Study About Detection Technology Of Batch Transportation Of Multi-product Pipeline Based On V-cone Flowmeter

With the rapid economic development, the need of energy increases further. China's construction of multi-product pipeline has entered a high-speed stage. Since construction of multi-product pipeline was started lately, and batch transportation of multi-product pipeline is difficult and complex, there is still a big gap at the computation of mixed oil length, the detection of mixed oil interface and the treatment of mixed oil compared with foreign countries. If V-cone flowmeter technology is introduced into batch transportation of multi-product pipeline, we can solve the persistent problems of multi-product pipeline, for example, the detection of mixed oil interface, the cutting of mixed oil segment and so on.In this paper, by using a computational fluid dynamics software-Fluent software, V-cone flowmeter is numerical simulated in multi-product pipeline, the characteristics and working principle of V-cone flowmeter are recounted, numerical simulation model of batch transportion of multi-product pipeline is established, and the law of flow field of V-cone flowmeter in multi-product pipeline is analyzed. With the use of quadrilateral meshes, the quadrilateral grids with large ratio simulate the tubular flow field. The number of grids reduces apparently. The grids near the cone are set thickly, then become thin gradually. The shorter the distance to both sides of the pipeline, the thinner the grids are. By using RNG turbulence model, the relationship between Reynolds number of mixed oil and discharge coefficient of V-cone flowmeter is obtained, the law of the pipe wall surface friction coefficient with its position is summarized. The surface friction rapidly reaches peak in the angle point, is significantly higher than other locations, so the angle point endures a lot of shear stress.Numerical simulation model of the pressure loss of V-cone flowmeter is established. In the case of the same equivalent circulating area, the law of variation of pressure loss of V-one flowmeter in multi-product pipeline is simulated. Compared with orifice plate flowmeter, the pressure loss of V-cone flowmeter is less than one third. When the mixed oil is transported at different velocity, the pressure loss coefficients of V-cone flowmeter change slightly. By technical and economic analysis, V-cone flowmeter can save a lot of energy consumption compared with orifice plate flowmeter. This keeps in line with national long-term development of energy-saving.In order to solve the problems about calculation of mixed oil model in multi-product pipeline, mixed oil mechanisms of different oils by batch transportation is analyzed. Based on the fluid turbulent characteristics, simplified model of mixed oil segment is obtained, the formula of mixed oil volume is given, and the error between theory formula and empirical formula of mixed oil volume is discussed. The mixed oil volume of the oil with small viscosity at first is bigger than the oil with large viscosity at first, the ratio is 1.09. Simplified model and Fick's law is used to obtain the basic equations of mixed oil concentration, then establish one-dimensional and two-dimensional model of mixed oil concentration. The method of Chebyshev integration is used to calculate one-dimensional mixed oil concentration of terminal pipeline. This method has a high precision in calculating the mixed oil concentration, it can be used to guide the actual mixed oil cutting.In this paper, the importance of batch transportation of oil-water during running rest is introduced, the characteristics of mixed segment of oil-water and the differential pressure principle of flow measurement are analyzed, several typical flow models are compared, the mathematical model of mixed segment of batch transportation is established, which is based on the principle of differential pressure of V-cone flowmeter. The model coefficient is calculated by data fitting method. The formula that can measure the flow of mixed segment of oil-water is obtained completely and is viable by experiment test. The features of batch transportation of gasoline and water are analyzed. Gasoline and water only can be mixed in the case of intensive agitation. In the process of batch transportation of gasoline and water, a true mixed segment of gasoline and water is formed, which is due to high Reynolds number, and intensive stirring. However, a long tail section followed mixed segment is not complete mix of gasoline and water. Characteristics of batch transportation of gasoline and water make it impossible to detect interface of mixed oil by the method of density. Based on the mathematical model of mixed segment of batch transportation, a new method detecting interface of mixed oil by water content is obtained. This method can guide the cutting of mixed oil, test the operability of the important components for cutting of mixed oil and lay a foundation for the working order of batch transportation.Interface detection of mixed oil segment is an important process for batch transportation of multi-product pipeline. The principle, experimental apparatus and experimental step of interface detection of mixed oil in multi-product pipeline are introduced in detail. Two different oil samples, thickened water and water, brine and water are used to simulate batch transportation. This purpose is to discuss the effect of viscosity and density on pressure difference signals of V-cone flowmeter. By contrast and analysis, differential signal can detect the location of interface of mixed oil and appearance time.Based on the above-mentioned study, an expert system is designed, which can detect interface of mixed oil and realize automatic cutting of mixed oil segment.