Investigating the Role of Mixing Chamber Geometry in the Performance of Steam Jet Ejectors

Abstract

This study explores the optimization of supersonic ejector efficiency by investigating key parameters: the total length of the converging mixing chamber and constant area section (s + L), the half angle of the mixing chamber \({{\varphi }_{1}}\), and the length of the constant area section L. Through computational fluid dynamics (CFD) simulations, the sum of the length of the converging mixing chamber and constant area section was varied between 8D to 10D (D refers to the ejector throat diameter), revealing that exceeding this range negatively impacts both the entrainment ratio ER and pressure ratio PR. Therefore, a length of 8D was chosen for optimal performance. While Engineering Sciences Data Unit (ESDU) suggests a range of 2° to 10° for \({{\varphi }_{1}}\), our study shows that increasing \({{\varphi }_{1}}\) beyond 2° results in decreased ejector performance. Performance curves were derived and discussed for \({{\varphi }_{1}}\) values of 2° to 6°. Additionally, the constant area length was varied from 1D to 5D while maintaining the sum of the lengths of the converging mixing chamber and constant area section at 8D. The study found that a constant area length of 3D best satisfied design requirements, as it provided the highest entrainment ratio while maintaining a suitable pressure ratio within the designed range. These findings underscore the importance of carefully considering these parameters to achieve optimal ejector performance.