Design Optimization And PIV Internal Flow Investigation Of Vortex Pump

Vortex pump with special structure and the internal flow field is complex, because of its advantages of non-clogging in the operation, it is widely used in the field of industrial slurry transportation, urban sewage, agricultural production and aquaculture, especially more widely used in the field of slurry transportation. However, the efficiency of the vortex pump is generally low and the energy consumption is large, in the process of pulp transport, not only wastes water resources, brings environmental pollution, but also increases the energy consumption of pulp transportation. The impeller of the vortex pump is semi-open type, and is installed in the rear pump cavity, the front pump cavity is a wide open cavity area, because of the high requirement of no blockage, the impeller outlet has a certain distance from the volute inlet. As a result, there is a phenomenon of inflow and outflow in the front end of the impeller blade when the pump is running, and there are many complex flows in the non-leaf cavity, which leads to a large hydraulic loss of the vortex pump, the impeller does not convert all the energy to the pressure of the medium,but part of the energy is transferred into the through flow and circulation flow in the non-vane cavity, this is the main reason leading to the low efficiency and low head of vortex pump.In this paper, a prototype pump of model SCP200-400 is taken as an example,analysis of structural parameters of the vortex pump with the specific speed ns is 186,based on orthogonal optimization design method, PCAD optimization design software,CPF numerical software, PIV particle imaging tachymeter, and pressure pulsation test, a variety of methods are used to analyze the flow characteristics of the vortex pump, so as to study the internal flow mechanism, the main contents of the study are as follows:1. Taking the prototype pump of model SCP200-400 as an example, the structural characteristics of the pump are analyzed by combining the external characteristics, based on the CFD numerical calculation software, analysis of the grid independence and the turbulence model, to find out the mesh number and better turbulence model suitable for the pump, provide the basis for the optimization design of prototype pump in the following study.2. The structural parameters and experimental results of the prototype pump are analyzed to find out the main structural parameters affecting the performance of the pump,main structural parameters were determined: impeller outer diameter D2, blade number Z,blade outlet width b2, blade outlet angle?2, blade inlet angle?1.Associating the orthogonal optimization design and hydraulic design based on PCAD, 4 level numbers per factor were chosen for the time and orthogonal array L16 (4s) was adopted, generating 16 schemes. Based on the configurations decided in the former chapter, numerical simulations of the 16 schemes in rated flow rate were carried out. Appling orthogonal analysis, influence of varied factors on efficiency and head was acquired , and following that, single factor effect was analyzed to determine the major factor and the minor. In order to find out the main structure parameters that affect the performance of the vortex pump more accurately, the factors and the number of levels in a much narrower range were re-selected, to conduct a second orthogonal experiment. Finally, a better scheme was obtained.3. When the vortex pump is used to transport the paper pulp, sediment and other media, the solids are relatively abrasive in the flow components, especially the erosion of the impeller blade surface is more serious, resulting in increased pump instability.However, in the actual operation process, due to the existence of the solid phase, and the transparency of the sewage is not high, it is difficult to study the solid flow and distribution in the flow field by means of experimental shooting. Therefore, through the CFD software to calculate the case with difference of particle diameter sizes set by 0.1 mm, 0.5 mm, 1.0mm and different kinds of solid volume fraction set by 1%, 5%, 10% at rated conditions. Analysis of the influence on the internal flow of the vortex pump, and the solid slip velocity and solid concentration on the distribution of the pump wall was analyzed. Study on the wear of solid relative to the impeller surface.4. In order to research the internal flow mechanism of vortex pump, three kinds of model impellers with different impeller parameters were designed and processed into the model. The external characteristic experiment was carried out and compared with the numerical results. Based on the PIV particle imaging velocity measurement technique, the flow mechanism of the internal flow of the vortex pump is explored and the complicated flow model in the non-vane cavity is analyzed from the flow characteristics of the internal flow field. It was found that the blade was more likely to produce a variety of different vortices when the blade angle was large. When the blade angle was reduced, the flow channel became narrower, and the binding force of blade to liquid was strengthened. In the case of constant flow rate, the flow velocity in the narrow flow channel is large, and the flow rate of the liquid flowing from the blade face to the back is offset by weakening, not easy to form a vortex. The relative flow velocity in the non-vane cavity increases with the increase of the flow rate. In turn, the absolute flow in the non-vane cavity, i.e., the circulation flow velocity decreases with the increase of flow rate. The circulation velocity in the inner ring surface is obviously stronger than that in the outer ring surface. Besides,in the inner ring surface, the run-through flow is the main flow way.5. By layout of the monitoring points on the volute of model pump, the vortex pump internal flow field was studied from another perspective. With methods of experiment and numerical simulation, the pressure pulsation characteristics in the flow field of the volute and the transient static pressure fluctuation caused by asymmetric flow in the volute are studied, and characteristics of unstable operation of vortex pump was researched. In the study, it is found that the main frequency at the volute is not equal to blade frequency, but at the shaft frequency district around. It indicates that the main cause of the pressure fluctuation in the volute is the shaft frequency, rather than the blade frequency of the pump.