Against the source-load imbalance caused by daily-scale periodic fluctuations in grid loads, this study investigates performance optimization methods for ejectors within compressed air energy storage (CAES) systems. The aim is to improve the overall efficiency of CAES systems in terms of power generation during energy release, as well as enhance their operational control capabilities during actual operation. In CAES systems, the ejector performs the dual functions of regulating the state parameters of the working gas and introducing low-pressure exhaust gas. This critically affects the system efficiency.

By taking a 10 MW-class CAES demonstration system under construction as the research subject, this study combines response surface methodology with Computational Fluid Dynamics (CFD) numerical simulation to analyze the ejector’s entrainment performance under varying working gas pressures, entrainment exhaust gas pressures, and outlet backpressure conditions. This determines the ejector’s efficient operating range. Subsequently, the volume of the storage tank is designed based on the entrainment performance results of the ejector and the variable pressure operating conditions during the energy release process of the CAES system. The power generation capacity of the CAES system is then predicted using a theoretical model.

The entrainment performance of the ejector is sensitive to variations in the working gas pressure and the entrainment exhaust gas pressure. Optimal entrainment characteristics are achieved when the working gas pressure is between 10.0 and 11.75 MPa, and the entrainment exhaust gas pressure is 5.6 MPa. The outlet back pressure of the ejector significantly affects the structure of the internal flow field and the operational window of the CAES system. Higher back pressure results in a narrower operating pressure range, necessitating larger storage tank volumes and reducing energy release efficiency. When the back pressure is 8.0 MPa, the ejector operates efficiently within a working pressure range of 10.00~12.00 MPa, achieving an energy utilization efficiency rate of 10.46%. A CAES system with a 2.2×10³ m³ storage tank can sustain continuous operation at design power for 4.0 hours under a back pressure of 8.0 MPa. Its energy conversion efficiency is 16.67%, with cumulative energy released for power generation reaching 5.01×10⁴ kW·h. This represents a 2.04% improvement on systems without an ejector.

Defining the high-efficiency operating range of the ejector and rationally configuring the air storage tank volume can effectively enhance the power generation capabilities of the CAES system, providing a foundation for optimizing the system and formulating operational strategies in engineering practice.