Design of the minimum liquid height in the compression cylinder of the multi-stage ionic liquid compressor for hydrogen refuelling stations

Ionic liquid compressors are suitable for high-pressure hydrogen refuelling stations. The initial liquid piston height is a critical parameter in designing ionic liquid compressors. Sufficient initial liquid column height can effectively prevent hydrogen leakage and exposure of the solid piston. However, there is a lack of basis for selecting the initial ionic liquid column height in the compression cylinder. The gas-liquid interface in the multi-stage compression is investigated by an experimentally verified numerical simulation model. The results show that in the low-pressure stage of the ionic liquid compressor, the initial liquid piston height can equal to the piston stroke, but in the high-pressure stage, the solid piston could be exposed to the hydrogen, so it is necessary to increase the initial liquid piston height. By analyzing the fluctuation characteristics in the cylinder, it is found that there is a minimum initial liquid piston height in each stage to ensure effective sealing. The minimum liquid piston height for the first to the fifth stage is 52 mm, 40 mm, 44 mm, 51 mm, and 54 mm, respectively.