Study On The Characteristics Of The Flow Field In The Riser

Airlift pump has no moving parts and its structure is simple.So,it is very suitable for many engineering fields,such as dredging,oil exploration,coal mining and chemical liquid delivery.Airlift pump system in the process of ascension,the interaction mechanism is complex of the gas-liquid-solid phase,ascending movement characteristics of gas-liquidsolid phase is difficult to grasp,which is greatly limits the performance of the airlift pump system.Therefore,the article studied is mainly based on image processing technology to the flow pattern characteristics analysis in the risers.the main contents as follows:(1)The article has studied the gas-liquid-solid flow pattern characteristics.Using high-speed camera shooting the dynamic image of gas-liquid-solid flow pattern in riser under different working conditions,base on the distribution characteristics of bubble,dividing the flow pattern,on this basis,the image processing technology is used to obtain the gray histogram of the flow image gray,and calculate the gray level co-occurrence matrix of the image,illustrates the five kinds of texture feature parameters changing with the time.Results show that the extraction of the flow pattern of image texture characteristic parameter indexes can better reflect the flow characteristic,which can proven the flow pattern characteristic of the mixed fluid,which provides an effective method for analysis the characteristics of riser's flow pattern.(2)The structure and motion characteristics of the flow field in the riser are revealed.With the help of high speed camera,the gas-liquid-solid flow pictures was captured.By these pictures,the gas and solid's moving rules can be obtained.However,the liquid in fact is a continuous phase.Its moving rules can't be get in the flow pictures.So,a LDV(Laser Doppler Velocimety)was used to measure the liquid velocity field.The results showed that: the flow patterns in the riser periodic alternate: churn flow-intensive bubble flow-sparse bubble flow-annular flow-mass flow-churn flow,in which,the churn flow is most conducive to upgrade solid particles;In the riser,bubbles rise in spiral shape.In fact,this kindof moving is a irregular spiral motion.As an irregular spiral upward movement,the movement law is rising-falling-rising which was reflected by the solid particles.the liquid's velocity distribution in tube's cross-section trends to be a frustum-shaped.Near the wall,the liquid velocity gradient is very big.However,the velocity in center location becomes gently,which is also bigger than other locations.