Experimental investigation on the influence of central airflow on swirl combustion stability and flame shape

Huang, Li-Hsin; Liu, Changchun; Deng, Tiandiao; Jiang, Hua; Wu, Pengzhi

doi:10.1007/s10973-020-10399-2

Cited by 7 publications

(4 citation statements)

References 28 publications

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“…Threshold segmentation of pictures from photography and high-speed video recordings is a cheap and efficient way to obtain flame characteristics. Several relevant studies to obtain flame characteristics from image processing can be found in [4][5][6][7][8][9][10][11][12], which are generally based on the intermittency distribution approach. The flame height and lift-off of propane turbulent jet diffusion flames attenuated by carbon dioxide at ambient temperature and pressure were studied by Tao et al [9].…”

Section: Introductionmentioning

confidence: 99%

Properties of turbulent non-premixed methane/air flames in a miniature-scale swirl burner under different coaxial airflow swirl numbers

Sheykhbaglou¹

2023

fuen

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This study investigates the dynamics and properties of non-premixed methane/air flames under three swirl numbers by segmenting flame images using the Otsu thresholding technique. Under three operating conditions, the lean blow out (LBO) and flame length, lift-off height, maximum width, flame angle, and flame pulsing displacements in terms of flame center of gravity, length, and width are measured and compared. A high-speed camera is used to record video of flames, and the image processing of frames collected from a high-speed video was accomplished by using the intermittency distribution method to quantitatively compare flame attributes. The findings show that increasing the swirl number from 0.5 to 0.7 generally has an unfavorable effect on the LBO at given fuel flow rates, and the LBO of flames under 35° (0.6 swirl number) and 40° (0.7 swirl number) swirlers has decreased up to about 15% and 40%, respectively when compared with a 30° swirler (0.5 swirl number). Additionally, observations indicate that the flame length (𝐿) and lift-off height (𝐿𝑂) drop as the swirl number rises, although the flame width (𝑊) and angle (𝛼) show an ascending tendency. Besides, flame lift-off reveals an increasing-decreasing trend with an increment in the airflow, and flame length decreases as the airflow rate increases. It was also observed that flame pulsating displacements in terms of center of gravity (𝛿𝐶𝐺), length (𝛿𝐿), and width (𝛿𝑊) increases with an increase in the fuel flow rate, and as the swirl number is increased, 𝛿𝐶𝐺 and 𝛿𝐿 lessens, while 𝛿𝑊 increases.

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Section: Introductionmentioning

confidence: 99%

Properties of turbulent non-premixed methane/air flames in a miniature-scale swirl burner under different coaxial airflow swirl numbers

Sheykhbaglou¹

2023

fuen

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“…They discovered that a larger central air flow might significantly enhanced the mixing of fuel and air. For a certain equivalence ratio, Huang et al [16] showed that the inclusion of central air could improve the flame stability and optimize the flame shape. In addition, several studies had demonstrated that increasing the central air in a swirl burner could effectively decrease the emissions of NO x [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Influence of Central Air on Flow and Combustion Characteristics and Low-Load Stabilization Performance of a Babcock Burner

Huang

Wang

et al. 2023

Processes

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On a cold single-phase test stand, the effect of central air on the exit flow field of Babcock, Germany, burner was investigated. Industrial measurements were taken for a 700 MW wall-fired pulverized-coal utility boiler with above burners. Gas temperature, gas composition and concentration in the burner area were measured at 444 MW, 522 MW and 645 MW loads, respectively. Only when the central air mass flow was zero did a center reflux zone exist in the burner outlet area. The steady combustion of faulty coal was aided by early mixing of primary and secondary air, which was made possible by the decreased central air mass flow. At all different loads, the pulverized coal in center region took a long distance to ignite. The temperature in center steadily dropped as central air mass flow decreased, while the temperature in secondary air region gradually rose. Within 1.5 m from the primary air duct outlet, the highest CO concentration was 25 ppm and the highest O2 concentration was close to 21% under all loads. The gas concentration near sidewall was more influenced by load. With all valves opening of burner center air at 30%, the boiler was able to operate safely and stably without oil at a load of 262 MW. The furnace chamber temperature in burner area reached 1056.1 °C.

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“…Image processing of photos obtained from photography and high-speed video recordings is an effective method to investigate the flame characteristics. Some related works to calculate flame shape from image processing can be found in [21][22][23][24][25][26][27][28] The examined literature indicates that the effects of low and high swirl of coaxial air and fuel type on the combustion and flame characteristics of a miniature-scale swirl burner have not been examined. So, in this study, a series of experiments were conducted to study the effect of swirl strength of coaxial airstream on the blow-out limits, flame lift-off height, length, width, as well as NO x and CO emissions under methane/air and n-butane/air non-premixed flames.…”

Section: Introductionmentioning

confidence: 99%

Effects of coaxial airflow swirl number on combustion and flame characteristics of methane/air and n-butane/air flames in a miniature-scale swirl burner

Sheykhbaglou¹,

Robati²

2022

Eng. Res. Express

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In this paper, the effects of coaxial airflow swirl number on blow-out limit, flame characteristics, and emission performance of non-premixed methane/air and n-butane/air flames in a miniature-scale swirl burner are investigated experimentally. Swirl numbers ranging from 0 to 0.72 have been chosen to be examined. It was observed that increasing the vane angle does not increase the blow-out limit monotonically and a swirler with 30° vane angle (0.50 swirl number) results in the greatest blow-out limit. Besides, it was found out that methane outperforms n-butane in the blow-out limit at the same fuel flow rates. The intermittency distribution approach was used to determine flame properties such as lift-off height, length, and width. It was found that the lift-off variation with coaxial airflow Reynolds number at the specified fuel flow rates yields an inverted V-shape for Sn ≥0.50. The tip of these plots indicates the airflow rate at which the swirl shows its influence, and after this point, the lift-off height begins to decrease. It was also observed that the airflow related to this point decreases with an increase in the swirl number at a certain fuel flow rate. Furthermore, the results revealed that at high airflow rates, the flame width rises as the swirl number increases. Also, raising the swirl number and airflow Reynolds number reduced the flame length. It was also observed that n-butane/air flames have longer and wider flames than methane/air flames. Additionally, adding swirl to the airflow rate typically reduces NOx and CO concentrations and n-butane/air flames exhibit lower levels of NOx and higher levels of CO than methane/air flames under the same operating conditions.

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Experimental investigation on the influence of central airflow on swirl combustion stability and flame shape

Cited by 7 publications

References 28 publications

Properties of turbulent non-premixed methane/air flames in a miniature-scale swirl burner under different coaxial airflow swirl numbers

Properties of turbulent non-premixed methane/air flames in a miniature-scale swirl burner under different coaxial airflow swirl numbers

Influence of Central Air on Flow and Combustion Characteristics and Low-Load Stabilization Performance of a Babcock Burner

Effects of coaxial airflow swirl number on combustion and flame characteristics of methane/air and n-butane/air flames in a miniature-scale swirl burner

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