Date of Award

9-1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Aeronautics and Astronautics

First Advisor

Rodney D. W. Bowersox, PhD

Abstract

This study investigated the flame holding properties of recessed cavities in supersonic flow using numerical analysis techniques. A simplified analytical model indicated that an important property for flame holding was the lower residence time. Several chemical kinetic rate models for hydrogen and hydrocarbon combustion were compared. The perfectly stirred reactor model also indicated that trace species diffusion should increase flame spreading rate, and that heat loss reduces flame holding limits. After nonreacting calibration, two-dimensional simulations confirmed the perfectly stirred reactor results for blowout limits. Also, the effect of trace species diffusion on flame spreading was shown to be negligible, and the reduced flammability with heat loss was confirmed. Lowering the temperature of the inflow boundary layer was shown to reduce the flammability limits. Three-dimensional cavities were shown to generate axial vorticity and slightly enhance flame spreading. The methodology developed in this research provides a design guide for the size of cavity required to provide flame holding for a scramjet combustor. Also, reduction of heat losses was shown to be a method to improve flame holding performance without increasing the cavity size.

AFIT Designator

AFIT-DS-ENY-96-12

DTIC Accession Number

ADA324246

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