Study Of Cable Fire Spread Behavior And Temperature Distribution Patterns In Confined Spaces

In recent years,the number of urban underground space in the world is increasing,and most of the underground space buildings are narrow and restricted space,the cable is mostly arranged in the narrow and restricted space,with urbanization,the process of information technology continues to accelerate,the cable has become one of the indispensable industrial products,in its convenience for people’s lives,but also because of short circuit,arc,poor contact,overload and other reasons caused by fire accidents.It is urgent to carry out research on the fire spreading behavior and temperature distribution law of cables in narrow and restricted spaces under different environmental conditions,so as to provide theoretical basis and data support for fire risk assessment,fire prevention and control in long narrow confined spaces.This thesis investigates the influence of longitudinal ventilation speed,cable gap,cable layer spacing and ambient air pressure on the fire propagation behavior and temperature distribution of cables in confined spaces by conducting experiments and numerical simulations of cable fires in confined spaces,and clarifies the changes of cable flame pattern,mass loss rate,fire propagation speed and temperature distribution in confined spaces with the above factors,and establishes a prediction model for the fire propagation speed of cables in confined spaces coupled with longitudinal wind speed,cable layer spacing and cable gap,The prediction model of cable fire propagation rate in confined space with coupled longitudinal wind speed,cable layer spacing and cable gap was established.The main conclusions are as follows:(1)The cable flame inclination gradually increases with the increase of reverse ventilation speed in the narrow restricted space,and the cable flame appears branching phenomenon with the increase of cable layer spacing,and the flame branching phenomenon is most obvious when the cable layer spacing is 15 cm.Cable flame fusion behavior gradually disappears with the increase of cable gap,when the cable gap is15 cm,three separated flames are formed in the same layer of cable.The cable mass loss rate,cable fire spread speed and maximum temperature of narrow restricted space decrease with the increase of longitudinal ventilation speed and cable layer spacing,and increase first and then decrease with the increase of cable gap,when the reverse wind speed is 0.80m/s and the cable layer spacing is 15 cm,the cable mass loss rate is the smallest,the cable fire spread speed is the smallest and the maximum temperature of narrow restricted space is the smallest,when When the cable gap is 4cm,the mass loss rate of the cable is maximum,the cable fire propagation speed is maximum,and the maximum temperature of the narrow restricted space is maximum.(2)The prediction model of cable fire propagation speed coupled with longitudinal ventilation speed in narrow restricted space and cable layer spacing is established using the method of dimensional analysis,and the prediction model of cable fire propagation speed coupled with cable gap and cable layer spacing is established,and the model prediction results are in good agreement with the experimental results under different working conditions.(3)The temperature above the cable fire source in the narrow confined space decreases gradually with the increase of ambient air pressure.The power exponential fitting of the longitudinal distribution of the dimensionless temperature rise in the confined space under different working conditions is found to be good.