Abstract
The effect on the dynamic stability of combustors with and without flame holders were investigated experimentally and computationally with thermal loads of 3, 5, and 9 kW. Three different cases were studied, large flame holder (LFH), small flame holder (SFH) and no flame holder (NO_ FH). Flame topology was investigated in these three cases. Moreover, lean propane–air premixed combustion were also considered for two models, turbulent flame speed closure (TFC) and coherent flame (CFM). These models were investigated using different turbulent kinetic energies and turbulence dissipation rates. Experiments were performed with mean inlet velocities of 16.5, 17, 29.2, 30.8, and 52.6 cm/s, excess air ratios (λ) of 1.6, 1.65, 1.7, and 1.8. The results showed that the flame topology and location are more sensitive to the increase in the excess air ratios and thermal loads in the large flame holder than in the small flame holder. Heat transfers and species distributions caused by combustion are also investigated for the large and small flame holders; in both cases, flame stability was sustained, and the flame front position moved upward regarding to the flame holder region.
Highlights
A basic understanding of combustion processes, including mixing is vital
For the same combustion condition, the distributions of O2 and CO2 species in large flame holder (LFH) is above position in small flame holder (SFH) along the axial distance of the combustor which indicated that the flame topology is more stable compared to SFH case due to larger area of the flame holder
Flame topologies were observed for lean premixed propane–air during combustion
Summary
A basic understanding of combustion processes, including mixing is vital. Simultaneously, major issues on flame stabilization [1] should be resolved. MATHEMATICAL AND COMPUTATIONAL MODELING The dynamic stability of flames is a key indicator of combustion processes and depends on several parameters, such as turbulence, inlet temperature, mixing, and geometry of combustors. QQ = mṁ ffLLLLLLff where QQ is the thermal load of combustion, mṁ ff is the mass flow rate of fuel flowing into the combustor, and LLLLLLff is the low heat value of fuel and for propane is 46.39 kJ/g.
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