# The Period of Ignition Delay for Methane-Air Mixture with Hydrogen and Ethylene Additives
## 4 Selection and Validation of the Kinetic Ignition Model  
Since in this work, the period of the ignition delay of methane with additions of ethylene and hydrogen is considered, the analysis of studies related to the combustion of these gases is carried out. It was compared to 29 studies connected with combustion kinetic mechanisms. The combustion of pure gas in air gives the limiting case for the mixtures under consideration. Checking of combustion kinetic mechanisms allows estimating possible discrepancies between calculations and experimental data. The calculations were carried out for the closed reactor of constant volume with adiabatic walls. The kinetic mechanisms for modeling the combustion process were considered in the work selected on the basis of analysis of the literature data GRI-Mesh 3.0, NUIGMesh 1.1, and AramcoMech 3.0. All the experimental data presented have some differences related to the accuracy of assessing the onset of ignition (based on pressure sensors, sensors for the concentration of an additive in a gas, a laser or optical recording system), the locations of the detector system, the geometric features of the tube, the purity of the mixture, and a sufficient holding time to obtain a homogeneous mixture. However, the accumulated experimental data allows us to determine the approximate ignition delay time for each mixture in Table 1. Table 1 summarizes the experimental data for validating kinetic mechanisms. From the obtained analysis, it can be seen that the vast majority of works are devoted to the study of the ignition delay time of pure gases. This suggests that supplementation research is poorly understood and promising for the future. In the overwhelming majority of works, including the data of the article's authors, stoichiometric ratios of fuel to air were considered, so outside these conditions, there is great potential for research. The practical impact of this work is that these results allow estimating possible discrepancies between calculations and experimental data. Also, it lets researchers see new fields for their investigations, such as new mixtures of fuel or new research conditions. A comparison of the experimental data on the ignition delay period given in the literature and the ignition delay period calculated in this work is shown in Figures 2-4 for the ignition delays of methane, hydrogen, ethylene, and methane-hydrogen mixture, respectively. The figures show close experimental points for characteristic pressures; lines in the graph indicate the results of calculations based on kinetic mechanisms. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Fuel**} & \multirow{2}{*}{**Literary Sources**} & \multicolumn{3}{c}{**Ranges of Ignition Regimes**} \\ \cline{3-5}  & & **P, Bar** & **T, K** & \(\Phi\) \\ \hline CH\({}_{4}\) & [32, 36, 37, 39, 40, 41, 50, 51], data of article authors & 0.6–286.0 & 860–2000 & 0.5–2.0 \\ H\({}_{2}\) & [42, 43, 44, 51] & 0.2–87.0 & 850–4445 & 0.1–2.0 \\ C\({}_{2}\)H\({}_{4}\) & [33, 47, 49] & 1.3–60.0 & 1020–2220 & 1.0–3.0 \\ CH\({}_{4}\) + H\({}_{2}\) & [50, 51, 52] & 1.0–50.0 & 850–2000 & 0.3–2.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Experimental data. Figure 3: The summary graph of the ignition delay time dependence on temperature for the stoichiometric mixture H\({}_{2}\) + air. Figure 2: A summary graph of the ignition delay period dependence on temperature for stoichiometric mixture of CH\({}_{4}\) + air. In Figure 2, it is clearly explained that numerical modeling of kinetic models AramcoMech3.0 and NUIGMech1.1 differs from the results of GRI-Mesh3.0. Such differences could be explained by the discrepancy in the number of including reactions. This also is the reason for some incline of the curves with the temperature below 1200 K for AramcoMech3.0 \(\mu\)NUIGMech1.1. There is a sufficient coincidence between experimental data and results of numerical calculations with the pressure 1 and 10 bar.