Dynamic Numerical Simulation Of Local And Integral Pipe Coupling With Gases And Particles

In the exploitation of oil,natural gas,coal bed methane and chemical production,there are a large number of transportation pipelines,which are often accompanied by various solid particles when transporting gas or liquid media.Due to the fluctuation of transportation pressure and particle collision and accumulation,the vibration of pipelines is often too large,which is easy to cause pipeline media leakage,rupture and failure accidents.Is often encountered in engineering and to solve the technical problems.Due to the interaction between pipe and particle flow,the mechanism of vibration failure caused by particle flow becomes more complex,which is also a hot topic in the study of fluid-structure coupling.Based on the engineering background of coalbed methane gathering and transportation pipeline,this paper uses computational mechanics software to establish a numerical analysis model and calculation method of the coupling dynamics between pipeline and gas and particles,and discusses the vibration effects of typical pipeline particle flow.Through the establishment of the substructure database and the design of the calling algorithm,the purpose is to apply the numerical simulation of the coupling of pipeline and particle flow to the engineering pipeline,so as to avoid the phenomenon that the calculation workload is too much and the PC is difficult to complete.According to the governing equation of fluid and particle,and the principle of interaction and interaction between fluid and particle,the bidirectional coupling algorithm of gas and particle group is established.Based on the bidirectional coupling model of gas and particle group,combined with the finite element method of pipe structure mechanics,a direct dynamic analysis method of pipe and gas and particle coupling was established,and a solution program was written by Delphi platform.By numerical simulation of the experimental condition of coupling vibration of pipe and particle flow,the average amplitude of pipeline vibration acceleration is obtained,and the error is less than 18% compared with the experimental results,which shows the reliability of the dynamic direct analysis method of coupling of pipe and particle flow established in this paper.Orthogonal experiment was used to study the influence law of particle size,mass concentration,flow rate and pipe diameter or viscosity on typical pipe vibration.The results show that:(1)The influences of four factors on straight pipe in descending order are velocity,pipe outer diameter,mass concentration and particle size respectively.Among them,the influence of velocity is 3.6 times of pipe outer diameter,7.2 times of mass concentration and 8 times of particle size.When the flow velocity increases,the gas pressure loss increases,the particle group motion velocity increases,and the pipeline vibration acceleration increases.When the inlet flow velocity is 10m/s,the straight pipe vibration evaluation index is 2.6 times of that when the inlet flow velocity is 4m/s.(2)The influence of four factors on the bending pipe in descending order is velocity,viscosity,mass concentration and particle size,among which the influence of velocity is 1.7 times of viscosity,3.9 times of mass concentration and4.4 times of particle size.When the flow velocity increases,the gas pressure on the elbow wall increases and the pipeline vibration acceleration increases.The evaluation index of the elbow vibration when the inlet flow velocity is 10m/s is 2.7 times that when the inlet flow velocity is 4m/s.In the numerical simulation of the coupling of the integral pipeline and particle flow,the integral pipeline is first divided into several substructures,and the unknown quantity of each substructure is reduced based on the substructure pipeline model reduction method,and then the coupling dynamics of the substructure pipeline and particle flow are directly analyzed.Based on Delphi 7 software and SQL Server 2019 database platform,a substructure database which can automatically store and invoke numerical simulation results is established.Secondly,according to the force balance condition and displacement coordination condition on the interface,the substructures extracted from the database are connected successively,and the substructure connection analysis method of coupling the whole pipeline with gas and particles is established.Based on MATLAB software platform and built by substructure join algorithm,developed a whole pipeline and the coupling of the gases and particles substructure cohesion analysis program.The substructure connection algorithm and the direct method are used to simulate the 1.5m straight pipe and the 90° bend pipe respectively.The results show that the pipeline amplitude errors calculated by the two methods are both less than 15%,and the influence of the four factors range is the same as that of the direct method,which proves the reliability of the substructure connection algorithm.The substructure connection algorithm is used to analyze the vibration of the straight bending straight combination pipeline.The results show that: The vibration of the pipeline is the most intense at the middle position of the composite pipeline,and the vibration acceleration at the middle position is 1.93 times of the vibration acceleration at the entrance position and 1.84 times of the vibration acceleration at the exit position.The direction of the most intense vibration is the longitudinal position of the composite pipeline,and the longitudinal vibration acceleration is 1.79 times of the transverse position and 1.80 times of the axial position.It can be seen that the direct analysis of the coupling dynamics of gas and particle groups and the substructure connection analysis method established in this paper can provide a numerical simulation method for the study of the vibration mechanism of pipeline particle flow and the safe and efficient transportation.