Effect Of Splitter Blade Geometric Parameters On Hydraulic Performance Of Low Specific Speed Centrifugal Pump

The low specific speed centrifugal pump is characterized by small flow and high lift.It is widely used in various fields related to fluids.Its structural characteristics are that the flow path is narrow and narrow,and the outlet width is small,which leads to large hydraulic loss.The disc friction loss is more serious,resulting in lower operating efficiency,and even the unit will generate vibration and noise,and the internal flow is unstable.How to improve the performance of low specific speed centrifugal pumps has become a problem that cannot be ignored.This paper takes a low specific speed centrifugal pump as the research object,the specific speed n_s=32,the number of blades is 6.In the first part,aiming at the large error of SST k-?turbulence model in calculating the external characteristics of centrifugal pumps under small flow conditions,the influence degree of four parameters on the calculation of the external characteristics of centrifugal pumps is analyzed by changing the values of model parameters?*,?₁,A₁ and?₂.In the second part,the design method of shunt blades is used to study the influence of geometrical parameters of shunt blades on the performance of centrifugal pumps.Firstly,the number of impeller blades is determined,which are 3+3,4+4 and 5+5?long blade number+shunt blade number?schemes respectively.The external characteristics of centrifugal pumps are calculated,and the number of blades is determined to be 5+5by comparing the calculated results.The effects of three different parameters on the flow characteristics of centrifugal pumps are analyzed,namely,the inlet diameter of shunt blades D_in,the outlet thickness of shunt blades L_outut and the position adjustment coefficient K_i.Finally,steady and unsteady calculations are carried out for the prototype pump and the optimal centrifugal pump respectively.The main research contents and conclusions are as follows:?1?The SST k-?turbulence model is used to calculate the external characteristics of centrifugal pumps under small flow conditions.The results show that there is a big error between the calculation results and the test results.Therefore,by adjusting the values of model parameters?*,?₁,A₁ and?₂,the errors between calculation results and test results are reduced,and different parameter schemes are designed by combining the orthogonal experimental design method and the control variable method.The calculation results show that the parameter A₁ has the greatest influence on the calculation of centrifugal pump head,and when the initial value of A₁ is 1.5 times,the calculation results are closer to the test results.The calculation of the lift and efficiency of centrifugal pump has a great influence.When the initial value of?₁ is 2 times,the calculation results are closer to the test results.The parameters?₂ and?*have the least influence on the calculation of the lift and efficiency of centrifugal pump.?2?Under the design conditions,study the influence of the geometric parameters of the splitter blades on the external characteristics of the low specific speed centrifugal pump.Comparing the external characteristics,it is found that the optimal scheme is n₂₂,D_in=232.5mm,L_out=5mm,and the efficiency of the pump is the highest when K_i=0.97,?=48.69%,which is 2.2%higher than the efficiency calculated by the original model pump.For 4.761,the head meets the design requirements.?3?Under design conditions,steady simulation of prototype pump and 27 kinds of centrifugal pump with shunt vanes is carried out.The results show that the inlet diameter is 201.5mm,the outlet thickness is L_out=5mm,and the low pressure area at the impeller inlet is the smallest;the turbulent kinetic energy at the corresponding position between the outlet of the impeller runner and the volute tongue is the largest,and the turbulent kinetic energy at this position becomes smaller and smaller with the increase of the inlet diameter of the shunt vane,With the increase of number K_i,the turbulent kinetic energy increases and the turbulent fluctuation is obvious at this position.The eddies on the impeller of the prototype pump are mainly on the back of the blade,while the eddies on the impeller of the shunt blade are mainly on the working face.?4?The unsteady numerical simulation of the prototype pump and the optimized shunt vane centrifugal pump is carried out under the design condition.The results show that the maximum pressure fluctuation amplitude corresponding to each monitoring point in the impeller and volute of the separated vane centrifugal pump is obviously smaller than the maximum pressure fluctuation amplitude on the impeller of the prototype pump;compared with the prototype pump,the low pressure distribution range at the impeller inlet of the shunt vane centrifugal pump is smaller,and the same At the same time,the inlet and outlet pressure of shunt vane centrifugal pump impeller is smaller than that of prototype pump,and the distribution range of swirl area in shunt vane impeller channel is smaller than that in prototype impeller channel,which reduces energy loss in impeller,improves streamline in channel and optimizes flow field structure.