Fundamental investigation on the impact of a swirling through-flow in a rotating cavity on the formation of acoustic modes

• Applicant: Professor Dr.-Ing. Dieter Brillert
• Subject Area: Hydraulic and Turbo Engines and Piston Engines
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429153912

Impeller side clearances in turbomachines usually are confined by the outer walls of the hub and the shroud disk of the radial impeller and the inner walls of the casing. The rotor stator cavities are filled with fluid and because of a leakage at the seals there is a through-flow radial inward or radial outward depending on the operating conditions of the machine. Beside the complex flow structure in the side cavities pressure fluctuations occur which excite the fluid volume to vibrations. The existing coupling of the fluid and the disk structure leads to vibrations of the disk which are able to provoke considerable damage at the disks. Particularly in case of high pressure and a corresponding high density of the fluid the excited vibrations can be harmful. In addition, the existing flow structure and the fluid parameters have a strong impact on the development of acoustic modes in the cavities and influence the vibration characteristic of the impeller disks significantly.The acoustic excitation of the fluid and the disk will be reproduced in this project in a specially raised test facility and the impact of disk rotation, amount of through-flow, through-flow direction and cir-cumferential velocity component of through-flow on the formation of acoustic modes will be investi-gated experimentally. The available generic test facility is essential for specification of the boundary conditions for the tests which shape the vibration behavior. In order to reach the target of investigat-ing basic phenomena it is important to use a disk geometry which is not subject to the technical re-quirements of a hub or a shroud disk of a turbomachine. Supporting the aspired basic research the disk should be approximated by a flat surface and the casing should be realized flat and without any rims as well. In this way an “academic” rotor stator cavity is generated. In this way the gained basic findings can be adopted not only for turbomachines but can contribute to a general understanding of the vibration behavior of a disk in a fluid filled cavity excited by acoustic pressure fluctuations.

• DFG Programme: Research Grants