Investigation On Pumping Performance Of Non-Axisymmetric Supersonic Ejector

The ventilation system is set up in the lubricating oil system for the turbofan engine.It ensures the lubricating oil chamber properly works to prevent the leakage of lubricating oil.The axial ventilation system in which the core component is an efficient ejector is a kind of ventilation equipment.Due to size limitation and the need for discharging out a small amount of residual oil in lubricating oil chamber,ejector is generally designed as non-axisymmetric structure.Aiming at a specific non-axisymmetric supersonic ejector in a turbofan engine,the pumping performance is numerically and experimentally investigated in the current study.The influence of aerodynamic and structural parameters is analyzed to provide reference for the ejector design.The FLUENT software was used to simulate the asymmetric supersonic ejector.Holding on the aerodynamic parameters,the influence of throat area ratio,length-diameter ratio and convergent degree on performance of ejector was studied numerically.The influence of primary-secondary flow pressure ratio,temperature ratio and compression ratio on ejection performance of ejector was studied numerically under the same structure condition.The results indicate that under certain boundary conditions,the pumping ratio increases first and then decreases with the increase of the throat area ratio.The shock wave just does not appear at the outlet of the straight section while the pumping ratio is maximum,The influence of length-diameter ratio and convergent degree on pumping ratio is the same as that of throat area ratio,but the effect of throat area ratio is the most significant among them.The pumping ratio increases first and then decreases with the increase of the primary and secondary flow pressure ratio.The pressure difference between the upper and lower walls at the entrance and exit of the straight section is greater with the increase of pressure ratio.The pumping ratio increases gradually and the mixing length of primary and secondary flow decreases with the increase of temperature ratio.The pumping ratio decreases with the increase of the compression ratio.The pumping ratio decreases significantly when the compression ratio reaches a certain value.Besides the numerically analysis,experimental tests were performed for a certain ejector model.The effects of pressure ratio,temperature ratio,compression ratio and primary nozzle position on the pumping performance were experimentally analyzed.The results indicate that the factors mentioned above have similar influence rules with that from CFD results.A pumping ratio formula in function of geometrical and aerodynamical parameters is fitted according to the data from numerical simulations and experiments.The relationship between pumping ratio and various variables is well described by the formula.