Internal Flow Analysis To Suction Chamber And Other Over-current Components

Centrifugal pump is widely used in power plants, oil, chemical industry, urban water supply, agricultural irrigation and drainage sectors. The suction chamber is an indispensable part of pump; it can not be give little consideration when designing. That is because the quality of suction chamber will have a direct impact on the performance of pump cavitations and efficiency standards. Therefore, when design suction chamber, only in the condition of smallest hydraulic losses we should ensure that: 1) in order to create an relative stability of the flow on impeller at the design point, the velocity along all the sections of the suction chamber should be evenly distributed as soon as possible; 2) divert the velocity of suction chamber into the necessary velocity which the impeller inlet required. Half-spiral suction chamber are connected in the imports, and then respectively link to the two suction impeller imports by cross the outside wall of casing. Compared with average one, this chamber has a complex structure and a special internal flow. Therefore, our research has a theoretical significance to some extent, which also supplies us with more valuable information for analyzing suction internal flow and designing high-effective double-suction pump.In recent years, computational fluid dynamics (CFD) analysis has been used to simulate the three-dimensional turbulent flow of a centrifugal pump. This paper considers 250GS65 double-suction centrifugal pump as a subject and uses the given parameters to carry out hydraulic design to suction chamber; the calculations for suction chamber, impeller and casing's flow field at different operating points are carried out with commercial software code, FLUENT. Thus the distributions of velocity and pressure are obtained. The main research works are as follows:Firstly, after a lot of literatures were reviewed, the latest developments and applications of CFD in the numerical simulation for a centrifugal pump were summarized. The 3D turbulent flow of centrifugal pump is simulated based on the continuity equation and the time-averaged Reynolds-Averaged-Navier-Stokes equations (RANS), the Realizable k-εturbulent model, with the finite volume method and SIMPLE algorithm in unstructured grid and structured grid.Second, the processes of 3D solid modeling of suction chamber are introduced in detail, and the three models (including suction chamber, impeller and casing) are meshed by the software package, GAMBIT.Third, the steady calculations are carried out with a multiple frame of reference system. In additional, the internal velocity field and pressure field are analyzed and compared, the analysis of internal flow in suction chamber should be specialized.Respectively carrying out a numerical simulation at the design point (Q = 485 m3 / h) and off-design points (1.5Q and 0.5Q), then we observe the distribution of circular velocity V_u and axial velocity V_m on the outlet of suction chamber, and find whether there is separation phenomenon. Furthermore, assuming the liquid has no viscosity, (that is, the ideal fluid), we go on observing what changes have taken place in the results of the simulation. Finally, the simulation results are analyzed after the viscosity of fluid has changed, and a better understanding of separation phenomenon has been given.The results show that the outlet velocity of suction chamber is distributed more evenly and also have no eddy under 1.0 Q and 1.5Q conditions, V_u and V_m are well distributed so as to provide uniform velocity to the impeller inlet, under 0.5Q condition, the velocity distribution is disorderly due to the occurrence of second backflow in the impeller inlet. There is no eddy and off-flow phenomenon outside casing in different conditions as well as the viscosity of liquid increased, the above phenomenon are all demonstrate that the hydraulic design is reasonable.At the same time, the simulation was carried out at the design point (Q = 485 m3 / h) and off-design points (1.2Q and 0.8Q), and the flow characteristics about casing and impeller have been analyzed in this paper, Then assume the fluid has no viscosity and observe the simulation results.We can find out from the simulation results that the distribution of relative velocity was corresponding with theory in impeller at different points; static pressure and velocity of the blade were in line with the law. Velocity in each section of casing was also satisfy the regulation of V_u R=const.This paper shows the flow field inside a centrifugal pump is very sophisticate, but what we have obtained from this paper can provide a theoretical basis for the optimal design. It will have great significance to the development of design theory and method of this kind of centrifugal pump.