| Radio Frequency Quadruple(RFQ)accelerator is the most commonly used acceleration structure in linear acceleration.The RF power dissipation on the internal surface of the cavity make the cavity heat and deformation,cause frequency shift,which affects the beam quality and transmission efficiency.For continuous wave(CW)conditions,the thermal stability of the radio frequency quadrupole(RFQ)is an important concern during commissioning.The cooling system is utilized to maintain the thermal stability,to limit the structural deformation and tune the frequency.It is necessary to study the cooling process of RFQ,which is used to simulate the temperature rise,the deformation and the frequency shift.From the heat transfer and fluid dynamics points of view,the RFQ cavity cooling is a complex processes of the coupled the heat transfer between the cavity structure and the cooling medium in the thermal environment,and the flow heat transfer within the medium.The RFQ cooling process considering the fluid flow can be studied to obtain more complete analysis results and see the cooling effect of the cooling process more intuitively through the temperature parameters of the cooling fluid.It is of practical significance for the stable operation of the RFQ accelerator and accident prevention.Focus on the thermal stability of CW RFQ accelerator,the detailed 3D multi-field coupling analysis combined with fluid dynamics is carried out including electromagnetic(EM),thermal-fluid coupled analysis and structural simulation in the thesis.The researches for this topic are conducted as follows:(1)Considering the influence of machining and assembly errors on the cavity frequency,high requirements are put forward for machining accuracy and shape and position tolerances.The machining and assembly process of cavity is introduced.Through the precision requirement and tuning,the influence of processing error on RFQ frequency is eliminated,and the test shows that cavity performance meet the design requirements.(2)According to the RFQ cavity structure and the actual shape of the U-cooling channel,a 3d model of cavity and fluid was established.The multi-field coupling research of electromagnetic,heat-flow coupling analysis and structure analysis was completed.Combined with fluid dynamics and CFD software,the model parameters were optimized.The effect of water temperature on the deformation,stress andfrequency of cavity was studied.(3)In the beam experiment,the relevant parameters of the fluid are obtained through the monitoring device of the water cooling system.The simulation results under the same conditions are compared with the experimental results,the validity of the simulation model and result is proven.(4)For fluid flow heat transfer,the transient conjugate heat transfer between the cavity and the fluid and the coupling analysis between the cavity thermal field and the flow field are realized by combining the flow field and thermal analysis through the heat flow coupling numerical calculation.The results of transient simulation verify with the ones of experimental.(5)In practical engineering design,it is necessary to take into account the workload,calculation time and hardware performance requirements of the heat flux coupling simulation calculation.On the basis of the formula,aimed at the thermal problem of RFQ,the correction formula of heat transfer coefficient is provided.Under the same experimental conditions,thermal analyses by empirical formula and by the correction were conducted.The wall temperature results of each cooling channel calculated by the two methods were compared with the the coupling analysis under experimental conditions.The results show that the modified heat transfer coefficient can reduce the error,and obtain a result closer to the experimental simulation.The combination of numerical simulation method and the running experiment results will make it possible to evaluate more precise the heat stability of the RFQ accelerator.Heat flow coupling analysis provides an effective numerical test platform and parameter optimization design method for RFQ cavit y cooling passage design in engineering practice.The innovations of this paper are as follows:(1)The multi-field coupling of RFQ accelerator was studied by finite element analysis,and the cooling process of RFQ accelerator cavity was analyzed by using fluid dynamics theory and software.The transient conjugate heat transfer analysis between the RFQ accelerator cavity and the cooling fluid has been realized for the first time in China.(2)The experimental data were obtained through the water cooling system.The numerical coupling calculation of CW RFQ accelerator and the beam experimental results were verified for the first time through the cooling system of RFQ accelerator in China.(3)Aiming at the heat transfer problem of RFQ accelerator,the heat transfe r coefficient formula is modified,and the error of empirical formula and coupling simulation is reduced. |
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