An Advanced Stochastic Model for Threshold Crossing Studies of Rotor Blade Vibrations

AIAA Journal ◽  
1972 ◽  
Vol 10 (8) ◽  
pp. 1100-1101 ◽  
Author(s):  
GOPAL H. GAONKAR ◽  
KURT H. HOHENEMSER
Keyword(s):  
Stochastic Model ◽  
Rotor Blade ◽  
Threshold Crossing ◽  
Blade Vibrations

Analyzing rotor-blade vibrations in gas-turbine units

1983 ◽  
Vol 15 (5) ◽  
pp. 636-642
Author(s):  
E. A. Igumentsev
Keyword(s):  
Gas Turbine ◽  
Rotor Blade ◽  
Blade Vibrations

scholarly journals Control of Rotor-Blade Coupled Vibrations Using Shaft-Based Actuation

2006 ◽  
Vol 13 (4-5) ◽  
pp. 255-271 ◽  
Author(s):  
René Hardam Christensen ◽  
Ilmar Ferreira Santos
Keyword(s):  
Active Control ◽  
Mode Shape ◽  
Rotor Blade ◽  
Experimental Control ◽  
Dynamical Characteristics ◽  
Blade Vibrations ◽  
Blade System ◽  
Bladed Rotor ◽  
Controllability And Observability ◽  
Interaction Phenomena

When implementing active control into bladed rotating machines aiming at reducing blade vibrations, it can be shown that blade as well as rotor vibrations can in fact be controlled by the use of only shaft-based actuation. Thus the blades have to be deliberately mistuned. This paper investigates the dynamical characteristics of a mistuned bladed rotor and shows how, why and when a bladed rotor becomes controllable and observable if properly mistuned. As part of such investigation modal controllability and observability of a tuned as well as a mistuned coupled rotor-blade system are analysed. The dependency of the controllability and observability on varying rotational speed and mode shape interaction phenomena between parametric and basis mode shape components are also analysed. Numerical results reveal a limitation of the achievable controllability and observability, once quantitative measures of modal controllability and observability converge toward steady levels as the degree of mistuning is increased. Finally, experimental control results are presented to prove the theoretical conclusions and to show the feasibility of controlling rotor and blade vibrations by means of shaft-based actuation in practice.

Stochastic properties of turbulence excited rotor blade vibrations

AIAA Journal ◽  
1971 ◽  
Vol 9 (3) ◽  
pp. 419-424 ◽  
Author(s):  
GOPAL H. GAONKAR ◽  
KURT H. HOHENEMSER
Keyword(s):  
Rotor Blade ◽  
Blade Vibrations ◽  
Stochastic Properties

Measurements of Self-Excited Rotor-Blade Vibrations Using Optical Displacements

1984 ◽  
Vol 106 (1) ◽  
pp. 44-49 ◽  
Author(s):  
A. P. Kurkov
Keyword(s):  
Strain Gage ◽  
Rotor Blade ◽  
Inlet Pressure ◽  
Turbofan Engine ◽  
Displacement Spectra ◽  
Displacement Sensors ◽  
Optical Displacement ◽  
Blade Vibrations

During the operation of a turbofan engine at part speed, near stall, and elevated inlet pressure and temperature, several vibratory instabilities were excited simultaneously on the first fan rotor. The torsional and bending contributions to the main flutter mode were resolved by using casing-mounted optical displacement sensors. Strain-gage spectra were used to identify other instabilities in the blade-deflection spectra. The characteristics of optical-displacement spectra and their role of monitoring rotor-blade vibrations are discussed.

scholarly journals Identification of Flap Motion Parameters for Vibration Reduction in Helicopter Rotors with Multiple Active Trailing Edge Flaps

2011 ◽  
Vol 18 (5) ◽  
pp. 727-745 ◽  
Author(s):  
Uğbreve;ur Dalli ◽  
Şcedilefaatdin Yüksel
Keyword(s):  
Rotor Blade ◽  
Helicopter Rotor ◽  
System Response ◽  
Trailing Edge ◽  
Blade Root ◽  
Helicopter Rotor Blade ◽  
Blade Vibrations ◽  
Trailing Edge Flaps ◽  
Trailing Edge Flap ◽  
Blade Loads

An active control method utilizing the multiple trailing edge flap configuration for rotorcraft vibration suppression and blade loads control is presented. A comprehensive model for rotor blade with active trailing edge flaps is used to calculate the vibration characteristics, natural frequencies and mode shapes of any complex composite helicopter rotor blade. A computer program is developed to calculate the system response, rotor blade root forces and moments under aerodynamic forcing conditions. Rotor blade system response is calculated using the proposed solution method and the developed program depending on any structural and aerodynamic properties of rotor blades, structural properties of trailing edge flaps and properties of trailing edge flap actuator inputs. Rotor blade loads are determined first on a nominal rotor blade without multiple active trailing edge flaps and then the effects of the active flap motions on the existing rotor blade loads are investigated. Multiple active trailing edge flaps are controlled by using open loop controllers to identify the effects of the actuator signal output properties such as frequency, amplitude and phase on the system response. Effects of using multiple trailing edge flaps on controlling rotor blade vibrations are investigated and some design criteria are determined for the design of trailing edge flap controller that will provide actuator signal outputs to minimize the rotor blade root loads. It is calculated that using the developed active trailing edge rotor blade model, helicopter rotor blade vibrations can be reduced up to 36% of the nominal rotor blade vibrations.

