Transient modeling of quench and recovery of LNG-HTS hybrid energy transmission system based on multi-field coupled analysis

In a novel high temperature superconducting (HTS) hybrid energy transmission system, the liquefied natural gas (LNG) and electricity are transported together along the energy pipeline to attain very high energy transmission efficiency. The liquid nitrogen (LN₂) is used to provide a low temperature environment and can also restrain the quench phenomenon as a protective medium. As the safety of the system is the biggest concern, a one-dimensional model with the quasi static state method is originally proposed in this paper to analyze the quench and recovery behavior. The model firstly introduces the electromagnetic analysis into the thermal and flow analysis, combining intricate interaction of phase change, fluid flow, heat transfer and current sharing. In this paper, the complete quench and recovery characteristics can be obtained when the system is subjected to the default current or thermal disturbance. The results indicate that under a specific condition, the quench of the system can be recovered by itself including different stages, going through the cooling process of film boiling, nucleate boiling, transient boiling and forced convection in turn. The recovery time caused by the default current is much longer than that caused by thermal disturbance and it has a power law relation with the velocity of LN₂. For the quench process caused by the default current, the maximum temperature of the system decreases with the increase of LN₂ velocity. For the thermal disturbance, the maximum temperature almost keeps constant. The proposed model can predict the quench and recovery behavior in advance, which is significant for the stable operation and design of the hybrid energy transmission system.