| In the inverse design method for water pumps, the blade loading is a link between the shape of blade and the internal flow characteristics of pumps. However, there is still no definite selection method for it. In this study, the double suction centrifugal pumps with a specific speed ranging from90to180are taken as research objects to carry out in-depth studies on the relationship between the characteristics of blade loading and the performance of double suction centrifugal pumps.Firstly, the application process of blade loading curves in inverse design method was analyzed, and the equation&calculation step for the three-segment loading curves were established. Under this basis, for12double suction centrifugal pumps with good performance, flow characteristic analysis and inverse calculation for blade loading curves were carried out, and a relationship between the loading curve parameters and hydraulic performance of water pump was established. The study found that too forward of the main loading point on the shroud streamline may result in a lower pressure and poor suction performance in the impeller inlet, and too backward of the aft-loading point position of the shrouds and hubs streamlines may cause secondary flow near the impeller exit and result in a reduced efficiency and strong pressure pulsation. Therefore, in the relative meridian streamline coordinates, for a better cavitation characteristic, the main loading points on the shroud are mainly in the range of0.24-0.65, and the values should reduce along with the increment of the specific speed; for a higher efficiency characteristics, the pre-loading points on the shroud are mainly distributed in the range of0.59-0.75, as well as the aft-loading points on the hub are mainly distributed in the range of0.53-0.67, and both of the values will increase along with the increment of specific speed; for a lower pressure fluctuations, the aft-loading points on the shroud are mainly distributed in the range of0.75-0.86, as well as the aft-loading points on the hub are mainly distributed in the range of0.69-0.86, and both of them will decrease along with the increment of specific speed. Based on the above loading curve characteristics, the "RNG loading curves" for guiding the design of impellers of double suction centrifugal pumps were formed.There is a blade adjustment method named "RNG blade adjustment method" was proposed for smoothing the blade surfaces by adjusting the shape of the meridional section curves with no change of the loading curves of shroud and hub streamlines. For this method, the shape of the meridional section curves were convex type arcs, and the radius gradually increased from inlet to outlet according to a specified rules. The blades obtained from this method had smooth surface and overall good hydraulic performance.Combining the RNG loading curves established and the RNG blade adjustment method, the "RNG loading technique" for guiding the hydraulic design of impellers of double suction centrifugal pumps was formed. Based on this technique, a remodeling optimization design was carried out for impellers of two double suction centrifugal pumps, and the two optimization objectives were higher efficiency and lower pressure pulsation. After the efficiency-improving targeted remodeling design, the optimal point efficiency was increased by2.4%; after the pressure pulsation-reducing targeted remodeling design, the peak value of pressure pulsation was reduced by about50%under the designed conditions. The research findings had been used in the actual pumping stations of the large-scale Yellow River diversion irrigation project and other projects.The investigation achievements provided a new route of design method for double suction centrifugal pumps impellers, and they have important engineering significance&application value for improving the efficiency and operation stability of double suction centrifugal pumps... |
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