Structure Design And Performance Test Of On-board Aluminum Alloy Cryostat For Electrodynamic Suspension Train

High temperature superconductor(HTS)has great application prospects in electrodynamic suspension train because of its higher critical temperature,larger engineering critical current density and better mechanical properties.In order to make the HTS magnet exert better suspension performance,we usually select 20-40 K as the working temperature range of the magnet.However,the current cryostats often use stainless steel as the main material,which increase the weight of the superconducting magnet system(including the superconducting magnet and the cryostat).At the same time,the force transmission mechanism transmits the electromagnetic force of the superconducting magnet through the outer vessel of the cryostat,which increases the difficulty of designing the cryostat.In addition,the complex electromagnetic environment of superconducting electrodynamic suspension train also generates eddy current loss on the surface of the superconducting magnet,which increases heat leakage of the cryostat.Therefore,from the perspective of light weight,this thesis selects aluminum alloy,which can mitigate the eddy current loss of high temperature superconducting magnet as the main material,optimizes the design of the force transmission support structure to improve the stress environment of the cryostat,and develops a set of onboard cryostat for electrodynamic suspension train.First of all,the structure of the cryostat was designed by the three-dimensional design software CATIA.The 6061-T6 aluminum alloy was selected as the main material of the outer vessel and radiation shield of the cryostat to reduce the eddy current loss of the magnet.At the same time,the radiation shield and the multi-layer thermal insulation material were used to reduce the heat leakage of the system.In order to transmit the electromagnetic force on the HTS magnet to the bogie directly,we designed a new support structure with G-10 material and 304 stainless steel for the cryostat,which would also reduce the heat leakage.The force condition of the superconducting magnet and its cryostat was improved at the same time.Secondly,based on the ANSYS Workbench multi-physics simulation software,the strength of the outer vessel and the support structure were checked,respectively,especially the more comprehensive strength analysis of the brittle parts such as the G-10 support rods,which verified the mechanical structure design of the cryostat rationality.Then,based on the theory of heat transfer,the heat leakage of the cryostat was calculated,and compared with the cooling capacity diagram of the refrigerator.It was estimated that the superconducting magnet could be reduced to 20 K or even lower temperature.The feasibility of the cryostat to achieve the cooling target was verified using the theoretical calculation.Finally,according to the design and simulation results,the fabrication and performance test of the cryostat were completed.Using copper coil equivalent superconducting coil and resistance sheet equivalent heat source to simulate the thermal load of each component,when the superconducting magnet was excited,the operation performance of the cryostat under practical application conditions was verified by the experiment.The results of the cooling experiment showed that the minimum temperature of the copper coil can be reduced to 19 K and the radiation shield can be reduced to about 60 K,which was in good agreement with the heat leakage calculation results.However,due to the unsatisfactory heat interception effect of the radiation shield heat sink on the G-10 support rod,the magnet temperature could not be further reduced.For the heat loading experiment,the temperature of the radiation shield increased to 85 K,the temperature of the magnet skeleton and the copper coil was almost unchanged,when the radiation shield was loaded with the conduction heat leakage of the copper current lead.The experimental results were basically consistent with the initial design goals.When the heat corresponding to the excitation current of 300 A was set as an input,the maximum temperature of the copper coil and the magnet skeleton was 37 K,which was lower than the critical temperature of the superconducting magnet of 300 A,and was still in the best working temperature of the superconducting magnet(20-40 K).This result verified the proposed cryostat design.