High-pressure ignition behaviors of methane/ethane/propane-n-heptane mixtures representing natural gas-diesel dual fuel

Considering that natural gas is the key transition fuel towards the carbon-neutral future, the objective of the present study is to gain insight into evolution features of natural gas-diesel dual fuel during ignition process. Firstly, new experimental data of ignition delay times for the stoichiometric methane/ethane/propane-n-heptane mixtures, which is of significance for validating and optimizing chemical kinetic models of the dual fuel at engine-relevant conditions, were acquired through a shock-tube facility at pressure of 40 atm within temperature range of 1200 to 1600 K, and quantitative influences of components of the fuel mixtures on ignition were determined. Then importance of species including typical radicals and alkenes during ignition processes were identified. Besides, stage characteristics of the fuel mixtures during ignition processes were analyzed. The result shows that the ignition of real natural gas which contains some ethane and propane is greatly different from that of methane. It can be seen that the C2 substances are significant to control ignition of the mixtures. For methane-n-heptane and methane/ethane-n-heptane mixtures, the whole ignition process can be divided into decomposition and oxidation stages. While for the fuel mixtures containing propane and n-heptane, it seems to be more reasonable to divide the whole ignition process into three stages, i.e., decomposition, mixed and oxidation stages.