Measurement of Local Structure of Turbulent Premised Flame by Using an Ion Probe Method and Laser Ibmography

紊流预混火焰的火焰结构通常表示为皱褶层流火焰模型，因此燃烧速率表示为局部燃烧速度和火焰表面积的函数。在之前的研究中，我们采用分形燃烧模型来模拟火花点火发动机的湍流传播过程。但由于局部燃烧速度受火焰拉伸和火焰曲率的影响，局部燃烧速度由层流燃烧速度变化而来。局部燃烧速度模型是模拟模具湍流燃烧模型的关键，本文研究了分析区域对火焰曲率PDF分布的影响。从火焰几何形状求出火焰曲率时，必须选择最优分析区域。随着湍流强度的增加，火焰曲率的平均半径减小，火焰曲率的PDF分布趋于轴对称。发现火焰曲率的无量纲半径是考虑混合密度的无量纲湍流强度的函数。用离子探针法测量了火焰厚度的特征值，并将离子探针法测量的火焰厚度与预热区厚度进行了比较。证实了离子探针法测得的厚度与层流火焰预热区的厚度成正比。在今后的研究中，将采用激光层析成像和离子探针法同时测量湍流前提火焰的火焰结构。

Generally the flame structure of turbulent premixed flames is expressed as a wrinkled laminar flame model Therefore the burning rate is expressed as a function of the local burning velocity and the flame surface area In our previoia studies the fractal burning model for modeling a flame surface area was used for the simulation of turbulent propagation process in a spark ignition engine. However as the local burning velocity is affected by the flame stretch and flame curvature, the local velocity is changed from the laminar burning velocity. The local burning velocity model is essential for modeling die turbulent burning model In present study the effect of the analyzing area on the PDF distribution of flame curvature was investigated. When the flame curvature is obtained from the flame geometry, the optimal analyzing area must be chosen. As the turbulence intensity increase, the mean radius of flame curvature decreases and the PDF distribution of flame curvature becomes to be axial symmetry. It was found that the non-dimensional radius of flame curvature is expressed as a function of the non-dimensional turbulence intensity considered the mixture density.The characteristic value of flame thickness was measured by using ion probe method Tte flame Ihiclmess measured by ion probe method was compared with the thickness of preheat zone. It was confirmed that the thickness obtained by ion probe method is proportional to the thickness of the preheat zone of the laminar flame.In the future study the laser tomography and ion probe method simultaneously are applied for the measuring the flame structure of turbulent premised flames.