Dynamics of Near Limit Diffusion Flames at Elevated Pressures and Temperatures

The effects of cool flame chemistry and thermal radiation on the flame regimes and flammabilility limits of diffusion flames at elevated pressures and temperatures on dimethyl ether/air mixtures have been examined numerically. Three different flame regimes, cool flames, mild flames, and hot flames, are found. For near limit flames, the hot flames are bounded by a radiation extinction limit and a stretch extinction limit. The mild flame has a stretch extinction limit at high stretch rate. The cool flames have a reignition limit at low stretch rates and a stretch extinction limit at high stretch rate. Both pressure and temperature have significant impact on the flame regimes and their flammable regions. A new near limit diffusion flame flammability diagram, which includes all three flame regimes, is obtained.