Study On 3-D Calculation Of Turbulent Flow And Measurements Of PIV In The Centrifugal Pump With Splitting Vanes

The low specific speed centrifugal pump that characteristics is high water-head and little discharge, is widely applied in regions of the petrochemical Engineering and the aerospace Engineering. Whether it is designed according to a tradition method, its efficiency will be low and easy to be hump for the head curve and over load. Using long and short blades is an effective way to settle these problems. Both of the numerical simulation and PIV are adopted to study internal flow pattern of three centrifugal pumps with splitting vanes under the following conditions: with different deflected position of splitting vanes, at operating and non-operating points etc., the 3-D turbulent flow laws of centrifugal pumps with long and short blades are analyzed and obtained preliminarily.The main work and achievements are as follows:1,In order to study the influence of the deflected position of short splitters on flow field, 3 pairs of centrifugal pump impellers with long and short blades are designed by increasing the discharge coefficient and combined with the velocity modulus. The outline of long blades is single circular arc and its short blades are located within long blades. The inlet of each short blade is located on the same circle and its outlet angle is also equal to that of the long blade. The position of all short blades is deflected to the suction face of the long blade and the schemes of the deviated angles of 0°,5°and 10°are designed respectively.2,The Pro/Engineer software is applied to model rectangle spiral casing and AutoCAD and Gambit are utilized to model centrifugal pump impeller with splitting vanes. The computation domains of spiral casing and impeller have been respectively decomposed by structured grid.3,Based on numerical simulation for whole centrifugal pump, numerical calculation is applied for the 3-D incompressible turbulent flow about three pairs of centrifugal pump impellers with long and short blades. First of all, the Navier-Stokes equation under Cartesian coordinate system is converted into the form under random curvilinear coordinate system and discretized with Finite Volume Method. The equations are closed by the standard k ?εturbulent model corrected considering rotation and curvature, SIMPLEC algorithm applied, iterative and corrected equation is created and makes momentum equation and continuity equation coupled. A static and dynamic coupled and intersected face of rotary impeller and pump wall is treated with a multiple coordinate system. By turbulent numerical simulation, the pressure and velocity distribution of three centrifugal pump impellers are obtained under the following conditions: with different deflected position of splitting vanes, at operating and non-operating points. The exterior characteristics parameters are also predicted. The velocity and pressure field characteristics of 3 pairs of impeller with splitter vanes are contrasted and analyzed. The law of velocity and pressure distribution of the turbulent internal flow about the centrifugal pump impeller with long and short blades is obtained preliminarily. The proper deflected position scheme of the short blades is put forward.4,The particle image velocimetry(PIV)was applied to investigate the different flow patterns of three low specific speed centrifugal pump impeller with deviated short splitter vanes. At design load,maximum load and minimum load,the internal flow fields have been obtained respectively and the distributions of relative velocity have also been revealed. The experimental result shows that the influence on flow fields is significant for three deviated short vane schemes. While the inlets of short splitter vanes rotate to the pressure sides of long vanes related to the outlets,the distribution of relative velocity near the outlet of impeller passage was not uniform and a low velocity zone exists in the vicinity of the outlet of short vane working side. On the contrary,if the inlets of short splitter vanes rotate to the suction sides of long vanes,the relative velocity near the outlet was well-distributed. Comparing the calculation results and PIV Experimental results, it's obvious that parameters variation is consistent on the whole. But the value between calculation and Experiment is deviated to some extend, the reason of the difference has been analyzed in the paper.