分级燃烧室主燃级旋流组织与火焰稳定机制研究

In order to fulfill the stricter emission regulations of ICAO (International Civil Aviation Organization), most of the engine manufactors turn to lean staged low emission combustor design. Lean staged combustor possesses the advantages of lower pollutant emissions and shorter liner length. The state of the art staged combustor design features multi-swirling flow and partially premixed combustion in the main stage. Previous application and investigation demonstrate that the main flame has the risk of unstable combustion. In this research proposal, the stability mechanism of the main flame in multi-swirling flow environment and the interaction between the main flame and the pilot flame will be studied. The staged injector will be experimentally diagnosed on the single sector model combustor with optic access, by means of advanced dynamic measurement techniques. LES (Large Eddy Simulation) of reacting flow will be utilized to deepen the understandings. The research targets of this proposal is to identify the correlations between unsteady coherent flow structures (e.g. recirculation zone, shear layer and precessing vortex core) and the stability of the main flame, and obtain the interaction mechanisms between the main flame and the pilot flame. On this basis, the critical creterion of the main flame stability in multi-swirling flow environment will be obtained, which will provide fundamental research basis for the development of lean staged low emisssion combustor.

为了满足民用航空对污染物排放越来越严格的要求，国际主要民用发动机公司倾向于采用贫油分级低排放燃烧室设计方案，其对于降低污染物排放、缩短燃烧区长度具有显著效果。先进分级燃烧室主燃级多采用多级旋流组织方案，以部分预混方式燃烧，已有的应用和实验研究表明，其具有燃烧不稳定风险。本项目拟以分级燃烧室主燃级多级旋流火焰稳定机制和主燃级与预燃级火焰相互作用为研究主题，以单头部光学可视模型燃烧室为载体，借助先进动态实验测量技术，并辅助以大涡模拟，力求阐明多级旋流流场内剪切层、回流区、进动涡核等非定常拟序结构对主燃级火焰稳定性的影响机制，以及两级火焰相互作用机制，在此基础上形成主燃级多级旋流环境下燃烧稳定性的判定准则，对分级燃烧室的研发提供理论支撑。

为了有效支撑先进分级燃烧室的设计研发，本项目针对分级燃烧室主燃级的旋流组织方案和火焰稳定特性开展研究，目标是研究主燃级多级旋流组织设计参数对流场结构、燃油浓度分布与火焰稳定性的影响规律，阐明火焰稳定性与流场结构和燃油浓度分布之间的内部关联。为此，本项目开展了主燃级分层隔板长度、主燃级旋流强度对分级燃烧室流场、燃油分布和点熄火特性影响的试验研究，并在燃油流量过渡条件和高空左边界条件下分别研究了分级燃烧室的火焰稳定性。研究发现，扩大燃油分布的径向范围和中心燃油浓度、增大回流区径向尺度是改善火焰稳定性的有效措施；随燃油流量降低速率增加，熄火油气比降低，其物理机制在于较短的减油时间减少了燃烧室的热损失，增大了熄火时的燃烧温度；高空左边界熄火油气比随高度增大而增大，并且在临近熄火状态，火焰POD模态由周向模态变为轴向模态，全局CH*信号频谱上出现频率为340HZ左右的尖峰信号。本文研究发现可为分级燃烧室主燃级旋流组织设计提供指导。