Acoustic Excitation of Turbomachinery Blisks

Aircraft turbine
Aircraft turbine

During operation, rotor blades of aircraft turbines are subject to high dynamic forces introduced by the working fluid. To assess the structural health of the blades, dynamic analyses are carried out in rotating and stationary operating conditions in the lab. Especially for stationary tests, it is crucial to artificially replicate the typical excitations acting on the rotor blades during operation, known as engine order excitation. A software package designed by m+p international enables engineers to generate an engine order excitation and analyze the dynamic responses of the turbomachinery blisks in the safety of the laboratory.

Simplified bladed disks (blue) with pressure field (gray) representing three engine order excitations

Measured time history (a) at each blade tip under excitation with engine order 3 at 1,200 Hz. Phase-referenced spectra (b) of the blade responses in the frequency range from 1,180- 1,220 Hz
Measured time history (a) at each blade tip under excitation with engine order 3 at 1,200 Hz
Phase-referenced spectra (b) of the blade responses in the frequency range from 1,180 - 1,220 Hz

In his article, Dr. Sebastian Schwarzendahl, product manager with m+p international, describes acoustic excitation using loudspeakers, which is well suited for excitation frequencies above 1,000 Hz. The experimental setup was developed together with the Institute of Dynamics and Vibration Research (IDS) at Leibniz Universität Hannover, Germany, and is used in several scientific research projects.

The experimental setup at IDS consists of a simplified bladed disk with 10 blades. In the center, the blisk is clamped on a vibration isolation table. Loudspeakers are mounted on a rigid plate and placed beneath each blade. Acoustic amplifiers are used to drive the loudspeakers. The input signals (excitation) are generated using m+p VibRunner hardware. Multiple m+p VibRunner chassis may be combined into a single multichannel system, providing high output and input channel counts.

Read more in the 3-page article “Acoustic excitation of turbomachinery blisks”, Aerospace Testing International Showcase 2018.

 

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