TY - JOUR

T1 - Global quenching of premixed CH4/air flames

AU - Yang, S. I.

AU - Shy, S. S.

N1 - Funding Information:
The authors thank C. C. Lee and K. Z. Peng for their assistance in conducting these experiments. SSS thanks Professors Forman Williams, Norbert Peters, Kal Seshadri, and Paul Ronney for stimulating discussions on turbulent combustion. This research was continuously supported by the National Science Council, Taiwan (grants 90-2212-E-008-044,042), and was greatly appreciated.

PY - 2002

Y1 - 2002

N2 - Global quenching of premixed CH4/air flames with turbulent straining, equivalence ratio, and radiative heat loss effects is explored in a cruciform burner. The burner equipped with a pair of counter-rotating high-speed fans and perforated plates provides downward propagating flames through near-isotropic intense turbulence, where flame-turbulence interactions are not influenced by ignition. Several CH4/air flames with different degrees of radiative heat loss, from small (N2-diluted) to large (CO2-diluted), are investigated. Each case covers a range of the equivalence ratio (φ) with turbulent intensities (u'/SL) as much as 100, where SL is the laminar burning velocity, in which high rates of strain are achieved until, ultimately, global quenching of flames occurs. A Bradley's Karlovitz number, defined as K = 0.157(u'/SL)2 = 0.157Ka, is used to quantify global quenching boundaries of these turbulent flames, where ReTReT-0.5 and Ka are the turbulent Reynolds and Karlovitz numbers, respectively. For pure CH4/air flames, the critical value of K for global quenching of rich/lean CH4 flames must be greater than 1.0/6.2. Values of Kc are very sensitive to φ, because Kc increases significantly as φ gradually approaches 1 from either lean or rich sides, with the maximum Kc occurring possibly near φ = 1. By comparing N2- and CO2-diluted flames of the same SL, it is found that global quenching of lean/rich CH4 flames is/is not influenced by the radiatvie heat loss, respectively. The larger the radiative heat loss, the smaller the value of Kc for lean CH4 flames, in which values of Kc decrease from 4 (N2-diluted) to 3 (CO2-diluted) where SL ≈ 10 cm/s and φ = 0.62. On the other hand, Kc ≈ 1.3 for both N2- and CO2-diluted rich CH4 flames where SL ≈ 10 cm/s and φ = 1.20-1.45. These experimental results are important to the understanding of global quenching processes for turbulent premixed combustion.

AB - Global quenching of premixed CH4/air flames with turbulent straining, equivalence ratio, and radiative heat loss effects is explored in a cruciform burner. The burner equipped with a pair of counter-rotating high-speed fans and perforated plates provides downward propagating flames through near-isotropic intense turbulence, where flame-turbulence interactions are not influenced by ignition. Several CH4/air flames with different degrees of radiative heat loss, from small (N2-diluted) to large (CO2-diluted), are investigated. Each case covers a range of the equivalence ratio (φ) with turbulent intensities (u'/SL) as much as 100, where SL is the laminar burning velocity, in which high rates of strain are achieved until, ultimately, global quenching of flames occurs. A Bradley's Karlovitz number, defined as K = 0.157(u'/SL)2 = 0.157Ka, is used to quantify global quenching boundaries of these turbulent flames, where ReTReT-0.5 and Ka are the turbulent Reynolds and Karlovitz numbers, respectively. For pure CH4/air flames, the critical value of K for global quenching of rich/lean CH4 flames must be greater than 1.0/6.2. Values of Kc are very sensitive to φ, because Kc increases significantly as φ gradually approaches 1 from either lean or rich sides, with the maximum Kc occurring possibly near φ = 1. By comparing N2- and CO2-diluted flames of the same SL, it is found that global quenching of lean/rich CH4 flames is/is not influenced by the radiatvie heat loss, respectively. The larger the radiative heat loss, the smaller the value of Kc for lean CH4 flames, in which values of Kc decrease from 4 (N2-diluted) to 3 (CO2-diluted) where SL ≈ 10 cm/s and φ = 0.62. On the other hand, Kc ≈ 1.3 for both N2- and CO2-diluted rich CH4 flames where SL ≈ 10 cm/s and φ = 1.20-1.45. These experimental results are important to the understanding of global quenching processes for turbulent premixed combustion.

UR - http://www.scopus.com/inward/record.url?scp=0037481096&partnerID=8YFLogxK

U2 - 10.1016/S1540-7489(02)80223-1

DO - 10.1016/S1540-7489(02)80223-1

M3 - 會議論文

AN - SCOPUS:0037481096

VL - 29

SP - 1841

EP - 1847

JO - Proceedings of the Combustion Institute

JF - Proceedings of the Combustion Institute

SN - 1540-7489

IS - 2

Y2 - 25 July 2004 through 30 July 2004

ER -