| With the continuous improvement of the urban sewage standard and requirements of energy-saving, the development of an efficient non-clogging sewage equipment appears more imminent. Therefore, a series of relevant research of screw-centrifugal pump with single blade was carried out in this paper under the support of National Twelfth Five-Year Technology Support Program "The key technology research and engineering application of efficient environmentally friendly pump"(2011BAF14B01). The main content of the research and creative achievements obtained in this paper are as follows:1. Two design methods of screw-centrifugal pump with single blade were described. Based on the specific design parameters, a conformal mapping method was applied to design the impeller’s hydraulic diagram and the pre-counterweight was conducted.2. The polyhedral meshes was successfully applied on the numerical calculation of screw-centrifugal pump, and the accuracy of this numerical calculation method was verified after compared with the results of external characteristic test.3. The performance of the screw-centrifugal pump with different shape of import and export side and different height of blade or different tongue radius of volute were discuessed, and the mechanism of various design parameters through the analysis on internal flow field was revealed. Also the performance variation of the pump with different blade-tip clearance size was considered. And compared with the test results, it is reckoned that the minimum clearance should be controlled less than0.5mm in installation.4. The centrifugal sewage pumps with multi blades, single blade and dual channel of similar specific speed were designed. On the basis of the test results, they were converted to the same power as the single blade type screw-centrifugal pump. By comparing their maximum particle passing diameters, blade outlet area, high-efficiency area width and the trend of lift and power curve, the results show that the single blade type has the maximum particle diameter and export flow area, and also has a gentle power curve and steep lift curve, but its efficiency is slightly lower than the multi-blade type.5. Through a transparent water tank and the impeller bottom cover, we were able to observe the process of particles and long fiber passing through the import of impeller with high speed camera by using frequency conversion start-up. It is found that there are two ways of particles passing through the import side and impeller. This reveals the reason why screw-centrifugal pump with single blade could prevent clogging and has no harm to the transmission medium.6. In terms of the impeller’s counterweight, a method which combines parametric modeling and virtual prototype simulation technology to solve the dynamic balance issue was proposed. Results show that this method can control the dual side unbalanced mass less than20grams, so it has higher accuracy, not to mention saving a lot of time and cost.7. By means of transforming the prototype, the measurement of pressure pulsation, vibration and true signal of axis orbit at different position under submerged condition were achieved. Results show that the vibration reaches its minimum point at the design condition. No matter the flow is increasing or decreasing, the vibration will increase. With the increase of the blade-tip clearance size, the vibration at the bottom bushing and motor strengthens significantly, while the variation at the volute tongue and its foundation are not obvious. After analyzing the axis orbit and the pressure pulsation, their regularities of distribution and changing trend according to different blade-tip clearance size and different counterweight were obtained.8. The numerical calculations show good agreement with pressure pulsation tests. And by analyzing the prediction of internal flow filed, the reason for the change in pressure pulsation curve was revealed. The prediction of radial force numerical calculation results was studied, which confirmed the calculation’s correctness by comparing with axis orbit tested in the experiment. The comparison of the numerical prediction of the impeller surface trace distribution and the oil film test was performed, it is found that some typical flow phenomena, like tip leakage, circulation and whirlpool, co-exist in the screw-centrifugal pump with single blade. |
