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状火焰的合奏，应该不稳定并具有正曲率或负曲率，并受到优先扩散的影响。在这项研究中，研究了不稳定地撞击空气或燃料侧的微型空气或燃油射流所紧张的瞬时层状反流扩散火焰。激光雷利散射法显示了局部火焰灭绝和重新点燃过程。考虑到详细的化学动力学和多组分扩散的时间依赖性数值计算很好地预测了实验证据的特征，并揭示了在火焰曲率和优先扩散相对于火焰曲率和优先扩散的瞬时行为的过程。在灭绝过程中，瞬态火焰可以在不存在稳定火焰的相当高的拉伸速率下即时存活。（2）在局部灭绝后，微型空气射流撞击在局部灭绝后观察到重新点燃。重新点燃后的温度显着高于原始火焰的温度。由于相对于凹弯的优先扩散，H^2的浓度引起了这种高温。（3）在形成可燃烧的预混合气体混合物后，无反应的高水平和随后的火焰繁殖的高水平混合物形成后，将重新点燃。这是由于H^2稀释是由于与凸曲率相关的优先扩散而引起的。（5）揭示了拉伸/压缩和周期性波动的火焰结构。

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）。

Kenji Yoshida: "Transient Local Extinction and Reignition Behavior of Diffusion Flames Affected by Flame Curvature and Preferential Diffusion" Proc.of 27th Symposium (International) on Combustion. (発表予定). (1998)

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）会议记录（待提交）。