Analysis of an Axial Compressor Blade Vibration Based on Wave Reflection Theory

1984 ◽  
Vol 106 (1) ◽  
pp. 57-64 ◽  
Author(s):  
J. A. Owczarek
Keyword(s):  
Rotor Blade ◽  
Wave Reflection ◽  
Axial Compressor ◽  
Compressor Blade ◽  
Rotor Blades ◽  
Wave Reflections ◽  
Blade Vibration ◽  
Blade Vibrations ◽  
Reflection Theory ◽  
Prediction Techniques

The paper describes application of the theory of wave reflection in turbomachines to rotor blade vibrations measured in an axial compressor stage. The blade vibrations analyzed could not be explained using various flutter prediction techniques. The wave reflection theory, first advanced in 1966, is expanded, and more general equations for the rotor blade excitation frequencies are derived. The results of the analysis indicate that all examined rotor blade vibrations can be explained by forced excitations caused by reflecting waves (pressure pulses). Wave reflections between the rotor blades and both the upstream and downstream stator vanes had to be considered.

Non-Synchronous Aeroacoustic Interaction in an Axial Multi-Stage Compressor

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Anne-Lise Fiquet ◽  
Christoph Brandstetter ◽  
Stéphane Aubert ◽  
Mickael Philit
Keyword(s):  
Rotor Blade ◽  
High Speed ◽  
Acoustic Mode ◽  
Blade Vibration ◽  
Unsteady Pressure ◽  
Multi Stage ◽  
Engine Order ◽  
Major Interest ◽  
Blade Vibrations ◽  
Magnet Coil

Abstract Non-engine order rotor blade vibration is an aeroelastic phenomenon of major interest for compressor designers resulting from excitation of rotor blade modes through aerodynamic instabilities. Indicators for a comparable type of instability, caused by propagating acoustic modes, have been observed in an experimental multistage high-speed compressor by Safran Helicopter Engines. It is intended to understand the cause of these instabilities by combining experimental data and numerical simulations. Unsteady pressure measurements were carried out by case-mounted and stator-mounted transducers. Rotor tip-timing and magnet-coil sensor systems were installed to measure the blade vibrations. Experimental results show non-engine order signatures in the unsteady pressure signal coherent to the shifted frequency of blade vibrations. In the present paper, the waveform of these oscillations is analyzed in detail, showing a dominant propagating acoustic mode interacting with vibrations of rotor 2. The root cause for the non-synchronous oscillations is identified as an acoustic mode that is cutoff downstream of rotor 3. During the test, the mode changes its frequency and circumferential order, affecting the amplitude of associated blade vibrations.

Effects of Flow Control on Forced Response and Performance of a Transonic Compressor

2002 ◽  
Author(s):  
S. Todd Bailie ◽  
Wing F. Ng ◽  
Alfred L. Wicks ◽  
William W. Copenhaver
Keyword(s):  
Flow Control ◽  
Rotor Blade ◽  
Forced Response ◽  
Strain Gages ◽  
Complex Flow ◽  
Compressor Blades ◽  
Transonic Compressor ◽  
Engine Order ◽  
Blade Vibrations ◽  
And Performance

The main contributor to the high-cycle fatigue of compressor blades is the response to aerodynamic forcing functions generated by an upstream row of stators or inlet guide vanes. Resonant response to engine order excitation at certain rotor speeds is especially damaging. Studies have shown that flow control by trailing edge blowing (TEB) can reduce stator wake strength and the amplitude of the downstream rotor blade vibrations generated by the unsteady stator-rotor interaction. In the present study, the effectiveness of TEB to reduce forced blade vibrations was evaluated in a modern transonic compressor rig. A row of wake generator (WG) vanes with TEB capability was installed upstream of the rotor, which was instrumented with strain gages. Data was collected with and without TEB at various rotor speeds involving resonance crossings. Using 0.8% of the compressor core flow for TEB along the full WG-span, rotor blade strain was reduced by 66% at the first torsional resonance crossing. Substantial reductions were also achieved with only partial span TEB. The results demonstrate the effectiveness of the TEB technique for reducing rotor vibrations in the complex flow environment of a closely-spaced transonic stage row. Moderate increases in stage performance were also measured.

Sign in / Sign up

Export Citation Format

Share Document