Numerical Simulation Study On Fire Separation Distance Of Wooden Structure Buildings In Ancient Commercial Street

Most of the ancient commercial streets have a small building spacing,which is inherently inadequate for fire prevention,and often was used wooden structures.Once the fire occurs,it is non-renewable,which will cause great economic and cultural losses.Previous studies have mostly focused on the analysis of the fire spread between wood structures,and there is insufficient research on the quantitative relationship between the fire separation distance of wooden structures on ancient commercial streets and multiple external factors.Changes in the external environment wind speed may affect the fire smoke temperature and heat radiation intensity near the buildings across the street,which in turn affect the fire spread characteristics.Certain external wind speed conditions may be most conducive to the spread of fire.Therefore,when fires with different fire source powers occur in wooden structures,each fire power may correspond to the existence of the smallest fire separation distance,and further research is needed.This article takes an ancient commercial street as the research object.The critical temperature and heat radiation intensity are used as the judgment indicators of the ignition of the wooden structure across the street during the fire,and the environmental wind speed,building spacing,fire source power,sprinkler system Whether it is effective or not,the fire dynamics simulation software FDS is used to carry out numerical simulation of fire smoke movement in a series of fire scenarios,the distribution characteristics of smoke temperature and heat radiation intensity are analyzed,and the relationship between fire separation distance and fire source power and environmental wind speed In order to provide suggestions and reference for the fire protection renovation plan of the wooden structure buildings of ancient commercial streets with the inherent shortage of fire separation distance.Research indicates:The results show that:(1)when the building spacing is within 3m,the combined action of high temperature ignition and thermal radiation ignition causes the fire to spread to the building directly opposite;when the building spacing is above 3m,the fire is mainly caused by thermal radiation ignition.(2)the thermal radiation intensity is greatly affected by the environmental wind speed.The thermal radiation intensity first increases with the increase of the environmental wind speed,and then decreases with the increase of the environmental wind speed after reaching the maximum value.Under the conditions studied in this paper,when the ambient wind speed is about 4m/s,the heat radiation intensity reaches the maximum value.The required fire separation distance between the wooden buildings of the ancient commercial street is related to the environmental wind speed and fire source power.There is a minimum fire separation distance for each fire source power,and the minimum fire separation distance depends on the fire source power.When the power of the fire source is 3MW?20MW,the linear relation between the minimum fire distance L and the power Q of the fire source is L=0.25Q+2.50.(3)when the building spacing is greater than 7.3m,the fire will not ignite the timber structure building directly opposite the ancient commercial street;When the building spacing is within the range of 3m?7.3m,the automatic sprinkler system should be installed in the wood structure building,and when it is less than 3m,the rapid response sprinkler system should be used.Fire retardant coating can improve the critical temperature and thermal radiation intensity of wood structure building fire,when the building spacing is less than 3m,it is recommended to paint fire retardant coating.This paper can provide reference value for future research on the fire spacing problem and protection scheme of the same type of ancient street buildings.