Evan P. Oren

Date of Award

9-1-2018

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Jeffrey R. Komives, PhD.

Abstract

Scramjets, or supersonic combustion ramjets, are a key component for the development of powered hypersonic vehicles. The flameholding strategy used in this engine creates a recirculation region by creating a cavity in one side of the combustor. This highly unsteady region is difficult to interrogate through conventional means. A novel optical observation technique called hyperspectral imaging has been developed to examine the scramjet combustion chamber. The hyperspectral camera is capable of generating an interferogram at hundreds to thousands of wavelengths. These data are integrated across the line-of-sight with no information on three-dimensional (3D) location of origin. A model must be used to extrapolate spatially-resolved two dimensional (2D) data to a three dimensional domain. With no a priori data to inform otherwise, the current model assumes that the scramjet flowfield is uniform in the spanwise direction. This does not agree with understanding of compressible ow theory of shock dominated and turbulent flows. This work simulates a non-reacting scramjet combustor using hybrid Reynolds-Averaged Navier Stokes (RANS)/Large Eddy Simulation (LES). The spanwise character is analyzed through instantaneous and time-averaged statistics. It is shown that the flow is not well approximated as two-dimensional, especially in the cavity where fuel is transported and mixed with air. Complete time histories of spanwise lines were collected and total time-averaged means were compared against 200 µs windowed means. These time windows correspond with the time it takes the hyperspectral camera to create a single scan. Turbulent time scales are calculated and their ramifications on the collection process of the hyperspectral camera are considered. The viscous-dampened region in the cavity has integral timescales on the order of the collection time of each interferogram.

AFIT Designator

AFIT-ENY-MS-18-S-068

DTIC Accession Number

AD1063520

Comments

AFIT designator on cover page: AFIT/GAE/ENY/MS-18-S-068.

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