Effects of Flame Structure and Inert Gases on Extinction Properties in DME Diffusion Flames

Experimental studies are conducted on extinction of non-premixed dimethyl ether (DME) flames stabilized in the counterflow configuration. Studies are carried out by injecting a fuel stream made up of fuel and inert gas (N₂ or CO₂) from one duct and an oxidizer stream made up of O₂ and inert gas (N₂ or CO₂) from the other duct. Critical conditions of extinction are measured by increasing the flow rate of the counterflowing streams until the flame extinguishes. Numerical studies are also performed using detailed chemistry at conditions corresponding to those used in the experiments and compared with measurements. The present study highlights the examination of the influence of flame temperature, flame structure and kind of inert gas on extinction properties of DME. To examine the effect of flame temperature, inert gas is introducing to both fuel and oxidizer sides in such a way that the stoichiometric mixture fraction, Z_st, is not changed, which means flame structure is not changed. To examine the effect of flame structure, Z_st is varied by removing inert gas from oxidizer side (oxygen-enriched air) and introducing it to the fuel side (diluted fuel) in such a way that the adiabatic flame temperature is not varied. To examine the effect of kind of inert gas, N₂ is replaced with CO₂ and both results are compared.