Date of Award


Document Type


Degree Name

Master of Science in Aeronautical Engineering


Department of Aeronautics and Astronautics

First Advisor

Marc D. Polanka, PhD.


One of the major efforts for turbine engine research is to improve the thrust to weight of the system. One novel concept for accomplishing this is the use of an Ultra-Compact Combustor (UCC). The UCC attempts to shorten the overall combustion length (thereby reducing weight) by performing the combustion in the circumferential direction along the outside diameter of the core flowpath. One of the major benefits of this design is enhanced combustion due to the establishment of a high-g field in the circumferential cavity. AFIT and the Air Force Research Laboratory (AFRL) have been teamed for several years in understanding the fundamental aspects of this design. Prior to the research presented in this report, work has focused around small-scale missile-sized combustors. There is a current push within AFRL to investigate this system for a larger, fighter-sized engine. AFIT has led this push by performing Computational Fluid Dynamic (CFD) simulations to scale the UCC. This thesis outlines this overall effort. Increasing the diameter of the UCC presents several challenges including how to control the fluid velocity in the circumferential cavity and how to turn the centrifugal combustion flow back to the axial direction into the high-pressure turbine rotor while presenting a uniform temperature across the turbine blades. Several numerical parameter studies have been conducted to establish relationships to predict tangential velocity based on cavity inlet conditions and determine a configuration that minimizes pressure losses through the combustor section. As a result of these investigations a 0.75m diameter UCC combustor design has been developed along with a hybrid turning vane which replaces the last compressor vane and high pressure turbine vane.

AFIT Designator


DTIC Accession Number



This thesis received the 2011 AFIT Commandant's Award.