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.

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

6-DOF Single-Inertial Mass, Isotropic Accelerometer With Optical Displacement Sensors

2006 ◽  
Author(s):  
Vladimir Chapsky ◽  
Vladimir Portman ◽  
Ben-Zion Sandler
Keyword(s):  
Light Source ◽  
Optical Sensors ◽  
Optical Measurement ◽  
Data Gathering ◽  
Inertial Mass ◽  
Symmetrical Structure ◽  
Mathematical Algorithm ◽  
Displacement Sensors ◽  
Optical Displacement ◽  
Experimental Apparatus

A novel design of high isotropy single mass six-degree-of-freedom (6-DOF) accelerometer has been developed and investigated. In the accelerometer, six spatial coordinates (three linear and three angular) of the inertial mass and their derivatives are observed by simple measurement of linear displacements of six optimally chosen points of the inertial mass. Calculation of the six acceleration components is then possible according to a specially developed mathematical algorithm. To provide the isotropy of the device’s sensitivity and to achieve the accuracy in the measurement of the linear and angular accelerations, three subsystems of the device — inertial, suspension, and measurement subsystems — have a spatially symmetrical structure. To provide the symmetrical structure of the inertial subsystem, the proof mass is manufactured from uniform material and has a cubic shape. All structural cavities in this cube (light guides and a light source cavity) are symmetrical relative to three coordinate axes. To provide the symmetry of suspension subsystem 24 elastic supports (springs) are mounted by three in all vertexes of the cube in the directions of X-, Y- and Z-axes. The springs have the same dimensions and stiffness. The damping elements (the rubber insets) are inserted into the springs. They are made of the same material and have the identical dimension. The measurement subsystem consists of six differential optical displacement sensors and the light source which is mounted in the center of the cube. Each optical sensor is based on three-component position-sensitive detectors (PSD) of a segmented type. This design ensures output signals that are independent of fluctuations in light source brightness and of optical and electromagnetic interferences. Optical sensors are mounted on the frame of the accelerometer and situated symmetrically opposite to the centers of the square faces of the cube. Six orts of measurement directions form three orthogonal pairs. The experimental model of isotropic 6-DOF accelerometer with differential optical measurement subsystem is manufactured, adjusted and tested. For this purpose the experimental apparatus consisting of the stand with standard accelerometers and computer-controlled data gathering and analysis system (multi-channel amplifier, analog-digital converter and LabView software system) is developed. The preliminary experiment results show that proposed device has high level of signal isotropy and it is hoped to have a good perspective for industrial application were it can replace the complex gyroscopic and combined multi-axis devices.

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.

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

Methodology for the design, production, and test of plastic optical displacement sensors

2016 ◽  
Vol 5 (4) ◽  
Author(s):  
Maik Rahlves ◽  
Christian Kelb ◽  
Eduard Reithmeier ◽  
Bernhard Roth
Keyword(s):  
Large Scale ◽  
Mechanical Performance ◽  
Mechanical Test ◽  
Numerical Models ◽  
Testing Machine ◽  
Displacement Sensor ◽  
Optical Simulation ◽  
Displacement Sensors ◽  
Optical Displacement ◽  
Design Production

AbstractOptical displacement sensors made entirely from plastic materials offer various advantages such as biocompatibility and high flexibility compared to their commonly used electrical and glass-based counterparts. In addition, various low-cost and large-scale fabrication techniques can potentially be utilized for their fabrication. In this work we present a toolkit for the design, production, and test of such sensors. Using the introduced methods, we demonstrate the development of a simple all-optical displacement sensor based on multimode plastic waveguides. The system consists of polymethylmethacrylate and cyclic olefin polymer which serve as cladding and core materials, respectively. We discuss several numerical models which are useful for the design and simulation of the displacement sensors as well as two manufacturing methods capable of mass-producing such devices. Prior to fabrication, the sensor layout and performance are evaluated by means of a self-implemented ray-optical simulation which can be extended to various other types of sensor concepts. Furthermore, we discuss optical and mechanical test procedures as well as a high-precision tensile testing machine especially suited for the characterization of the opto-mechanical performance of such plastic optical displacement sensors.

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