Date of Award

3-22-2018

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Marc D. Polanka, PhD.

Abstract

An Ultra-Compact Combustor (UCC) is novel alternative to axial flow combustors commonly used in gas turbine engines. The UCC offers multiple benefits to engine design. First, the UCC aims to increase the thrust-to-weight ratio of an aircraft gas turbine engine by decreasing the size, and thus weight, of the engine's combustor. This is done by utilizing a Circumferential Cavity (CC) wrapped around the main core flow which hosts the combustion event, allowing a shortened combustor length. Second, within the CC, the combusting mixture is subjected to a high centrifugal loading which aids combustion by improving both flame propagation and residence time. Finally, the architecture of the UCC allows a unique cooling scheme to be employed for the Hybrid Guide Vane (HGV). The primary objective of this research was to obtain improved performance of the combustor via improved control over the flow splits and distribution within the combustor. The combustion dynamics were investigated both computationally and experimentally to find the design space were successful operation was established. The secondary objective was to design a film cooled HGV by controlling the mainstream flow and directing a portion of it into the vane. Combustor performance was improved by redesigning the outer ring and back plate to improve control of the fuel and air injection and subsequent mixing with the goal of maximizing the fuel burned within the CC. Evaluations using Computational Fluid Dynamics (CFD) were implemented to help guide the design and understand the combustion dynamics. The outer ring and back plate were then manufactured and tested to compare with the original design. These components allowed a new level of control over the UCC never before examined which was then characterized by developing an operating profile for the various controllable aspects. The redesign and unprecedented controllability allowed the UCC to operate at previously unobtainable equivalence ratios and produce a nominal 15% increase in exit temperatures. Similarly, CFD was utilized to guide the design of a film cooled HGV which drew in compressor air at the stagnation region of the airfoil as the coolant. Using CFD the effects of the required internal supports on flow dynamics and cooling effectiveness were explored. The final manufactured HGV was then prepared for future experimental testing and evaluation.

AFIT Designator

AFIT-ENY-MS-18-M-250

DTIC Accession Number

AD1056560

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