Application Cases

Experiment Name: Dynamic Torque Excitation and Rotor Bending-Torsional Coupled Vibration Experiment

Experiment Content: Dynamic torque excitation is applied to a rotating rotor while monitoring its bending vibration. The experiment aims to observe and analyze whether the rotor exhibits combined frequency vibrations in the bending direction that are associated with the frequency of the dynamic torque excitation, in order to verify the imbalance bending-torsional coupling effect.

Research Direction: Dynamic Torque Excitation, Bending-Torsional Coupled Vibration

Testing Equipment: ATA-309C power amplifier, double-disc coupling, torsional exciter, signal generator, etc.

Experiment Process:

Figure: Real Photo of the Experiment

At the end of the experimental rotor system, a double-disc coupling, torsional exciter (brushed DC motor), power amplifier, and signal generator are added. The signal generator outputs a signal composed of a superposition of sinusoidal voltage and DC voltage signals, i.e., an AC+DC signal. The signal is input into the power amplifier, which then outputs an amplified voltage. The amplified DC voltage component is used to counteract the electromotive force generated by the torsional exciter (DC motor) being driven by the rotor, while the amplified sinusoidal voltage is used to create a fluctuating torque. This torque is transmitted through the coupling to the single-disk mid-span rotor, causing torsional vibration.

In the experiment, with a constant rotational speed and appropriate DC voltage signal and amplification factor, the signal generator outputs a frequency-sweeping sinusoidal voltage signal superimposed in a certain frequency range, achieving frequency-sweeping torque excitation of the rotating rotor. Displacement sensors are used to monitor the lateral vibration of the rotor, and torque sensors are used to monitor the torque fluctuations in the shaft system.

Experimental Results:

Figure: Time-Domain Signal Plot

Figure: Lateral and Torsional Waterfall Plots

1. The time-domain signal plot indicates that the shaft system exhibits dynamic frequency-sweeping torsional vibration, and the amplitude of the lateral displacement of the rotor disk changes with the frequency of the torsional excitation.

2. The waterfall plot obtained from the time-domain signal shows that, first, due to the application of frequency-sweeping torsional excitation to the rotor system, a torsional frequency line ωt appears in the torsional waterfall plot. Secondly, and more importantly, the bending vibration exhibits combined frequency response lines ω+ωt and ω-ωt symmetrically distributed around the rotational frequency line ω, which is consistent with the theoretical research conclusions on bending-torsional coupling. Thirdly, when these combined frequencies coincide with the bending mode frequencies, the corresponding combined response amplitudes reach their peaks, indicating that the combined frequencies can excite resonance.

Power Amplifier Recommendation: ATA-309C Power Amplifier

Figure: Specification Parameters of the ATA-309C Power Amplifier