Comparison of the performance enhancement of vacuum ejector by means of structure optimization and bypass methods

Abstract

The ejector can create a vacuum environment without electricity and produce no pollutants, making it widely used in various fields. However, during the working process, a large amount of high-pressure air needs to be continuously supplied to maintain the vacuum level. Given the current energy shortages, it is essential to enhance the entrainment capacity and reduce the energy requirements of the vacuum ejector. To achieve this goal, a two-stage vacuum ejector (TSVE) and structure optimization are adopted. While achieving the same vacuum level (80 kPa or 90 kPa), the air consumption (m˙p) and entrainment ratio (Er) of vacuum ejectors with various shapes are compared. Through structural optimization, five high-performance vacuum ejectors (Pp < 0.6 MPa, Er > 0.65) are selected. Computational Fluid Dynamics (CFD) is applied to observe the mixing processes in the vacuum ejector. In addition, the optimized vacuum ejector and TSVE are compared to the original one. An experimental system is designed for this purpose. The findings indicate that both methods can enhance the performance of the vacuum ejector. However, the benefits of TSVE are more pronounced at lower vacuum levels, while the advantages of the optimized vacuum ejector become more obvious as the vacuum level increases.