Mechanical Engineering for Society and Industry

A liquid–gas ejector (LGE) is a vacuum-generating device that uses high-pressure liquid to entrain and compress gas and is widely applied in industrial processes. However, undesired recirculation within the suction chamber may reduce entrainment effectiveness and overall ejector performance. This study experimentally investigates the effect of a confined suction chamber on the performance of a  vertical downward flow. The modified chamber was designed to restrict the interaction zone between the liquid jet and the surrounding gas, thereby reducing circulation losses. The performance of the confined suction chamber was compared with that of a conventional suction chamber under the same operating conditions by evaluating suction pressure, static pressure distribution, flow ratio, and efficiency. The results show that the confined suction chamber produced lower throat pressure and altered pressure recovery along the throat and diffuser, indicating changes in the entrainment processes. It also delivered higher suction performance and greater maximum efficiency than the conventional configuration. The analysis indicates that, at a flow rate of 0.327 L/s, the confined suction chamber produces a lower absolute pressure of 44 kPa absolute than the conventional suction chamber, which records 54 kPa absolute. The highest efficiency obtained with the confined suction chamber was 9.94% at a flow ratio of 0.82, compared with 8.23% at 0.87 for the conventional chamber.