The Research On Fluid Leakage Characteristics On Centrifugal Pump

In order to balance the axial force,the balance hole in the lower part of the rear cover of the impeller is widely used in the structural design of the centrifugal pump.The balance hole communicates with the balance chamber and the suction side,reducing the liquid pressure in the balance chamber,reducing the pressure acting on the rear cover,thereby eliminating or reducing the axial force.But because the liquid from the balance chamber back to the suction side,resulting in a balanced hole leakage,changing the internal flow field of the centrifugal pump,resulting in volume loss,reducing the efficiency of the centrifugal pump,even the pump performance is also affected.Therefore,it is important to provide accurate measurement and calculation of the amount of liquid leakage in the centrifugal pump.And because of the theoretical study of the internal flow field of centrifugal pump is not adequate,the measurement of leakage of experimental means to implement difficulties,accurate measurement and calculation of centrifugal pump liquid leakage has become an industry problem.In this paper,the internal flow field structure and leakage characteristics of centrifugal pump are studied by theoretical analysis,experimental measurement and numerical simulation.The calculation method of liquid leakage in centrifugal pump is put forward,which has played a certain role in engineering practice.The main research work in this paper The main research work in this paper are as follows:1.The dimensionless parameters were introduced,the velocity distribution of the axial position and radial position of the pump chamber was obtained,and the influence of the axial clearance of each pump cavity on the liquid flow characteristics of the pump chamber was analyzed.The results show that the liquid thickness of the outflow zone and the boundary layer is about 20% of the gap value of the pump chamber when the axial gap of the pump chamber is 10 mm,and the thickness of the two regions increases with the increase of the axial gap.The thickness is about 30% and 50% of the axial gap when the axial gap is 8mm and 4mm respectively,the corresponding turbulence core area thickness is reduced.When gap value is 1mm,the thickness of the turbulent core region is very small,and the radial velocity difference between the different axial positions is larger,and the radial velocity is the largest in the axial direction.2.In order to study the influence of different axial gap of pump cavity on balance chamber pressure and leakage,RNG k-e turbulent model were used to perform numerical simulations for the whole flow channel model of pump cavity gap that value is 1,4,8,12,16,20 mm,the distribution law of balance chamber pressure and leakage,then the relation curve and leakage calculation formula of velocity coefficient and gap-diameter ratios.The pressure of the surface of entrance of balance holes and the wall of close lid decrease with the increasing of pump cavity gap,and this change is more obvious when the axial gap is from 4mm to16 mm,and the leakage of pump cavity flow channel increase with the increasing of pump cavity gap at the same flow condition.For the same pump cavity gap,the leakage of pump cavity flow channel decrease with the increasing of the flow rate.3.The relation curve between velocity coefficient and gap-diameter ratio and the calculation formula of leakage are obtained.The velocity coefficient relate to the drug coefficient of the pump chamber,the drug coefficient of the seal ring and the drug coefficient of the balance hole.According to the relation curve,velocity coefficient is increases with the increase of gap-diameter ratio.The relation curve and the calculation of formula can be used to estimate the velocity coefficient and the solution of the leakage coefficient in the test.The relationship curve can be used to estimate the ratio of the total runner velocity coefficient in the range of 0.006 to 0.127,and then combined with the leakage calculation formula can obtain the pump chamber flow liquid leakage in different pump cavity axial gap.4.Based on the dimensional analysis,the expression of leakage of the balance hole was established.The coordinate of the leakage of the balance hole was obtained in the condition of different speed of the impeller via numerical simulation of the IS80-50-315 centrifugal pump.Using the Origin software to polynomial fitting of the coordinate points,the function of the balance hole leakage is established.The results show that the rotation of the impeller hinders the flow of liquid from the equilibrium chamber to the suction side of the centrifugal pump,and the faster the speed,the greater the resistance of the leakage liquid and the smaller the leakage of the equilibrium hole.5.The leakage experiment of the pump cavity is carried out by using the floating impeller test bench,and the leakage characteristics of different balance holes are mainly studied by the leakage test device.Under the condition that the seal ring radius is 89 mm,length is 15 mm and the same impeller balance hole in different diameters,the pressure of pump cavity runner that gap value is 6mm and leakage were test,then different pump cavity diameter balance liquid leakage characteristics of pump cavity was indirectly obtained in the different balance diameter.6.By using dimensional analysis and numerical simulation,the function of the leakage of balance hole was obtained,then leakage of pump cavity runner was fixed The leakage method is used to determine the leakage of the pump chamber,which can be used as a reference for the study of the leakage characteristics of centrifugal pump balance hole by means of dimensional analysis,numerical simulation and experimental measurement.