The numerical analysis of the effect of geometrical factors on natural gas ejector performance

Supersonic ejectors are applied to increase production and recovery from mature oil and gas fields. Compared to compressors, natural gas ejectors are a cost-effective way to boost the production of low pressure natural gas wells. In this study, two main ejector geometrical factors, the primary nozzle exit position (NXP) and the mixing tube length to diameter ratio (R), are investigated based on the CFD technique. Additionally, these two geometrical factors are proved to be influential factors with respect to ejector performance, including not only the entrainment ratio but also the pressure ratio. The numerical results show that the optimum NXP for the entrainment ratio varies from 3.6 to 7.2 mm, but for the pressure ratio, it is in the range of 1.2–7.2 mm. The optimum value R decreases with increasing primary flow pressure, and the optimum R for the entrainment ratio varies from 2 to 8, but for the pressure ratio, it is in the range of 3–7. The CFD technique is found to be an effective performance predictor and also provides an insightful understanding of the flow and mixing process within the ejector. This study may provide a beneficial reference for the design of supersonic ejectors and may be helpful for further applications in boosting natural gas production.