Effect of hydrogen enrichment on the auto-ignition of lean n-pentane/Hydrogen mixtures at elevated pressure

To understand the synergistic effect of hydrogen-enriched combustion of hydrocarbons in the high temperatures, ignition delay times of lean (φ = 0.5) n-pentane/hydrogen mixtures with various hydrogen volumetric contents (X_H2 = 0–95%) were measured in a shock tube at pressures of 2, 10 and 20 atm. As expected, the ignition delay time of n-pentane is decreased when doping with hydrogen. Interestingly, the effect of hydrogen addition on auto-ignition is nonlinear. Note that even the hydrogen proportion is as large as 95%, the ignition delay time of the binary mixture exhibits the n-pentane-like activation energy and pressure dependence characteristics. Reasons for the above-mentioned behaviors were analyzed.