Date of Award


Document Type


Degree Name

Master of Science


Department of Aeronautics and Astronautics

First Advisor

Marc D. Polanka, PhD


Ultra Compact Combustors are a novel approach to modern gas turbine combustor designs that look to reduce the overall combustor length and weight. A previous study integrated an Ultra Compact Combustor into a JetCat P90 RXi turbine engine and achieved self-sustained operation with a length savings of 33% relative to the stock combustor. However, that combustor could not operate across the full stock engine performance range due to flameout at increased mass ow rates as reactions were pushed out of the primary zone. To ensure reactions stayed in the primary zone, a new design with a larger combustor volume was conceived maintaining the same axial dimensions. The primary zone's volume was increased without changing the length by utilizing bluff body stabilization, which resulted in a space savings when compared to the previous backward-facing step stabilized configuration. A new design was investigated computationally for generalized ow patterns, pressure losses, exit temperature profiles, and reaction distributions at three engine power conditions. The computational results were compared to stock combustor experimental results to show the validity of this new Ultra Compact Combustor, with a turbine inlet temperature of 1080 K and a pattern factor of 0.67. The combustor was then built and tested in the JetCat P90 RXi without rotating turbomachinery. The engine was force fed air and the combustor ignited at an air mass ow rate of 30 g/s and an equivalence ratio of 0.21. The combustor responded well to changes in air and fuel ow rates, maintaining a stable flame from ignition through the idle condition. Rotating turbomachinery was added and the combustor operated with an air assist of 3,000 RPM up to a maximum engine speed of 25,000 RPM, 19% of the maximum engine speed, at an exit gas temperature of 982 K, a 19 K increase over the stock.

AFIT Designator


DTIC Accession Number