Numerical assessment on the performance of two-stage ejector to boost the low-pressure natural gas

Increasing production and recovery from low-pressure natural gas fields in China is highly desirable. A two-stage ejector (TSE) is proposed to deal with this situation. The effect of the second stage geometrical factors (area and length to diameter ratios) on the TSE performance is analyzed through the numerical technique, as well as the operational factors. Results show that the improvement effect becomes larger under relatively larger induced pressure and area ratio. However, choosing a lower area ratio is more suitable because its performance is superior at low induced pressure. An optimal length to diameter ratio exists for the maximum entrainment ratio, and it varies with operational factors. In the present study, it's a good choice when the length to diameter ratio equals to 5. TSE has better entrained capacity compared than single stage ejector, when the primary or induced pressure is higher than the design value. Meanwhile, TSE has better entrained capacity when the pressure of the first stage induced inlet is higher than that of second stage induced inlet.