纵向风对通道火灾烟气竖向分层特性的影响

Effects of Longitudinal Air Flow on Smoke Stratification in Channel Fire

研究了纵向风对通道火灾热分层和烟颗粒分层特性的影响.纵向风可能使通道内的分层流出现Kelvin-Helmholtz流动不稳定性,并导致烟颗粒向下部空间扩散;当纵向风较大时,烟气层的热分层稳定性被破坏,导致烟颗粒与冷空气出现强烈掺混,烟颗粒层显著变厚.通道火灾的热分层和烟颗粒分层特性与Froude数或Richardson数关联紧密.实验初步得到了出现Kelvin-Helmholtz流动不稳定和热分层不稳定的临界条件.

This paper experimentally investigated the effects of longitudinal air flow on the characteristics of tempera-ture stratification and smoke density stratification in channel fires.Longitudinal air flow could cause Kelvin-Helmholtz instabilities of stratified flows.A relatively larger longitudinal air velocity resulted in unstable stratification,thus leading to a strong mixing between smoke layer and the fresh air and a significantly thickened smoke layer.Fur-ther studies revealed that temperature stratification and smoke density stratification were dependent upon Froude num-ber and Richardson number.Critical conditions for instability of fire-induced stratified flows were obtained.