Effects Of Staggered Arrangement Blades On Fluid And Structural Characteristic Of Double-suction Centrifugal Pump

Centrifugal pumps are widely used in various fields of national economy.Especially,the single stage double-suction centrifugal pump has a very extensive application in the auxiliary system of thermal power and nuclear power plants,petrochemical industries and other industrial processes.For a single stage double-suction centrifugal pump,energy performance,cavitation performance,changes of the performance curve,the operation stability of the variable condition,fluid & structural vibration and noise etc.have different special requirements with different industrial processes.The subject combined with the development work of the main oil pump(MOP)in the oil-supply system of 60 Hz steam turbine sets.In order to improve the operation stability and the reliability of MOP design,fluid and structural characteristics of single stage double-suction centrifugal pump with high rotational speed and high pressure ratio were studied,and effects of staggered arrangement blades on energy performance of the double-suction centrifugal pump,pressure fluctuation in the volute,static and dynamic characteristics of the rotor were also discussed.The specific research contents and conclusions of this paper were as follows:(1)For the special operation environment requirements of the oil system of steam turbine sets,the relative research status and basic theories were introduced,and the technical route and research methods of the numerical simulation were established.(2)Combined with a MOP in the oil-supply system of 60 Hz steam turbine sets whose specific speed is 30 and outlet pressure is 2.5MPa.For two arrangements blades,the numerical simulations of the 3D steady flow in the centrifugal pump were computed by CFX software.The results indicate that the rule of flow field inside the pump with staggered arrangement blades is good,the pressure distributions of each part are consistent,which can meet the requirements of characteristic curve.The efficiency increased at low flow rates and decreased at large flow rates with staggered arrangement blades.The head and shaft power slightly decreased.(3)Based on the results of steady calculation,the 3D unsteady flow in the centrifugal pump with staggered arrangement blades was numerically simulated.The time domain and frequency domain of volute outlet and monitoring points in the volute were analyzed,and the pressure pulsation in the pump volute with the symmetrical blades was analyzed comparatively.The research results indicate that the pressure pulsation in the volute has a clear periodicity,whose domain frequency is 720 Hz,and double that of the symmetry blades.Pressure pulsation of the outlet of pump and the pressure fluctuation in the volute got more intense with the increase of flow and closer to the volute tongue respectively.Compared with the symmetrical blades,the amplitude of pressure fluctuation in the volute was significantly reduced,especially at the outlet which reduced the maximum of 79.36%.(4)Based on the FSI,the static analysis and modal analysis for rotor of the centrifugal pump with staggered arrangement blades were carried out by ANSYS Workbench software,the reliability of its structure were predicted and assessed,and the mechanical properties of the rotor of centrifugal pump with symmetrical blades were analyzed comparatively.The results show that that the maximal deformation and equivalent stress of the rotor are all in the safe range,and the each order critical speed of rotor is much higher than its working speed,so the probability of resonance is very low.Compared with the symmetrical blades,the total deformation and equivalent stress of rotor with staggered arrangement blades increased,and each order natural frequencies slightly decreased.The results mentioned above give a great guiding significance for reducing pressure pulsation in the volute,vibration and noise of structure of single stage double-suction centrifugal pump with low specific speed and high rotational speed,and play a role in engineering project for optimizing the design of MOP and improving the operation stability of the oil-supply system of steam turbine sets.