A novel central annular slit ejector: Flow characteristics analysis and experimental performance investigation

This study proposes and investigates a novel central annular slit ejector structure, which demonstrates improved entrainment ratio and isentropic efficiency compared to conventional central ejectors under high-pressure-ratio and large-flow-rate conditions. The ejector utilizes an annular nozzle to discharge high-pressure fluid, enabling simultaneous entrainment of low-pressure fluid on both the inner and outer sides of the high-pressure stream. This design increases the contact area, reduces flow losses, and enhances mixing efficiency. A systematic analysis of the flow characteristics, performance curves, and entropy generation distribution was conducted using computational fluid dynamics simulations combined with entropy generation analysis theory. Comparative studies with conventional central ejectors were performed. The results indicate that the novel structure reduces entropy generation rate under varying expansion and compression ratios, promotes more uniform velocity distribution, and shortens the mixing section length, leading to higher entrainment ratio and isentropic efficiency. Furthermore, an experimental platform was established to validate the numerical simulations. The experimental results agree well with the simulations, under the operating condition with an expansion ratio of 3.5 and a compression ratio of 1.6, the maximum isentropic efficiency of the experimental apparatus can reach 37.5 %. This study provides a new structural design solution for ejectors to achieve efficient and stable operation across a wide range of working conditions.