Study On The Deviation Mechanism Of Fluid Flow In Tail Flue And Uniformization Method For Its Velocity And Concentration Distribution

The deviation of fluid flow caused by turning in flues is one of the main reasons for the uneven heat transfer of heat exchange equipment as well as the wear and tear of tubes and walls. Those problems can not only influence the boiler efficiency, but also bring great harm to the safety and economical operation of power plants. Therefore, the study on the mechanism of the deviation of fluid flow, which could lead to a more generally applicable equalization structure, is helpful in solving the problems mentioned above.So far, many experimental studies and numerical simulations on fluid flow in curved flues have been done, and many well-designed equalization arrangements have also been proposed, while there is still no detailed explanation for the mechanism of the deviation of gas velocity and particle concentration. As the price of coal is getting higher and higher nowadays, quality of the coal burnt in different plants varies from time to time. The parameters of particles change with the coal and combustion condition, which leads to great effect on the fluid flow, and thus seriously affect the heat transfer efficiency and safety of the heat exchanger. But current papers generally show a certain lack of the studies on the effect of the parameters of particles, and the equalization of particle concentration is also overlooked in most equalization studies.Hence, the computational model of 90°curved tail flue is set up in this paper. Based on varying flue shapes and parameters of fluid, the influence on the fluid pressure, velocity and particle concentration of the changes is investigated by means of numerical simulation. The flow parameters of fluid flowing in 90°curved tail flue with different equalization arrangements are also comparatively analyzed to find a more effective equalization arrangement for the fluid velocity and particle concentration.The results of this study indicate that different structural parameters and fluid parameters can influence the flow in 90°curved tail flue on different levels and tendencies. Besides, increasing the number of guide plates which are among the most widely used equalization arrangements has different influence on fluid velocity and particle concentration. Further more, the effect of joint utilization of straight plate and curved plate is not always positive but depends on their relative position. The work done in this thesis offers theoretical support and numerical reference to both the optimizing design of 90°curved tail flue and safety and economy of the power plant.