... the design and development phases are dynamic in nature. These can jeopardize engine certification and lead to major delays and increased program costs. A real challenge is the characterization of damping and the related dynamic behavior of rotating and stationary components and assemblies, and of the fluid...

... damping/forcing to detailed blade geometry changes can be very efficiently obtained by solving equivalently three steadylike adjoint equations. Several case studies are presented to illustrate the validity and effectiveness of this new concurrent approach. A blading shape optimization will typically...

...Pieter Groth; Hans Mårtensson; Niklas Edin Turbines operating at high pressure in high velocity flow are susceptible to flutter. As reduced frequencies become sufficiently low, negative aerodynamic damping will be found in some modes. Ensuring that the total system damping is positive over...

... stiffness and damping while traditional frequency mistuning analysis only perturbs the stiffness. It was found that maximum blade amplitudes are significantly influenced by the perturbation of the imaginary part (damping) of unsteady aerodynamic modal forces. This is contrary to blade frequency mistuning...

... sensible to the addition of small perturbations such as the aerodynamic forces. Since the determination of the aerodynamic vibrational correction (damping and frequency) requires knowing the mode shape, the aerodynamic corrections of the N a − 1 cluster modes are now unavoidably coupled together. Moreover...

... unsteady aerodynamic work will exceed the damping provided by the mechanical bladed-disk system, and blade flutter will occur. Addressing the potential for flutter during design and development is difficult. Simple tests prove inadequate as they fail to reveal the proximity of flutter unless...

... close agreement of the computed and measured resonant peaks. These resonant peaks demonstrate either a fairly linear behavior or a nonlinear one like the jump effect of blade resonance amplitudes, or elastic impacts between the shrouds. Also, the damping performance for different contact configurations...

... of stabilizing damping forces to the work of destabilizing aerodynamic cross-coupled stiffness forces to predict the onset of whirl instability. The MS method thus indicates that unstable or self-excited whirling (sometimes called whipping) at one of the system’s natural frequencies is initiated when...

...B. Ertas; A. Gamal; J. Vance This paper presents measured frequency dependent stiffness and damping coefficients for 12-bladed and 8-bladed pocket damper seals (PDS) subdivided into four different seal configurations. Rotating experimental tests are presented for inlet pressures at 69 bar (1000 psi...

... elements which allow for friction stresses under variable normal load, unilateral contacts, clearances, and interferences. Examples of application of the new approach to the analysis of root damping and forced response levels are given and numerical investigations of effects of contact conditions at root...

... to represent the flow in a nonlinear time-accurate fashion on unstructured meshes of mixed elements. The structural model is based on a standard finite-element representation. The fluid mesh is moved at each time step according to the structural motion so that changes in blade aerodynamic damping and flow...

... neck mouth y = state variables Y f = fuel mass fraction Z = acoustic impedance normalized by ρ c α = acoustic damping coefficient γ = specific heat ratio Γ = plane wave attenuation factor ζ = pressure loss coefficient...

... 2004 01 October 2003 01 March 2004 09 02 2005 vibrations damping finite element analysis discs (structures) nonlinear equations turbines mechanical contact Blade mistuning is inevitable in practical bladed disks and is usually caused by small imperfections...

... to superimpose different rotor upstream gap effects and rotor downstream gap effects on the middle row rotor aerodynamic damping. In addition, a gap influence coefficient approach has been developed for investigation of all the possible gap spacing combinations of M upstream stator-rotor gaps and N downstream...

..., “A Rational Method for Optimizing Shroud Damping,” ASME Paper 96-GT-402. Sanliturk , K. Y. , Imregun , M. , and Ewins , D. J. , 1997 , “ Harmonic Balance Vibration Analysis of Turbine Blades With Friction Dampers ,” ASME J. Vibr. Acoust. , 119 , pp. 96 – 103 . Yang , B.-D...

... damping, or control authority of aeromechanical feedback stabilization. They indicate that the phase between the pressure disturbances and the actuation is central to assess the impact of aeromechanical interactions on compressors stability. Based on the present development of models and metrics...

.... Manuscript received by the IGTI December 2002; final revision March 2003. Paper No. 2003-GT-38475. Review Chair: H. R. Simmons. 16 June 2003 01 December 2002 01 March 2003 26 03 2004 friction time-domain analysis vibrations mechanical contact damping numerical analysis...

..., and thus should be avoided by designing sufficiently rigid structures to prevent casing ovalization or other structurally induced variations in tip clearance. Control authority, a metric developed in the first part of this paper, provided a useful interpretation of the aeromechanical damping of the coupled...

... presents predicted and measured dynamic characteristics, demonstrating how a clearance, which diverges axially from inlet to outlet, increases the maximum effective damping of a honeycomb-stator seal, even though the average clearance is increased. The results also show a strong negative direct stiffness...

...R. M. Mathison; M. G. Dunn; M. M. Weaver; A. Dushko Air film damping systems have attracted considerable interest within the gas turbine industry because of their effectiveness at controlling modes of vibration without environmental limitations. Though still in the early stages of development, air...