Study On The Contamination Model Of The Batch Transportation Of Multi-product Pipeline And The Calculation Methods Of The Models

With the development of our country economy,a lot of multi-product pipelines have been constructed.Multi-product pipelines carry several different oil products through the same pipeline,which is known as the batch transportation.In the batch transportation,two such batched products contact with each other without physical barrier,so they will be mixed and generate a contamination plug.When the contamination plug passes the middle distribution station or the final station,we would cut the tail and the head of the contamination plug into the mixed oil tank,the methods and the time of which would cause many different lengths of the contamination plug.So how to track the faces of the contamination plug and control the length of the contamination plug is the most important part of enhancing the economic benefit.At present,according to different practical situations of the mixed oil,different multi-product pipeline companies summarize different contamination models to predict the volume of the contamination plug and decide when to cut the tail and the head of the contamination plug.On the other hand,a lot of scholars synthetically study on the situation of the pipeline contamination to propose some universally applicable contamination models.First of all,this paper is to investigate and analyze the scope of the application of each model and after that one-dimensioned contamination model is recognized as the most adaptive method for the engineering calculation.A comparison is made between seven different common discrete forms of the one-dimensioned contamination model to choose an exact and effective calculation method.According to the analysis of the contamination calculation,the hydraulic transient model and the contamination model could influent each other at the same time,so the paper solves the hydraulic transient model and the contamination model in a coupled way and proposes a coupled contamination-hydraulic model.To solve the coupled model,the hydraulic transient model is calculated firstly,in which the mass flow and the pressure are chosen as the solution parameters.The mass flow and the pressure of the pipeline obtained from solving the hydraulic transient model are used to solve the one-dimensioned contamination model to obtain the concentration distribution of the trailing oil product in the contamination plug.The concentration distribution obtained from the model is used to calculate the hydraulic transient model once again.Repeat the above steps to obtain the solution,until the solution coincides with the required accuracy and then begin the next calculation of the time step.The variation of the faces of the contamination plug with the time is also obtained after the calculation of the contamination model,which could give the guide advice to the cutting of the tail and the head of the contamination plug.At last,the multi-product batch transportation simulation program is programmed by the computer language Visual C++.Through this program,we could analyze how the influent factors affect the length of the contamination plug and the concentration distribution of the trailing oil product in the contamination plug and then a calculation is made on a specific product pipeline to figure out the length of the contamination plug,the concentration distribution and track the change of the faces of the contamination plug over time.