Investigation On Prediction Method And Wear Mechanism In Liquid-solid Two Phase Flushing Oil Pipeline

The characteristic of Chinese energy structure is rich in coal and lack of oil. So the development of coal liquefaction project is an important measure to energy structure and energy security. The coal liquefaction process involves multiphase flow transportation which contains pulverized coal, minerals and other solid phase. The pressure piping erosion thinning perforation mechanism is very complex when the pipeline is in the liquid-solid two phase system. Therefore, revealing pipeline erosion mechanism under the action of liquid-solid two phase and establishing quantitative wear prediction method is important to pipeline risk assessment and the safe operation.In this paper, the research object is the small diameter(DN20) flushing oil pipeline of MOGAS ball valve of a coal direct liquefaction company. Firstly, we use independent design of rotating liquid-solid two phase flow test to study the erosion behavior of A182F347 material of flushing oil pipeline. Secondly, the wear mathematical model which is revised by experiment is used to simulate the flow field of flushing oil pipeline, and then the parameters distribution of internal of the pipeline flied, such as, velocity, erosion rate, particle tacking, are got. So wear prediction method of science is established. The main contents and conclusions are as following:(1) The fluid dynamics method is used to analysis the flow characteristic of the two kinds of rotary liquid-solid flow system experiment device. Through the distribution of phase fraction, velocity, moving direction on the field, the erosion-wear experiment scheme was determined.(2) The relations between erosion rate and slurry concentration, rotation speed, impact angle, are found with the help of rotary liquid-solid wear test. This test reveals the wear mechanism of the flushing oil pipeline material. The experiment results show that: 1) the erosion rate increases with the increasing of slurry concentration(4%~10%); 2)the curve between erosion rate and slurry impacting angle exists two peaks; 3) the relation between the erosion rate and impacting speed is exponential function and the speed index is 2 which can revise the mathematical erosion model.(3) Using the revised erosion model and particle trajectory model, the flow characteristic of the internal of flushing oil pipeline field can be numerically predicted. The predicted results: 1) the flow in the elbow is secondary flow which is influenced by the curvature radius of bend; 2) the erosion rate of the lateral wall of elbow is bigger than the erosion rate of the inner wall of elbow; 3) the smaller the radius of curvature of the elbow, the elbow wall maximum erosion rate is higher. The numerical forecasts agree with the case analysis.The innovation points of this paper: 1) numerical simulation is used to optimize the experimental apparatus, and the experiment on the experimental apparatus reveals wear mechanism of material which is on the two phase fluid system; 2) the establishing mathematical model of flushing oil pipeline which is revised by experiment makes the quantitative prediction of erosion assessment to be true; 3) the erosion prediction method which is a combination of numerical prediction, wear experiment and case analysis is reasonable, when the numerical forecasts agree with the case analysis.