Date of Award

3-2020

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Brian T. Bohan, PhD

Abstract

In a novel approach to gas-turbine power production, an engine was designed and analyzed to use both a single-stage centrifugal compressor and single-stage radial in- ow turbine configured back-to-back. This air path reduced the axial length of the engine up to 60%, providing additional modularity in a gas-turbine engine that could be used to improve mobility of ground-based power units or increase the survivability of aircraft through the use of distributive propulsion. This increased modularity was made possible by the use of a circumferential ow combustor that substantially decreased the axial length of the burner and negated the need to return compressor radial ow to the axial direction, as found in conventional combustion approaches. The Disk-Oriented Engine was designed to incorporate swirling inlet ow from a centrifugal compressor and exhaust directly into a radial in-ow turbine, while still maintaining the initial swirl pattern out of the compressor. The configuration of the combustion cavity was evaluated through computational fluid dynamics. An iterative design approach was used to achieve desired ow characteristics and combustion dynamics through geometry shaping and placement of air supply holes. The result of this design process was a computational combustor model that accepted swirling inlet ow, dispersed that air and fuel about a unique u-bend circumferential combustion cavity, and exhausted in the radial direction to feed a radial in-ow turbine. Sustained combustion was simulated at design conditions with a 3% total pressure loss in the combustor and a turbine inlet pattern factor of 0.24, indicating that such a design could operate as a gas-turbine engine, while reducing axial length up to 60% compared to traditional systems of similar size and performance. Computational results were compared to experimental tests on fuel-air swirl injectors, providing qualitative and quantitative insight into the stability of the flame anchoring system. From this design, a full-scale physical model of the Disk-Oriented Engine Combustor was designed and built for combustion analysis and characterization.

AFIT Designator

AFIT-ENY-MS-20-M-281

DTIC Accession Number

AD1101540

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