Modelling the Cylinder Cooling in an Oil-free Reciprocating Air Compressor

Oil-free air compressors are widely applied in new energy vehicles, pharmaceutical, textile, food and the chemical industry for providing clean air. However, high temperature inside the cylinder due to compression heat and oil-less lubrication may lead to premature failure of the self-lubricating sealing rings and the grease-lubricating bearings. This paper presents the simulation of the cylinder cooling in an oil-free reciprocating air compressor for new energy vehicles. Based on the modelling, the cooling channel outside the cylinder was optimized to enable more effective cooling with limited air flow, obtaining lower temperature level of the cylinder, and therefore higher reliability of the sealing rings and bearings. The results show that the heat transfer model of the cylinder with numerical simulation is effective in predicting the cylinder temperature level as well as the cooling capacity of the air flow. The heat exchange efficiency of the compressor can be improved significantly by applying the optimized cooling duct structure. Compared with the model A, the maximum cylinder temperature was decreased by 13.1°C in the model B, and it also was decreased by 6.3°C in the model C. (paper)