内涵喷管关键几何参数对巡航工况超大涵道比短舱气动性能的影响研究

To reduce fuel consumption， pollution emissions， and aerodynamic noises further， the civil turbofan develops toward ultra-high bypass ratio （UHBPR）. The increase of drag and weight of the nacelle caused by increasing engine size will decrease or counteract even the benefits brought by increasing the bypass ratio. To improve nacelle aerodynamic performance further， the overall performance parameter of the inlet， cowl， and exhaust system was defined firstly. And the influence of key geometric parameters of the core nozzle on the aerodynamic performance of the UHBPR nacelle was conducted and the related flow mechanism was analyzed. The results show that the contraction ratio of the core cowl and the length-diameter ratio of the core nozzle have an obvious effect on the engine thrust loss caused by the UHBPR nacelle and the maximum variation of thrust loss is 10.77% and 13.40% respectively. The smaller contraction ratio of the core cowl and the length-diameter ratio of around 0.9 are favourable for decreasing the thrust loss. The change of the contraction ratio of the core cowl， the length-diameter ratio， and the core nozzle exit angle can affect the issues including the Mach number before the shock wave， the location and strength of the shock wave， and shock wave-boundary layer interaction. In addition， the geometric parameter above can affect pressure distribution around the plug， and the Mach number distribution on the core nozzle exit plane. As a result， the thrust of the core cowl， the plug， and the core nozzle is affected significantly. The fan nozzle is supercritical and the core nozzle is subcritical at cruise condition， so the geometric parameters of the core nozzle will affect the mass flow rate and thrust of the core nozzle but the performance of the fan nozzle. The variation of the core nozzle mass flow rate could change the mass flow rate of the engine and affect the ram drag， additional drag and cowl drag further.