Date of Award


Document Type


Degree Name

Master of Science


Department of Aeronautics and Astronautics

First Advisor

Marc D. Polanka, PhD.


As aircraft power requirements continue to grow, whether for electrical systems or increased thrust, improved engine efficiency must be found. An Ultra-Compact Combustor (UCC) is a proposed apparatus for accomplishing this task by burning in the circumferential direction as a main combustor or an Inter-Turbine Burner (ITB). In order for the UCC to be viable it is important to study the effects of feeding the core and circumferential flows from a common gas reservoir. This research effort has developed a diffuser, for the AFIT Combustion Laboratory, that is capable of 80/20, 70/30, and 60/40 mass flow splits between the core and cavity for flow emanating from a single source. The diffuser was fabricated robustly so that the single flow source may consist of a vitiated air, such as that from a small jet engine, or a clean air source of compressed air. Chemical analysis software (CHEMKIN) was applied to assist in the prediction of which flow split would produce the best results and testing of this prediction was initiated. A second important issue for UCC development is the assessment of the effects of g-loading on atomized fuel sprays within a UCC because it is important to stabilize the flame in the cavity. To this end, fuel spray experiments have been conducted over a g-load range of 0 to 3000 to examine how atomized fuel behaves within the circumferential cavity. Results gathered from high speed imaging showed that as g-load increased, fuel carried toward the outside diameter of the circumferential cavity. Results were obtained for combinations of fuel pressure, and cavity air mass flow rate. In summary, a new rig has been developed that will facilitate future endeavors into UCC research.

AFIT Designator


DTIC Accession Number