Visualization of blow-off events in bluff-body stabilized turbulent premixed flames

被引：86

作者：

Dawson, J. R. ^{[1
]}

Gordon, R. L. ^{[1
]}

Kariuki, J. ^{[1
]}

Mastorakos, E. ^{[1
]}

Masri, A. R. ^{[2
]}

Juddoo, M. ^{[2
]}

机构：

[1] Univ Cambridge, Dept Engn, Hopkinson Lab, Cambridge CB2 1TN, England

[2] Univ Sydney, Dept Aerosp Mech & Mechatron Engn, Sydney, NSW 2006, Australia

来源：

PROCEEDINGS OF THE COMBUSTION INSTITUTE | 2011年 / 33卷

基金：

英国工程与自然科学研究理事会;

关键词：

Turbulent premixed flame; Extinction; Stabilization; Bluff-body; VELOCITY OSCILLATIONS; DYNAMICS; IGNITION;

D O I：

10.1016/j.proci.2010.05.044

中图分类号：

O414.1 [热力学];

学科分类号：

摘要：

Confined and unconfined turbulent methane-air lean premixed flames stabilized on an axisymmetric bluff-body of diameter d = 25 mm have been examined close to the blow-off limit and during the extinction transient, with OH* chemiluminescence, flame tomography and OH-PLIF operated at 5 kHz, allowing a quantification of the duration of the blow-off event. Blow-off was approached by increasing the bulk velocity U-b or decreasing the equivalence ratio and the flame shape changed from conical to cylindrical with decreasing length. Close to blow-off, the flame closed on the axis and was about 2d long, and just before the blow-off condition it took an "M" shape with reaction fronts inside the recirculation zone (RZ). During the blow-off event, fresh reactants entered the RZ from the forward stagnation region and significant fragmentation of the flame occurred, with branches of the flame remaining anchored on the bluff-body edge and separate flame pockets moving randomly inside the RZ. Overall blow-off occurred with the gradual elimination of these flame fragments. The integrated OH* emission decreased slowly to zero as the flame surface decreased over a period of about 15d/U-b. The results suggest that the blow-off event in recirculating flames lasts long compared to the residence time in the RZ and the structure of the flame close to extinction supports the underlying assumptions behind well-stirred reactor concepts of blow-off. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

引用

页码：1559 / 1566

页数：8

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