Study On Thermal Response Of Gas Cylinder Of Tube Trailer In Jet Fire

The clean energy natural gas has been widely used in industry,society,and routine life due to its cheap price,convenient exploitation,and transportation.The natural gas is usually stored as CNG,which is mainly transported by the tube trailer at home and abroad.Huge economic losses and human injuries may be sudden fire happen.And natural gas is flammable and explosive,so its safety in fire accidents has attracted a lot of attention.Gas cylinders of tube trailer need to do the fire tests,in which the thermal responses of the gas cylinder in fire or high temperature environment are studied to evaluate safety performance of cylinders.The fire tests of the gas cylinder are risky,which may cause the explosion accidents.So the researchers always used the numerical simulations to get the thermal response of the gas cylinder in the fire.In order to reduce the test risk,speed up the research progress,save economic costs,obtain more accurate results in a shorter time,the high-temperature safety performance of the gas cylinder are studied in more detail.And it also could observe the flow fields’ data that is not available in experiment.In this work,the thermal response of gas cylinders in jet fire test was studied by experiments and numerical simulations respectively.Large volume fiber wound gas cylinder was selected,and the inside medium was high-pressure air.Based on the experiment,the three-dimensional numerical simulation of the gas cylinder in fire test was completed.And the law on the time-depended pressure and temperature field of the cylinder in the jet fire test was obtained.The results of the research are stated as below:(1)Due to limited computing resources in the modern industry,it is difficult to verify grid-independent of the 3D model of jet fire,especially for the small-hole jet fire.A two-dimensional model instead of the three-dimensional model was used to deduce the mesh resolution,and its exploratory validation was carried out.It is found that the laws of grid-independent in two-dimensional and three-dimensional jet fire simulations are consistent.But the accuracy of parameters such as combustion field,flow field and temperature field of the two-dimensional model cannot be guaranteed.It is suggested that the two-dimensional model can be used to optimize the mesh size of the jet hole in the large-scale jet fire simulation.This method can save lots of computational resource.(2)The fire test of fiber-wound gas cylinder was carried out,and its numerical simulation was completed,and the thermal response of the gas cylinder and its inside medium was obtained.The results showed that the heat flux at the bottom of the cylinder is the largest,which is the most vulnerable part of the gas cylinder.The thermal response process can be divided to two stages.In the first stage,the temperature and pressure were almost constant.Then,they increased linearly in the second stage.The simulation data is in good agreement with the experiment,and the accuracy of the numerical model can be verified.These works are helpful to systematically design fire test experiment and can be used to predict the failure time of pressure vessels in the future.And these also have a certain reference value for safety performance assessment and accident rescue of the pressure equipment.(3)The effect of the fire-proof baffle of gas cylinder installed on the tube trailer was studied,and the fire test of the composite gas cylinder with baffle was carried out.The three-dimensional numerical simulations were also established to study the thermal responses of the gas cylinders with and without baffles.The results of experiment and simulation were compared to verify the accuracy of the numerical model.Then,the simulations results are compared to evaluate the effects of the baffles.It is showed that the gas temperature and pressure in the cylinder would rise much more rapidly without baffle.And the thermal responses of the medium in the cylinder are quite different whether the gas cylinder has a baffle.It can be concluded that the baffle of the gas cylinder has a significant protective effect in the fire environment.