Turbofan engines are one of the most popular propulsion systems used in commercial aircraft due to their high thrust and good fuel efficiency. To reduce noise generated from turbofan engines-powered aircraft, a number of control approaches have been developed. The dominant noise sources include the fan and the high-speed ‘hot’ and ‘cold’ jet. In engineering applications, the noise control approaches include: 1) active control, 2) geometric shape optimization, and 3) passive control (including acoustic boundary control). Because they are considered the most reliable and effective noise reduction methods, the geometric shape optimization and passive control are preferable by the engine manufacturers. In this work, we briefly overview the noise reduction technologies that have great potential to be applied or implemented on turbofan engines. The research and development progress made on the active control, passive control, and geometric shape optimization are reviewed and discussed, aiming to provide an useful guidance on next-generation low-noise turbofan engines. The fundamental noise damping mechanisms of thermos-viscous and vortex shedding are finally overviewed via cases studies.

涡扇发动机因其高推力和良好的燃油效率而成为商用飞机中最流行的推进系统之一。为了减少由涡轮风扇发动机驱动的飞机产生的噪音，已经开发了许多控制方法。主要噪声源包括风扇和高速“热”和“冷”射流。在工程应用中，噪声控制方法包括：1）主动控制，2）几何形状优化，3）被动控制（包括声学边界控制）。因为它们被认为是最可靠和最有效的降噪方法，所以几何形状优化和被动控制受到发动机制造商的青睐。在这项工作中，我们简要概述了在涡扇发动机上具有巨大应用或实施潜力的降噪技术。对主动控制、被动控制、几何形状优化等方面的研究和开发进展进行了回顾和讨论，旨在为下一代低噪声涡扇发动机提供有益的指导。最后通过案例研究概述了热粘性和涡旋脱落的基本噪声阻尼机制。