PhD Proposal by Luke Humphrey

Event Details
  • Date/Time:
    • Monday February 15, 2016
      1:00 pm - 3:00 pm
  • Location: Food Processing Technology Building Auditorium (Room 102)
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Summaries

Summary Sentence: Ensemble-Averaged Dynamics of Harmonically Excited Turbulent Premixed Flames

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Committee:

 Dr. Tim Lieuwen (Advisor)

 Dr. Jerry Seitzman

 Dr. Devesh Ranjan

Title: Ensemble-Averaged Dynamics of Harmonically Excited Turbulent Premixed Flames

 

 

 

 

Abstract:

 

 

Combustion instability is a significant problem for modern, lean, premixed combustors. This instability arises through a feedback loop between heat release and harmonic acoustic and/or hydrodynamic oscillations. Although there is a substantial body of research which examines this problem for laminar flames, virtually all practical, high power, combustion systems operate in a turbulent environment. Prior studies of turbulent flames have utilized a “quasi-laminar” approach, which utilizes the time-averaged flame position, and ensemble-averaged disturbance field, as inputs to a problem which is essentially identical to the laminar problem. Although this approach shows promise, it does not capture any dynamical effects. In this work, I analyze an ensemble-averaged turbulent burning velocity closure proposed by Shin and Lieuwen (2013), who showed that the ensemble-averaged turbulent burning velocity for a harmonically forced flame is proportional to the ensemble-averaged flame curvature. The strength of this dependence is characterized by the turbulent Markstein length, which relates ensemble-averaged flame curvature to the turbulent, ensemble-averaged burning velocity.

 

The research I propose expands upon the results of Shin and Lieuwen (2013) by showing that their flame speed closure and definition for the ensemble-averaged turbulent burning velocity can provide a governing equation for the ensemble-averaged flame position, and allows development of reduced-order models for flame position and heat release dynamics. Because the turbulent displacement and consumption Markstein lengths are a critical component of the flame speed closure, I propose to characterize their dependence on harmonic forcing amplitude, turbulence intensity, and turbulence length scale, through analysis of a numerically simulated turbulent flame. In addition to this analytical modeling, I propose to develop a new experimental facility designed to allow investigation of a turbulent, premixed, V-flame attached to a harmonically oscillating flame holder. This facility will be used to examine the ensemble-averaged flame position and heat release and characterize the turbulent flame speed dependence on ensemble-averaged flame curvature.

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PhD proposal defense
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  • Created By: Jacquelyn Strickland
  • Workflow Status: Published
  • Created On: Feb 4, 2016 - 5:19am
  • Last Updated: Oct 7, 2016 - 10:16pm