旋流器出口结构对旋流火焰的影响研究

Effects of Burner Exit Geometries on Swirl Flames

关键词:  LES-PDF  旋流火焰  熄火  通道结构

Key words:  LES-PDF  Swirl flame  Local quenching  Quarl structure geometry

摘要:

为了更深入地理解非预混旋流火焰，采用大涡模拟（LES）耦合PDF燃烧模型，结合OH-PLIF及PIV同步测量实验，综合研究了两种通道结构对非预混旋流火焰模式的影响。结果表明，欧拉随机场PDF方法可以较精确地预测到旋流流场及精细的火焰结构，包括局部熄火。不同的通道结构将显著影响流场结构，由于湍流/化学反应的相互作用，火焰将会出现局部熄火及火焰抬升现象。由于无通道相比于扩张通道的回流区更小，局部熄火现象也更为严重。同时，在恰当当量比下，无通道结构的OH及CH₂O等中间基在低温区分布更为广泛，表明更多的低温化学反应得以进行，为下游抬升火焰的稳定提供了有利条件。

Abstract:

To deeply understand the non-premixed swirl flame，the effects of two burner exit geometries on the non-premixed swirl flames modes were studied by performing OH-PLIF，PIV measurements and coupling LES with PDF combustion model numerically. The results showed that the stochastic PDF method can predict the swirl flow fields and detailed flame structures including local extinction. Two different quarl geometries played significant roles on the flow fields thus leading to the local extinction and lift-off. The recirculation zone is smaller in the non-quarl case which causes a more serious quenching state. Meanwhile，at the stoichiometric equivalence ratio，the OH and CH₂O distributions in the no-quarl exit were broader than the quarl exit at the low temperature regime. This indicated that many low-temperature reactions took places，providing beneficial conditions for the lift-off flame stabilization.