狭长通道内火灾烟气层的沉降特征

escent of smoke layer in a long channel when carrying out hot smoke tests with small fires was presented. An experimental method using infrared beams is used to track the smoke layer interface front. The arrival time of the smoke layer interface front to a designated position would be measured by the abrupt attenuation of the infrared beam intensity. Field measurements were carried out in an underground long channel of length 96 m. Diesel pool fires up to 1.5 MW were studied. The results on tracking the smoke layer interface front were compared with the measurements by using thermocouples, thermal resistors and visual observations. This method is demonstrated to be useful for tracking the smoke layer interface front under small fires. Therefore, the method is suitable for studying the smoke layer descending in hot smoke tests for evaluating smoke management systems in long channels. The Descending of smoke layer was tracked at 7 m, 39 m and 79 m away from the fire. Results showed that the smoke layer at cross section of 79 m away from the fire descended much faster than that of 7 m and 39 m. The smoke layer seemed to descend faster at positions further away from the fire due to longitudinal air entrainment at the smoke layer interface.