Simulation Research on Ejector for Natural Gas Engine with High Exhaust Gas Recirculation Rate

In view of engine knock, a technical solution was proposed to achieve a natural gas engine with a high exhaust gas recirculation (EGR) rate by utilizing a zero-power consumption ejector. Firstly, the structural parameters of the ejector were designed and calculated under specified operating conditions. Subsequently, the ejector simulation model was established, and the model was verified using experimental data. Furthermore, the ejection performance variations of the ejector with structural parameters were analyzed, and the influence of structural parameters on ejection performance was obtained. Lastly, a novel sensitivity evaluation index for structural parameters was introduced to examine the extent of their influence on ejection performance. The results show that as the length of the mixing section and the diffuser section increase, the entrainment coefficient (μ) increases. Conversely, as the diameter of the mixing section (d₃), the angle of the diffuser section (θ_s), and the distance from the nozzle outlet to the mixing section (L_NXP) increase, μ increases first and then decreases. The maximum value of μ is observed at d₃ = 46.1 mm, θ_s = 4°, and L_NXP = 57.33 mm, respectively. Among the structural parameters, d₃ exhibits the most significant influence on μ, with a corresponding sensitivity index of 0.88. However, L_NXP had the least impact on μ, with a sensitivity index of 0.05.