Dynamic Liquid Nitrogen Level Detection of Cryostats Onboard the HTS Maglev Vehicle

For the safe operation of high-temperature superconducting (HTS) Maglev vehicles, the liquid nitrogen (LN2) level in the onboard cryostat should be monitored in real-time during the whole running process. The previous method of LN2 level detection was proposed by using resistance sensors or liquid volume meters as the testing equipment to estimate the liquid level. However, the fluctuation of LN2 level causes great disturbance for the liquid level detection, which leads to unsteady detection and loss of valid data. In this paper, an effective method for LN2 level detection under dynamic conditions is proposed. First, the static evaporation of LN2 in rectangular and circular containers are measured by PT100 platinum resistances. And then, a self-developed simple hardware is designed for onboard cryostats, further improving the HTS maglev vehicle performance. Furthermore, the state estimation theory, which uses particle filter algorithm, is employed to eliminate the interference caused by fluctuation of the LN2 level. The real-time measurement results illustrate that the proposed dynamic liquid nitrogen level detection is able to meet the requirements of the LN2 level detection with high precision.