Abstract
Characteristics of microjet hydrogen diffusion flames stabilized near extinction are investigated numerically. Two-dimensional simulations are carried out using a detailed reaction mechanism. The effect of burner wall material, thickness, and thermal radiation on flame characteristics such as flame height and maximum flame temperature are studied. Results show that the flame stabilizes at lower fuel jet velocities for quartz burner than steel or aluminum. Higher flame temperatures are observed for low conductive burners, whereas the flame length increases with an increase in thermal conductivity of the burner. Even though thermal radiation has a minor effect on flame characteristics like flame temperature and flame height, it significantly influences the flame structure for low conductive burner materials. The burner tip and its vicinity are substantially heated for low conductive burners. The effect of burner wall thickness on flame height is significant, whereas it has a more negligible effect on maximum flame temperature. Variation in wall thickness also affects the distribution of H and HO2 radicals in the flame region. Although the variation in wall thickness has the least effect on the overall flame shape and temperature distribution, the structure near the burner port differs.
Highlights
Miniaturization of electrical and mechanical devices demands micro power generators with high specific energy density and increased operational lifetimes [1,2,3,4,5,6]
The present computational study showed that flames stabilize on burner the quartz burner flame structure is investigated numerically by adopting three different materials at lower fuel jet velocities than that of steel or aluminum burners
These results confirmed that the burner wall thermal conductivity and heat recirculation through burner walls play a significant role in flame stabilization
Summary
Miniaturization of electrical and mechanical devices demands micro power generators with high specific energy density and increased operational lifetimes [1,2,3,4,5,6]. Combustiondriven microdevices utilize liquid hydrocarbons, which have a high specific energy density compared to advanced electric batteries. Investigations on flame stability and structure of micro flames are essential for the design of micro combustors. Micro diffusion flames always encounter stability problems such as quenching and blowoff. Flame quenches at the tube wall for lower fuel flow velocities. Many studies [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25] were conducted to analyze the flame structure and characteristics of micro diffusion flames, which were recently reviewed by Maruta [26] and Nakamura et al [27]
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