Energy Efficiency Analysis of Pneumatic Vacuum Generators Based on the Exergy Field Method

The pneumatic vacuum generator is widely used in the field of industrial automation. However, it consumes a significant amount of expensive compressed air. Driven by green manufacturing and emission reduction, it is of practical significance to conduct sophisticated analyses on the energy process and energy efficiency of pneumatic vacuum generators. In this study, a novel energy efficiency evaluation method, i.e. exergy field method, is proposed by integrating exergy theory and CFD numerical simulation. The proposed method could accurately quantify the energy loss and spatial-temporal distribution in the vacuum generator, thereby providing new insights into the analysis, evaluation, design, and optimization of vacuum generators. Firstly, the product exergy, fuel exergy, and exergy efficiency of the vacuum generator are defined using exergy theory, which provides the theoretical foundation for further analyses. Secondly, CFD numerical simulation is conducted to analyze the internal flow field and exergy field of a specified pneumatic vacuum generator. Finally, the impacts of different inlet pressures on the exergy efficiency of vacuum generators are investigated. Besides, the proposed exergy field method is compared with traditional indicators such as compressed air consumption, vacuum degree, and suction flow rate. The results indicate that the inlet pressure has a significant impact on the exergy efficiency of the vacuum generator, and there is always an optimal critical point for maximum efficiency despite evaluation indicators. In terms of the pneumatic vacuum generator investigated in this study, the optimal values of the vacuum degree, suction flow rate, pressure exergy, temperature exergy, and kinetic energy exergy are all achieved at the inlet pressure of 0.3MPa, while the optimal exergy efficiency is achieved at 0.26MPa. Finally, the relationship and differences between the exergy field method and other traditional methods are discussed.