Numerical modeling of air ejectors covering supersonic, subsonic and closed-port operations

Abstract

The physics and modeling of air ejectors in on- and off-design conditions have been extensively addressed in the past, reaching a good level of maturity. However, to achieve a robust model at system scale integrating an ejector, there is a need for developing 0D models suitable to tackle abnormal functioning modes, such as cases where the ejector works in subsonic conditions, reverse flows, or closed ports. Based on state-of-the-art models, a new 0D model has been built in the current work, where proper subroutine implementations allow covering normal and abnormal operations of convergent nozzle ejectors. The current research also focuses on understanding the physical behavior of air ejectors for aeronautical applications. In this regard, CFD-RANS simulations are used to perform model verification and calibration as well as to gain knowledge of the whole operational envelope. The regimes reproduced by the 0D model, and validated by CFD, cover the normal operating mode with different choking regimes, the occurrence of a subsonic primary flow, and the closed secondary port case. Additional cases are run to assess other features of the ejector behavior, such as the influence of geometrical properties on the choking mechanism and the impact of thermal effects.