Numerical Simulation On The Temperature Change Of Large Capacity Cylinders For Tube Trailers During Refueling And Natural Cooling

As a cleaner fuels,natural gas has been has been more and more widely applied in the industry and daily life.The tube trailer,which is the main tool of natural gas transportation,has been the focus of public attention by its security and efficiency of transportation.Rely on science and technology development,the tube trailer for the storage of large volume of compressed natural gas cylinder was received a leap-forward development.However,if refueling the large capacity cylinders by a false way,it may cause the cylinder structure damage.Therefore,the thermo-mechanical phenomenon on the large capacity cylinder filling process has become one of the problems to be solved.In this paper,a common large volume of compressed natural gas cylinder was selected to research,which total length is 10980 mm,volume is about 2500 L,and working pressure is 20 MPa.the thermal state concerning large volume steel cylinder,hoop-wrapped and fully-wrapped composite cylinder during filling are investigated.On the basis of simplification of the physical model of filling large volume cylinders in primary filling station,and computational fluid dynamics(CFD)software Fluent 17.2 was applied to simulate the refueling process during 1800 s within a CNG cylinder and the cooling process during 5400 s.It is emphatically analyzed that the flowing direction of gas,temperature distribution in the cylinder and the temperature patterns of the wall in and after fast filling.The simulation results show as follows:(1)The rapid temperature rise mechanism and simulation method of fast filling of low volume vehicle cylinder can be applied to large volume cylinders,it may yet distinguish concerning temperature rising regular and control strategy between them.(2)The depth-diameter aspect ratio of cylinder model as much as 19.4.When the gas enters the vesssel,it is almost free from the constraint of the geometry of the cylinder,it results in the formation of a more stable compression domain in the middle and rear part of the cylinder.Thus,the end of bottom is the most concentrated area of the high-temperature region.After the filling,the wall of tail will raising last for some time because of CNG overheated.It is also one of the most important factors that threaten the safety of gas cylinders(3)Through the thermal analysis of three kinds of cylinders,the mainly conclusion are presented: Firstly,the temperature of CNG in the storage by research are over to 170?.Secondly,the state of charge of cylinder only about 75%.Thirdly,the hoop-wrapped composite cylinder is the highest temperature among the them,which are all below the allowable temperature.The works of this paper can provide guidance for the temperature rise control of large capacity cylinder of tube trailers,and offer necessary theory and numerical methods for guiding safe operation and standards formulation of security fueling.