“…The same trend also proves the results reported by Zhang et al. 48 and Yan et al. 34 When the equivalence ratio is reduced, the flame propagation speed decreases, 43 and thus the combustion does not occur completely in the combustion chamber.…”
In the present investigation, the effects of inner diameter and length of porous wall on flame stability limits, temperature distribution, methane conversion, and pressure drop in a premixed burner are numerically analyzed. The governing equations are solved by the control volume method, considering Re-Normalization Group k-ɛ for turbulence modeling and eddy dissipation concept for turbulence–chemistry interaction modeling. The simulations are performed for various porous walls with the inner diameter of 30, 40, and 50 mm and the length of 22, 44, and 66 mm. The results demonstrate that the increase in inner diameter of porous wall causes an increase in the lower flame stability limit and a decrease in the upper flame stability limit, gas and solid temperatures, pressure drop, and methane conversion. Also, the maximum solid and gas temperatures in the porous wall and methane conversion are related to the porous wall with 44 mm length. Furthermore, the methane conversion and pressure drop increase with the rise in the equivalence ratio. Finally, it can be said that the change in inner diameter of porous wall is more important than the length of porous wall in the studied phenomena.
“…The same trend also proves the results reported by Zhang et al. 48 and Yan et al. 34 When the equivalence ratio is reduced, the flame propagation speed decreases, 43 and thus the combustion does not occur completely in the combustion chamber.…”
In the present investigation, the effects of inner diameter and length of porous wall on flame stability limits, temperature distribution, methane conversion, and pressure drop in a premixed burner are numerically analyzed. The governing equations are solved by the control volume method, considering Re-Normalization Group k-ɛ for turbulence modeling and eddy dissipation concept for turbulence–chemistry interaction modeling. The simulations are performed for various porous walls with the inner diameter of 30, 40, and 50 mm and the length of 22, 44, and 66 mm. The results demonstrate that the increase in inner diameter of porous wall causes an increase in the lower flame stability limit and a decrease in the upper flame stability limit, gas and solid temperatures, pressure drop, and methane conversion. Also, the maximum solid and gas temperatures in the porous wall and methane conversion are related to the porous wall with 44 mm length. Furthermore, the methane conversion and pressure drop increase with the rise in the equivalence ratio. Finally, it can be said that the change in inner diameter of porous wall is more important than the length of porous wall in the studied phenomena.
“…22 The behavior is similar to that reported by Zhang et al. 47 Figure 10.Methane conversion rate at the middle of the combustion chamber with porous and solid bluff bodies for different equivalence ratios and V i = 0.75 m/s.…”
The effects of porous and solid bluff bodies in the combustion chamber on flame stability limits, gas and solid temperature distributions, pressure drop, methane conversion rate, and CO and NO emissions are examined numerically. The porous and solid bluff bodies are made of SiC with the inner diameter of 50 mm, the outer diameter of 90 mm, and the length of 22 mm. In this study, Renormalization Group k–ε is used for modeling of turbulence. Eddy dissipation concept is selected for modeling of the interaction between turbulence and chemistry. A reduced mechanism based on GRI 3.0 consisting of 16 species and 41 reactions is employed to model methane combustion. The results indicate that the upper flame stability limit can be diminished by adding porous bluff body in the combustion chamber instead of the solid bluff body. Besides, the pressure drop, CO and NO emissions in the combustion chamber with solid bluff body are higher than those of porous bluff body, while the methane conversion rate increases by replacing porous bluff body instead of solid bluff body in the combustion chamber.
“…The blow-off limit correlates positively with the blockage ratio. Yan et al [116,117] studied the CH 4 /air combustion characteristic in a hollow hemispherical bluff body and a micro combustor with a regular triangular pyramid bluff body. Blockage ratio shows the great impact on flame stabilization and CH 4 conversion.…”
With the improvement and development of micro-mechanical manufacturing technology, people can produce an increasing variety of micro-electromechanical systems in recent years, such as micro-satellite thrusters, micro-sensors, micro-aircrafts, micro-medical devices, micro-pumps, and micro-motors. At present, these micro-mechatronic systems are driven by traditional energy power systems, but these traditional energy power systems have such disadvantages as short endurance time, large size, and low energy density. Therefore, efforts were made to study micro-energy dynamical systems with small size, light gravity, high density and energy, and long duration so as to provide continuous and reliable power for these systems. In general, the micro-thermal photoelectric system not only has a simple structure, but also no moving parts. The micro-thermal photoelectric system is a micro-energy power system with good application prospects at present. However, as one of the most important structural components of micro-thermal photoelectric systems, the microburner, is the key to realize the conversion of fuel chemical energy to electric energy in micro-thermal photoelectric system. The studies of how to improve the flame stability and combustion efficiency are very necessary and interesting. Thus, some methods to improve the performance of micro-burners were introduced and summarized systematically, hoping to bring some convenience to researchers in the field.
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