Spark ignition probability and minimum ignition energy transition of the lean iso-octane/air mixture in premixed turbulent combustion

Long Jie Jiang, Shenqyang (Steven) Shy, Minh Tien Nguyen, Shih Yao Huang, De Wei Yu

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


This paper measures turbulent spark ignition probability and minimum ignition energy (MIE) of the pre-vaporized iso-octane/air mixture at an equivalence ratio ϕ = 0.8 at 373 K with Le ≈ 2.98 over a wide range of turbulent intensities (u′/SL), where Le is the mixture's effective Lewis number and SL is the laminar burning velocity. Ignition experiments using a fixed 2-mm electrode gap are conducted in a large dual-chamber, constant-temperature/pressure, fan-stirred 3D cruciform burner capable of generating near-isotropic turbulence. Spark discharges having nearly square voltage and current waveforms are created for accurate determination of the ignition energy (Eig) across the electrodes. MIE [tbnd] Eig(50%) that is determined statistically from many repeated experiments at a given condition using a range of Eig to identify an overlapping energy band within which ignition and non-ignition coexist even at the “same discharge Eig”, where the subscript “ig(50%)” indicates 50% ignitability. Results show that the increasing slopes of MIET/MIEL = Г versus u′/SL change drastically from linearly to exponentially when u′/SL is greater than a critical value of 4.8, which is much smaller than previous rich methane data (Le > 1) at ϕ = 1.2 with (u′/SL)c ≈ 16 and at ϕ = 1.3 with (u′/SL)c ≈ 24, revealing MIE transition. The subscripts T and L represent turbulent and laminar properties. When a reaction zone Péclet number PeRZ =u′ηkRZ is used for scaling, it is found that both present lean iso-octane and previous methane data can be collapsed onto a general correlation of Г1 = 1 + 0.4PeRZ in the pre-transition and Г2 ∼ PeRZ4 in the post-transition with the transition occurring at (PeRZ)c ≈ 4.2, showing similarity on MIE transition. ηk is the Kolmogorov length scale of turbulence and αRZ is the reaction zone thermal diffusivity estimated at the instant of kernel formation.

Original languageEnglish
Pages (from-to)87-95
Number of pages9
JournalCombustion and Flame
StatePublished - 2018


  • Lean iso-octane
  • Lewis number
  • Minimum ignition energy transition
  • Premixed turbulent combustion
  • Reaction zone Péclet number
  • Spark ignition probability


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