| The cantilever multistage centrifugal pump has compact structure and is convenient for use,it is widely used in many fields,such as petrochemical industry,building water supply,farming irrigation and mine drainage.In the past research of centrifugal pump,hydraulic performance has always been research focus in design process,however,the noise performance has also attracted researchers' attention with the progress and development of society,therefore,multistage centrifugal pump with excellent noise performance will have strong product competitiveness.In the actual design process of multistage centrifugal pumps,the improvement of hydraulic performance and noise performance is not entirely consistent.In order to balance the relationship between the two aspects,a cantilever multistage centrifugal pump was selected as the research object,a method combining theoretical analysis,numerical simulation and experimental verification is applied to study the influence of pump chamber radial clearance on hydraulic and noise performance.The main research contents are outlined as follows:(1)The development background of water pump industry was analyzed,and the research status of the hydraulic and noise performance was concluded to determine the research object,methods and main contents;theories and basic control equations,including fluid and acoustics,were analyzed and summarized.(2)The three-dimensional whole flow field model of multistage centrifugal pump was established,a set of grid models were determined by analysing grid independence,and numerical simulation head was verified by test method;three kinds of pump chamber radial clearance schemes were designed,steady and unsteady numerical simulations were carried out by CFX14.5 software to compared external characteristics,the internal flow field and the radial force distribution of the impeller,The results show that water ring,formed at the edge of the impeller by cutting impeller blade,which can play roles in collecting and buffering for water flow from impeller,it is beneficial to improve internal flow state of multistage centrifugal pump.(3)The frequency distribution of pressure fluctuation in impeller,guide vane and pump chamber was analyzed in depth.Firstly,the time step and calculation time of unsteady simulation were determined through error analysis;secondly,the study found that rotor-stator interaction is the main reason for pressure fluctuation of multistage centrifugal pump,the frequency domain distribution is influenced by the number of impeller blades and guide vane blades,obvious enhancement phenomenon of pressure fluctuation occurs at the common multiple frequency of impeller blade frequency and guide vane blade frequency;thirdly,pump chamber radial clearance has little effect on pressure fluctuation,but the amplitude of scheme 1 is slightly lower than other schemes.(4)Based on dipole sources from unsteady simulation,internal sound field was carried out by Acoustics modular of LMS Virtual.Lab software to study the sound pressure level frequency response in the inlet and outlet points.The study found that amplitude of the sound pressure level decreases with increasing of frequency;there are obvious peak values at impeller blade frequency,guide vane blade frequency and common multiple frequency,especially,the peak value at the common frequency is the most obvious;change rules of sound pressure level amplitude of different schemes are not same at different frequencies.(5)Based on the circumcision blade scheme,the possibility that reducing the pressure fluctuation and noise amplitude by changing the number of impeller blades was studied.Firstly,the number of impeller blades decreased from 6 to 5,the head of numerical simulation still meets the design requirements;secondly,pressure fluctuation amplitude decreases,and the optimization scheme avoids peak enhancement phenomenon in 0~2000Hz,it also has better noise performance,full frequency mean values of sound pressure level in inlet and outlet points reduce by 5.92 dB and 5.31 dB respectively compared with the original scheme;finally,the head and pressure fluctuation tests were carried out on multistage centrifugal pump test rig,the test results are in agreement with the simulation results... |
PDF Full Text Request