The effects of CH₄ addition on DME non-premixed cool flames

Methane has poor reactivity at low temperatures, which limits its utilization in internal combustion engines. However, this issue can be remedied through the use of DME/CH₄ blends. In this paper, the effects of CH₄ addition on DME non-premixed cool flames are investigated. The extinction limits and flame structures of both hot and cool flames are measured using a counterflow burner and planar laser-induced fluorescence (PLIF). The experimental results show that steady DME/CH₄ non-premixed cool flames can be established in a counterflow burner. It is found that the addition of CH₄ into DME reduces the extinction strain rates of cool flames but increases the extinction strain rates of hot flames. Furthermore, the peak CH₂O mole fraction in both hot and cool flames decreases as the CH₄ mole fraction increases. Several DME/CH₄ reaction mechanisms are compared with the experimental data. Modeling results using the mechanism of Wang et al. show the most agreement with the experimental trends, but a significant quantitative disagreement is still apparent for the low-temperature cool flames.