An extended mechanism model of gaseous ejectors

Abstract

An accurate and convenient theoretical model on ejector is valuable to the performance analysis and structure design. To address the problem, the paper develops an extended mechanism model with merely five parameters (four velocity coefficients and an area ratio characterizing the second limit state) under the hypothesis of ideal gas for gaseous ejectors to reveal the working characteristics. The paper discovers that the choking of the primary flow in the motive nozzle is a requisite of the double-choking theory and the physical realizable prerequisites are specifically proposed for the normal operation and performance analysis of the whole ejector. Model validation and performance comparison against existent models including the Sokolov-Zinger model, simplified constant-pressure mixing model, and compound-choking based real gas thermodynamic model have demonstrated its feasibility, compatibility and superiority. Moreover, the analytical whole-operating-condition characteristics coincide fairly well with the experimental data from added platform bench tests. The mean relative error (MRE) of the primary mass flowrates is −5.72% (±0.39%). The MREs of the entrainment ratios are 0.37% (±1.00%) while up to 5.05% (±12.58%) at the critical and subcritical modes, respectively. The research results can provide effective theoretical guidance on characteristic analysis and geometric design.