非预混火焰热斑产生和演化的理论计算

Analytical Calculation of Generation and Evolution of Hot Spots in Non-Premixed Flames

关键词:  非预混火焰  格林函数法  热斑的产生和演化  理论计算 

Key words:  Non-premixed flame  Green’s function method  Generation and evolution of hot spots  Analytical calculation

摘要:

对于非预混火焰来说,燃烧反应区被扩散掺混作用控制,火焰体现出比较强的分布式特征,在扰动较大的情形下,火焰面会出现被撕裂的特征。这种情况下,热斑的产生和演化问题就成了非预混火焰稳定性研究中的一个重要问题。以一个理想二维平板非预混火焰为研究对象,在伯克-舒曼经典假设的前提下,通过格林函数法理论计算非预混火焰热斑的产生与演化的整个过程。研究发现较小的St数、较大的Pe数以及较快的对流速度有利于热斑向燃烧区下游的传播。这些结果将有助于理解非预混燃烧不稳定性的相关机理以及发展相应的控制方法。 

Abstract:

In non-premixed flames, the combustion zone is controlled by the mixing process between fuel and oxidizer. The chemical reaction occurs in a finite space and shows obviously distributed characteristics. The flame surface (or stoichiometric contour) may be split due to flow perturbations. Under these circumstances, the generation and evolution of hot spots become a key problem in stability analysis of non-premixed flames.Based on the Burke-Schumann assumptions, the generation and evolution of hot spots were analytically calculated for an idealized, two-dimensional, flat, non-premixed flame by Green’s function method. The results show that a smaller Strouhal number, a larger Peclet number or a faster convective velocity causes the hot spots to move farther downstream. These results are valuable for a better understanding of the mechanisms of non-premixed combustion instability, which is beneficial to the development of accurate control techniques.