Research On Internal Flow And Unsteady Characteristics Of Deep-well Multi-stage Molten Salt Pump

Molten salt pumps are widely used in the chemical and new energy fields,and the demand is constantly increasing,which puts forward new requirements for their design and research.Referring to the structure of deep well pump,this article designs and optimizes the impeller and spatial guide vane of multistage molten salt pump,and analyzes the internal flow of multistage molten salt pump under different guide vane wrap angle and blade inlet setting angle.At the same time,considering that the internal flow field of multistage molten salt pump is more complex than that of single stage centrifugal pump,it is easy to produce greater pressure pulsation due to the dynamic and static interference between impeller and spatial guide vane and the influence of pump shaft rotation,which will cause damage to the operation of pump,the phase interleaving of impeller is studied for multistage molten salt pump.Based on the five stage centrifugal pump arranged in sequence,four sets of model schemes are established,which impeller phase not staggered?Scheme A?,impeller phase staggered 1/2 of a space guide vane flow channel?Scheme B?;impeller phase staggered 1/?Z-1?of a space guide vane flow channel?Scheme C,where Z represents the number of impeller blades?,and impeller phase staggered 1/?Z₁-1?of a space guide vane flow channel?Scheme D,where Z₁represents the number of space guide vane?.The three dimensional steady state numerical simulation and three dimensional transient numerical simulation of the multistage molten salt pump are carried out under four model schemes,and the internal flow and pressure fluctuation characteristics of the multistage molten salt pump under four staggered schemes are analyzed and studied.The specific conclusions are as follows:1.The guide vane blade wrap angle has a greater impact on the multistage molten salt pump head.With the increase of the blade wrap angle,the overall lift of the multistage molten salt pump increases;the impact on the pump efficiency is small,When the wrap angle increases to more than 105°,the efficiency curve of the pump tends to be stable.When the wrap angle is 120°,the high efficiency area of the pump is large.The pressure distribution and streamline distribution in impeller and guide vane can be improved with the increasing of wrap angle.When wrap angle is 120°,the pressure distribution and streamline distribution are better.2.The inlet angle of the guide vane blade has little effect on the efficiency of the pump,and it has a greater effect on the head under nondesign conditions;it has a significant effect on the internal flow of the multistage molten salt pump,and the guide vane rectification effect is the best when?₃=10°.3.After steadily analysing the multistage molten salt pump found that when the impeller phase interleaving changes,the head and efficiency of the pump do not change much,and the optimal operating point was around 1.2Q_d.4.In multistage molten salt pumps,the propagation of pressure pulsation signals between stages is very obvious.When the impeller phase is staggered,the pressure pulsation in the impeller is dominated by high frequency signals with a frequency greater than or equal to the main frequency.As the flow rate increases,the low frequency fluctuations in the impeller subside and the intensity of the high frequency fluctuations decreases.In this model,the pressure pulsation in the impeller is the shaft frequency frequency doubling pulsation,the main frequency of the pulsation is half of the leaf frequency,and the secondary frequency is the product of the shaft frequency and the integral multiple of the number of guide vane blades.The pressure pulsation in the impeller is affected by the effect of the impeller trail,the dynamic and static interference of the impeller guide vane,and the interstage coupling of the pulsation.The impeller phase interleaving can improve the amplitude of the pressure pulsation inside the impeller.5.The pressure pulsation in the guide vane is also dominated by high-frequency signals.The pressure pulsation is represented by the shaft frequency double frequency pulsation,and the pulse main frequency is half of the leaf frequency.The interleaving of the impeller phase can improve the internal pressure of the guide vane.The amplitude of pulsation can also eliminate low frequency fluctuations and reduce the intensity of high-frequency pulsations.