| For axial flow pumping stations where blade angle can be fully adjusted,when there are errors in factory assembly or installation and debugging,or aging and failure of blade adjusting mechanism components,it will lead to deviation or even failure of blade angle adjustment,so that the blade angle of each pump is not exactly same,result to blade angle deviation.The deviation of blade angle will not only lead to the decrease of pumping station flow and efficiency,and affect the hydraulic performance of the pump,but also lead to the increase of unit vibration,uneven force of the blade,the increase of radial force of the bearing,and affect the safe and stable operation of the pumping station.At present,the research on the blade angle of pump device mainly focuses on the hydrodynamic characteristics of pumping stations with the same blade angle,and there are few researches on the hydrodynamic characteristics of axial flow pump with the blade angle deviation.In this study,based on numerical simulation,the hydrodynamic characteristics of different types of blades in two-way flow channel pump device were studied with blade angle deviation.The numerical simulation results are verified by model test to ensure the accuracy of calculation.Specific research contents include:(1)The influence of a blade angle deviation on the hydrodynamic characteristics of the pump device.The hydrodynamic characteristics were studied when the blade angle deviation of the impeller increased by 2° or decreased by 2°.The results show that:1)When the blade angle increases by 2°,the pump head increases by 4.9%,the maximum efficiency decreases by 1.53%,and the high efficiency zone shifts to the high flow zone.At the impeller inlet,the low pressure area near the blade increases,and the pressure difference between the blade pressure surface and the suction surface increases,so that the outflow velocity on the blade increases,leading to unstable outflow.The backflow area in the impeller chamber and guide blade increases,and the axial velocity distribution uniformity at the impeller outlet and guide blade outlet decreases by 14.6%and 9.32%.The amplitude of pressure fluctuation at the impeller outlet flange increases more,and the dominant frequency of pressure fluctuation at the central measuring point of guide vane changes.2)When the blade placement Angle decreases by 2°,the pump head decreases by 7.3%,the maximum efficiency decreases by 1.48%,and the high efficiency zone shifts to the low flow zone.The low pressure area near the blade at the impeller inlet decreased,the pressure difference between the blade pressure surface and the suction surface decreased,and the axial velocity distribution uniformity at the impeller outlet and guide blade outlet decreased by 5.22%and 6.12%,respectively.The main frequency and amplitude of the pressure fluctuation at the outlet hub of the impeller are more affected,and the main frequency and amplitude of the pressure fluctuation at the outlet of guide vane change greatly under the design condition.3)The overall force of the impeller changes.The axial force,equivalent stress and deformation on the blade increase with the increase of the blade angle and decrease with the decrease of the blade angle.The mechanical characteristics on the blade without deviation are also affected.An increase of blade angle of 2° has a greater effect on radial force.The increase or decrease of a mounting angle has no effect on the modal characteristics of the impeller.(2)The influence of the same direction deviation of two angles on the hydrodynamic characteristics of the pump device.When two blades of the impeller are changed in the same direction,that is,when the angle of two blades increase by 2° and decrease by 2° at the same time,the hydrodynamic characteristics are studied respectively.The results show that:1)When the angle of two blades increases by 2°,the pump head increases by 10.5%,the maximum efficiency decreases by 1.28%,and the high efficiency zone shifts further to the high flow zone.This type of deviation has the greatest influence on the static pressure distribution,the uniformity of axial velocity distribution and vorticity distribution of impeller outlet and guide vane outlet.It has great influence on the amplitude of pressure fluctuation at impeller outlet.The main frequency and amplitude of pressure fluctuation in the middle of guide vane change the most under the condition of low flow rate and design condition.The amplitude of the outlet bell changes the most under the condition of low flow rate.When the axial force increases further,the maximum equivalent stress and deformation are generated under design condition and large flow condition.2)When the two blade angles decrease by 2°at the same time,the pump head decreases by 14.1%,the maximum efficiency decreases by 1.13%,and the high efficiency zone further shifts to the small flow zone;The amplitude variation of pressure fluctuation in the middle of the guide vane is relatively small in each working condition.The amplitude variation of pressure fluctuation at the outlet of the guide vane is the largest in the working condition of small flow,and the amplitude variation of pressure fluctuation at the outlet of the water inlet is the largest in the design working condition.The axial force decreases further.3)The radial force of the impeller increases when the blade angle of two blades is in the same direction as that of one blade.It has no effect on the modal characteristics of impeller.(3)Influence of reverse deviation of two angles on hydrodynamic characteristics of pump device.The hydrodynamic characteristics of the impeller are studied when the angle of one blade increases by 2° and the angle of the other blade decreases by 2°.The results show that:1)the pump head changes little,the maximum efficiency decreases by 2.17%,and the high efficiency zone does not move significantly;The positions of high pressure and low pressure areas in the middle of the guide vane changed,and the static pressure distribution among the guide vanes was greatly different.The reflux area inside the guide vane increases,and the outflow phenomenon is the most serious.More vortices are generated at the guide vane outlet.2)The pump device produces greater hydraulic vibration,the inlet bell main frequency and its amplitude change the most,and the impeller outlet rim has a higher amplitude;The amplitude in the middle of guide vane varies greatly under off-flow condition.Under the design condition,the amplitude of guide vane outlet and outlet bell is large.3)The axial force of blade wheel has little change;However,the radial force is the largest,the equivalent stress and deformation are the largest under the condition of small flow,and the difference of the equivalent stress and deformation between blades is the largest.It has no effect on the modal characteristics of impeller. |
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