Study On Unsteady Vortex Characteristics Of Centrifugal Pump Based On DDES Model

A single-stage single-suction centrifugal pump was taken as the research object,for its partial working conditions,re-hydraulic design of the impeller;The Delayed Detached Eddy Simulation method was used to study the internal pressure pulsation characteristics of the centrifugal pump,the structure and evolution of unsteady vortex in the flow channel.Firstly,for the partial operation of single-stage single-suction centrifugal pump,1.2Q operating point was the most efficient.based on the velocity coefficient method,the impeller was re-hydraulic designed.steady numerical simulation with FLUENT simulation software.results: The highest point of the efficiency curve was restored to 1.0Q operating condition,the normal operation of the pump.At the same time,the overall efficiency of the pump had increased by 2.04%,and the efficiency of a single impeller had changed from 89.3% of the original to 95.33% after optimization,an increase of 6.03%.With CFD-POST post-processing analysis software,the internal flow characteristics of the pump before and after the design were compared and analyzed.Compared with the original model,under the rated condition,the velocity streamline and dynamic pressure of design model were more uniform and regularly distributed,the disturbance area was greatly reduced,and the turbulent kinetic energy was significantly reduced,the area of negative pressure near the blade fillet was reduced.Compared with the blade load,the static pressure load on the working face of the original model blade was higher than that of the design model.The static pressure load on the back of the design model blade was higher than the original model,The pressure gradient of the impeller of the design model was smaller than the original model.Secondly,the unsteady numerical simulation of centrifugal pump with Delayed Detached Eddy Simulation was carried out to study the structure and evolution of unsteady vortex in the flow channel.Compared with the vorticity cloud images,the DDES turbulence model can clearly see the small vortex formed by the collapse of the large vortex and can simulate the fine flow field structure better than the RNG k-epsilon turbulence model.In the process of vortex moving with the fluid,it was accompanied by the phenomena of vortex initiation,fusion,migration,rupture,dissipation and so on.The flow had a significant effect on the distribution of vortices in the flow channel.As the flow rate increased,the vortex gradually decreased and the vorticity value decreased gradually.Finally,DDES turbulence model was used to study the pressure fluctuation in centrifugal pump.Compared the pressure pulsation characteristics in the flow path of the two impellers,the pressure in the flow channel of the design model was reduced.It was found that the time-domain and frequency-domain curves of import and export of impeller were the same,but the middle position was different.In the third section of the volute along the radial direction,the pressure pulsation was greatest at the inlet,and as the diameter increased,the pressure coefficient fluctuations gradually decreased.Along the axial direction,as the axial distance increased,the pressure coefficient fluctuations also gradually decreased;the pressure pulsation at the position of the tongue was much larger than other positions of the volute;Dynamic and static interference between the blade and the volute was the main cause of pressure pulsation.