| Cryogenic transmission pipeline is an important part of helium cryogenic refrigeration refrigeration system,transmission system and distribution system.It is used to transmit different types,temperature zones and flow of cryogenic working medium to various equipment of the system.The structure,performance and heat leakage of cryogenic transmission pipeline directly affect the working efficiency of helium cryogenic refrigeration system,and whether the cryogenic working medium transmitted to each equipment can meet the use requirements.However,little research has been done oncryogenic transmission pipelines with large diameter and long distance trarsportation in the liquid helium temperature zone,and there are still manydifficulties,including: How to minimize heat leakage in the process of liquid helium transmission,the manufacturing and installation of long distancetransmission pipeline,the structure layout and the requirements of sealingperformance under the condition of large flow,etc,make it difficult to manufacture and assemble large diameter liquid helium transmission pipeline.and the process requirements are high.In this thesis,the space engine test platform needs to be transported fromthe large high-pressure liquid helium tank to the experimental chamber ata large flow rate during the working process,so as to realize the ultra-high vacuum and take away a large amount of heat load.In the long-distance transmission of liquid helium,low temperature joints are needed to realize the connection,and the heat load of the joints is huge,which affects the transmission efficiency.The structural design,heat leakage calculationand thermal stress analysis of large diameter liquid helium transmission pipeline are studied theoretically and experimentally.First of all,the structure design of the large-flow liquid helium transmission pipeline is carried out,and a support structure with compact structure and excellent thermal insulation performance is formed by heat-structure coupling analysis and optimization.The results show that the structure has certain advanced properties.Secondly,with the low temperature pipe joint as the main research object,the temperature distribution,stress distribution and sealing structure compression of the whole pipe joint are analyzed,and the method to reduce the heat leakage and cold leakage of the pipe joint is put forward,which is practical and economical.Finally,the liquid helium transmission pipeline is built to detail the assembly process,installation sequence,welding precautions and leakage detection process of the weld seam.All parts of the design meet the requirements,and the liquid helium transmission pipeline is evacuated,which provides a reference for the design of similar low-temperature transmission pipeline in the future. |
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