Study On Cavitation Control Of Centrifugal Pump By Bionic Nodules At The Leading Edge Of Blades

Pump equipment manufacturing,as one of the basic disciplines in the field of science and technology,plays an important role in maintaining national economic security.The market has increasingly high requirements for pump performance,and cavitation is an important issue that is difficult to avoid.The occurrence of cavitation phenomenon not only leads to a decline in the performance of centrifugal pumps,but also induces the generation of surge and noise,damages the flow passage components of centrifugal pumps,and causes a series of problems such as cavitation damage.Therefore,studying cavitation mechanism and exploring cavitation control strategies have important application value.This article mainly takes a centrifugal pump with low specific speed as the research object,arranges biomimetic nodules on the leading edge of the blade,and uses a combination of experimental and numerical methods to study the impact of biomimetic nodules on the hydraulic performance,cavitation performance,cavitation development,and pressure pulsation of the centrifugal pump.It is confirmed that this method can effectively control the cavitation of the centrifugal pump,improve the cavitation performance of the centrifugal pump,and analyze the cavitation control mechanism.Then,the bionic nodules were placed on two centrifugal pumps with different specific speeds,verifying the universality of the bionic nodules in controlling cavitation in centrifugal pumps.(1)This article first introduces the main background of the topic,briefly describes the concept,harm,and utilization of cavitation research progress,as well as the main research methods of cavitation flow.The active and passive cavitation control methods and the application of bionics in cavitation control are reviewed.Based on the current research status of the "nodule effect" of humpback whale fins and related situations that have been applied in the field of fluid mechanics,it is determined to apply bionic nodules to centrifugal pumps to study their impact on the cavitation characteristics of centrifugal pumps.(2)The basic situation of the three centrifugal pumps used in this article is introduced,including the main design parameters,the hydraulic diagrams of the impeller and volute,the principle and steps of the external characteristic test,and the principle and steps of the cavitation performance test.Carry out hydraulic performance test and cavitation performance test on model pump 1(ns=30),and hydraulic performance test on model pump 2(ns=67)and model pump 3(ns=116)to obtain test data,laying a foundation for subsequent research work.(3)The numerical simulation method in this paper adopts the Reynolds time averaged method,the SST k-ω turbulence model modified by introducing a density function to the turbulent viscosity,and the Z-G-B cavitation model.Complete the 3D modeling work,mesh division,mesh independence verification,and grid boundary layer Y+value verification of the three model pumps.The numerical simulation of steady-state hydraulic performance and transient cavitation performance was conducted,and the numerical simulation results were in good agreement with the experimental results,meeting the error requirements,verifying the accuracy of the numerical calculation method.(4)Referring to relevant research,a total of six biomimetic nodules with different parameters were arranged on Model Pump One(ns=30),where the protrusion amplitudes of biomimetic nodules were f=(0.025±0.005)l and f=(0.05±0.005)l,where l is the average linear distance from the inlet edge to the outlet edge of the blade,with a spacing of 4mm between node vertices and a wave number of 5 nodules.The two biomimetic schemes effectively reduced the volume of bubbles in each stage of cavitation and made the development of bubbles more stable in the initial stage of cavitation;Reduce the main frequency amplitude of pressure pulsation at multiple positions within the centrifugal pump;Effectively improving the head of centrifugal pumps in the stage of cavitation development and fracture cavitation;The pair vortices generated at the biomimetic structure will change the impeller vorticity field,reducing the low-pressure area at the impeller inlet and reducing the turbulent kinetic energy in the impeller channel,achieving the effect of suppressing cavitation and limiting its development.Biomimetic nodules can effectively suppress the occurrence of cavitation in centrifugal pumps and improve their cavitation performance(5)The bionic nodule parameters used in two schemes that can improve the cavitation performance of centrifugal pumps are arranged on centrifugal pumps with different specific speeds.For model pump 2(ns=67),both bionic models effectively improve the lift of the centrifugal pump during the cavitation development and fracture cavitation stages,reducing the volume of cavitation in the impeller flow passage,reducing the cavitation accumulation area,and moving a large number of cavitation accumulation areas towards the impeller outlet,changing the development characteristics of the cavitation morphology,improving the cavitation development,and playing a role in suppressing cavitation and improving the cavitation performance of the centrifugal pump;Using the heave amplitude scheme for model pump 3(ns=116)reduces the cavitation volume in the impeller flow passage,maintaining the characteristic of first decreasing and then slightly increasing the lift as cavitation develops,effectively improving the lift of centrifugal pumps during both cavitation development and fracture cavitation stages.Using the heave amplitude scheme reduces the volume of cavitation during the initial and developing stages of cavitation,which has a certain control effect on the cavitation of centrifugal pumps.However,it will cause the cavitation on the near wall surface of the blade to diffuse into the impeller flow path,and when cavitation is severe,it will diffuse to the working surface of adjacent blades,blocking the flow path,and exacerbating cavitation.The universality of biomimetic nodules to control cavitation in centrifugal pumps has been verified,but how to arrange biomimetic nodules in medium to high specific speed centrifugal pumps needs further research.