Study On Working Rule Of Ventilation System Of Gas Pipe Tunnel After Leakage

In recent years,China's economy has achieved a rapid development.With the improvement of the material foundation,people' demand for a good living environment in the city has become stronger.Underground utility tunnel is an effective measure to realize the unified management of underground pipelines,representing the future of the city.And its construction will gradually enter the stage of full implementation and outbreak.How to avoid the occurrence of high-risk tunnel accidents while developing utility tunnels,how to ensure the normal operation of high-risk tunnel protection system,and how to ensure the further expansion of accidents after leakage accidents has become a further developing problem of China's utility tunnel business.Especially,gas pipe tunnel is a typical representative of high-risk tunnels,and its main form of accidents in the operation is gas leakage,while ventilation system is the main means of dealing with gas leakage.Therefore,it is important to improve the reliability of ventilation systems of gas pipe tunnel.The gas pipe tunnel and its ventilation system in the underground utility tunnel are studied in this paper.The working process of the entire ventilation system of the gas tunnel,the impact on the environment inside the tunnel and different leakages are studied under the abnormal condition of the gas pipe(gas leakage).The factors affect the gas leakage diffusion results under the normal ventilation conditions of the ventilation system were studied.Furthermore,the abnormal conditions(gas leakage)of the gas tunnel and the influencing factors of the ventilation system under the operating conditions of the accident ventilation were in-depth studied.The operating state of the fan was monitored,and its connection with the ventilation system was established,which can provide theoretical support for establishing a good ventilation system for gas pipe tunnel in the future.Aiming at different ventilation conditions of ventilation system of gas pipe tunnel,a finite element model of gas leakage in gas pipe tunnel was established by using computational fluid dynamics method.Three different influencing factors of gas leakage speed,leakage hole's diameter and leakage position of the gas pipe tunnel on the gas leakage result under the normal ventilation conditions were simulated.The importance of the gas diffusion factor was determined in a decreasing order of the leakage hole's diameter>leakage speed>the leakage position.The effects of three different working conditions,such as exhaust speed,initial gas concentration and vent size,on the operating law of the ventilation system after gas leakage were studied.The influence of the size of the vent on the operating law of the ventilation system was found to be most than the exhaust speed,and greater than the initial gas concentration.Therefore,it is known that in the actual working conditions of the gas pipe tunnel operation,when the large hole's leakage occurs,it is necessary to take the method of prolonging the accident ventilation time to eliminate the danger;appropriately reducing gas transport pressure in the gas pipe can also achieve the purpose of reducing the risk.When the gas leakage position is known,the space between the position of the leakage hole and the air outlet is the main diffusion area,and the worker needs to enter the gas pipe tunnel from the side of the area before the air inlet side of the leakage port.In the design process,the method of increasing the size of the vent and increasing the power of the fan can reduce the dangerous working time of the ventilation system.At the same time,a design on a simulation test bench of the gas pipe tunnel is carried out,which includes five systems:a tunnel model,a gas leakage system,a ventilation system,a detection system,and a data acquisition and storage system.Using the built test bench to test the typical working conditions in the simulation,the simulation results were compared with the test results,then the connection between the operating state of the ventilation system and the environment inside the tunnel was established.The results show that the vibration speed of the same fan is directly related to the exhaust speed.The vibration speed parameter can be used as a criterion to judge the effectiveness of the ventilation system.It can guide the treatment of the abnormal condition of the gas pipe tunnel and the safety evaluation of the ventilation system.Figures:56,Tables:20,References:55.