TY - JOUR

T1 - High-pressure burning velocities measurements for centrally-ignited premixed methane/air flames interacting with intense near-isotropic turbulence at constant Reynolds numbers

AU - Liu, Chien Chia

AU - Shy, Shenqyang Steven

AU - Peng, Ming Wei

AU - Chiu, Chien Wen

AU - Dong, Yi Chih

N1 - Funding Information:
The continuous support by the National Science Council , Taiwan under the Grants ( NSC 97-2221-E-008-085-MY3 ; 98-2221-E-008-058-MY3 ; 98-3114-E-008-004 ; 100-3113-E-008-004 ; and 100-ET-E-008-001-ET ) is gratefully acknowledged. The authors would like to thank three anonymous reviewers for their constructive and valuable comments.

PY - 2012/8

Y1 - 2012/8

N2 - This paper measures high-pressure turbulent burning velocities (S T) of lean methane spherical flames at constant turbulent Reynolds numbers (Re T≡u'L I/ν), where u' and L I are the r.m.s. turbulent fluctuation velocity and the integral length scale of turbulence and ν is the kinematic viscosity of reactants. This is achieved by adopting a recently-built double-chamber, fan-stirred cruciform burner with perforated plates that can be used to generate intense near-isotropic turbulence with negligible mean velocities while controlling the product of u'L I in proportion to the decreasing ν at elevated pressure (p) up to 1.2MPa. Results show that when Re T is fixed ranging from 6700 to 14,200, values of S T decrease similarly as laminar burning velocities (S L) with increasing p in minus exponential manners, revealing a global response of burning velocities to pressure. In general, the higher Re T, the higher S T/S L at any fixed p. It is found that the curves of S T/S L as a function of u'/S L all exhibit very strong bending under constant Re T conditions. These results not only reveal that the important effect of Re T on high-pressure S T/S L enhancement, but also suggest that recent findings related with the promotion effect of increasing pressure on S T primarily due to the enhancement of flame instabilities via the thinner flame without any discussion on the influence of Re T elevation at elevated pressure should be reconsidered. Moreover, we found that the modified values of S T at mean progress variable c̄≈0.5 show good agreements between Bunsen-type and spherical flames, suggesting that S T determined at flame surfaces with c̄=0.5 may be a better representative of itself regardless of the flame geometries. Finally, various general correlations of ST,c̄=0.5 are compared and discussed. It is found that the present scattering data under different p and Re T conditions can be merged onto a single curve of (ST,c̄=0.5-S L)/u'=0.14Da 0.47, where Da is the turbulent Damköhler number.

AB - This paper measures high-pressure turbulent burning velocities (S T) of lean methane spherical flames at constant turbulent Reynolds numbers (Re T≡u'L I/ν), where u' and L I are the r.m.s. turbulent fluctuation velocity and the integral length scale of turbulence and ν is the kinematic viscosity of reactants. This is achieved by adopting a recently-built double-chamber, fan-stirred cruciform burner with perforated plates that can be used to generate intense near-isotropic turbulence with negligible mean velocities while controlling the product of u'L I in proportion to the decreasing ν at elevated pressure (p) up to 1.2MPa. Results show that when Re T is fixed ranging from 6700 to 14,200, values of S T decrease similarly as laminar burning velocities (S L) with increasing p in minus exponential manners, revealing a global response of burning velocities to pressure. In general, the higher Re T, the higher S T/S L at any fixed p. It is found that the curves of S T/S L as a function of u'/S L all exhibit very strong bending under constant Re T conditions. These results not only reveal that the important effect of Re T on high-pressure S T/S L enhancement, but also suggest that recent findings related with the promotion effect of increasing pressure on S T primarily due to the enhancement of flame instabilities via the thinner flame without any discussion on the influence of Re T elevation at elevated pressure should be reconsidered. Moreover, we found that the modified values of S T at mean progress variable c̄≈0.5 show good agreements between Bunsen-type and spherical flames, suggesting that S T determined at flame surfaces with c̄=0.5 may be a better representative of itself regardless of the flame geometries. Finally, various general correlations of ST,c̄=0.5 are compared and discussed. It is found that the present scattering data under different p and Re T conditions can be merged onto a single curve of (ST,c̄=0.5-S L)/u'=0.14Da 0.47, where Da is the turbulent Damköhler number.

KW - High-pressure premixed turbulent combustion

KW - Intense near-isotropic turbulence

KW - Turbulent burning velocities

KW - Turbulent damköhler and karlovitz numbers

KW - Turbulent reynolds number

UR - http://www.scopus.com/inward/record.url?scp=84862339950&partnerID=8YFLogxK

U2 - 10.1016/j.combustflame.2012.04.006

DO - 10.1016/j.combustflame.2012.04.006

M3 - 期刊論文

AN - SCOPUS:84862339950

VL - 159

SP - 2608

EP - 2619

JO - Combustion and Flame

JF - Combustion and Flame

SN - 0010-2180

IS - 8

ER -