Design, Fabrication, and Experimental Evaluation of a Centrifugally-Tuned Passive Balancer
Open Access
- Author:
- Lay, Kenjiro
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 06, 2023
- Committee Members:
- Jose Palacios, Thesis Advisor/Co-Advisor
Puneet Singla, Committee Member
Amy Pritchett, Program Head/Chair
Jacob Willem Langelaan, Committee Member - Keywords:
- Passive Balancing
Balancer
Rotor
Rotorcraft
Structural Dynamics
Dynamics
Vibration
Vibration Suppression - Abstract:
- Passive balancing systems have been shown to counter mass eccentricity in a rotary system, lowering vibration amplitudes. Such systems reduce vibration between the first two natural frequencies of the system (i.e., in the supercritical regime). In subcritical operations (i.e., below the first fundamental frequency), the balancing masses move to the location of the imbalance, degrading performance and increasing the vibration amplitude of the system. To mitigate the lack of performance of a passive balancing system pre-resonance, it is suggested to lock the balancing masses in place until the system is spinning faster than its critical speed. In this study, a balancer with a clamping mechanism, capable of preventing balancing mass movements prior to the supercritical operation, was designed, fabricated, and experimentally evaluated. By using springs under centrifugal loading to clamp and release the balancing masses, the system is thought to be passive, needing no external influence to operate other than its rotational speed. The balancer achieves two configurations: conventional (where the clamps are fully retracted) and clamp (where the clamps are fully engaged). The experiments in this work use a rotating shaft with a critical speed of 720 RPM. The pre-resonance subcritical and supercritical steady state speeds used were 480 RPM and 1500 RPM. Centrifugal clamps were designed to release the balancing masses at 1000 RPM. It was shown that the balancer in its conventional configuration increased the subcritical vibration amplitude by 45%, whereas supercritical amplitude decreases by 84%. With the introduction of centrifugal clamping of the balancing masses pre-resonance, normalized subcritical performance was improved by 104%, since the masses were locked in their optimal balancing position. The centrifugal clamps prevented the movement of the masses in subcritical operation, eliminating unwanted vibrations. The centrifugal clamps reliably released masses during supercritical operation where the masses were shown to assume their optimal balancing position, thus performing on par with the conventional configuration. During spin down from supercritical speeds, the inertia of the masses prevents them from being clamped in the optimal balancing position.