• KAUST Research Conference: Combustion in Extreme Conditions

KAUST Research Conference
Combustion in Extreme Conditions

March 5-8, 2018

AgendaTalk Details

New Measured Regime Diagram of Premixed Turbulent Combustion for Extreme Turbulence

09:15 - 09:45 KAUST

Level 0 lecture hall between Al-Jazri and Al-Kindi (buildings 4 and 5)

  • James F. Driscoll

    James F. Driscoll

​Abstract: 

It is proposed to replace the predicted Borghi regime diagram for turbulent premixed flames with a new Measured Regime Diagram that better fits the present measurements and those from previous studies. Thicknesses of preheat and reaction layers were measured along with the probabilities of broken and distributed reactions for 27 cases using CH, OH and formaldehyde laser imaging diagnostics. A new Michigan Hi-Pilot burner provides extreme turbulence levels (u’/SL) up to 243 and integral scales up to 43 mm, which are 5 to 10 times that of previous studies. Two boundaries on the predicted Borghi diagram do not agree with the measurements: the boundaries of broadened preheat layers (BP) and broken reactions (BR). Instead, we propose a new BP boundary that shows good agreement with the measurements. It is explained by replacing the idea that Kolmogorov eddies must fit inside the flame with the idea that broadening occurs when the turbulent diffusivity exceeds molecular diffusivity. One implication for flamelet modeling is that the new measured regime diagram shows that the BP-TR regime (of Broadened Preheat, Thin Reaction layers) extends over a much larger range than is predicted by the Borghi diagram. Broken reactions, which define the upper boundary of the BP-TR regime, were not observed even for turbulence levels u’/SL of 243, which is five times the predicted value.