Soot and OH distribution at the smoke point of diluted propylene-hydrogen mixture diffusion flames in cross-flow

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Title Soot and OH distribution at the smoke point of diluted propylene-hydrogen mixture diffusion flames in cross-flow
Creator Goh, S. F.; Gollahalli, S. R.
Publication type report
Publisher American Flame Research Committee (AFRC)
Program American Flame Research Committee (AFRC)
Date 2004
Description An experimental study of smoke point diffusion flames in cross-flow is presented from the perspective of understanding the role of hydroxyl (OH) radicals and oxygen molecules on soot concentration. The laser induced incandescence (LII) and the laser induced fluorescence (LIF) techniques were employed to determine soot and OH concentrations. A propylene gas jet flame from a circular tube burner (diameter=3.2 mm) with a range of exit velocities (4.2 to 34 m/s) corresponding to a Reynolds number range of 520 to 6065 was subjected to a cross-flow with velocities ranging from 2 to 4 m/s. About 10% (by mass) of hydrogen was mixed with propylene to keep the flame attached to the burner at all cross-flow, jet velocity, and dilution conditions. Nitrogen was added to the fuel stream to reduce smoke formation. This paper presents the measurements in flames with the critical mass flow rate (CFMFR) of pure fuel at the smoke point, and with different fractions of the CFMFR diluted with nitrogen to achieve the smoke point, in the cross-flow with a velocity of 3 m/s. The soot and OH concentration contours in the plane normal to the cross flow stream exhibit a kidney shape. In most instances, high OH concentration was measured at the outer rim of the flame, whereas soot concentration was noted to be highest at the center of the flame or middle of the kidney-shaped vortex. Overall, the flame at the 100% CFMFR had a higher soot concentration than the 60% CFMFR flame, except at 25% of the flame length away from the burner. On the other hand, the 10% CFMFR flame had a higher soot concentration than the 20% CFMFR flame. The overall OH concentration at 25% of the flame length of the 100% CFMFR flame was the lowest, and that in the 10% CFMFR flame was the highest. The flame trajectory and the momentum flux ratio, which govern the fuel-air mixing intensity, played an important role on the behavior of soot and OH concentrations. The transition from momentum to chemical domination of smoke emission when the fuel flow rate was changed from higher to lower CFMFR was governed by the change in the dependence of soot oxidation on oxygen to that on hydroxyl radicals. The hypothesis based on the distinction between the dominance of physico-chemical processes in chemical and momentum controlled regions found in flames in quiescent surroundings is valid also in flames in cross-flow.
Type Text
Format application/pdf
Language eng
OCR Text Show
Metadata Cataloger CLR; AM
ARK ark:/87278/s6w71nzs
Relation has part Goh, S. F., & Gollahalli, S. R. (2004). Soot and OH distribution at the smoke point of diluted propylene-hydrogen mixture diffustion flames in cross-flow. American Flame Research Committee (AFRC).
Format medium application/pdf
Rights management American Flame Research Committee (AFRC)
Setname uu_afrc
Date Created 2020-02-18
Date Modified 2021-05-06
ID 1527061
Reference URL