| With rapid development of technology and growing awareness of environmental protection,traditional transport modes such as railways,highways,waterways and aviation can no longer meet requirements of rapid development of modern society.These problems such as traffic congestion,energy crises and environmental pollution have severely restricted sustainable development of both social economy and ecological environment.Therefore,it has become an inevitable trend to seek a low-carbon,environmentally friendly and efficient transport mode.The pipeline hydraulic transportation of piped carriages train was a set energy conservation and environmental protection in one of a new type of transport mode,which not only can better alleviate the oil price increase caused by the energy shortage,but also effectively settle several problems of the atmospheric pollution and the traffic congestion.Combining the National Natural Science Foundation Project “Research on Energy Consumption of Piped Carriages Train Hydraulic Transportation(51179116)”,the theoretical analysis,numerical simulation and experimental studies were used to research the bidirectional fluid-structure interaction between the fluid domain within the horizontal pipe and the solid domain for the piped carriages train in the technique of the pipeline hydraulic transportation of piped carriages train.The flow velocity distributions,pressure distributions,vorticity magnitude distributions,speed characteristics,pressure drop characteristics,mechanical efficiencies and mechanical properties of the water flow within the pipe transporting the piped carriages train were analyzed comprehensively.At the same time,based on the principle of minimum design cost,an optimization model within the horizontal pipe transporting the piped carriages train was established successfully.The main conclusions in this paper were as follows:(1)The simulated values of the hydraulic characteristics of the flow field within the horizontal pipe were basically consistent with the experimental values when the single piped carriage and the double piped carriages transported along the horizontal pipe.With the increase of the diameter ratio,the average speeds of the single piped carriage and the double piped carriages showed an increasing trend.The instantaneous speeds of both the single piped carriage and the double piped carriages had irregular fluctuations in a smaller range over time.The average spacing between the double piped carriages at the steady stage was slightly smaller than the initial spacing at the static stage.For these reasons,the initial spacing at the static stage can be regarded as the average spacing of transporting the double piped carriages.(2)The FARO-LDI 3D laser scanning system was used to obtain surface cloud data of the piped carriages train.The geometrical model within the horizontal pipe transporting the piped carriages train was established by using Auto CAD software,and the fluid domain within the horizontal pipe and the solid domain of the piped carriages train for the geometrical model were meshed by using ICEM CFD software.The momentum averaged Navier-Stokes equations and the RNG k-? turbulent model were adopted to solve the flow field characteristics inside the horizontal pipe.The User-Defined Functions and the rigid body motion equations were used to solve the transient dynamic response characteristics of the piped carriages train.(3)There was a “conical” back-flow area near the front end of the single piped carriage,and the axial velocity near the rear end of the single piped carriage appeared exponential distributions.The radial velocity within the horizontal pipe was mainly distributed near the front and rear ends of the single piped carriage,and the direction of the radial velocity dispersed from the center of the pipe to the pipe internal wall.The circumferential velocity inside the horizontal pipe was distributed near the front and rear ends of the single piped carriage,and the direction of the circumferential velocity near the front and rear ends of the single piped carriage was consistent.The high pressure area of the flow field within the horizontal pipe existed near the front and rear ends of the single piped carriage,and the low pressure area distributed at the entrance location for the annular slit area and near the front end of the single piped carriage.The vorticity magnitude of the internal flow field inside the horizontal pipe was mainly distributed at the entrance location of the annular slit area and at the interface between the annular slit flow and the back-flow fluid when the single piped carriage transported within the horizontal pipe.With the increase of the diameter ratio,the pressure at the upstream flow field of the single piped carriage decreased first and then increased,and the pressure drop near the front end of the single piped carriage increased.(4)As the diameter ratio and the pipe flow rate increased,the average speed coefficient of the single piped carriage presented a trend of increase.With the increase of the diameter ratio,the average pressure drop coefficient of the pipe transporting the single piped carriage decreased first and then increased,and when the diameter ratio was 0.7,the average pressure drop coefficient of the pipe transporting the single piped carriage reached the minimum.As the diameter ratio increased,the mechanical efficiency of the single piped carriage increased first and then decreased,and when the diameter ratio was 0.7,the mechanical efficiency of the single piped carriage reached the maximum.As the pipe flow rate and diameter ratio increased,the average drag coefficient and the average lift coefficient around the single piped carriage gradually increased.(5)There was a back-flow area near the front end of the double piped carriage,and there was a high velocity area near the interior wall of the pipe at the downstream flow field of the double piped carriages.The radial velocity within the horizontal pipe was distributed near the front and rear ends of the double piped carriages.The circumferential velocity within the horizontal pipe was distributed near the front and rear ends of the double piped carriages,and the direction of the circumferential velocity near the front and rear ends of the double piped carriages was consistent.The high pressure area existed near the front end of the double piped carriages.There was a low pressure area at the entrance location of the annular slit area of the double piped carriages 1,while there was no low pressure area at the entrance location of the annular slit area of the double piped carriages 2.The vorticity magnitude within the horizontal pipe was distributed at the entrance location of the annular slit area and at the interface between the annular slit flow and the back-flow fluid when the double piped carriages transported within the horizontal pipe.As the diameter ratio increased,the pressure at the upstream flow field of the double piped carriages 1 decreased first and then increased,and the pressure drop near the front end of the double piped carriages gradually increased.With the increase of the spacing,the pressure at the upstream flow field of the double piped carriages 1 increased.With the increase of the spacing,the pressure drop near the front end of the double piped carriages 1 gradually decreased,while the pressure drop near the front end of the double piped carriages 2 remained unchanged.