Simulation of ignition delay time of compressed natural gas combustion

This research mainly aims to simulate compressed natural gas (CNG) combustion to create a valid reaction mechanism that can be used to determine the effects of temperature, pressure, equivalent ratio, diluents composition, and CNG composition on the ignition delay time profile in a combustion reaction. The combustion reaction involves many elementary reactions; therefore, in this study, the stages of important reactions were identified by sensitivity and rate of production analyses. In this study, CNG was represented by three components, namely, methane, ethane and propane (CH₄/C₂H₆/C₃H₈). The model is arranged according to the literature and validates the experimental data for CH₄/C₂H₆/C₃H₈/O₂/N₂ mixture in the temperature (T) range of 1039-1553 K, initial pressure (P) range of 1.1-40.0 atm, and equivalent ratio (Φ) = 0.5, 1.0, and 2.0 using a shock tube. The software used in this study is Chemkin 3.7.1. The ignition delay time profile for CNG combustion has been successfully reproduced by the kinetic model. The slowest ignition delay time for the composition of 88% CH₄/8% C₂H₆/4% C₃H₈ with an initial temperature range of 1100-1500 K is 37.2 ms (P=2 atm, T=1100 K, and Φ=2.0) and the fastest IDT is 0.033 ms (P=30 atm, T=1500 K, and Φ=0.5). For constant ethane or propane composition, the increase in methane composition will cause slower ignition.