Aerodynamic damping of vibrations in rotor blades

1986 ◽  
Vol 80 (3) ◽  
pp. 997-997
Author(s):  
Brian Barry ◽  
Christopher Freeman
Keyword(s):  
Rotor Blades ◽  
Aerodynamic Damping ◽  
Damping Of Vibrations

Influence of Stagger Angle Variation on Aerodynamic Damping and Frequency Shifts

2007 ◽  
Author(s):  
I. Sladojevic´ ◽  
A. I. Sayma ◽  
M. Imregun
Keyword(s):  
Structural Properties ◽  
Natural Frequencies ◽  
Rotor Blades ◽  
Angle Variation ◽  
Frequency Shifts ◽  
Aerodynamic Damping ◽  
Aerodynamic Loading ◽  
Aeroelastic Model ◽  
Aero Engine ◽  
Stagger Angle

The paper presents the results of a study focusing on aerodynamic non-uniformities and their effect on frequency and damping variations. Small tolerances of stagger angle or camber can affect the aerodynamic loading of rotor blades, without significantly altering the structural properties. This investigation looks into the degree of change of natural frequencies and damping of the aeroelastic model caused by blade stagger angle variations. The model used in the study is a simplified aero-engine fan model. The investigation involved three different patterns at two operating speeds. The results suggest that damping in a mis-staggered structure is more prone to variation than frequencies.

Interaction of Concurrent Forced Response and Flutter Phenomena in a Compressor Stage

2017 ◽  
Author(s):  
Zhiping Mao ◽  
Robert E. Kielb
Keyword(s):  
Excitation Frequency ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Rotor Blades ◽  
Single Frequency ◽  
Response Frequency ◽  
Unsteady Pressure ◽  
Aerodynamic Damping ◽  
Frequency Domain Methods ◽  
The Impact

This paper studies a subsonic compressor case with concurrent forced response and flutter by using the Harmonic Balance method, and was inspired by historical experimental data. Forced response was observed when the rotating speed was approaching a crossing on the Campbell diagram, where flutter appeared to be suppressed. CFD simulations are conducted by using a quasi-3D configuration at the mid-span of one stage of a 3.5-stage compressor. Due to the constraint of frequency domain methods, the research is conducted in the vicinity of the 1T-44EO crossing with a small frequency shift between flutter frequency and external excitation frequency. The influence from flutter to forced response is observed: a one-way crosstalk at forced response frequency is observed, presented as the anomaly of unsteady velocity and unsteady pressure near the rear section of rotor blades and in the rotor wake region. The anomaly is speculated as the presence of increasing intensity of shedding vortices induced by the vibration of the blade. To further prove the impact of this viscous effect, a numerical experiment was performed with inviscid rotor blades. In contrast to the crosstalk at forced response frequency, no obvious influence on the unsteady behavior is detected at the flutter frequency, and this observation is confirmed at multiple vibration amplitudes. Considering the relationship between unsteady pressure at flutter frequency and aerodynamic damping, we conclude the influence of forced response on the aerodynamic damping is negligible. In addition, a linearity of unsteady pressure at the flutter frequency vs. vibration amplitude is uncovered. The discoveries provide a proof to linearity assumption and single-frequency simplification widely adopted by industry in flutter simulations.

Aeroelastic Stability of Welded-in-Pair Low Pressure Turbine Rotor Blades: A Comparative Study Using Linear Methods

2004 ◽  
Vol 129 (1) ◽  
pp. 72-83 ◽  
Author(s):  
Roque Corral ◽  
Juan Manuel Gallardo ◽  
Carlos Vasco
Keyword(s):  
Stokes Equations ◽  
Low Pressure ◽  
Rotor Blades ◽  
Mode Shapes ◽  
Bladed Disks ◽  
Aerodynamic Damping ◽  
Low Pressure Turbine ◽  
Bladed Disk ◽  
Stabilizing Effect ◽  
First Time

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 solving the linearized Reynolds averaged Navier-Stokes equations on a moving grid. First the basics of the stabilizing mechanism of welding the rotor blades in pairs is investigated using two-dimensional analyses and the Panovsky and Kielb method. It is concluded that the stabilizing effect is due to the suppression of unsteady perturbations in one out of the two passages providing for the first time a physical explanation to engine data. Three-dimensional effects are then studied using the actual mode shapes of two bladed disks differing solely in the shroud boundary conditions. It is concluded that the increase in the aerodynamic damping, due to the modification of the mode shapes caused by welding the rotor blades in pairs, is smaller than that due to the overall raise of the reduced frequencies of a bladed disk with an interlock design. The modification of the flutter boundaries due to mistuning effects is assessed using the reduced order model known as the Fundamental Mistuning Model. A novel extension of the critical reduced frequency stability maps accounting for mistuning effects is derived and applied for both, the freestanding and welded-in-pair airfoils. The stabilizing effect of mistuning is clearly seen in these maps. Finally, the effect of mistuning on low-pressure-turbine bladed disks is studied. It is shown that the modification on the stability limit of the interlock bladed disk is negligible, while for the welded-in-pair configuration a 0.15% increase of the damping relative to the critical damping is found. This qualitative difference between both configurations had not been reported before.

Calculating the aerodynamics of vertical axis wind turbines

2012 ◽  
Vol 34 (3) ◽  
pp. 169-184 ◽  
Author(s):  
Hoang Thi Bich Ngoc
Keyword(s):  
Wind Turbine ◽  
Incidence Angle ◽  
Vertical Axis ◽  
Rotor Blades ◽  
Vertical Axis Wind Turbine ◽  
Horizontal Axis Wind Turbine ◽  
Velocity Triangle ◽  
Relationship Of ◽  
The Relationship

Vertical axis wind turbine technology has been applied last years, very long after horizontal axis wind turbine technology. Aerodynamic problems of vertical axis wind machines are discussible. An important problem is the determination of the incidence law in the interaction between wind and rotor blades. The focus of the work is to establish equations of the incidence depending on the blade azimuth, and to solve them. From these results, aerodynamic torques and power can be calculated. The incidence angle is a parameter of velocity triangle, and both the factors depend not only on the blade azimuth but also on the ratio of rotational speed and horizontal speed. The built computational program allows theoretically selecting the relationship of geometric parameters of wind turbine in accordance with requirements on power, wind speed and installation conditions.

Three-Dimensional Strains on Twisted and Swept Composite Rotor Blades in Vacuum

2020 ◽  
pp. 1-16
Author(s):  
Cheng Chi ◽  
Anubhav Datta ◽  
Inderjit Chopra ◽  
Renliang Chen
Keyword(s):  
Three Dimensional ◽  
Rotor Blades
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