ISSN Online: 2688-7231
ISBN Online: 978-1-56700-524-0
Proceedings of the 26thNational and 4th International ISHMT-ASTFE Heat and Mass Transfer Conference December 17-20, 2021, IIT Madras, Chennai-600036, Tamil Nadu, India
Numerical Investigation on the Lewis Number Effects on the Turbulent Premixed Swirl Stabilized Propane-Air Flames
Аннотация
Interaction of Coherent Precessing Vortex Core(PVC) as
well as the preferential diffusional effects on the turbulent
premixed swirling propane-air flames at different Lewis
numbers (Le) with high Karlovitz (Ka) and low Damkohler
Number (Da) values were studied numerically. For this, the
swirl burner reported in the literature having swirl number
S=1.05 was adapted, recreated and simulated using ANSYS
Fluent. Computational analysis was initiated with propaneair
mixture having equivalence ratio, ∅=2 (Le=0.879) at 573K and 1 bar, using RANS and DDES. Present simulation
results were successfully validated with the experimental
data from literature. DDES showed good agreement with experiments. With the same model, the combustible mixtures having ∅=1(Leeff =1.36) & ∅=0.6(Le=1.735), keeping the Reynolds number nearly same were simulated. Time-averaged axial velocity and temperature indicated that the flames stabilized in the Inner shear layer( ISL) where strong vortices dominates. Flame, at stoichiometric condition, was anchored most upstream due to its relatively shorter reaction time and was the longest among the three due to higher fuel mole fraction. Borghi diagram reveals
that flame region in fuel rich condition(Le<1) was most
stretched, thickest, reaction controlled and Kolmogorov
eddies controls the flame zone too. Stoichiometric condition
is least corrugated though its RMS velocity magnitude &
integral length scale values were comparable to rich and
lean conditions respectively. Time series analysis indicates
that in the fuel lean condition, vortices shed early and with
greater frequency from the ISL in the combustion chamber
as compared to other two conditions forming relatively stronger PVC that even stabilizes the flame with Le>>1 having Ka is nearly 100 and Da<1.