Study On The Influence Of Guide Vane Structure On Flow Characteristics Of Centrifugal Pump With Low Specific Speed

Over the years,centrifugal pumps are playing an increasingly important role in industry and production,especially low specific speed centrifugal pumps,are widely used in petrochemical,aerospace,nuclear power,medicine and other important fields of national economy.Practical experience shows that the guide vane structure has a significant influence on the flow characteristics of centrifugal pumps.In this paper,the guide vane of the centrifugal pump with low specific speed is designed and modified,and the unsteady numerical simulation of the full flow field of the centrifugal pump is carried out to explore the influence of the guide vane structure of the centrifugal pump with low specific speed on its flow characteristics.The main research contents are as follows:(1)Two schemes of guide vane structural modification of centrifugal pump are determined,the wrap angle of guide vane and the relative installation position of guide vane and impeller are changed,and the three-dimensional drainage basin model of centrifugal pump before and after guide vane modification is established.The flow field of the centrifugal pump was divided into grids and the mesh independence was verified.The RNG k-? model was used to simulate the centrifugal pump before and after the guide vane modification under rated conditions.(2)The external characteristics,pressure pulsation and vibration of the original low specific speed centrifugal pump under-different flow rates were studied.Compared-with the numerical simulation results under different flow rates,it is found that the two have a strong consistency,so it can be concluded that the numerical simulation results have credibility.Under the experimental conditions,the pressure pulsation in the guide vane runner and impeller runner tends to be stable and the vibration on the left side of the pump shaft increases as the flow rate increases closer to the rated working condition.Through numerical simulation under different flow rates,it can also be found that when getting closer to the rated working condition,the pressure pulsation in the impeller and guide vane passage tends to be more periodic.(3)Based on the numerical simulation results of the whole flow field before and after the modification,the pressure pulsation of the impeller and guide vane at the rated working condition of the centrifugal pump with low specific speed was analyzed.The results of the analysis show:for the pressure pulsation at guide vane passage,the predominant components in pressure spectra locate at the 3 blade passing frequency,6 blade passing frequency and 12 blade passing frequency.For the pressure pulsation at impeller passage,the predominant components in pressure spectra locate at the 6 blade passing frequency.As the guide vane retrofits,pressure pulsation changes regularity.(4)A comparative study is carried out on the external characteristics of the centrifugal pump before and after the the guide vane modification,and the distribution of static pressure,velocity,turbulent kinetic energy and entropy production of the middle section of the guide vane and impeller is analyzed.The results show that the guide vane modification has a significant impact on the external characteristics of the centrifugal pump,and the distribution of the entropy production is consistent with the external characteristics.At the interface between guide vane and impeller,the static pressure and entropy generation are obviously stratified,and the parameters present a certain gradient change in the rotor-stator interference area.In general,the modification of the clearance between the impeller and guide vane brings about more significant changes in the external characteristic of the centrifugal pump than that of the guide vane wrap angle.