Study of Effects of Hydraulic Parameters on the Motion of the Free Piston in Ionic Liquid Compressors in Hydrogen Refuelling Stations

The innovative ionic liquid compressor, in which the free piston is in place of the cranked connecting rod piston the hydraulic free piston, is a promising type of compressor for hydrogen refuelling stations. It is necessary to calculate and analyse the motion of the free piston, which is crucial for the performance of the compressor and determined by the hydraulic system. This paper developed a fluid–structure interaction method for the effects on the piston dynamic characteristics of three major hydraulic parameters: buffer clearance, oil charging flow rate, and oil overflow pressure. The results showed that the buffer clearance influenced the asymmetry of the piston motion and the actual location of the BDC by changing the piston velocity and the oil pressure, with the most optimum value of 0.5 mm. The actual BDC was also affected by the oil charging flow rate, which determined the minimum oil pressure, with the most optimum value of 120 L/min. The actual position of TDC was affected by the oil overflow pressure, which can reduce the impact. The most ideal value was 32.5 MPa.