Gas Supersonic Ejector Performance with Droplet Injection: a combined CFD and Thermodynamic modelling approach

摘要

The variations in limiting pressure and efficiency of supersonic ejectors when droplets are injectedin the vapour core before the diffuser were assessed numerically. Results of a CFD and athermodynamic model were used for a combined global and local perspective. In comparison withexperimental data of a R134a ejector under typical refrigeration conditions, the CFD model predictsthe double-choke entrainment ratio with an accuracy of 5% and the thermodynamic model has adeviation of about 18% (Resp. 2.5%) in terms of double-choke entrainment ratio (Resp. limitingpressure). Both models are in excellent agreement in terms of pressure, Mach number andtemperature internal profiles. Results show that, for an injection fraction of 10%, the peak pressurein the shock train is reduced by 31%. Nonetheless, the net effect is a reduction of the exergycontained in the main gas as other factors (e.g.: lower main gas temperature) are introduced.