Extinction of Counterflow Diffusion Flames in Counter and Co-Rotating Finite Jets with General Lewis Numbers

Abstract The extinction of counterflow diffusion flames in counter and co-rotating finite-jets is experimentally and theoretically investigated. In the experimental study of methane and butane diffusion dames, the critical minimum values of oxidizer concentration as a function of the jet angular velocity ω is determined for various values of the jet linear velocity. It is found that the oxidizer concentration at extinction decreases to a minimum value at the critical angular velocity ω = ωr, and thereafter increases with the jet angular velocity. This tendency is similar to that observed earlier for the limiting fuel concentration at extinction. Also, the tests for the extinction of methane flames in counter versus co-rotating jets show that the difference between the results for the two flows appears for ω > ωr, i.e. after the onset of the secondary recirculating flow. Under the latter condition, the limit-oxygen and fuel concentrations are found to be higher in counter versus co-rotating jets. In the th...