Research On Start-up Wave Propagation And Compression Characteristic Of Gelled Crude Oil

In order to solve the problems existed in the research of start-up model of gelled crude oil pipeline and provide more instruction for the practical application,the paper makes use of the laboratory experimental loop to study the start-up process of gelled crude oil pipeline,and then programmatically simulates the compression and start-up wave propagation properties based on some relevant theories.It needs a tiny period of time for peristaltic pump flow to reach the rated value from zero at start-up initial stage,so experimental and programming simulation methods are applied to explore the initial flow transient process of the peristaltic pump.The greater start frequency,the longer it takes to reach the rated flow,and if the start frequency under different temperatures is same,the transient processes are same.The result of the assumption that flow of peristaltic pump linearly increases to rated value from zero is the same as the actual effect,so the calculation result can be used for later simulation study.This paper presents a new method under the rules of least squares principle to solve the parameters in the thixotropic model as well as start-up yield stress by using a hyperbolic thixotropic model with four parameters.Particle swarm optimization(PSO)algorithm is exploited to solve the nonlinear equations,whose convergence speed is very fast.This method overcomes the defects of previous research and the reliability is higher making great contribution to the later simulation research.The equivalent compression coefficient under low pressure is defined to describe the compressibility of gelled crude oil and for the purpose of solving it,the start-up model of gelled crude oil pipeline under constant flow rate is newly built.The varying rules of oil pressure during the standing processes under constant and dropping temperatures are explained in detail in this paper.The model’s calculations demonstrate that within certain limits if the temperature is lower,the shutdown time is longer,the previous shear rate is lower and the static cooling rate is greater,the equivalent compression coefficient under low pressure will be larger.By using LS-SVM regression method,a predication model is set up for the equivalent compression coefficient under low pressure and compared with multiple regression model,its regression and prediction precision is higher,so it can be used to practical application.Put forward a new way to calculate the value of start-up wave velocity and the results show that start-up wave velocity increases rapidly first and then decreases gradually as the start time rises,and the first grow stage is due to the initial flow transient process of the peristaltic pump.The value of start-up wave velocity is far less than those of sound wave and transient wave velocities,that is closely related to the structural characteristics of gelled crude oil and start-up conditions.Using the way of fitting sample data,start-up wave velocity formula is obtained which includes three parameters: the equivalent compression coefficient under low pressure,start-up flow rate and time.This formula possesses good fitting effect and certain reference value,but it lacks theoretical basis and is better to be amended in future research.