Study On The Temperature Distribution Of Utility Tunnel Fire

In order to meet the needs of rapid economic growth and urbanization,the utility tunnel arises at the historic moment.This kind of building belongs to the narrow and long semi-closed structure,which will pose a direct challenge and threat to public safety in case of fire.Generally speaking,there are firewalls and fire doors in the utility tunnel.The fire prevention facilities have a significant impact on the spread characteristics and temperature distribution of the thermal plume,which will cause a large number of smoke gathered under the ceiling and make the temperature near the closed end significantly increase.So the risk of damage to the utility tunnel structure and internal facilities were aggravated.Therefore,a deep understanding of the fire temperature distribution of the utility tunnel has important theoretical reference value for the design and layout of the utility tunnel detection system as well as the fire rescue.This study carried out a series of experiments on the 1:10 scale test bench.It explores the influence of the heat release rate,the location of fire source and the slope of utility tunnel on temperature distribution.The dimensionless maximum temperature prediction model,the dimensionless longitudinal temperature attenuation model and the dimensionless transverse temperature prediction model have been got.The research results for utility tunnel fire prevention has certain theoretical reference value and practical significance.The following aspects were studied in this paper.Scale tests were carried out to study the influence of heat release rate(HRR)and the longitudinal position of fire source on the temperature distribution in the case of nonslope utility tunnel fire.The propane used as fuel,the fire source was moved along the longitudinal centerline of the utility tunnel,and 9 different fire source positions were set.The gas flow rate was adjusted through the rotor flowmeter to change the HRR,and 10 different HRRs were set.According to the analysis,it is found that the dimensionless maximum temperature rise in the far-field region has a linear relationship with dimensionleaa HRR in the logarithmic coordinate,and the dimenless maximum temperature rise in the near-field region has a power function relationship with the dimensionless HRR in the logarithmic coordinate.When the fire source is closed to the closed end of the utility tunnel,the longitudinal temperature presents an asymmetrical distribution,and the temperature is higher at the side near the closed end.The dimensionless longitudinal temperature attenuation models of the upstream and downstream of the fire source are obtained.When the HRR is constant,the transverse temperature decreases with the increase of the distance between the fire center and the closed end of the utility tunnel,and the dimensionless transverse temperature rise prediction model is obtained when the distance between the fire center and the closed end of the utility tunnel is less than 0.68m.The influence of the HRR and the longitudinal position of fire source on the temperature distribution of utility tunnel which the slope were 2%、5%、6%respectively were studied by scale tests.The results show that the distribution of the maximum temperature under different slopes can be divided into the far-field region and the nearfield region.With the increase of the slope,causing the chimney effect increase,and the temperature jump phenomenon appears between the two regions.According to the analysis,a dimensionless prediction model of the maximum temperature rise considering the influence of the slope is obtained.When the HRR is fixed,the upstream longitudinal temperature of the fire decreases with the increase of the slope,and the downstream longitudinal temperature of the fire is less affected by the slope.Under different slopes,when the distance between the fire center and the closed end of the utility tunnel is more than 0.68m,the transverse temperature tends to be a constant.And when the distance between the fire source and the closed end of the utility tunnel is less than 0.68m,the dimensionless tranverse temperature rise prediction model considering the influence of the slope of the tunnel is proposed.