Measurements of Premixed-Flame Propagation in Intense Turbulence

預混火焰傳播於強烈紊流中之實驗量測

施聖洋(S. S. Shy) ； 林文基(W. J. Lin) ； 魏建樟(J. C. Wei)

《中國航空太空學會學刊》 31卷3期 (1999/09) Pp. 207-213

https://doi.org/10.6124/TAASRC.199909_31(3).06

摘要

Turbulent burning velocities of methane-air mixtures at atmospheric stoichiometry are measured in a three-dimensional form of fully developed turbulent flow field. The intense turbulence is generated in a new cruciform burner that consists of two cylindrical vessels. The long vertical vessel is used to provide a stable downward propagating premixed flame at one atmosphere via ignition and simultaneous opening of four large venting valves at its top. The horizontal vessel is equipped with two identical counter-rotating eight bladed fans at each end, driven by electric motors which are synchronized to the same speed. The motor-driven fans with controllable frequencies up to 7, 620 rpm can generate two intense counter-rotating large vortical streams. Each of both turbulent streams passes through a specially designed perforated plate, intertwining with each other. Thus, a nearly isotropic turbulence with large turbulent intensities (up to 450 cm/s) located in the core region between two perforated plates can be generated, as verified by extensive LDV measurements. Four methods, including a two-camera method, the hot-film anemometer, the photo-detector, and an ion-probe method, are applied to measure turbulent burning velocities. Among them, the ion-probe method has least uncertainty within 30%. It is found that when the normalized turbulent intensity (u'/S(subscript L)) is less than unity, values of the normalized turbulent burning velocity (S(subscript T)/S(subscript L)) increase linearly with u'/S(subscript L), where S(subscript L) is the laminar burning velocity. The S(subscript T)/S(subscript L) plots tend to depart from the linearity as u'/S(subscript L)＞1 and bend gradually towards the horizontal for larger u'/S(subscript L) up to 11. These results are compared to earlier premixed gaseous experiments using different apparatuses. Discussion of the similitude and discrepancies among these experiments is offered.

關鍵字

預混紊流燃燒 ； 紊流燃燒速度 ； 彎折效應 ； 離子探針量測

並列摘要

Turbulent burning velocities of methane-air mixtures at atmospheric stoichiometry are measured in a three-dimensional form of fully developed turbulent flow field. The intense turbulence is generated in a new cruciform burner that consists of two cylindrical vessels. The long vertical vessel is used to provide a stable downward propagating premixed flame at one atmosphere via ignition and simultaneous opening of four large venting valves at its top. The horizontal vessel is equipped with two identical counter-rotating eight bladed fans at each end, driven by electric motors which are synchronized to the same speed. The motor-driven fans with controllable frequencies up to 7, 620 rpm can generate two intense counter-rotating large vortical streams. Each of both turbulent streams passes through a specially designed perforated plate, intertwining with each other. Thus, a nearly isotropic turbulence with large turbulent intensities (up to 450 cm/s) located in the core region between two perforated plates can be generated, as verified by extensive LDV measurements. Four methods, including a two-camera method, the hot-film anemometer, the photo-detector, and an ion-probe method, are applied to measure turbulent burning velocities. Among them, the ion-probe method has least uncertainty within 30%. It is found that when the normalized turbulent intensity (u'/S(subscript L)) is less than unity, values of the normalized turbulent burning velocity (S(subscript T)/S(subscript L)) increase linearly with u'/S(subscript L), where S(subscript L) is the laminar burning velocity. The S(subscript T)/S(subscript L) plots tend to depart from the linearity as u'/S(subscript L)＞1 and bend gradually towards the horizontal for larger u'/S(subscript L) up to 11. These results are compared to earlier premixed gaseous experiments using different apparatuses. Discussion of the similitude and discrepancies among these experiments is offered.

並列關鍵字

premixed turbulent combustion ； turbulent burning velocities ； the bending effect ； ion-probe measurements