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Keywords: damping
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Journal Articles
Article Type: Research Papers
J. Turbomach. January 2011, 133(1): 011021.
Published Online: September 23, 2010
... 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. Blade geometry and flow field (mach number...
Journal Articles
Article Type: Research Papers
J. Turbomach. January 2010, 132(1): 011010.
Published Online: September 16, 2009
...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...
Journal Articles
Article Type: Research Papers
J. Turbomach. October 2009, 131(4): 041008.
Published Online: July 2, 2009
... 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...
Journal Articles
Article Type: Research Papers
J. Turbomach. April 2009, 131(2): 021016.
Published Online: January 29, 2009
... 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...
Journal Articles
Article Type: Research Papers
J. Turbomach. January 2009, 131(1): 011009.
Published Online: October 17, 2008
... 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...
Journal Articles
Article Type: Research Papers
J. Turbomach. January 2008, 130(1): 011002.
Published Online: December 14, 2007
... 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...
Journal Articles
Article Type: Research Papers
J. Turbomach. October 2007, 129(4): 724–729.
Published Online: August 29, 2006
... 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...
Journal Articles
Article Type: Technical Papers
J. Turbomach. October 2006, 128(4): 725–737.
Published Online: February 1, 2006
...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...
Journal Articles
Article Type: Technical Papers
J. Turbomach. April 2006, 128(2): 403–410.
Published Online: September 28, 2005
... 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...
Journal Articles
Article Type: Technical Papers
J. Turbomach. April 2007, 129(2): 412–420.
Published Online: June 3, 2005
... 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...
Journal Articles
Article Type: Technical Papers
J. Turbomach. April 2005, 127(2): 372–379.
Published Online: May 5, 2005
... abatement damping modal analysis acoustic field combustion finite element analysis transfer functions acoustic pulses flames acoustic intensity acoustic wave velocity In gas turbines operating with lean premix flames, the suppression of acoustic pulsations is an important...
Journal Articles
Article Type: Technical Papers
J. Turbomach. January 2005, 127(1): 128–136.
Published Online: February 9, 2005
... 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...
Journal Articles
Article Type: Technical Papers
J. Turbomach. July 2005, 127(3): 589–598.
Published Online: January 10, 2005
... 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...
Journal Articles
Article Type: Technical Papers
J. Turbomach. October 2004, 126(4): 654–662.
Published Online: December 29, 2004
..., linear and nonlinear forces and external, excitation forces. The linear forces usually comprise inertia forces, elastic deformation forces, and viscous damping or material damping forces. Nonlinear forces considered here are forces of nonlinear interaction at the contact interfaces. The linear forces...
Journal Articles
Article Type: Technical Papers
J. Turbomach. January 2004, 126(1): 52–62.
Published Online: March 26, 2004
... 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. See Haynes 11 for impact of choice of loading distribution...
Journal Articles
Article Type: Technical Papers
J. Turbomach. January 2004, 126(1): 184–192.
Published Online: March 26, 2004
... surfaces where the fixed restraints are imposed on all displacements. The patch where the shrouds can contact, and friction and normal interaction forces appear is marked in Fig. 15 ( b ) in dark gray. Vibrations are excited by forces applied to one of the blades at its tip. The damping loss factor...
Topics: Friction, Stress
Journal Articles
Article Type: Technical Papers
J. Turbomach. January 2004, 126(1): 63–72.
Published Online: March 26, 2004
..., 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...
Journal Articles
Article Type: Technical Papers
J. Turbomach. October 2006, 128(4): 717–724.
Published Online: March 1, 2004
... 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...
Journal Articles
Article Type: Technical Papers
J. Turbomach. July 2005, 127(3): 557–563.
Published Online: March 1, 2004
...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...
Journal Articles
Article Type: Technical Papers
J. Turbomach. January 2007, 129(1): 72–83.
Published Online: March 1, 2004
...Roque Corral; Juan Manuel Gallardo; Carlos Vasco The aerodynamic damping of a modern low pressure turbine bladed-disk with interlock rotor blades is compared for the first time to that obtained when the rotor blades are welded in pairs through the lateral face of the shroud. The damping is computed...