Abstract:

This study measures the ignition delay times of C₂H₄/O₂/Ar stoichiometric mixtures under Ar diluent mole fractions of 75% and 96% using the shock tube. The experimental temperatures range from 1092 to 1743 K and the pressures range from 1.3 to 3.0 atm (1 atm = 101325 Pa). The logarithm of the ignition delay time is found to be a linear function of the reciprocal temperature. The ignition delay time is shorter in the lower diluent concentrations, as well as decreasing with increasing temperature. Moreover, detonation (or deflagration to detonation) is observed in the lower but not the higher diluent concentrations. In comparative simulations of four different mechanisms, the LLNL mechanism best fits the experimental results. Reaction path analysis shows that the ethylene oxidation paths are affected by temperature rather than diluent rate. With increasing temperature, the number of ethylene oxidation paths decrease from four to three because of the predominance of the reverse reaction C₂H₄ + H (+ M) → C₂H₅ (+ M).

Key words: Shock tube, Ethylene, Ignition delay, Deflagration, Detonation, Oxidation