| Multistage centrifugal pumps are widely used in various high energy consumption fields due to their easy installation and the ability to meet different head requirements by increasing or decreasing the number of stages.In response to the national green and low-carbon economic development mode,it is urgent to improve the conveying performance of multistage centrifugal pumps and reduce energy consumption.The radial guide vane,converting the kinetic energy of transmission medium into pressure energy,is an important fixed flow passage component of the multistage centrifugal pump connecting the two-stage impeller.However,due to the complex structure of flow field,the proportion of hydraulic loss is high in the flow process and there are unstable flow phenomena such as circulation and eddy current at the leading edge of the blade,between the blades and at the outlet.As a result,the flow loss in the anti-guide vane increases,the overall conveying performance of the pump decreases and in severe cases,the flow excitation occurs,which affects the operation stability of the pump.Therefore,structural optimization of radial guide vanes is a key measure to reduce the hydraulic loss of this component and improve the conveying performance of the pump.In this paper,the self-designed multistage centrifugal pump was taken as the research object,and the numerical simulation was used to carry out the radial guide vane structure optimization.The internal flow characteristics and hydrodynamic characteristics of multistage centrifugal pump with different inlet angles of the anti-guide vane and streamlined anti-guide vane optimization schemes were investigated.The main research contents and conclusions are as follows:(1)Real-type pump impeller with actual parameters required is obtained based on pump similarity theory,and design parameters of multistage centrifugal pump are determined combined with the simulation results.Then the radial guide vanes and volutes of multistage centrifugal pump are designed and selected.Finally,the components are modeled and assembled by threedimensional software to ensure the integrity and feasibility of the structure.(2)To investigate the influence of inlet angle parameters on the conveying performance and operation stability of multistage centrifugal pumps,the original value α5=35° is increased or decreased by 10° and two inlet angle optimization schemes of α5’=25° and α5"=45° are developed.The full flow path of three anti-guide vane schemes is calculated and analyzed by numerical simulation.The hydraulic performance of multistage centrifugal pumps of three different inlet angles of anti-guide vanes at different flow rates is investigated.At the same time,the optimization degree of inlet angle change on centrifugal pump flow characteristics is elaborated through flow velocity characteristics inside the anti-guide vane and the vane load distribution.Based on the entropy generation theory,the influence of inlet angle change on the loss distribution in the anti-guide vane is summarized.It is found that the water loss of the anti-guide vane mainly consists of the outer edge circulation loss,the inlet impact loss,the blade back off-flow loss and the outlet mixing loss.Under the design condition,characteristics of the internal pressure pulsation in the anti-guide vane channel are analyzed,and the relationship between the inlet angle parameters and the main frequency amplitude and the shaft frequency amplitude of the pressure pulsation is revealed.In addition,the flow field in downstream components with changed inlet angle of the anti-guide vane is analyzed,and the optimum inlet angle is α5=25°.(3)A streamlined anti-guide vane structure is designed and developed based on the anti-guide vane with an inlet angle of α5’=25°.According to the numerical simulation results,the influence of the modified guide vane on the external characteristics and internal flow field of centrifugal pump is studied.In terms of external characteristics,the head of the streamlined anti-guide vane is further improved compared with the prototype centrifugal pump.In terms of internal flow field,the streamlined anti-guide vanes weaken the impact on the blade head,making the off-flow area decrease and migrate to the middle of the flow channel,which increases the effective flow area,obviously enhances the diversion effect,and reduces the area of vortices generated by shear flow near the trailing edge of the blade due to convergence of low-speed wake fluid with high-speed flow in the mainstream.By comparing and analyzing the main frequency amplitude of pressure fluctuation of different guide vane types,it is found that the streamlined anti-guide vanes significantly reduce the influence of static and dynamic interference on pressure fluctuation,so the pump has the best operational stability.In addition,the influence of the structure change of the anti-guide vane on the flow field in the downstream components is also analyzed.It is found that streamlined anti-guide vanes further optimize the pump performance based on inlet angle optimization. |
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