Research on Minimum Ignition Energy Testing of Normal-Alkane Vapors

Minimum Ignition Energy (MIE) is a critical parameter for assessing the combustion and explosion risks of liquid fuels under specific conditions. However, systematic testing methods for long-chain alkanes remain underdeveloped. In this study, an experimental apparatus was developed based on American Society for Testing and Materials Standard ASTM E582-21 to measure the MIE of liquid fuel vapors. Through systematic measurements of the minimum ignition energy (MIE) of alkane vapors, this study examines the influence of vapor concentration on MIE and elucidates the dependence of ignition energy on carbon chain length. System sensitivity parameters were calibrated using propane/air mixtures, establishing optimal testing conditions as a 2.0 mm electrode gap and a 14.0 pF capacitance. The measured minimum ignition energy (MIE) values for C₅–C₈ alkane vapors at their respective sensitive volume fractions were 0.197 mJ (at 3.4 vol%), 0.253 mJ (at 3.3 vol%), 0.303 mJ (at 3.0 vol%), and 0.323 mJ (at 2.8 vol%). The experimentally determined MIE values for C₅–C₈ alkane vapors demonstrate close agreement with literature data, confirming the reliability of the experimental system and methodology for MIE determination of liquid fuel vapors. Furthermore, the study reveals a characteristic V-shaped correlation between MIE and vapor concentration, along with a consistent shift in the sensitive concentration toward fuel-rich conditions relative to stoichiometric proportions. Extended measurements of C₉–C₁₁ alkanes revealed MIE values of 0.523 mJ (at 2.8 vol%) for n-nonane, 0.857 mJ (at 2.5 vol%) for n-decane, and 1.127 mJ (at 2.0 vol%) for n-undecane. Notably, the results demonstrate a substantial increase in MIE with carbon chain length, showing a 471% rise from C₅ to C₁₁. A nonlinear regression analysis confirmed a strong correlation between MIE and carbon chain length (R² = 0.98).