TY - JOUR

T1 - Measurement and scaling of minimum ignition energy transition for spark ignition in intense isotropic turbulence from 1 to 5 atm

AU - Shy, S. S.

AU - Shiu, Y. W.

AU - Jiang, L. J.

AU - Liu, C. C.

AU - Minaev, S.

N1 - Publisher Copyright:
© 2016 The Combustion Institute. Published by Elsevier Inc.

PY - 2017

Y1 - 2017

N2 - This paper presents high-pressure minimum ignition energies (MIE) and their scaling from measurements on spark discharges in lean methane/air mixtures at the equivalence ratio φ = 0.6 by cylindrical electrodes with flat ends in near-isotropic turbulence over a range of turbulent intensities (u′/SL = 0-50), from 1 to 5 atm, using a large dual-chamber, constant-pressure, fan-stirred explosion facility, where SL is the laminar burning velocity. Voltage and current waveforms of spark discharges with nearly square profiles are carefully generated for accurate determination of MIE, commonly defined as the 50% successful ignitability. Applying high-speed schlieren imaging, we observe a drastic change of kernel development from turbulent flamelet to distributed like with island formation and local quench even at 5 atm, when u′/SL is greater than some critical values depending on p. It is found that the scaling slopes of MIET/MIEL versus u′/SL change abruptly from a linear increase to an exponential increase when u′/SL > (u′/SL)c, showing ignition transition. The subscripts T and L represent turbulent and laminar properties, MIEL ≈ 6.84 mJ (1 atm), 2.81 (3 atm), and 2.11 (5 atm), and the transition occurs at (u′/SL)c ≈ 12 (1 atm), 24 (3 atm), and 34 (5 atm). It is also found that the above scattering MIET/MIEL data at different u′/SL and p can be merged together into a single curve when scaled with a pressure-corrected kernel (reaction zone, RZ) Péclet number, Pe∗ = PeRZ(p/p0)-1/4, showing the first and fourth power dependence before and after MIE transition at a critical Pe∗ ≈ 3.6. PeRZ = u′ηk/αRZ, ηk is the Kolmogorov length scale of turbulence, αRZ is the thermal diffusivity estimated at the instant of kernel formation, and p0 = 1 atm. These results reveal a self-similar spark ignition phenomenon.

AB - This paper presents high-pressure minimum ignition energies (MIE) and their scaling from measurements on spark discharges in lean methane/air mixtures at the equivalence ratio φ = 0.6 by cylindrical electrodes with flat ends in near-isotropic turbulence over a range of turbulent intensities (u′/SL = 0-50), from 1 to 5 atm, using a large dual-chamber, constant-pressure, fan-stirred explosion facility, where SL is the laminar burning velocity. Voltage and current waveforms of spark discharges with nearly square profiles are carefully generated for accurate determination of MIE, commonly defined as the 50% successful ignitability. Applying high-speed schlieren imaging, we observe a drastic change of kernel development from turbulent flamelet to distributed like with island formation and local quench even at 5 atm, when u′/SL is greater than some critical values depending on p. It is found that the scaling slopes of MIET/MIEL versus u′/SL change abruptly from a linear increase to an exponential increase when u′/SL > (u′/SL)c, showing ignition transition. The subscripts T and L represent turbulent and laminar properties, MIEL ≈ 6.84 mJ (1 atm), 2.81 (3 atm), and 2.11 (5 atm), and the transition occurs at (u′/SL)c ≈ 12 (1 atm), 24 (3 atm), and 34 (5 atm). It is also found that the above scattering MIET/MIEL data at different u′/SL and p can be merged together into a single curve when scaled with a pressure-corrected kernel (reaction zone, RZ) Péclet number, Pe∗ = PeRZ(p/p0)-1/4, showing the first and fourth power dependence before and after MIE transition at a critical Pe∗ ≈ 3.6. PeRZ = u′ηk/αRZ, ηk is the Kolmogorov length scale of turbulence, αRZ is the thermal diffusivity estimated at the instant of kernel formation, and p0 = 1 atm. These results reveal a self-similar spark ignition phenomenon.

KW - High-pressure turbulent spark ignition

KW - Intense isotropic turbulence

KW - Minimum ignition energy transition

KW - Self-similar ignition

KW - Turbulent flamelet and distributed like kernels

UR - http://www.scopus.com/inward/record.url?scp=84994493189&partnerID=8YFLogxK

U2 - 10.1016/j.proci.2016.08.049

DO - 10.1016/j.proci.2016.08.049

M3 - 期刊論文

AN - SCOPUS:84994493189

SN - 1540-7489

VL - 36

SP - 1785

EP - 1791

JO - Proceedings of the Combustion Institute

JF - Proceedings of the Combustion Institute

IS - 2

ER -