Fluid Numerical Analysis In Feed-water System Pipes Of The Super Critical Power Unit

Recently, the super critical power unit has been widely used. However, there come out some new technical problems, which need to be solved further. For example, one of the problems is the determination of design safety threshold of high pressure feed-water pipe. The super critical power unit has very much higher steam parameter. Furthermore, the feed-water system pipe is the part that the liquid pressure is the highest in the whole plant, especially the outlet part of the feed-water pump. The liquid pressure of this part will be up to 28～29MPa in the super critical power unit, even will higher in the ultra-super critical power unit. The pressure change and the flow characteristic of liquid in the pipe have related closely with each other, so it is greatly important to analyze the fluid in the feed-water pipe of the super critical power unit. Because of the rapid development of the Computational Fluid Dynamics, it becomes possible to analyze the fluid in the pipe rapidly and conveniently. In this thesis, it has done some numerical analysis of the fluid in the pipe by adopting CFD method (including stable flow and unstable flow), and it also has done some relative research into the change rule of the fluid pressure in the pipe.This thesis, to use software FLUENT 6, has calculated the fluid value about the high pressure feed-water pipe (including recirculation pipe) between the outlet of feed-water pump of the super critical power unit and the electric valve, including the stable working condition and the instantaneous working condition due to the open and close of the valve. The instantaneously unstable working condition includes the electric valve normally closed, and rapidly closed (that is extreme condition). According to the calculated results, there put forward the tactics that can promise the feed-water pipe running safely.Valve is the very important part in the feed-water system, especially starting or stopping the unit, and adjusting the load of unit. It plays a very important role in making the system running safely. So this thesis, to use CFD method, has studied the influences that different operation ways of the valve in the feed-water system do to the fluid in the pipe, and has put forward the ways that how to reduce the influence from valve operation when the valve closed suddenly. If wanting to know the feed-water pipe's function and state overall, except the fluid value needs to be calculated, the stress and the vibration of the feed-water pipe itself must be analyzed in the fluid changing process in the pipe. The result of fluid calculation can be regarded as the boundary condition of stress analysis, loading to the model. However, the FLUENT software and the relative stress analysis software have the different grid, so the flow calculated data can not load as the boundary condition. So this thesis has studied and solved the way of data-transferring between the FLUENT software and the relative stress analysis software.At last, this academic degree thesis gives the summary to the fluid analysis in the feed-water pipe of the super critical power unit, and also gives a promising research future about this subject.