Investigation of Transient Flamelets Behavior in Turbulent Diffusion Flames

湍流扩散火焰中瞬态小火焰行为的研究

• 批准号: 09450093
• 负责人: TAKAGI Toshimi
• 金额: $ 7.87万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09450093/
• 关键词: Turbulent Diffusion Flames; Extinction; Preferential Diffusion; Flame Curvature; Flame Temperature; Numerical Analysis; Laser-Rayleigh Scattering Method; 再着火

The turbulent diffusion flame is supposed to be an ensemble of the laminar flamelets which should strained unsteadily and have positive or negative curvature, and be affected by preferential diffusion. In this study, transient laminar counterflow diffusion flames strained by unsteadily impinging micro air or fuel jet from air or fuel side were investigated. Two-dimensional time-dependent temperature measurements by laser Rayleigh scattering method showed the local flame extinction and reignition process. Time-dependent numerical computations taking into account detailed chemical kinetics and multicomponent diffusion predicted well the characteristics of the experimental evidence and revealed the processes dominating the transient behavior of the flame with respect to the flame curvature and preferential diffusion.(1) Transient local flame extinction is observed where the micro jet impinges. During the process of the extinction, the transient flame can survive instantaneously under the quite high stretch rate where the steady flame cannot exist.(2) Reignition is observed after the local extinction by the micro air jet impingement. The temperature after reignition becomes significantly higher than that of the original flame. This high temperature is induced by the H^2 concentration due to the preferential diffusion in relation to the concave curvature.(3) The reignition is induced after the formation of combustible premixed gas mixture of high level of unreactedness and the consequent flame propagation.(4) The reignition is hardly observed after the extinction by micro fuel jet impingement. This is due to the H^2 dilution due to the preferential diffusion in relation to the convex curvature.(5) Flame structure with stretch/compression and periodic fluctuation was revealed.

湍流扩散火焰被认为是层流火焰的集合体，层流火焰应具有正曲率或负曲率，并受到优先扩散的影响。本文研究了空气侧或燃料侧微射流非定常冲击下的瞬态层流逆流扩散火焰。利用激光瑞利散射法对火焰的二维温度场进行了测量，揭示了火焰的局部熄灭和再燃过程。考虑到详细的化学动力学和多组分扩散的时间相关的数值计算预测以及实验证据的特点，并揭示了主导火焰的瞬态行为的火焰曲率和优先扩散的过程。(1)在微射流冲击的地方观察到瞬态局部火焰熄灭。在火焰熄灭过程中，瞬态火焰可以在相当高的拉伸率下瞬间存活，而稳定火焰是不可能存在的。(2)在微射流冲击作用下，局部熄火后，观察到再点火现象。重新点燃后的温度变得明显高于原始火焰的温度。这种高温是由H^2浓度引起的，这是由于与凹曲率有关的优先扩散。(3)在形成高水平的未反应性的可燃预混气体混合物和随后的火焰传播之后，诱导再点火。(4)微喷熄火后，几乎没有再点火现象。这是由于相对于凸曲率的优先扩散导致的H^2稀释。(5)揭示了拉伸/压缩和周期波动的火焰结构。

项目成果

Kenji Yoshida: "Structural Studies on Locally Strained Diffusion Flames (3rd Report, Analysis on Local Flame Extinction and Reignition Phenomena of Unsteady Strained Flames)" Transactions of Japan Society of Mechanical Engineering (B). 64-626. 3471-3478 (

Kenji Yoshida：“局部应变扩散火焰的结构研究（第三次报告，不稳定应变火焰的局部火焰熄灭和重燃现象的分析）”日本机械工程学会学报（B）。

Kenji Yoshida: "Structure and Characteristics of Negatively Strained Diffusion Flame" 2nd Asia-Pacific Conference on Combustion (ASPACC99). (to be appeared). (1999)

Kenji Yoshida：“负应变扩散火焰的结构和特征”第二届亚太燃烧会议（ASPACC99）。

Kenji Yoshida: "Transient Local Extinction and Reignition Behavior of Diffusion Flames Affected by Flame Curvature and Preferential Diffusion" The 27th Symposium (International) on Combustion. (掲載予定). (1999)

Kenji Yoshida：“受火焰曲率和优先扩散影响的扩散火焰的瞬时局部熄灭和重燃行为”第 27 届燃烧研讨会（国际）（即将出版）。

Kenji Yoshida: "Unsteady Behavior of Locally Strained Diffusion Flames Affected by Curvature and Preferential Diffusion" The 5th ASME/JSME Thermal Engineering Joint Conference. (発表予定). (1999)

Kenji Yoshida：“受曲率和优先扩散影响的局部应变扩散火焰的不稳定行为”第五届 ASME/JSME 热工程联合会议（即将发表）。

吉田憲司: "局所歪を伴う拡散火炎に関する研究(第2報 火炎構造と消炎現象の解析)" 日本機械学会論文集(B2編). 64巻623号. 2348-2356 (1998)

Kenji Yoshida：“具有局部应变的扩散火焰的研究（第二次报告：火焰结构和消光现象的分析）”日本机械工程师学会会刊（B2版）第64卷，第623期。2348-2356（1998年）。 ）