High-speed centrifugal blower for experimental aeroacoustics

自达·芬奇观察到旋涡脱落以来，旋涡脱落现象一直是研究的主题。在横流中，钝体周围的边界层发生分离，从而产生旋涡脱落。边界层分为两个剪切层，它们在近场中拖曳和卷曲，形成周期性的涡街。在包含诸如圆柱体的钝体的管道的情况下，当涡流脱落频率与该管道的声学自然频率之一重合时，可能出现反馈周期，其中涡流脱落充当声源并激励声学驻波，该驻波反过来增强了剥落过程，从而产生了强烈的声学共振。这一过程被称为流激声学共振。在许多工程应用中，如换热器和锅炉的管束、压气机叶片的叶栅以及管道和径向扩散器中的导向/转动叶片，都会遇到含有钝体的管束，这些不利的运行条件可能会导致涡流脱落频率与管道的一种声学固有频率重合。这通常会导致流动激励的声学共振，并产生严重的噪声问题和/或过度振动。由于这一现象尚未被完全了解，它可能是危险的不可预测的，并可能导致发电和运输等许多应用中的灾难性故障。申请人在这方面的研究的主要目的是了解流动激励的声学共振的反馈周期。这需要在类似于上面提到的流动结构中产生自激声学共振。然而，除非气流速度足够高，以克服声学衰减造成的损失，否则不会发生自激声共振。这只能使用所要求的离心式鼓风机系统来实现，该系统能够在10英寸(25.4厘米)乘10英寸(25.4厘米)的横截面上产生速度高达220米/S的气流。

The vortex-shedding phenomenon has been a subject of research since it was observed by Leonardo da Vinci. Vortex shedding occurs due to the boundary layer separation around bluff bodies in cross-flow. The boundary layer separates into two shear layers that trail and roll-up in the near field forming a periodic vortex street. In the case of a duct containing a bluff body such as a circular cylinder, when the vortex shedding frequency coincides with one of the acoustic natural frequencies of the duct, a feedback cycle may occur where the vortex shedding acts as a sound source and excites an acoustic standing wave which, in turn, enhances the shedding process and thereby creates a strong acoustic resonance. This process is known as flow-excited acoustic resonance. In many engineering applications where ducts containing clusters of bluff bodies are encountered, such as tube bundles of heat exchangers and boilers, cascades of compressor blades and guide/turning vanes in ducts and radial diffusers, unfortunate operating conditions could lead to a coincidence between the vortex shedding frequency and one of the acoustic natural frequencies of the duct. This often leads to flow-excited acoustic resonance and the generation of acute noise problems and/or excessive vibrations. Since this phenomenon is not yet fully understood, it can be dangerously unpredictable and may cause catastrophic failures in many applications such as power generation and transport. The main objective of the applicant's research in this area is to understand the feedback cycle of the flow-excited acoustic resonance. This requires the generation of a self-excited acoustic resonance in flow configurations similar to those mentioned above. However, the self-excited acoustic resonance will not materialize unless the flow velocity is sufficiently high to overcome the losses due to acoustic damping.This can only be achieved using the requested centrifugal blower system, which is capable of producing air flow with a velocity as high as 220 m/s in a cross-section area of 10 inch (25.4 cm) by 10 inch (25.4 cm).