Thermal-structural coupled analysis and improvement of the diaphragm compressor cylinder head for a hydrogen refueling station

Abstract When applied in the hydrogen refueling station, the diaphragm compressor with super-high pressure ratio will experience a high discharge temperature of over 200 °C, especially for that with large capacity and horsepower. Considering the thermal stress, the structural strength and deformation of the cylinder head are crucial to the reliability and efficiency of the diaphragm compressor. In this paper, a thermal-structural coupled analysis was proposed, based on which the deformation and stress of the diaphragm compressor cylinder head under high-temperature and high-pressure conditions were obtained. And the fatigue life of the studs on the cylinder head was also estimated based on the stress results obtained in the thermal-structural coupled analysis. The experimental method was conducted for verifying the numerical results. The results indicated that during the operation of the compressor, the temperature in the discharge holes was the highest, resulting in not only plastic deformation but also large stress concentration, and the high thermal stress could reach up to the strength limit of the material. A structural improvement was therefore proposed to decrease the stress in the region of the discharge holes by cutting a larger hole and attaching a new separate one for valve installation. Further stress analysis showed that the stress in the same region of the improved structure was significantly reduced, which guaranteed the safety of the compressor.