Phenomenological Model for Hydrocarbon High-Temperature Autoignition

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Phenomenological Model for Hydrocarbon
High-Temperature Autoignition

• M. Petrova F. Williams
• Domenic Tassoni

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Combustion Model

• Hydrocarbons above 1000 K
• Four step chain process
• Fuel/Oxidizer Collision
• Fuel Consumption by free radicals
• Oxidizer Consumption by free radicals
• Chain Termination

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Role of Radicals in Combustion

• Combustion of hydrocarbons releases energy.
• This energy causes stable molecules to dissociate
  into reactive radicals
• OH, H, O are all common radicals
• These radicals cause more reactions which raises
  the temperature further.

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Allene (C3H4) Example

• Initiation Step
• C3H4 O2 ? C3H3 HO2
• Small concentrations of H also generated.
• Fuel Consumption Step
• H C3H4 ? CH3 C2H2
• Radical concentration decreases.

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Allene (C3H4) Example Cont.

• Oxidizer Consumption Step
• H O2 ? OH O
• Radical concentration increases.
• Termination Step
• 2O ? O2 or similar
• Responsible for primary heat release.

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Relevance

• Radical depletion rates can be used to determine
  autoignition times.
• Where ki is the reaction-rate of a step. Also, a
  and ß are condition specific parameters related
  to radical generation.

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Other Possible Uses for the Model

• Burning velocities
• Diffusion-flame extinction conditions
• Detonation cell sizes

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Thank You

• Questions?