TY - JOUR
T1 - Experimental study of the influence of Lewis number, laminar flame thickness, temperature, and pressure on turbulent flame speed using hydrogen and methane fuels
AU - Hsieh, Hao Yu
AU - Mousavi, Seyed Morteza
AU - Lipatnikov, Andrei N.
AU - Shy, Shenqyang (Steven)
N1 - Publisher Copyright:
© 2024 The Combustion Institute
PY - 2024/1
Y1 - 2024/1
N2 - To experimentally explore the influence of Lewis number Le, laminar flame thickness δL, pressure P, and unburned gas temperature Tu on turbulent flame speed ST, a set of conditions is designed by adjusting nitrogen mole fraction in lean H2/O2/N2 (Le=0.35) and stoichiometric CH4/O2/N2 (Le≈1) mixtures. The adjustment is performed by simulating complex-chemistry laminar flames to obtain the same laminar flame speeds SL not only for different fuels, but also for different pressures (1, 2, and 5 atm). The mixtures are characterized by significantly different SL at Tu=300 K and 400 K, whereas variations in δL with the temperature are sufficiently weak. Moreover, laminar flame thicknesses are approximately equal for H2-based and CH4-based mixtures at the same P, but are significantly decreased with increasing pressure. For this set of conditions, ST is measured by applying schlieren imaging techniques to film expansion of centrally ignited, statistically spherical flames in homogeneous isotropic turbulence generated by a dual-chamber, constant-pressure, fan-stirred explosion facility. Analyses of the measured data show the following trends. First, turbulent flame speed is increased by both P and Tu, whereas ST/SL is decreased with increasing Tu. Second, turbulent flame speed measured at different P and Tu can be predicted by allowing for SL(P,Tu) and δL(P,Tu). Thus, the present data do not call for explicitly substituting normalized pressure or temperature into a turbulent flame speed approximation. Third, ST is increased with decreasing laminar flame thickness. Fourth, speeds of the lean H2/O2/N2 flames are higher when compared to the stoichiometric CH4/O2/N2 flames, with this difference is increased (reduced) by P (Tu, respectively). Fifth, all measured data on ST can quantitatively be described by substituting SL and δL with the counterpart characteristics of highly strained twin laminar flames. The latter finding supports leading point concept of premixed turbulent combustion.
AB - To experimentally explore the influence of Lewis number Le, laminar flame thickness δL, pressure P, and unburned gas temperature Tu on turbulent flame speed ST, a set of conditions is designed by adjusting nitrogen mole fraction in lean H2/O2/N2 (Le=0.35) and stoichiometric CH4/O2/N2 (Le≈1) mixtures. The adjustment is performed by simulating complex-chemistry laminar flames to obtain the same laminar flame speeds SL not only for different fuels, but also for different pressures (1, 2, and 5 atm). The mixtures are characterized by significantly different SL at Tu=300 K and 400 K, whereas variations in δL with the temperature are sufficiently weak. Moreover, laminar flame thicknesses are approximately equal for H2-based and CH4-based mixtures at the same P, but are significantly decreased with increasing pressure. For this set of conditions, ST is measured by applying schlieren imaging techniques to film expansion of centrally ignited, statistically spherical flames in homogeneous isotropic turbulence generated by a dual-chamber, constant-pressure, fan-stirred explosion facility. Analyses of the measured data show the following trends. First, turbulent flame speed is increased by both P and Tu, whereas ST/SL is decreased with increasing Tu. Second, turbulent flame speed measured at different P and Tu can be predicted by allowing for SL(P,Tu) and δL(P,Tu). Thus, the present data do not call for explicitly substituting normalized pressure or temperature into a turbulent flame speed approximation. Third, ST is increased with decreasing laminar flame thickness. Fourth, speeds of the lean H2/O2/N2 flames are higher when compared to the stoichiometric CH4/O2/N2 flames, with this difference is increased (reduced) by P (Tu, respectively). Fifth, all measured data on ST can quantitatively be described by substituting SL and δL with the counterpart characteristics of highly strained twin laminar flames. The latter finding supports leading point concept of premixed turbulent combustion.
KW - Differential diffusion effects
KW - Laminar flame thickness
KW - Lewis number
KW - Pressure
KW - Turbulent flame speed
KW - Unburned gas temperature
UR - http://www.scopus.com/inward/record.url?scp=85202347985&partnerID=8YFLogxK
U2 - 10.1016/j.proci.2024.105752
DO - 10.1016/j.proci.2024.105752
M3 - 期刊論文
AN - SCOPUS:85202347985
SN - 1540-7489
VL - 40
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 1-4
M1 - 105752
ER -