横向声波扰动下池火火焰失稳特性

Pool Flame Instability Characteristics under Transverse Acoustic Wave Disturbance

为理解声波灭火机制及声波扰动下的火焰动力学,进行了横向低频声波扰动乙醇池火燃烧实验.采用的低频声波频率范围为28~54 Hz,火焰位置处当地声压范围为0.10~1.25 Pa,通过改变声波导流管长度和声波导流管与火焰距离研究了声学基础参数、火焰现象学特征、火焰高度与宽度及其周期性脉动特性,并建立了耦合声波参数的火焰宽度与高度模型.研究结果表明:相比自由火焰,较低声压扰动使火焰形态与时序变化更加稳定,较大声压扰动会使火焰失稳;随当地声学雷诺数增加,火焰相对高度被声波压制而减小,火焰宽度由被挤压转变为被拓展状态;较低声压会调制火焰导致其周期性变得更稳定,相位变得规则,较高声压会扰乱火焰周期性,使得火焰脉动紊乱,相位变得混沌.

Ethanol pool flame experiments disturbed with transverse low-frequency acoustic wave were carried out to understand the mechanism of acoustic fire suppression and flame dynamics under acoustic disturbance.The acoustic frequency range was 28–54 Hz,and the local acoustic pressure range at the flame was 0.10–1.25 Pa.The basic acoustic parameters,phenomenological characteristics of flame,flame height and width,and flame periodic pulsation were explored with the changing acoustic duct length and distance between acoustic duct and flame.The relation model of flame width and flame height coupled with acoustic parameters was established.The results show that,compared with free flame,the lower acoustic pressure disturbance makes the flame shape and time series more stable,and the larger acoustic pressure disturbance makes the flame more unstable.With increasing Reynolds number locally,the relative flame height is suppressed by acoustic wave and declined,and the flame width changes from being compressed to being lengthened.In addition,lower acoustic pressure will modulate flame to stable periodicity and regular phase.Higher acoustic pressure will disturb flame periodicity,resulting in flame pulsation disorder and phase chaos.