Numerical Analysis Of Cavitation Performance Of Siphon Drainage Pump And Optimized Design Of Pipeline Structure

As a common water equipment in life,centrifugal pumps are widely used in industrial and agricultural production.However,the efficiency of the pumps is generally low and energy consumption is high.With the further improvement of operational requirements,it is increasingly urgent to optimize the design of centrifugal pumps to obtain higher performance.Cavitation performance is one of the main factors affecting the stable operation of centrifugal pumps.When cavitation occurs inside a centrifugal pump,the performance of the pump is greatly reduced.The vacuoles produced by cavitation not only damage the impeller and other over-flow components,but also cause vibration and noise during the operation of the device.In this paper,the effect of cavitation on the operating conditions of a siphon drainage pump unit under different impeller inlet pressure conditions are investigated.The influence of the siphon shape on the internal fluid flow state is also compared,and optimised design is carried out based on simulation results to improve siphon drainage pump cavitation performance and siphon tube drainage efficiency and stability.The main research contents are as follows:1.Solid Works software is used for modeling and assembly of siphon drainage pump with given design parameters.The model is divided into different types of grids,and the differences between the numerical simulation results of the different types of grid models are compared.The results show that the errors between the simulation and the experimental values are within the allowable error range.The structured grid model is closer to the experimental values for the same grid size and can represent the internal flow field details better.However,the structured gridding process is time-consuming and labour-intensive,making the simulation process considerably more difficult.The unstructured grid model can also ensure the accuracy of the calculation results and increase the speed of the calculation by encrypting the critical overflow areas and performing grid-independent analysis.Therefore,the unstructured grid model is selected for follow-up research in this paper.2.This paper analyzes the cavitation characteristics of the siphon drainage pump on the basis of the Realizable k-? turbulence model and the Rayleigh-Plesset cavitation model.The results show that as the inlet pressure of the siphon drainage pump impeller continues to decrease,the low pressure area inside the siphon drainage pump gradually diffuses outward from the impeller inlet,which provides the necessary conditions for the occurrence of cavitation.The cavitation area occurs on the back of the blade first,and then began to spread outward.As the cavitation intensified,the generated cavitation affected the flow field distribution inside the siphon drainage pump.3.This paper analyzes the cavitation performance and optimizes the structure of the siphon drainage pump by opening holes at impeller entrance.The results show that opening holes at the blades can improve cavitation performance of siphon drainage pump,and the effect of opening a hole at the entrance of the blade is more obvious.As the diameter of the opening-hole increases,the cavitation performance improvement rate of the siphon drainage pump tends to gradually slow down.Compared with the simulation results with optimization,the 4×1mm hole-opening scheme designed in this paper increases the head by 1.44% and the efficiency by 4.80% when operating under the design conditions.At the same time,the cavitation phenomenon of the siphon drainage pump is greatly suppressed.4.This paper verifies the numerical simulation results of the internal flow field of the siphon with and without optimization by building an experimental platform.The results show that the kinetic energy loss of the fluid inside the siphon decreases and the stability of the siphon drainage increases while the number of siphon corners is reduced.There are unavoidable resistance losses and man-made measurement errors in the experiment,the siphon flow value obtained by the siphon tube is generally lower than the simulation calculation result.After correction by the correction constant,the experimental value and the simulation result are basically consistent,indicating that the numerical simulation is reliable.