挂架科恩达效应对发动机喷管射流干扰数值研究

The jets of the engine fan and core nozzles form coaxial temperature and velocity shear layers, and induce flow phenomena such as shock wave reflection and shock wave/shear layer interaction. Coanda effect occurs when the pylon presents in or near the jets. A series of bad effects can be brought by the Coanda effect, such as the jet directions of the fan and core nozzles are changed, the topology of the shear layers is destroyed, the thrust loss of engine is increased, and the noise distribution is altered. This project is aiming at the fluid phenomena and effects introduced by the Coanda effect between the engine nozzle jets and pylon. The flow model will be simplified as coaxial jets and a wedge-like object. By developing and applying advanced Computational Fluid Dynamics (CFD) methods, the complicated fluid phenomena coupled with Coanda effect, shock wave, expansion wave and shear layer will be numerically investigated. The flow topology will be analyzed and depicted, and the fluid structure and mechanism will be studied. An analytical model is expected to be constructed to describe the thrust loss mechanism. The shape parametrical study of the wedge-like object will be conducted to analyze its effects on the thrust loss. Suggestions and guidance will be proposed for the engine/pylon integrated design.

发动机内外涵道喷管形成温度和速度分层的同轴射流，具有激波反射、激波/剪切层干扰等流动现象。挂架与射流的干扰还会诱发科恩达效应，引起一系列不利影响，如导致内外涵道的射流方向发生改变，剪切层拓扑被破坏，发动机推力减小，噪声场分布改变。本申请着眼于发动机喷管射流与挂架之间因科恩达效应产生的流动现象及其效应研究。将流动模型化为同轴射流与楔形物的干扰问题，发展并应用先进的CFD方法，数值模拟科恩达效应、激波、膨胀波、剪切层等共同形成的复杂流动现象，建立流动拓扑描述，研究其内在的流动结构与机理。建立流动模型，分析推力损失的机制，分析楔形物几何参数对推力损失影响关系，为飞机的发动机/挂架设计提供理论参考和依据。

发动机内外涵道喷管形成温度和速度分层的同轴射流，具有激波反射、激波/剪切层干扰等流动现象。挂架与射流的干扰还会诱发科恩达效应，引起一系列不利影响，如导致内外涵道的射流方向发生改变，剪切层拓扑被破坏，发动机推力减小，噪声场分布改变。本申请着眼于发动机喷管射流与挂架之间因科恩达效应产生的流动现象及其效应研究。发展并采用先进的WE-RANS/LES 方法模拟高速射流流场，以较小的代价提供更为准确、详尽的流场结构和非定常脉动信息。数值模拟科恩达效应、激波、膨胀波、剪切层等共同形成的复杂流动现象，研究其内在的流动结构与机理，对巡航飞行状态下挂架科恩达效应对高速射流干扰引起的推力损失和噪声影响分析提供理论依据。同时获得几何参数的影响规律，为挂架设计提供技术参考。