The localised forced ignition and subsequent flame propagation have been analysed for stoichiometric $\text{C}{\text{H}}_4-\text{C}{\text{O}}_2-\text{air}$ mixtures with different spatial distributions and mean levels of $\text{C}{\text{O}}_2$ dilution (i.e. mole fraction of $\text{C}{\text{O}}_2$ in $\text{C}{\text{H}}_4/\text{C}{\text{O}}_2$ blend) for different flow conditions (e.g. quiescent laminar condition and different turbulence intensities) using three-dimensional Direct Numerical Simulations. The $\text{C}{\text{H}}_4+\text{C}{\text{O}}_2$ mixture is taken to represent biogas, as $\text{C}{\text{H}}_4$ and $\text{C}{\text{O}}_2$ are its two principal constituents. A two-step chemical mechanism, which has been demonstrated to capture the effects of $\text{C}{\text{O}}_2$ dilution on the laminar burning velocity with sufficient accuracy, has been used for the purpose of a parametric analysis in terms of the mean value, standard deviation and integral length scale of the initial spatial Gaussian distributions of $\text{C}{\text{O}}_2$ dilution in the unburned gas. An increase of mean $\text{C}{\text{O}}_2$ dilution level was found to reduce the maximum values of temperature and the reaction rate magnitude of $\text{C}{\text{H}}_4$. Moreover, an increase of mean $\text{C}{\text{O}}_2$ dilution acts to reduce the probability of finding large reaction rate magnitudes of $\text{C}{\text{H}}_4$, which also leads to a decreasing trend of burned gas volume $\text{C}{\text{O}}_2$ irrespective of flow conditions. Furthermore, an increase in turbulence intensity acts to reduce the burned gas volume irrespective of mixture composition due to the enhancement of heat transfer from the hot gas kernel. However, the initial values of integral length scale and standard deviation of $\text{C}{\text{O}}_2$ dilution variation (i.e. $l_{\psi }$ and ${\sigma }^{\psi }$) have been found not to have significant influences on the burned gas volume for the parameter range considered here. Although a small value of $l_{\psi }$ promotes high rates of mixing of $\text{C}{\text{O}}_2$ within the unburned gas, the overwhelming probability of finding $\text{C}{\text{O}}_2$ dilution close to its mean value eclipses the effects of $l_{\psi }$ and ${\sigma }^{\psi }$ even under laminar conditions, and this trend strengthens further under high turbulence intensities due to enhanced mixing.

分析了局部强制点火和随后的火焰传播的化学计量 $\text{C}{\text{H}}_4-\text{C}{\text{Ø}}_{\mathrm{2个}}-\text{空气}$ 具有不同空间分布和平均水平的混合物 $\text{C}{\text{Ø}}_{\mathrm{2个}}$ 稀释度（即 $\text{C}{\text{Ø}}_{\mathrm{2个}}$ 在 $\text{C}{\text{H}}_4/\text{C}{\text{Ø}}_{\mathrm{2个}}$使用三维直接数值模拟针对不同的流动条件（例如静态层流条件和不同的湍流强度）进行混合）。这$\text{C}{\text{H}}_4+\text{C}{\text{Ø}}_{\mathrm{2个}}$ 混合物代表沼气，因为 $\text{C}{\text{H}}_4$ 和 $\text{C}{\text{Ø}}_{\mathrm{2个}}$是它的两个主要组成部分。两步化学机制已被证明可以捕获$\text{C}{\text{Ø}}_{\mathrm{2个}}$ 为了充分分析层流燃烧速度的稀释度，已将其用于初始空间高斯分布的均值，标准偏差和积分长度尺度用于参数分析。 $\text{C}{\text{Ø}}_{\mathrm{2个}}$在未燃烧的气体中稀释。均值的增加$\text{C}{\text{Ø}}_{\mathrm{2个}}$ 发现稀释水平降低了温度的最大值和反应速率的幅度。 $\text{C}{\text{H}}_4$。而且，均值的增加$\text{C}{\text{Ø}}_{\mathrm{2个}}$ 稀释作用降低了发现较大的反应速率幅度的可能性。 $\text{C}{\text{H}}_4$，这也导致燃烧气体量减少的趋势 $\text{C}{\text{Ø}}_{\mathrm{2个}}$不论流动条件如何。此外，湍流强度的增加起到减少燃烧气体体积的作用，而与混合物组成无关，这归因于来自热气体核的传热的增强。但是，积分长度刻度的初始值和标准偏差为$\text{C}{\text{Ø}}_{\mathrm{2个}}$ 稀释度变化（即 ${升}_{\psi }$ 和 ${\sigma }^{\psi }$对于此处考虑的参数范围，已发现）对燃烧的气体量没有显着影响。虽然价值不大${升}_{\psi }$ 促进高混合率 $\text{C}{\text{Ø}}_{\mathrm{2个}}$ 在未燃烧的气体中，发现的绝大多数可能性 $\text{C}{\text{Ø}}_{\mathrm{2个}}$ 接近其平均值的稀释会抵消 ${升}_{\psi }$ 和 ${\sigma }^{\psi }$ 即使在层流条件下，由于增强了混合，这种趋势在高湍流强度下也会进一步增强。