Characteristics Research Of Asymmetry Concentration Curve In Products Pipeline

The prediction accuracy of concentration curve affects batch interface tracking and mixed oil cutting.The formation mechanism of the asymmetry of concentration curve is not yet clearly clarified in detail so far.In order to have a better understanding of the asymmetry properties of concentration curve,the mechanism of asymmetric distribution of mixed oil concentration is studied in detail in this thesis.A new method is proposed to measure the asymmetry of concentration curve and quantitative analysis are carried out for each factor on the asymmetry distribution of concentration curve.Based on the convection-diffusion equation,a modified oil mixing model considering near wall adsorption effect is established.The reliability of the model is illustrated by the grid-independent test,comparison with the experimental data and empirical formula.The model shows a good agreement with Jablonski empirical formula.The error compared with the experimental results is less than 5%.Sensitivity analysis of the deviation volume and length ratio of the font and tail oil is carried out.Conclusions are:(1)Deviation volume has a negative correlation with diameter and mean velocity.When changing the impact factor for a change rate of 10%,the absolute value of the change rate of deviation volume is more than 15%;(2)Adsorption coefficient has a great impact on the length ratio of font and tail oil,while diffusion coefficient has a small impact;(3)Degree of influence of all factors considered on the total length of mixed oil,font oil,tail oil and trail oil are basically the same;(4)Assume the limit adsorption concentration in adsorption layer is 1,the reasonable value of adsorption coefficient a and b is around 0.4.At last,the least square method is used to fit the numerical simulation data,and fast calculation models are established separately for deviation volume,dimensionless trail length and ratio of font and tail length.