Theoretical and experimental study on improving diaphragm compressor design for hydrogen refueling stations through use of a free moving oil piston concept

The diaphragm compressor is the essential component of a hydrogen refueling station, but the traditional design method results in low cavity volumetric efficiency and high refilling oil pressure. This study proposes a design method using a free moving oil piston to optimize the cavity volume. This method allows the cavity volume to be utilized to the maximum, and a "zero pressure" stage occurs at the end of the suction process, which greatly improves the cavity volumetric efficiency and reduces the refilling oil pressure. To further examine and verify the superiority of this method, 90 MPa and 200 MPa diaphragm compressors were designed and produced for comparison, and their simulation study was conducted simultaneously. The results demonstrate that this proposed design method can raise the cavity volumetric efficiency of the 90 MPa diaphragm compressor in the experimental case from 0.37 to 0.66. Additionally, the benefit increases with the compressor pressure. For the case of a 200 MPa diaphragm compressor, the cavity volumetric efficiency increases from 0.19 to 0.64.