“…In their analysis in 2005, such a trend failed to be captured because the analysis did not include the thermal conduction processes through the burner. Hossain and Nakamura (2015) conducted a new series of numerical experiments by adopting a conductive burner with detailed chemistry. Their results showed that excess heating at the flame tip with a lower conductivity burner could modify the structure inside the micro-burner substantially to successfully reveal a tremendous reduction of hydrogen molecules at the burner exit (see Fig.…”
“…10. The numerical study on micro diffusion flames of hydrogen by adopting a conductive burner with detailed chemistry by Hossain and Nakamura (2015). Left: temperature and H radical contours at fuel jet velocity of 2.5 m/s and 0.25 m/s for a low conductivity (7.44 W/m-K) burner; right: profiles of reaction rate, species concentration, axial velocity, and temperature along the axis.…”
This article briefly reviews the recent works related to small-scale combustion and its potential impact into combustion science and engineering is presented. Followed by a simple description of the scale effect on combustion to highlight its "unique" feature, past related works are then summarized. The impact of heat recirculation appearing in combustion systems, which is the most prominent feature of a micro-or small-scale combustion system, is focused upon and is understood that exactly the same strategy promising better combustion performance is confirmed irrespective of flame type (either premixed or non-premixed). With respect to this, paying attention to the entire combustor design, to optimize within the target working range is a crucial matter when micro-scale combustion is adopted. Potential subjects to be covered to further promote these aspects in this field are then presented.
“…In their analysis in 2005, such a trend failed to be captured because the analysis did not include the thermal conduction processes through the burner. Hossain and Nakamura (2015) conducted a new series of numerical experiments by adopting a conductive burner with detailed chemistry. Their results showed that excess heating at the flame tip with a lower conductivity burner could modify the structure inside the micro-burner substantially to successfully reveal a tremendous reduction of hydrogen molecules at the burner exit (see Fig.…”
“…10. The numerical study on micro diffusion flames of hydrogen by adopting a conductive burner with detailed chemistry by Hossain and Nakamura (2015). Left: temperature and H radical contours at fuel jet velocity of 2.5 m/s and 0.25 m/s for a low conductivity (7.44 W/m-K) burner; right: profiles of reaction rate, species concentration, axial velocity, and temperature along the axis.…”
This article briefly reviews the recent works related to small-scale combustion and its potential impact into combustion science and engineering is presented. Followed by a simple description of the scale effect on combustion to highlight its "unique" feature, past related works are then summarized. The impact of heat recirculation appearing in combustion systems, which is the most prominent feature of a micro-or small-scale combustion system, is focused upon and is understood that exactly the same strategy promising better combustion performance is confirmed irrespective of flame type (either premixed or non-premixed). With respect to this, paying attention to the entire combustor design, to optimize within the target working range is a crucial matter when micro-scale combustion is adopted. Potential subjects to be covered to further promote these aspects in this field are then presented.
“…Oxy-fuel combustion has been investigated in detail to clarify the fundamental phenomena [1][2][3][4]. In addition, small-scale combustion has been treated to elucidate the characteristics of micro flames [5][6][7][8]. Thus, we can study the characteristics of micro methane-oxygen flames, based on the previous information on oxy-fuel and small-scale combustion.…”
We manipulated oxy-fuel combustion of methane in small scales to study the characteristics of micro counterflow diffusion flames under the gravity field. Methane-oxygen diffusion flames in counterflow burners were observed, where the burner distance was less than or equal to 1.0 mm and the apparent equivalence ratio was unity. The flame thickness and flame diameter were obtained as functions of the burner distance and gas flow rate. The minimum burner distance for the observation of flames became smaller as the gas flow rate increased. We obtained smaller values of the minimum burner distance when methane flowed out from the upper burner. The flame thickness and flame diameter decreased as the burner distance became smaller. In addition, the flame thickness and flame diameter had slightly larger values in the upper-methane case.
“…Several researchers have investigated in detail oxy-fuel combustion, and then the fundamental phenomena are clarified (Maruta et al, 2007;Toftegaard et al, 2010;Watanabe et al, 2011;Sevault et al, 2012;Kobayashi et al, 2013;Bongartz and Ghoniem, 2015;Shimokuri et al, 2015). Moreover, combustion in small scales, closely related with small power source, has been treated, and then the fundamental characteristics of micro flames are elucidated (Miesse et al, 2005;Chen et al, 2007;Ju and Maruta, 2011;Saiki and Suzuki, 2013;Hossain and Nakamura, 2015;Kadowaki et al, 2015). Based on the previous information on oxy-fuel combustion and micro flames, we can handle diffusion combustion of methane and oxygen in small scales.…”
Oxy-fuel combustion of methane in small scales was handled to investigate micro counterflow diffusion flames. We observed methane-oxygen diffusion flames in counterflow burners where the burner distance was less than 1 mm, and obtained the flame thickness and flame diameter as functions of the burner distance, inner diameter and gas flow rate. When burners with large inner diameter were used, counterflow diffusion flames were observed in small burner distance, and the flame thickness and flame diameter were large under the same conditions of burner distance and gas flow rate. The flame thickness and flame diameter decreased as the burner distance became smaller, and they increased as the gas flow rate became larger. Moreover, the flame stretch rate had a great influence on the flame thickness. As the flame stretch rate became larger, the flame thickness decreased monotonously, which depended on the inner diameter and gas flow rate. To scrutinize the dependence of flame thickness on the flame stretch rate, we normalized the flame thickness by the inner diameter and the average velocity of methane. We confirmed that the normalized flame thickness depended only on the flame stretch rate.
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