三级旋流燃烧室流动和点火过程中火焰传播特性

Characteristics of Flow Field and Flame Propagation of Ignition Process in Three-Staged Swirl Combustor

关键词:  三级旋流燃烧室  非预混燃烧  流动特性  点火过程  火焰传播

Key words:  Three-staged swirl combustor  Non-premixed combustion  Flow characteristics  Ignition process  Flame propagation

摘要:

为了研究三级旋流燃烧室的流动以及预燃级非预混燃烧特性，设计了三级旋流燃烧室试验结构方案与光学非接触测量方案，研究了总压损失与当量比对三级旋流燃烧室流动特性及火焰结构的作用和点火过程中火焰特征结构与特征时间的影响规律。研究结果表明：总压损失对燃烧室内热态流场结构无影响，其主要改变具体的速度值大小；在头部高速射流区存在内、外剪切层，随着流动向下游发展，高速气流紧贴壁面流动；火焰结构随着当量比变化存在“V”型火焰、过渡火焰以及包络火焰三种形态，过渡当量比在0.6左右；热态回流区扩张段扩张角度随总压损失的增大而增大，随着当量比增大先减小后增大；点火过程中存在大尺度火焰的熄灭与复燃，复燃火焰从回流涡附近以三维螺旋方式回传；随总压损失的增大，火核生成时间延长，火焰传播时间缩短，熄火复燃时间缩短；随当量比增大，火核生成时间延长，火焰传播时间先延长后缩短，熄火复燃时间缩短。

Abstract:

To study the flow and non-premixed kerosene-air pilot stage combustion characteristics of the three-staged swirl combustor， an experimental rig and non-contact optical measurement system of the combustor were designed. The effects of total pressure loss and equivalent ratio on flow and critical flame shape characteristics were investigated. In addition， characteristic time and critical flame structure in the ignition process were investigated. The results show that the total pressure loss has seldom effects on the reacting flow field structure of the combustion chamber， which mainly changes the specific velocity value. Moreover， there are inner and outer shear layers in the high-speed jet region of the combustor. As flow propagates downstream， the high-speed air flows along near-wall area. The flame structure changes with the equivalent ratio in three forms： V-shaped flame， transition flame and envelope flame， and the critical equivalence ratio of flame shape transition was near 0.6. The expansion angle of high speed region in combustor inlet increases with the rise of total pressure loss. While equivalent ratio increases， the expansion angle decreases initially and increases after the critical equivalence ratio. In the process of ignition， there exists large-scale flame extinction and reignition， during which the reignited flame propagates backward to the combustor in a three-dimensional spiral way from center recirculation vortexes. In addition， with the rise of total pressure loss， the formation time of ignition core increases， and a duration time drops both for flame propagation and reignition. With the rise of equivalent ratio， the time of ignition core formation increased and that of flame reignition decreased. The flame propagation time increased firstly and reduced after equivalent ratio exceeds the critical point.