Analysis Of Inner Flow Field And Its Hydraulic Performance Of Liquid-Ring Pump With Splitter Blades

Liquid ring pump is a kind of turbomachinery which uses liquid as intermediate medium to transfer energy and transport gas.Because of its simple structure,large flow,isothermal compression and other advantages,it is widely used in petrochemical industry,mining and agricultural engineering.Due to the structural characteristics of the impeller asymmetric installing,the flow distribution in the impeller passage of the liquid ring pump is extremely uneven during it work.That causes the violent pressure pulsation in the liquid ring pump,reduces the efficiency and service life of the liquid ring pump.To reduce the secondary flow vortex intensity,pressure pulsation and vibration in the liquid ring pump.The prototype of 2BEA-203 liquid ring pump was selected as research object,and designed the liquid ring pump with splitter blades according to the design theory of splitter blades and liquid ring pump.The inner flow,pressure pulsation and hydraulic performance of liquid ring pump with splitter blades were compared with that of the prototype pump by using numerical simulation combined with experimental test.Secondly,this paper also analyzed the effection of the short blade inlet diameter and the number of impeller with splitter blades on the internal flow field,external characteristics and pressure fluctuation.The main research contents and innovative achievements of this paper are as follows（1）The experimental test of hydraulic excitation characteristics and pressure pulsation were carried out.The results show that the change trend of efficiency and vacuum of liquid ring pump is consistent with that of numerical simulation.Because the leakage of axial gap is not considered in numerical simulation,the efficiency and vacuum of numerical simulation are higher than the experimental value.The amplitude and frequency spectrum of the pressure fluctuation at the shell of the liquid ring pump measured by the experiment are in good agreement with the numerical simulation.（2）The inner flow and hydraulic performance of liquid ring pump with splitter blades were compared with that of the prototype pump by using numerical simulation combined with experimental test.The results show that the impeller with splitter blades can improve the efficiency and vacuum significantly of liquid ring pump.The pressure of the shell in the exhaust region and compression region of liquid ring pump is reduced and the velocity gradient near the beginning of the exhaust port of the liquid ring pump are reduced too,the turbulent kinetic energy loss in the exhaust region and suction region of the liquid ring pump is decreased.The flow status in the exhaust region and compression region of the liquid ring pump changes average,and the shape of the gas-liquid interface of the liquid ring pump with splitter blades is smoother than that of the liquid ring pump with prototype impeller.（3）The pressure pulsation of liquid ring pump with splitter blades was compared with that of the prototype pump by using numerical simulation combined with experimental test,and the mechanism of partition features of pressure pulsation along circumference of pressure pulsation was analyzed.The results show that the pressure fluctuation amplitude of the liquid ring pump with splitter blades is smaller than that of the prototype impeller.Due to the geometric asymmetry of impeller and pump casing along circumference,the distribution of the volume fraction in the flow passage of impeller is inhomogeneous,which leads to obvious partition features of pressure pulsation along circumference.The pressure pulsation amplitude of the liquid ring pump casing from the suction region decrease firstly,and it reaches the minimum in the compression region.It increases again in the exhaust region.（4）The influence of short blades inlet diameter on the performance and pressure fluctuation in liquid ring pump was analyzed by numerical simulation.The results show that the length of short blade of liquid ring pump can not be too short or too long.The longer the short blade is,the more uneven the flow is at the inlet of the short blade of the liquid ring pump,the shorter the short blade is,the less the flow status in the impeller passage can be improved.When the inlet diameter of short blade is 0.65D₂,the efficiency of liquid ring pump is the highest,which is 17.7%.The vacuum of the liquid ring pump with splitter blades decreases firstly and then remains unchanged with the short blades inlet diameter increasing.When the short blade is0.6D₂,the gas-liquid interface shape is the smoothest,when the short blades is 0.65D₂the turbulent kinetic energy loss in the exhaust and suction region is the smallest.The short blades are too short to suppress the pressure pulsation.When the inlet diameter of the short blade is 0.75D₂,the pressure fluctuation amplitude of the liquid ring pump shell is the largest.The short blades with different length have the influence on the frequency spectrum of pressure fluctuation at the shell of liquid ring pump.（5）The influence of the splitter blade numbers on the performance and pressure fluctuation of liquid ring pump was analyzed by numerical simulation.The results show that the number of composite impeller blades should not be too much or too little.A lot of splitter blades will increase the import exclusion and blade friction loss.A fat of blades can not improve the flow status in the impeller channel.When the number of impeller with splitter blades is 12 long+12 short,the efficiency of liquid ring pump is highest,which is 19.36%.The vacuum of liquid ring pump with splitter blades does not change basically at first,and then increases gradually with the number of blades increasing.When the number of blades is 14 long+14 short,the flow status can be improved,the pressure gradient in the flow channel can be reduced,and the amplitude of pressure fluctuation can be suppressed.However,more blades will increase the extrusion at the inlet and outlet of the liquid ring pump,and that will lead to more turbulent kinetic energy loss.When the number of blades is 10 long+10short,the pressure gradient in the flow channel of liquid ring pump is large,which can not improve the flow status of liquid ring pump.