1. Phenomenological Model for Hydrocarbon High-Temperature Autoignition M. Petrova & F. Williams Domenic Tassoni

2. 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

3. 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.

4. Allene (C 3 H 4 ) Example Initiation Step: C 3 H 4 + O 2 → C 3 H 3 + HO 2  Small concentrations of H also generated. Fuel Consumption Step: H + C 3 H 4 → CH 3 + C 2 H 2  Radical concentration decreases.

5. Allene (C 3 H 4 ) Example Cont. Oxidizer Consumption Step: H + O 2 → OH + O  Radical concentration increases. Termination Step: 2O → O 2 or similar  Responsible for primary heat release.

6. Relevance Radical depletion rates can be used to determine autoignition times. Where k i is the reaction-rate of a step. Also, α and β are condition specific parameters related to radical generation.

7. Other Possible Uses for the Model Burning velocities Diffusion-flame extinction conditions Detonation cell sizes

8. Thank You Questions?