Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed Flames
Buoyant unstable behavior in initially spherical lean hydrogen-air premixed flames within a center-ignited combustion vessel have been studied experimentally under a wide range of pressures (including reduced, normal, and elevated pressures). The experimental observations show that the flame front o...
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| Format: | Article |
| Language: | English |
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MDPI AG
2014-07-01
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| Series: | Energies |
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| Online Access: | http://www.mdpi.com/1996-1073/7/8/4938 |
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| author | Zuo-Yu Sun Guo-Xiu Li Hong-Meng Li Yue Zhai Zi-Hang Zhou |
| author_facet | Zuo-Yu Sun Guo-Xiu Li Hong-Meng Li Yue Zhai Zi-Hang Zhou |
| author_sort | Zuo-Yu Sun |
| collection | DOAJ |
| description | Buoyant unstable behavior in initially spherical lean hydrogen-air premixed flames within a center-ignited combustion vessel have been studied experimentally under a wide range of pressures (including reduced, normal, and elevated pressures). The experimental observations show that the flame front of lean hydrogen-air premixed flames will not give rise to the phenomenon of cellular instability when the equivalence ratio has been reduced to a certain value, which is totally different from the traditional understanding of the instability characteristics of lean hydrogen premixed flames. Accompanied by the smoothened flame front, the propagation mode of lean hydrogen premixed flames transitions from initially spherical outwardly towards upwardly when the flames expand to certain sizes. To quantitatively investigate such buoyant instability behaviors, two parameters, “float rate (ψ)” and “critical flame radius (Rcr)”, have been proposed in the present article. The quantitative results demonstrate that the influences of initial pressure (Pint) on buoyant unstable behaviors are different. Based on the effects of variation of density difference and stretch rate on the flame front, the mechanism of such buoyant unstable behaviors has been explained by the competition between the stretch force and the results of gravity and buoyancy, and lean hydrogen premixed flames will display buoyant unstable behavior when the stretch effects on the flame front are weaker than the effects of gravity and buoyancy. |
| first_indexed | 2024-04-13T08:06:06Z |
| format | Article |
| id | doaj.art-b8566ecca18747b9af6477485f8fc988 |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-04-13T08:06:06Z |
| publishDate | 2014-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Energies |
| spelling | doaj.art-b8566ecca18747b9af6477485f8fc9882022-12-22T02:55:09ZengMDPI AGEnergies1996-10732014-07-01784938495610.3390/en7084938en7084938Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed FlamesZuo-Yu Sun0Guo-Xiu Li1Hong-Meng Li2Yue Zhai3Zi-Hang Zhou4School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, ChinaSchool of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, ChinaSchool of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, ChinaSchool of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, ChinaSchool of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, ChinaBuoyant unstable behavior in initially spherical lean hydrogen-air premixed flames within a center-ignited combustion vessel have been studied experimentally under a wide range of pressures (including reduced, normal, and elevated pressures). The experimental observations show that the flame front of lean hydrogen-air premixed flames will not give rise to the phenomenon of cellular instability when the equivalence ratio has been reduced to a certain value, which is totally different from the traditional understanding of the instability characteristics of lean hydrogen premixed flames. Accompanied by the smoothened flame front, the propagation mode of lean hydrogen premixed flames transitions from initially spherical outwardly towards upwardly when the flames expand to certain sizes. To quantitatively investigate such buoyant instability behaviors, two parameters, “float rate (ψ)” and “critical flame radius (Rcr)”, have been proposed in the present article. The quantitative results demonstrate that the influences of initial pressure (Pint) on buoyant unstable behaviors are different. Based on the effects of variation of density difference and stretch rate on the flame front, the mechanism of such buoyant unstable behaviors has been explained by the competition between the stretch force and the results of gravity and buoyancy, and lean hydrogen premixed flames will display buoyant unstable behavior when the stretch effects on the flame front are weaker than the effects of gravity and buoyancy.http://www.mdpi.com/1996-1073/7/8/4938lean hydrogen flameinitial spherical flamebuoyant behaviorsexperimental observation |
| spellingShingle | Zuo-Yu Sun Guo-Xiu Li Hong-Meng Li Yue Zhai Zi-Hang Zhou Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed Flames Energies lean hydrogen flame initial spherical flame buoyant behaviors experimental observation |
| title | Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed Flames |
| title_full | Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed Flames |
| title_fullStr | Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed Flames |
| title_full_unstemmed | Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed Flames |
| title_short | Buoyant Unstable Behavior of Initially Spherical Lean Hydrogen-Air Premixed Flames |
| title_sort | buoyant unstable behavior of initially spherical lean hydrogen air premixed flames |
| topic | lean hydrogen flame initial spherical flame buoyant behaviors experimental observation |
| url | http://www.mdpi.com/1996-1073/7/8/4938 |
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