(6)With increasing the diameter ratio and the pipe flow rate,the average speed coefficient of the double piped carriages showed an increasing trend.As the spacing increased,the average pressure drop coefficient of the pipe transporting the double piped carriages gradually increased.As the diameter ratio increased,the average pressure drop coefficient of the pipe transporting the double piped carriages decreased first and then increased,and when the diameter ratio was 0.7,the average pressure drop coefficient of the pipe transporting the double piped carriages reached the minimum.With the increase of the spacing,the mechanical efficiency of the double piped carriages increased first and then decreased,and when the spacing was 0.3 m,the mechanical efficiency of the double piped carriages reached the maximum.With the increase of the diameter ratio,the mechanical efficiency of the double piped carriages increased first and then decreased,and when the diameter ratio was 0.7,the mechanical efficiency of the double piped carriages reached the maximum.As the spacing increased,the average drag coefficient around the double piped carriages 1 decreased,while the average drag coefficient around the double piped carriages 2 increased.As the spacing increased,the average lift coefficient around the double piped carriage 1 increased,while the average lift coefficient around the double piped carriage 2 decreased.With the increase of the pipe flow rate and the diameter ratio,the average drag coefficient and the average lift coefficient around the double piped carriages showed a trend of increase.(7)There was a “conical” back-flow area near the front end of the three piped carriages,and there was a high velocity area near the internal wall of the pipe at the downstream flow field of the three piped carriages.The radial velocity within the horizontal pipe was distributed near the front and rear ends of the three piped carriages,and the radial velocity near the front end of the three piped carriage was higher than that near the rear end of the three piped carriages.The circumferential velocity inside the horizontal pipe was distributed near the front and rear ends of the three piped carriages,and the direction of the circumferential velocity near the front and rear ends of the three piped carriages was consistent.The high pressure area within the horizontal pipe was distributed near the front and rear ends of the three piped carriages.There was a low pressure area at the entrance location of the annular slit area of the three piped carriage 1,and there was no low pressure area at the entrance location of the annular slit area of the three piped carriage 2 and the three piped carriage 3.The vorticity magnitude within the horizontal pipe was distributed at the entrance location of the annular slit area and at the interface between the annular slit flow and the back-flow fluid when the three piped carriages transported within the horizontal pipe.As the diameter ratio increased,the pressure at the upstream flow field of the three piped carriages 1 decreased first and then increased,and the pressure drop near the front end of the three piped carriages gradually increased.With the increase of the spacing,the pressure drop near the front end of the three piped carriages 1 and the three piped carriage 2 gradually decreased,while the pressure drop near the front end of the three piped carriage 3 remained unchanged.(8)With the increase of the diameter ratio and the pipe flow rate,the average speed coefficient of the three piped carriages showed an increasing trend.As the spacing increased,the average pressure drop coefficient of the pipe transporting the three piped carriages gradually increased.With the diameter ratio increased,the average pressure drop coefficient of the pipe transporting the three piped carriages decreased first and then increased,and when the diameter ratio was 0.7,the average pressure drop coefficient of the pipe transporting the three piped carriages reached the minimum.As the spacing increased,the mechanical efficiency of the three piped carriages increased first and then decreased,and when the spacing was 0.3 m,the mechanical efficiency of the three piped carriages reached the maximum.As the diameter ratio increased,the mechanical efficiency of the three piped carriages increased first and then decreased,when the diameter ratio was 0.7,the mechanical efficiency of the three piped carriages reached the maximum.As the spacing increased,the average drag coefficient around the three piped carriages 1 decreased,while the average drag coefficient around the three piped carriage 2 and the three piped carriage 3 increased.As the spacing increased,the average lift coefficient around the three piped carriages 1 increased,while the average lift coefficient around the three piped carriages 2 and the three piped carriage 3 decreased.With the increase of the pipe flow rate and the diameter ratio,the average drag coefficient and the average lift coefficient around the three piped carriages showed a trend of increase.(9)Due to the interaction between the pipe fluid and the piped carriages train,the hydraulic characteristics of the internal flow field within the horizontal pipe transporting the piped carriages train appeared to be unsteady.The axial velocity distributions,radial velocity distributions,circumferential velocity distributions as well as vorticity magnitude distributions in the near-wall area of the piped carriages train were basically the same at different times and there was no periodic variation over time,when the piped carriages train transported within the horizontal pipe.With the migration time increased,the pressure distributions in the near-wall area of the piped carriages train gradually decreased.(10)Based on the principle of the lowest design total cost and taking into account the two aspects of both the fluid and the machinery,the optimization model of the pipeline hydraulic transportation of piped carriages train was established for the first time.The design total cost of the optimization model can be divided into the manufacturing cost of both the pipe and the piped carriage as well as the power cost of the pipe system.The purpose of the optimization model was to find the optimal pipe diameter of the optimization model of the pipeline hydraulic transportation of the piped carriages train and the power of the centrifugal pump unit required corresponding to the optimal pipe diameter.With the pipe diameter increased,the design total cost of the optimization model of transporting the piped carriages train decreased first and then increased.As the diameter ratio increased,the design total cost of the piped carriages train corresponding to the optimal pipe diameter decreased first and then increased.When the diameter ratio was 0.7,the design total cost corresponding to the optimal pipe diameter was the lowest when the piped carriages train transported within the horizontal pipe.As the diameter ratio increased,the power cost of the pipe system and the power of the centrifugal pump unit required corresponding to the optimal pipe diameter decreased first and then increased.As the spacing increased,the optimal pipe diameters were basically the same when the piped carriages train transported within the horizontal pipe.With the increase of the spacing,the total design cost of the piped carriages train and the power of the centrifugal pump unit required corresponding to the optimal pipe diameter presented an increasing trend.The research in this paper provided a rich theoretical basis for further research on the application of the piped carriages train in engineering practice. |
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