三级旋流燃烧室流动和点火过程中火焰传播特性

为了研究三级旋流燃烧室的流动以及预燃级煤油非预混燃烧特性，设计了三级旋流燃烧室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油气参数对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：在高速气流碰壁区存在内、外剪切层，剪切层的无量纲高度随总压损失变化较小，剪切强度随总压损失增大而增大；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，过渡当量比约在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；点火过程中，随总压损失的增大，火核生成时间增大，火焰传播时间减小，熄火复燃时间减小；随当量比增大，火核生成时间增加，火焰传播时间先增大后减小，熄火复燃时间减小。

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

In order to study the flow and non-premixed combustion characteristics of kerosene in the three-staged swirl combustor, the structure and non-contact optical measurement system of the combustor were designed. The effects of total pressure loss and equivalent ratio on flow and flame characteristics were investigated. In addition, characteristic time and flame shape in the ignition process were investigated. The results showed that there were internal and external shear layers in the high-speed airflow-wall interaction zones and its dimensionless height changed little with the total pressure loss, but the shear strength increased with the total pressure loss. The flame structure changed with the equivalent ratio in three forms: V-shaped flame, transition flame and envelope flame, and the critical ratio of the structure transition is near 0.6. The expansion angle of reacting center recirculation zone increased with the rise of total pressure loss. With the increase of equivalent ratio, this angle decreased before the critical ratio and increased after that point. In the process of ignition, there existed large scale flame extinction and reignition, during which the reignited flame propagated backward to the combustor in a three-dimensional spiral way from the vicinity of center recirculation vortexes. Moreover, with the rise of total pressure loss, the formation time of ignition core increased, and a duration time drop was found 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 were enhanced firstly and reduced after equivalent ratio exceeded the critical point.