Dynamics and flammability limit of stretched premixed flames stabilized by a hot wall

Dynamics and flammability limit of stretched, ultra-lean methane-air premixed flames stabilized by a hot wall were studied theoretically and numerically using the large activation energy asymptotic approach and the detailed chemistry, respectively. The appearance of hot wall resulted in new flame bifurcation. Except for the high temperature flame, there existed a hot wall stabilized low temperature flame that dramatically extends the flammable region of stretched flame to low stretch. Sub-limit flame could be stabilized by a hot wall and had a non-zero flame speed even with wall temperature less than its adiabatic flame temperature. The effect of radiation heat loss and Lewis number effect were suppressed by the hot wall, and that stretched flames at Lewis number below unity could extinguish at a finite distance from the wall. Numerical calculations with detailed chemistry below unity could extinguish at a finite distance from the wall. Numerical calculations with detailed chemistry well reproduced the prediction of the analytical results. Theoretical analysis qualitatively agreed well with the numerical calculation, but failed in the prediction of the low temperature flame at high stretch rate. Original is an abstract.