| Centrifugal pump is widely applied in various fields because of its simple structure,strong operability and good adaptability.In practical application,due to the unreasonable selection of the type selection,the design requirements of the installation and the poor cavitation performance of the centrifugal pump,the cavitation phenomenon occurs during the operation of the centrifugal pump,and the axial force which is not conducive to the operation of the centrifugal pump is produced,which affects the normal operation of the centrifugal pump.However,there are few studies on the axial force of centrifugal pump under cavitation condition.Therefore,it is necessary to study the axial force characteristics under cavitation condition.In this paper,the axial forc e characteristics of a centrifugal pump with different balance hole diameter and flow condition are studied by means of the combined method of cavitation test and numerical simulation.T he main work and conclusions are as follows:(1)Influence of impeller balancing hole diameter on cavitation performance of pump.A balanced hole set which can change the balance hole of different diameter on the same impeller is designed.By using a water r ing vacuum pump,the vacuum degree of the inlet is changed to change the cavitation state of the centrifugal pump.Under the three conditions of small flow rate,design flow rate and large flow rate,the test pumps with a balance hole diameter of 4,6,8 an d 11 mm were tested respectively.It is concluded that the impeller diameter has a certain effect on pump cavitation performance under the same flow rate,but it has little influence.In addition,when the balance hole diameter is the same,the flow rate also has a certain influence on the cavitation performance of the pump.(2)The effect of cavitation on the liquid pressure in pump chamber and balance chamber is studied.By opening a pressure measurement hole on the pump cover,the pressure values of the pump cavity and the balance cavity are measured.The relation curves of the pressure coefficient and the number of cavitation are drawn by the dimensionless treatment.The effect of cavitation on the pressure of the pump cavity and the balance cavity is analyz ed,and the change law of the pressure coefficient with Thomafactor is obtained.(3)The study of the effect of cavitation on the axial force.In this paper,a double sealing ring impeller with open balance holes is adopted.Because the diameter of the front seal ring and the diameter of the rear seal ring are equal,the axial force of the front and back pump cavity above the seal ring is the same,and the axial force can be counteracted each other when the axial force is calculated.The main component of the axial force is the cover force caused by the liquid pressure difference before and after the balance of the impeller cover plate.The relationship between the axial force coefficient and Thomafactor is drawn by the dimensionless treatment,the axial force characteristics under the cavitation condition are analyzed,the variation of t he axial force coefficient with Thomafactor is obtained.(4)Based on cavitation model,a steady numerical study of centrifugal pump under various conditions is carried out.Compared with the experimental results,the external characteristic curve and cavit ation performance curve of the centrifugal pump are consistent,and the numerical simulation results are reliable.Through numerical simulation,the distribution law of the flow field in the pump is analyzed,the internal pressure changes and cavitation st ate of the cavity are observed,then the axial force characteristics of the cavitation centrifugal pump are analyzed.It is concluded that the occurrence of cavitation will cause changes in the flow field,affect the distribution of pressure,and then have a certain effect on the axial force. |
PDF Full Text Request