Research On Dynamic Characteristics Of Piped Carriage In The Straight Pipe

With the rapid progress of national science and technology,the logistics industry is booming all over the country with the rapid development of Internet production.At present,the mainly ways of logistics transportation are railway,highway,sea and air transportation,which are basically based on the large consumption of oil and natural gas.Not only that,in the consumption of resources at the same time,human survival environment is also increasingly bad.And traffic congestion in big cities is a worldwide problem.It can be seen that the lack of resources,traffic congestion and environmental pollution have become the bottleneck of the development of social logistics industry.In the face of the contradiction between the increasing demand of urban logistics and the insufficiency of transportation capacity and efficiency,it is necessary to seek an efficient,energy-saving,environmental protection and new transportation mode.Piped carriage transportation is a new type of transportation mode with the above characteristics.In addition,it has the advantages of small floor area and good concealment,which is more suitable for the current demand.This paper combined the National Natural Science Foundation of China"Research on Energy Consumption of Piped Carriages Train Hydraulic Transportation(51179116)"and the project of Shanxi Natural Science Foundation of China"The Characteristics of Spiral Flow on Concentric Annular Gap of Piped Carriage Hydraulic Transportation"(2015011067)",the transport mechanism,hydraulic characteristics,wall stress,transport energy consumption and sensitive factors of the piped carriage when it were stationary and stably moving in the straight pipe section were studied by theoretical analysis,numerical simulation and physical experiment.Finally,the evaluation model based on weighted fuzzy TOPSIS is used to optimize the piped carriage,and the main conclusions were as follows:(1)Based on the theoretical analysis of the flow field characteristics and mechanical characteristics of the two working conditions,the velocity formula of the annular gap flow between the outer wall of piped carriage and the inner wall of pipe and the theoretical calculation formula of the wall shear stress of the piped carriage were derived.(2)Through COMSOL multiphysics software,the mathematical model of the dynamic characteristics of the piped carriage when it was stationary and moving was built,in which the boundary conditions were redeveloped and the distribution function of the inlet velocity was customized.And which was verified by physical experiments.(3)The pressure of pipe flow when the piped carriage was stationary and moving in the straight pipe section was analyzed.The results showed that the pressure difference between the front and rear end of the piped carriage was very large,and low-pressure area was formed near the front-end when the piped carriage was stationary.When it was moving,the pressure of pipe flow the near piped carriage changed periodically.(4)When the piped carriage was stationary and moving in the straight pipe section,the velocity distribution in the pipe changed greatly.There was a vortex region extending on the front-end of the piped carriage,in which there were symmetrical vortices,and the rotation direction was opposite when the piped carriage was stationary.When it was moving,the average velocity of piped carriage was greater than the average velocity of the pipe flow,and the axial velocity of concentric annular gap flow was smaller than the average velocity of pipe flow.(5)This paper analyzed the shear stress on the cylinder wall of piped carriage when it was stationary and moving in the straight pipe section.Results showed that the shear stress on the front and rear end of the piped carriage was concentric and circular distribution,and the maximum value of the wall shear stress on the cylindrical surface of the cylinder appearred between the two groups of feet at the front and rear end and close to the front and rear end of piped carriage when the it was stationary.When it was moving in the straight pipe section,the area with large shear stress on the cylinder wall was mainly concentrated on the front and rear end and near the front and rear end of the cylindrical wall of the cylinder,especially the rear area of the support feet of the piped carriage.(6)This paper analyzed the principal stress on the cylinder wall of piped carriage when it was stationary and moving in the straight pipe section.When it was stationary,the axial component of wall principal stress on the cylindrical surface of the piped carriage cylinder was similar to the maximum value area of the circumferential component of wall principal stress,which was mainly distributed near the position between two groups of feet on the rear-end of the piped carriage;the radial component of wall principal stress appearred a negative value in the area 15mm from the front and rear end,and the minimum value appearred between two groups of feet near the rear-end.When it was moving,the large areas of wall principal stress on the cylinder wall of piped carriage were mainly distributed in the area of 15mm near the front and rear end between the front and rear set of feet.(7)When the piped carriage was stationary and moving,the maximum value of the axial component of wall principal stress>the maximum value of the circumferential component of wall principal stress>the maximum value of the radial component of wall principal stress.The absolute value of the minimum value of the radial component of wall principal stress>the absolute value of the minimum value of the circumferential component of t wall principal stress>the absolute value of the minimum value of the axial component of wall principal stress.(8)This paper analyzed the energy consumption when the piped carriage was moving in the straight pipe section.Results showed that the unit volume energy consumption of the piped carriage with D_c×L_c=65mm×150mm was the smallest.And the Reynolds number of the pipe flow was the most sensitive to the energy consumption per unit volume,the diameter D_c of the cylinder was the second sensitive to the energy consumption per unit volume,and the sensitivity of the length L_c of the cylinder to the energy consumption per unit volume was smaller than the first two,that is,S_Re>S_Dc>S_Lc.(9)The model of piped carriage moving in the straight pipe section was optimized.Based on the maximum value of the stress on the cylinder wall of piped carriage,the unit volume energy consumption and the transportation efficiency of the piped carriage.The weighted fuzzy TOPSIS evaluation model was used to optimize the model of the piped carriage.Results showed that the piped carriage with D_c×L_c=70mm×150mm was the best model under this operation condition.The research results of this paper enrich the theory of piped carriage hydraulic transportation technology,and provide a more important reference value for the promotion and application of this technology.