纯氢阵列微管预混火焰结构及湍流燃烧速度测量

Structure of Pure Hydrogen Array Microtube Premixed Flame and Measurement of Turbulent Burning Velocity

为给出稀燃环境45~87 m/s流速下的纯氢微混火焰的湍流燃烧特性,采用阵列微管喷嘴模型燃烧室进行研究。通过粒子图像测速技术与羟基平面激光诱导荧光技术诊断火焰,研究了纯氢湍流火焰前锋面结构及火焰热态流场,得到火焰前锋面尺度信息及微混燃烧室湍流参数,包括火焰体积、火焰面密度、湍流强度、湍流积分尺度和湍流燃烧速度。研究结果表明:微混燃烧室出口的湍流强度随着来流速度线性增加,火焰前锋面凸向未燃气与凹向未燃气的概率基本相同,并且随着湍流强度的增加,火焰的小尺度结构和褶皱程度有所增加。这些变化导致火焰面密度的增加,从而增加了湍流火焰面积和湍流燃烧速度。此外,氢气微混火焰归一化湍流燃烧速度达到7~11,约是火焰面积比3.5~5.5的两倍,这主要是因为稀燃氢气火焰的路易斯数较低,导致火焰局部燃烧速率超过了层流燃烧速度。因此,稀燃纯氢微混湍流火焰的燃烧速度的增加主要由火焰面积的扩大和局部燃烧速率的增强共同影响。该研究为优化阵列微管喷嘴模型燃烧室及微混燃烧技术提供了理论依据和实验支持。

To investigate the turbulent burning characteristics of pure hydrogen micromix flames at various flow velocities ranging from 45—87 m/s under lean combustion conditions,an arrayed microtube nozzle model combustion chamber is employed.The flame is diagnosed using particle image velocimetry and hydroxyl plane laser-induced fluorescence techniques to examine the structure of the turbulent flame front and the thermal flow field of the flame.Details on the scale of the flame front and turbulent parameters of the micromix combustion chamber are obtained,including flame volume,flame surface density,turbulent intensity,turbulent integral scale,and turbulent burning velocity.The results suggest that the turbulence intensity at the outlet of the micromix combustion chamber linearly increases with the inflow velocity.The probabilities of the flame front protruding towards unburned gas and receding from unburned gas are nearly equal.As turbulent intensity rises,the small-scale structure and wrinkling degree of the flame also increase.These changes lead to an increase in flame surface density,thereby increasing the turbulent flame area and turbulent burning velocity.Additionally,the normalized turbulent burning velocity of the hydrogen micromix flames reaches 7—11,approximately twice the flame area ratio of 3.5—5.5.This is primarily attributed to the low Lewis number of lean hydrogen flames,causing the local combustion rate of the flame to surpass the laminar burning velocity.Therefore,the increase in burning velocity of lean pure hydrogen micromix turbulent flames is mainly driven by the expansion of the flame area and the enhancement of the local combustion rate.This research provides a theoretical basis and experimental support for optimizing the arrayed microtube nozzle model combustion chamber and micromix combustion technology.