摘要
回流燃烧室与直流燃烧室不同,结构复杂,为了研究回流燃烧室内的流动以及燃烧特性,采用粒子图像测速仪(Particle image velocimetry,PIV)测量对其冷态流场开展研究,通过火焰自发辐射手段得到了燃烧室火焰结构以及火焰传播过程。研究结果表明:回流燃烧室流场不具有对称性,内外壁面速度分布不相同,压损的改变对燃烧室流场结构影响较小,随着压损的增加,速度值增加。燃烧主要在主燃区和中间区进行,火焰呈一定的“月牙”形向外燃烧。燃烧室点火过程可分为火核生成阶段、火核发展阶段、点火成功阶段和火焰稳定阶段4个阶段,回流涡着火是成功点火的关键。熄火时,火核向回流区后部靠近,火焰根部逐渐远离旋流器出口位置,火焰从正常燃烧时的月牙形结构演变为单股火焰。
不同类型航空器对发动机燃烧室工作性能的要求侧重有所不同,对于小型涡扇,涡轴和涡喷航空发动机,为了充分利用空间,缩短轴距,常常采用回流燃烧室。但扩压器来流使回流燃烧室火焰筒进气的流动匹配较难,易出现积碳、冷却困难等一系列问
王晓峰
在国外,Santiago
总体来说,国外对燃烧室的点熄火性能已经开展了大量的试验和理论研究,但缺乏真实回流燃烧室点熄火过程的详细数据研究。回流燃烧室结构与常规燃烧室不同,复杂喷雾下的点熄火研究变得更为困难,而相关文献的数值计算与试验结果仍有一定的误差,本文以真实燃烧环境下的回流燃烧室为对象,开展回流燃烧室流动、火焰结构及点熄火过程试验研究。
回流燃烧室试验系统如

图1 试验测试系统示意图
Fig.1 Schematic view of test facility system
粒子图像测速仪(Particle image velocimetry,PIV)冷态试验采用NdYAG型激光器,BobcatB2041型摄像机以及Micro Pulse725型同步控制器,PIV 系统由 La Vision 公司生产,测量精度误差为±1%。粒子发生器由粉罐和ZB‑0.14/8型直联式空气压缩机组成,使用平均粒径为10 μm的MgO示踪粒子。同时,为了增加PIV计算中的有效数据率,保证有足够高的撒播密
通过高速相机拍摄火焰结构以及火焰传播发展的过程,相机分辨率为1 280 pixel×1 088 pixel,采样频率为1 000 Hz,为了尽可能减小火焰对拍摄结果的影响,试验采用波长430 nm,带宽10 nm的C
回流燃烧室光学测量示意图如

图2 光学测量示意图
Fig.2 Schematic diagram of optical measuring sections

图3 旋流器结构示意图
Fig.3 Schematic diagram of swirler
燃烧室冷态时a1子午面在不同总压损失下的速度云图及流线如




图4 不同总压损失下a1子午面速度流线及分布
Fig.4 Velocity streamline and distribution for a1‑meridian‑plane under different total pressures
燃烧室冷态时a1子午面上不同轴向位置处的轴向速度分布如




图5 不同位置轴向速度分布
Fig.5 Axial velocity distributions at different locations
燃烧室冷态时b1截面在不同总压损失下的速度云图及流线如



图6 不同总压损失下b1横截面速度流线及分布
Fig.6 Velocity streamline and distribution for b1‑cross‑section under different total pressures
由于试验拍摄的为灰色图像,本文通过Matlab对原始图像进行滤波和伪色彩处理,最后得到C

图7 al子午面C
Fig.7 Radical spontaneous emission images of C
在主燃区内,火焰是以一定扩散角度向燃烧室下游发展,并且高度逐渐增加,火焰对称,呈现月牙形状。
在中间区,上侧火焰长度较长,受到上主燃孔射流的影响,部分火焰被截断,在上主燃孔射流位置后,C
在上掺混孔处,产生速度较高的高速气流,截断了主流的高温燃气,同时大量混气已在主燃区和中间区完成燃烧,掺混区只存在少数燃油颗粒,难以形成剧烈燃烧,掺混区并无明显的高亮区域。
燃烧室b1截面C

图8 bl横截面C
Fig.8 Radical spontaneous emission images of C
燃烧室点火期间火焰亮度变化过程如

图9 回流燃烧室点火成功过程
Fig.9 Successful ignition process of reverse combustor
燃烧室点火失败期间火焰亮度变化过程如

图10 回流燃烧室点火失败过程
Fig.10 Ignition failure process of reverse combustor
燃烧室熄火期间火焰亮度变化过程如

图11 回流燃烧室熄火过程
Fig.11 Blowout process of reverse combustor
本文通过PIV与高速相机测量,开展了回流燃烧室流动与燃烧特性试验研究,主要得到以下结论:
(1)由于回流燃烧室的结构差异,流场不具有对称性。压损的改变对燃烧室流场结构影响较小,随着压损的增加,速度值增加。
(2)燃烧主要在主燃区和中间区进行,火焰呈一定的月牙形向外燃烧。
(3)燃烧室点火过程可分为火核生成阶段、火核发展阶段、点火成功阶段和火焰稳定阶段4个阶段,回流涡着火是成功点火的关键。熄火时,火核向回流区后部靠近,火焰根部逐渐远离旋流器出口位置,火焰从正常燃烧时的月牙形结构演变为单股火焰。
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