Performance analysis and optimization of a steam ejector through streamlining of the primary nozzle

Abstract A steam ejector uses high-pressure vapor as the power for operating in steam cycles. The ejector geometry and pressure of the motive flow significantly influence its performance. Here, a steam ejector used in a distilled water preparation system for medical injection was numerically studied to improve its performance under insufficient motive source, in the meantime, to guarantee its high efficiency under the designed motive pressure of 6.0 bar. Owing to the temporary insufficiency of the motive pressure of around 4.5 bar in a specific time period, the most convenient and inexpensive approach was to fine-tune the primary nozzle and replace it with no further changes in the ejector structure. Fifteen streamline nozzle profiles were established and the performance effect of the different structures is discussed. The entrainment ratio of the ejector with a streamlined nozzle could reach up to 19.79% and 8.04% higher than the original one under the motive pressures of 4.5 and 5.5 bar, respectively. In addition, their performance was similar under a designed motive pressure of 6.0 bar. The proposed ejector extends the high efficiency operating range of the on-site steam ejector and the results may contribute to the streamline ejector design.