## 3 Results and Discussion
### Analysis of the Impact of Process Parameters on Combustion Reaction
#### 3.3.2 Effect of Process Parameters on Surface Reaction  
(1) Inlet velocity  
As shown in the Figure 16 and Table 7, compared to the no-wall reaction, in the interior of the wall, the adsorption amount of methane is increased due to the participation of the catalyst, and the speed of methane passing through the channel is accelerated, thereby greatly increasing the combustion ratio and burning rate of methane. As the inlet velocity increases, the combustion ratio increases rapidly. When the inlet velocity is between 6 \(\times\) 10\({}^{-8}\) and 1 \(\times\) 10\({}^{-7}\) m/s, the methane consumption increases slowly; in comparison, \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Pore Size**} & **Inlet Methane** & **Outlet Methane** & **Combustion** \\  & **Mass Fraction** & **Mass Fraction** & **Ratio (\%)** \\ \hline
60 nm & 3.400000185 \(\times\) 10\({}^{-2}\) & 0.03391203284 & 0.26 \\ \hline
150 nm & 3.400000185 \(\times\) 10\({}^{-2}\) & 0.033903090516 & 0.20 \\ \hline
300 nm & 3.400000185 \(\times\) 10\({}^{-2}\) & 0.03390500322 & 0.28 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Effect of pore size on combustion reaction. Figure 14: Effect of inlet methane concentration on combustion reaction. Figure 15: Effect of pore size on combustion reaction. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Inlet Concentration** & \begin{tabular}{c} **Inlet Methane** \\ **Mass Fraction** \\ \end{tabular} & \
\begin{tabular}{c} **Outlet Methane** \\ **Mass Fraction** \\ \end{tabular} &
\begin{tabular}{c} **Combustion** \\ **Ratio, (\%)** \\ \end{tabular} \\ \hline
0.01687500067 & 0.01687500067 & 0.00717461854 & 57.5 \\ \hline
0.03400000185 & 0.03400000185 & 0.01191107742 & 65.0 \\ \hline
0.05624999851 & 0.05624999851 & 0.01790973172 & 68.2 \\ \hline \hline \end{tabular} (3)  
As shown in the Figure 18 and Table 9, unlike the bulk reaction, the combustion ratio increases with increasing pore size. When the pore size exceeds 150 nm, the rate change is particularly obvious, and the combustion ratio is close to 100%. Changes in methane consumption and the burning rate are greatly improved from the orifice position to the depth of 0.00000012 m. From this position to the outlet of the orifice, the burning rate of the 150 nm aperture has a slight downward trend, and the burning rate of the other two apertures has no obvious change; however, methane consumption continues to increase with increasing aperture. While analyzing with body-reaction, the aperture size at the wall should be controlled so that it is larger than 300 nm, and the aperture should be transitioned from 150 nm to the inside. In doing so, the gradual structure of the aperture is realized. Thus, the 300-nm aperture size of previous studies can be improved, and the performance of this type of methane sensor in coal mine underground can be enhanced.  
\begin{tabular}{c c c} \hline \hline
**Pore Size** & \begin{tabular}{c} **Inlet Methane** \\ **Mass Fraction** \\ \end{tabular} & \
\begin{tabular}{c} **Outlet Methane** \\ **Mass Fraction** \\ \end{tabular} &
\begin{tabular}{c} **Combustion** \\ **Ratio, \%** \\ \end{tabular} \\ \hline
60 nm & 3.400000185 \(\times\) 10\({}^{-22}\) & 0.0129 & 62.1 \\ \hline
150 nm & 3.400000185 \(\times\) 10\({}^{-2}\) & 0.0085 & 75.0 \\ \hline
300 nm & 3.400000185 \(\times\) 10\({}^{-2}\) & 0.0031 & 90.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Effect of pore size on combustion reaction. Figure 18: Effect of pore size on combustion reaction. considerably from the orifice to a 0.00000012 m hole depth, after which the combustion rate did not exhibit a significant change. Thus, the best combustion position of methane inside the orifice is determined to be at depths of 0-0.00000012 m, which complements previous conclusions regarding the reaction inside the orifice. Furthermore, the methane combustion rate increases with the increasing inlet concentration and velocity, proportional to the concentration change.