Numerical and Experimental Study of Flow Phenomenon Inside Gas Ejectors With Moist Gases Entrainment

Abstract

Gas ejectors can be found in a wide range of applications such as refrigeration and thrust augmentation. This paper focuses on the study of an ejector used in applications where moist gases are being entrained. In the first part of this work, the gas flow characteristics inside an ejector, as well as the ejector’s performance under various operating and geometric configurations, were studied with a three-dimensional computational model, which was validated against measurement data. In the second part, focus was given to the potential condensation or de-sublimation phenomena that may occur inside an ejector when water vapor is included in the entrained stream. An experiment using light-attenuation method was performed to verify the presence of a second phase, then the onset of phase change and the phase distribution were obtained numerically. A two-dimensional axis-symmetric model was developed based on the model used in the first part. A series of simulations were performed with various amounts of water vapor added into the entrained flow. It was found that both frost particles and water condensate could form inside the mixing tube depending on the operating conditions and water vapor concentrations. When the concentration exceeds 3%, water vapor could condense throughout the mixing tube. Some preliminary results of the second phase particles formed, e.g. critical sizes and distributions, were also obtained to assist with the design and optimization of gas ejectors used in similar applications.