Rotating Cyclic Systems with Order-Tuned Vibration Absorbers
Cyclic Structures Order-Tuned Absorbers Motivation & Background The Linear Problem The Nonlinear Problem Conclusions & Future Work Outline
Order-Tuned Vibration Absorbers –Den Hartog, Denman, Cronin, Shaw, Borowski, Duffy, … Vibration Characteristics of Bladed Disk Assemblies –Ewins, Srinivasan, Griffin, Whitehead, Pierre,… Localization –Pierre, Bajaj, Vakakis, … Linear Cyclic Systems –Pierre, Shapiro, Bajaj, Vakakis, … Nonlinear Cyclic Systems –Bajaj, Vakakis, Coller, King, … Relevant Previous Work
Background Bladed Disk Assemblies
Background Engine Order Excitation
Order Excitation Background
Self-tuning Impact Damper Tuned Dampers Sleeves Chamber & End Caps Turbine Blade
Order-Tuned Vibration Absorbers
Torsional Vibration Reduction
History – Torsional Vibration Reduction Early designs –Sizing, physical arrangement –Linear tuning: local path curvature Implementations –Light aircraft engines, WWII –Helicopter rotors,1980’s –Experimental/racing automotive engines,1990- Path designs for nonlinearities –Cycloids (Madden, 1980), Epicycloids (Denman, 1991), Subharmonic epicycloids (Lee & Shaw, 1995), General paths (Alsuwayian and Shaw, 2001)
Absorber Paths General Path Representation
Absorber Paths Linear Tuning –Frequency of small amplitude motions Circles –Easily manufactured –Strong nonlinear effects, softening, Cycloids –The tautochrone in uniform fields –Weak nonlinear effects, hardening, Epicycloid –The tautochrone in radial fields –Linear absorber motions at all amplitudes,
Mathematical Model Equations of Motion
Mathematical Model Equations of Motion
Mathematical Model
Cyclic Symmetry
The Linearized System Sector Model
The Linearized System System Model – M DOF/Sector
The Linearized System System Model – M DOF/Sector
Circulant Matrices Mathematical Preliminaries
Diagonalization of a Block Circulant Mathematical Preliminaries
The Fourier Matrix
Mathematical Preliminaries The Direct (Kronecker) Product
Linear Vibration (Block) Decoupling the EOM
Linear Free Vibration One DOF/Sector
Linear Free Vibration One DOF/Sector
Linear Free Vibration One DOF/Sector
Linear Forced Vibration Steady-State Response
Linear Forced Vibration Steady-State Physical Response
Linear Forced Vibration Blade Response (Absorbers Locked)
Linear Isolated Absorber Response Absorber Free, Blades Locked
Linear Response N Blades with Absorbers
Linear Response The Effects of Detuning, Weak Coupling (like N=1)
Linear Response The Effects of Detuning, Strong Coupling
Linear Response The Effects of Detuning
Linear Response Frequency Response (zero damping)
Nonlinear Blade Response Strong Coupling Weak Coupling One DOF/Sector (Blades) – Weakly Nonlinear
Nonlinear Blade Response One DOF/Sector (Blades) – Strongly Coupled
Nonlinear Blade Response One DOF/Sector (Blades) – Strongly Coupled
Nonlinear Blade Response One DOF/Sector (Blades) – Strongly Coupled
Nonlinear Blade Response One DOF/Sector (Blades) – Strongly Coupled
Nonlinear Blade Response One DOF/Sector (Blades) – Weakly Coupled
Nonlinear Blade Response One DOF/Sector (Blades) – Weakly Coupled
Nonlinear Blade Response One DOF/Sector (Blades) – Weakly Coupled
Nonlinear Blade Response One DOF/Sector (Blades) – Weakly Coupled
Nonlinear Blade Response One DOF/Sector (Blades) – Weakly Coupled
Nonlinear Blade Response One DOF/Sector (Blades) – Weakly Nonlinear
Linear Blade & Nonlinear Absorber Assumptions and Scaling Goal: Capture nonlinear absorber behavior
Linear Blade & Nonlinear Absorber N Blade/Absorbers, Weak Coupling
Linear Blade & Nonlinear Absorber N Blade/Absorbers, Weak Coupling
Linear Blade & Nonlinear Absorber Weak Coupling
Linear Blade & Nonlinear Absorber
Summary & Conclusions Linear System, Blades & Absorbers: absorber effective, no resonance zone Nonlinear System, Blades Only: traveling wave excitation limits some types of instabilities Nonlinear System, Blades & Absorbers: absorbers can be effective, but nonlinear absorber paths often lead to system resonance
Directions for Future Work Linear System: effects of damping, mistuning Nonlinear System, blades only: post-bifurcation analysis Nonlinear System, blades & absorbers: scaling for tautochronic (linear) absorber path, detailed parameter studies Mistuning: random and intentional – reduction or elimination of symmetry Experiments