Effect of Flow Distortion on Fuel Mixing and Combustion in an Upstream-Fueled Cavity Flameholder for a Supersonic Combustor

Typical studies of scramjet combustion employ as uniform a flowpath as possible. These studies are important to isolate the effects of a given combustor configuration. However, such studies tend to ignore the effects of a shock train created by the vehicle installation and that this shock train changes over the flight envelope. Consequently, the performance of a given configuration is measured without considering the considerable effects of this shock train or how it changes with different flight conditions. This thesis includes experimental and computational studies of the effects of an incident shockwave on the flowfield, fuel distribution and combustion within a cavity flameholder with upstream fuel injection. The effect of the shockwave location (on the upstream fuel jet or over the cavity) and shock angle are controlled by adjusting a shock generator mounted in the tunnel test section. The effect of fuel injection momentum ratio is also examined. Shadowgraphy is used to characterize the flowfield while planar laser induced fluorescence of the NO and OH molecules are used to measure the fuel mixing and combustion, respectively. These experimental data are compared with CFD solutions of the Reynolds Averaged Navier-Stokes equations provided in previous CFD work. The effect of the shock on the cavity shear layer is found to control the fuel distribution within the cavity. The shock on jet impingement forces the shear layer deep within the cavity and results in higher concentrations near the cavity centerline, but low mixing uniformity. The shock on cavity case causes the shear layer to separate upstream of the cavity, mixing uniformity is enhanced by the increased breakup of the fuel plume. Combustion is stronger and more uniform in the shock on cavity case, while it is limited to the edges of the cavity with shock impingement on the jet. The greater mixing afforded in the shock on cavity case reduces the fuel concentration near the centerline and permits stronger burning in the center of the cavity. Small changes in the fuel injection momentum ratio (doubling) do not strongly affect the pattern of fuel distribution in any case. Combustion in the shock on cavity case is reduced by increasing fuel injection momentum because the fuel concentration at the centerline is too high. Small increases in the shock angle did not strongly affect the results.

Name thesis:degree_name

MS

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Engineering and Applied Science: Aerospace Engineering

Grantor dc:publisher

University of Cincinnati

Year dc:date

2012

Author dc:creator

• Etheridge, Steven J.

Contributors dc:contributor

• Lee, Jongguen

• Aerospace Materials
• supersonic combustion
• shock generator
• cavity flameholder
• scramjet

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=ucin1353100774

OAI identifier oai:identifier

oai:etd.ohiolink.edu:ucin1353100774