| Space nuclear reactor power supply is an ideal power supply technology for spacecraft and space probe because of its high power density,long service life,light weight and small size.Liquid metal cooling is the main cooling method of space nuclear reactor power supply,and its liquid metal coolant is circulated by electromagnetic pump.Annular linear induction electromagnetic pump(ALIP)is the best choice for pumping coolant of liquid metal cooled space nuclear reactor power supply as a result of its natural advantages of good sealing,high safety and reliability,low maintenance cost and long life cycle.Therefore,it is of great engineering value and practical significance to carry out theoretical and numerical simulation research on the characteristics of ALIP.This dissertation takes ALIP as the research object,and focuses on the key scientific issues of electromagnetic field and fluid field distributions,the influence of end effects and eddy current in ducts,the electromagnetic and hydraulic characteristics and double supply frequency pulsation pressure characteristics of ALIP,then a series of researches such as the one dimensional field analytical calculation of the ALIP with end effects and eddy current effects of ducts,the derivation of equivalent circuit model,the numerical simulation of coupled 3D multi-physics(electrical-magnetic-fluid)and the suppression of double supply frequency pulsation pressure are carried out in depth.The main contents include:Firstly,a one-dimensional analytical model of ALIP considering the end effects and eddy currents in ducts is established,which provides an effective theoretical tool for the analysis of ALIP electromagnetic field,operating characteristics and the design for performance optimization.The analytical expressions of the fields(magnetic field,eddy current field and electromagnetic force field)in the annular channel are derived,and the corresponding components producing by the end effects in each field are separated,then the analytical expressions of electromagnetic and hydraulic characteristic parameters are obtained.Based on the analytical model,this dissertation reveals the distribution law electromagnetic field and force field,analyzes the characteristics of influence of end effects and conductive ducts eddy current effect,and investigates the electromagnetic and hydraulic characteristics of ALIP under multiple operating conditions.Then the relevant results are verified by experiments.Secondly,the improved ALIP equivalent circuit models are proposed,and which can compensate for the existing ALIP equivalent circuits with large calculation error when the end effect is significant and lay the foundation for the equivalent circuit research of ALIP.The ALIP equivalent circuit model EC-I with the resistance of conductive ducts but no end effects is developed,then the expressions of the impedance from EC-I are derived.Based on the mathematical expressions of electric and magnetic fields from the one-dimensional field analysis model,the end effects correction factors of each impedance parameter are calculated by the Poynting theorem,then the performance parameter expressions are obtained,and the improved ALIP equivalent circuit model EC-II is proposed.In EC-II,the liquid metal secondary is symbolized by a single impedance,and the output mechanical power is calculated by(1-s)P_e.When the end effect is significant,the calculation method((1-s)P_e)will cause some error because the wavelength difference between the end effect magnetic fields and the fundamental magnetic field is neglected.Therefore,on the basis of EC-II,the single impedance is divided into 3×3impedance matrix considering the difference of wavelength between end effect magnetic field and fundamental magnetic field according to the generation of power flow,furthermore,the improved ALIP equivalent circuit model EC-III is proposed and the expressions of the performance parameters are derived.The total output mechanical power of the EC-III is calculated by the output mechanical power of each impedance branch.Next,the three equivalent circuit performance parameter expressions are derived,then the performance of three equivalent circuits is calculated,compared and verified experimentally based on the actual ALIP parameters.And the application scenarios of different equivalent circuit models are revealed.Thirdly,the coupled 3D multi-physics field(electric-magnetic-fluid)numerical calculation approach for ALIP is proposed,which provides ideas for the ALIP numerical calculation based on multi-physics field coupling and offers analytical tools and some references for the design,parameter analysis and performance optimization of ALIP.The3D multi-physics field simulation model is established,based on this model,the 3D electromagnetic field distribution law in liquid metal fluid of ALIP is firstly revealed,then the influence of cogging effect and end effects are analyzed,and the difference between the 1D analytical model and 3D numerical model in terms of the influence of end effects is explained.Next,this dissertation analyzes the distribution characteristics of vortices formed in the annular channel under the closed valve condition and the influence of electromagnetic force and end effects on the radial distribution of flow velocity and pressure distribution in different axial positions in the flowing state.Then the electromagnetic characteristics(electromagnetic pressure,electromagnetic efficiency,double supply frequency pulsation pressure,etc.)and hydraulic characteristics(pressure with closed valve,hydraulic loss,head,hydraulic efficiency,etc.)of ALIP under multiple operating conditions are studied,and the influence of core saturation,inner core outer diameter,pump channel width and the circumferential air gap between adjacent stator cores on ALIP performance are analyzed.Finally,the relevant results are verified by experiments.Fourthly,based on the proposed ALIP multi-physics field coupling model,three suppression methods of double supply frequency pulsation pressure of ALIP are presented,namely,the winding grading at the outlet end,the inner core outlet end structure of cylindrical convex platform and the inner core outlet end structure of cylindrical convex platform with compensating conductive ring,which provide some reference for the research about double supply frequency pulsation pressure of ALIP.The performance of ALIP and suppression effect of double supply frequency pulsation pressure with different number of poles are compared,and the applicability of increasing the number of poles for suppression of double supply frequency pulsation pressure in a small ALIP is determined.The suppression effects of double supply frequency pulsation pressure for ALIP with the winding grading at both stator ends and only outlet end are both studied,and the best form for winding grading is determined by parametric analysis,then the suppression strategy of double supply frequency pulsation pressure with the winding grading at the outlet end only is proposed.The suppression mechanism of double supply frequency pulsation pressure with different outlet end structures of inner core are investigated,and the optimal outlet end structure of inner core is determined by parametric analysis,then the suppression strategy of double supply frequency pulsation pressure with the inner core outlet end structure of cylindrical convex platform is proposed.On this basis,the suppression effect of double supply frequency pulsation pressure with the conductive ring embedded in the inner core outlet end is investigated,then the suppression strategy of double supply frequency pulsation pressure based on the inner core outlet end structure of cylindrical convex platform with compensating conductive ring is presented. |
