基于PIV的不同受限形式下火羽流流场特性研究

为探究不同受限形式对火羽流流场的影响,采用精细热电偶技术和粒子图像测速(PIV)技术,监测扩散燃烧器在自由空间、侧壁空间和墙角空间下火羽流高度、温度和流场等,了解不同受限形式下火羽流流场特性。结果表明:当无量纲火源功率Q^*小于1.5时,无量纲火焰高度Lf/D随之线性增加;当Q^*超过1.5时,Lf/D增加幅度减小;在不同受限空间内的横向速度分布均服从近似高斯分布,且侧壁空间和墙角空间会使火焰中心产生一定偏离;Q^*为1.982时,涡旋直径为3.5~8 cm,涡度大小随侧壁面的增加逐渐增大,这是因为侧壁存在时涡旋会发生脱落,这种脱落导致短时间内释放大量热量,对火羽流存在拉伸作用从而促进燃烧,并进一步产生更大的涡旋。

Flow field characteristics of fire plume in different restricted forms based on PIV

In order to explore effects of different restricted forms on flow field of fire plume,fine thermocouple and PIV technologies were used to monitor fire plume’s height,temperature and flow field of diffusion burner in free space,side wall space and corner space,and then flow field characteristics in different restricted forms were studied.The experimental results show that when dimensionless source power Q^*is less than 1.5,dimensionless flame height Lf/D increases linearly which will become steady approximately when Q^*exceeds 1.5.Lateral velocity in different restricted spaces all conform to approximate Gaussian distributions,and sidewall space and corner space cause a certain deviation of flame center.Vortex diameter is between 3.5 and 8 cm at Q^*is 1.982,and its size gradually increase along with increase of side wall surface because vortex will fall off,which will release a lot of heat in a short time and exerts a stretching impact on fire plume.As a result,combustion reaction of fire is promoted,and then a larger vortex is generated.