Experimental Study Of The Flow Field Of Fiber Suspension In Open Impeller Centrifugal Pulp Pump

As an important power transmission equipment in the papermaking process,improving the performance of the pulp pump is of great significance in response to the national energy conservation and emission reduction policy.In this paper,the twisted three-blade open impeller centrifugal pulp pump was used as the research object.The influence of the suspension on the external characteristics of the pump and the internal flow field of the impeller was analyzed by external characteristic test and Particle image velocimetry test?PIV test?with clear water and hair fiber suspension as the medium.The stroboscopic test was used to study the distribution of hair fiber particles in the impeller flow channel.The concentration distribution and fiber orientation distribution of hair fiber particles in the impeller flow channel were analyzed.The above experimental research results can provide reference for the design of high efficiency pulp pumps.The main research work and results of this paper are as follows:?1?The relative velocity distribution of the middle section Z1 and the cross section Z2 near the back cover plate in the impeller passage of pulp pump under different flow rates was studied by PIV test.The test results show that:In the outlet region of impeller,the relative velocities of Z1 and Z2 sections are basically the same,but the relative velocities of Z1 and Z2 sections at other locations are quite different.?2?Through the PIV test,the relative velocity distribution of the liquid suspension of the hair suspension on the Z1 cross section was measured,and compared with the PIV result of the clear water,the relative velocity of the liquid phase fluid is lower than the relative velocity of the clear water due to the presence of the particulate phase under low flow conditions.And as the position moves toward the impeller exit,the speed difference between the liquid phase fluid and the clean water is decreasing.As the concentration of the suspension increases,the relative velocity of the liquid phase fluid decreases atr₀/r₂=0.6,r₀/r₂=0.7 and r₀/r₂=0.85?r₀ represents the radius of the measurement location,r₂ represents the outlet radius of the impeller?,and the relative velocity of liquid phase increases at r₀/r₂=1.With the increase of flow rate,the velocity difference between liquid phase fluid and clean water at r₀/r₂=0.6and r₀/r₂=0.7 decreases,the velocity difference at r₀/r₂=0.85 increases,and the velocity difference at r₀/r₂=1 basically remains unchanged.When the flow rate increases,the range of relative velocity of liquid phase fluid with the increase of suspension concentration at different radii in the impeller decreases.The existence of particle phase decreases the velocity variation of liquid phase from suction surface to pressure surface relative to that of clear water,and the velocity distribution in the flow channel is more uniform.?3?The distribution of solid particles in impeller runner with 0.1%and 0.2%concentration of suspension at different flow rates was measured by stroboscopic test.The stroboscopic test showed that under small flow conditions,near the impeller outlet area,the concentration of hair particles near the suction side of the blade is larger than the concentration of hair particles near the pressure surface,and the hair particles are oriented in the circumferential direction near the pressure side.Under the rated flow and large flow conditions,the hair particles are oriented in the radial direction in the flow channel near the suction surface.As the flow rate increases,the distribution of hair particles in the impeller flow passage is relatively more uniform.?4?The external characteristics of the pump when delivering clean water with gaps of 0.5mm and 0.9mm were measured by tests.And the external characteristic curves of the pump were measured when the clearance was 0.5mm and the concentration of hair suspension was 0.1%and 0.2%.The external characteristic test shows that when the distance between the impeller and the front and rear baffles increases,the head and efficiency of the pump decrease,and as the gap increases,the optimal operating point of the pump shifts to a small flow.The head and efficiency of the pulp pump when delivering the hair suspension are lower than the head and efficiency when the water is delivered,and as the concentration of the suspension increases,the head and efficiency of the pump are further reduced.There was no drag reduction phenomenon of fiber suspension flow when low concentration hair suspension was transported.