A volumetric-loss model for predicting flowrate characteristics of a 45 MPa diaphragm compressor in hydrogen refueling stations

Diaphragm compressors in hydrogen refueling stations are frequently subjected to off-design operation, making their flowrate characteristics essential for evaluating station refueling efficiency. In this study, a theoretical calculation model is developed to analyze the flowrate characteristics of a single-stage 45 MPa diaphragm compressor under a wide range of operating conditions. The model accuracy is validated against using volumetric efficiency data obtained during the pressurization process in a hydrogen refueling station. The results indicate that the measured flowrates agree well with the calculated values, with a maximum relative error not exceeding 5%. The effects of compression ratio and oil-gas pressure differential on the clearance expansion, oil expansion, valve loss and suction heating factors are further analyzed to reveal the mechanisms affecting the flowrate. Finally, a full-range volumetric-efficiency map is established and applied to storage-bank repressurization after vehicle refueling, supporting hydrogen supply optimization and practical refueling strategies.