Analysis Of Internal Flow Characteristics And Structure Dynamics Of Slanted Axial Pump Device

The slanted axial pump device has the advantages of small flow channel hydraulic loss,low excavation depth requirement and convenient installation,maintenance and maintenance.It is mostly used in the Yangtze River Delta,the Pearl River Delta and other regions.In the actual operation of the pumping station,the slanted axial pump device is prone to vibration,noise,blade cracks and other phenomena that affect the safe and stable operation of the pump device unit.In order to improve the hydraulic operation stability of this type of pump station device unit,the internal flow field and the structure dynamics characteristics of the impeller of the slanted axial pump device are studied.The main research work and conclusions are as follows:(1)The entropy generation distribution characteristics of each flow structure of the slanted axial pump device under different flow conditions are obtained.The internal streamlines of the elbow-shaped inclined inlet flow channel are smooth,and the area with high entropy production rate is concentrated in the outlet section,and it increases with the increase of the flow rate.The mainstream entropy production of the impeller is concentrated in the hub and rim area,and there is a large entropy production loss in the blade tail area.The wall entropy production is mainly produced by the tip clearance leakage.The high value area of the main flow entropy production rate of the guide vane body is located on the suction surface of the guide vane,and decreases with the increase of the flow rate.There is a large loss of entropy production in the elbow section of the outlet flow channel.(2)The pulsation change law of each flow structure characteristic monitoring point of the slanted axial pump device under different flow conditions is clarified.Under large flow conditions,the main frequency of the pulsation at the outlet of the elbow inlet is 4 times the rotation frequency.The main frequency of the pressure pulsation at the impeller outlet is 4 times the rotation frequency,and the low frequency is rich.The pressure amplitude is significantly lower than that of the impeller inlet,and the wave crest fluctuates.With the increase of the flow rate,the amplitude of the wave crest change gradually decreases,and the pressure pulsation amplitude tends to be stable;under the small flow condition and the optimal condition,the pressure pulsation at the outlet of the guide vane presents a large fluctuation,which is mainly affected by i4nfluence of low-frequency pulsation,the amplitude of pressure pulsation changes periodically under high-flow conditions.(3)The fluid-solid coupling method is used to analyze the stress and strain characteristics of the impeller under different flow conditions.The equivalent stress is concentrated at the root of the blade and decreases from the root of the blade to the blade rim.The blade rim releases stress through deformation,and the blade rim stress is small and deformation is big.With the increase of the flow rate,the maximum equivalent stress gradually decreases,the deformation displacement decreases,and the maximum deformation position moves from the water inlet edge of the blade to the water outlet edge.(4)According to the first similarity law of water pump and the principle of equal nD value,the change law of blade stress and strain under different geometrical dimensions is explored.As the geometric size of the impeller increases,the equivalent stress and deformation of the blade gradually increase,and the maximum deformation of the blade of each geometric size is concentrated on the water inlet edge of the blade rim.Using rain flow calculation method and Miner linear fatigue cumulative damage theory to analyze the blade fatigue,predict the life cycle of the impeller under different flow conditions,and give the distribution cloud diagram of the safety system of each area of the blade.