; consequently, there is no 180-degree flow turning required as in conventional radial flow gas turbines. This very simple and rugged gas turbine concept has the following major advantages: • Single rotating component (i.e., mechanically simple and compact gas turbine). • Portability. • Short axial span. • High tolerance to injection of particulate matter. • Simple construction; low manufacturing costs. This project included the conceptual design, structural and aerodynamic analysis, performance prediction modeling, detailed design, prototype fabrication, test rig instrumentation, compressor/turbine characterization, rotordynamic signature, combustor design, combustor testing, controls implementation, light-off testing, no-load testing, and performance testing of the gas turbine. Design analyses that were performed included 1-D thermodynamics, finite element structural and thermal, rotordynamic, 2-D blade path optimization, and 3-D Computational Fluid Dynamics (CFD). Testing of all individual gas turbine elements (compressor, combustor, and turbine) as well as the entire assembly was completed. Tests showed that stable gas turbine combustion was achieved up to 26,000 RPM. The gas turbine reached self-sustaining power at 21,000 RPM and 405°C firing temperature. Thus, the centrifugal gas turbine concept was demonstrated to function properly and to achieve positive power output. However, the design output power was not achieved because of combustion stability range limitations at speeds above 20,000 RPM. Maximum output power achieved was 1.4 kW at 23,000 RPM. Recommendations are provided to overcome these operational limitations in the next model centrifugal gas turbine.