Research on the ejection performance of an ejector with low pressure and back pressure

This study investigates the influence of back pressure on the mass ejection coefficient (u) of low-pressure methane-air ejectors through a combined approach of one-dimensional mathematical modeling and computational fluid dynamics (CFD) simulations. By establishing a quadratic relationship between u and back pressure (h_c), we reveal three distinct operational regimes: a slow growth phase, a rapid escalation phase, and a critical degradation phase. CFD results validate the theoretical model with a coefficient of determination (R²) of 0.9941 in the quadratic region. A key finding is the identification of a linear correlation between the critical back pressure (h_c,crit) and nozzle pressure (h_n), expressed as h_c,crit = - 0.0629 h_n + 0.8966 Pa. This work provides actionable guidelines for optimizing ejector geometry and operating conditions in residential gas appliances.