Experimental study of heat release induced choking in a supersonic circular combustor

Damiano Baccarella, Qili Liu, Brendan McGann, Tonghun Lee, Hyungrok Do

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Incipient unstart and choking are investigated experimentally in a direct-connect, constant-area supersonic combustor with circular cross-section (28 mm in diameter). The experiments were performed in the arc-heated hypersonic wind tunnel ACT-II of the University of Illinois at Urbana-Champaign using ethylene as a fuel. The long test time (up to 1 s) of the facility and the full visualization capabilities allowed by the circular geometry are important novelties compared to previous studies. Both intrusive and non-intrusive diagnostic techniques were used. Heat-flux measurements at the combustor exit revealed a negligible contribution of combustion heating to the stagnation enthalpy of the supersonic core, excluding thermal choking as possible cause of unstart initiation. This conclusion is supported by OH-PLIF images, showing that most of the OH is confined in the boundary layer and not in the supersonic core. Pressure distribution at the wall revealed a combustion induced pressure gradient in the combustor, but not sufficiently strong to explain a possible boundary layer separation. Pitot pressure measurements were used to evaluate stagnation pressure and Mach number at the combustor exit. The two quantities were found to be well correlated by Fanno relation, indicating a predominant effect of irreversibilities on the Mach number reduction leading to choking. Finally, OH-PLIF and chemiluminescence images of a pseudo-shock provided information on the flame structure during unstart, showing that combustion takes place mainly at the interface between the shock-train and the diffusion region.

Original languageEnglish (US)
Title of host publicationAIAA Aerospace Sciences Meeting
PublisherAmerican Institute of Aeronautics and Astronautics Inc, AIAA
Edition210059
ISBN (Print)9781624105241
DOIs
StatePublished - 2018
EventAIAA Aerospace Sciences Meeting, 2018 - Kissimmee, United States
Duration: Jan 8 2018Jan 12 2018

Publication series

NameAIAA Aerospace Sciences Meeting, 2018
Number210059

Other

OtherAIAA Aerospace Sciences Meeting, 2018
Country/TerritoryUnited States
CityKissimmee
Period1/8/181/12/18

ASJC Scopus subject areas

  • Aerospace Engineering

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