A Gas-Operated Bearing Damper for Turbomachinery—Theoretical Predictions Versus Experimental Measurements: Part II—Experimental Results and Comparison With Theory

1995 ◽  
Vol 117 (4) ◽  
pp. 750-756 ◽  
Author(s):  
P. Sundararajan ◽  
J. M. Vance
Keyword(s):  
High Temperature ◽  
Theoretical Model ◽  
Natural Frequency ◽  
Experimental Results ◽  
Experimental Measurements ◽  
Vibration Damper ◽  
Research Project ◽  
Theoretical Predictions ◽  
Present Design ◽  
Gas Damper

This is the second of two papers describing results of a research project directed at developing a gas-operated vibration damper for high-temperature turbomachinery applications. This part presents the experimental measurements made on a gas damper hardware and compares them with the theoretical predictions given in Part I. It is found that the isentropic theoretical model predicts the damper characteristics quite well. A maximum damping of 2310 N-s/m (13.2 lb-s/in.) was measured at a natural frequency of 118 Hz using the present design and the results suggest that significantly higher damping levels are possible with design modifications.

A Theoretical and Experimental Investigation of a Gas Operated Bearing Damper for Turbomachinery: Part II — Experimental Results and Comparison With Theory

1993 ◽  
Author(s):  
Padmanabhan Sundararajan ◽  
John M. Vance
Keyword(s):  
Experimental Investigation ◽  
High Temperature ◽  
Theoretical Model ◽  
Natural Frequency ◽  
Experimental Results ◽  
Experimental Measurements ◽  
Vibration Damper ◽  
Theoretical Predictions ◽  
Present Design ◽  
Gas Damper

Abstract This is the second of two papers describing results of a research project directed at developing a gas operated vibration damper for high temperature turbomachinery applications. This part presents the experimental measurements made on three variations of the gas damper hardware and compares them with the theoretical predictions presented in Part I. It is found that the isentropic theoretical model predicts the damper characteristics quite well. A maximum damping of 13.2 Ib-s/in was measured for a single actuator at a natural frequency of 100 hz using the present design and the results suggest that significantly higher damping levels are possible with design modifications.

Holographic measurement of the elastic–plastic boundary surrounding cold-expanded holes

1989 ◽  
Vol 24 (2) ◽  
pp. 103-106 ◽  
Author(s):  
R J Sanford ◽  
R E Link
Keyword(s):  
Holographic Interferometry ◽  
Experimental Results ◽  
Similar Process ◽  
Experimental Measurements ◽  
Cold Expansion ◽  
Elastic Plastic ◽  
Theoretical Predictions ◽  
Holographic Measurement

Experimental measurements of the elastic—plastic boundary surrounding split-sleeve cold-expanded holes in 7075-T651 aluminum were made using the technique of holographic interferometry. The levels of expansion investigated ranged from 1.5 per cent to 8.4 per cent. The experimentally determined elastic—plastic boundaries were compared with several theoretical predictions. The experimental results were also compared with the experimental results from another investigation of a similar process. Predictions of the elastic—plastic boundary based on the Hoffman—Sachs theory agreed with the experimental results for levels of cold expansion over the range 1.5—3 per cent expansion. The experimental results of this investigation predicted larger elastic—plastic boundaries than those measured in a separate investigation. Possible explanations for the differences are discussed.

A Theoretical and Experimental Investigation of a Gas-Operated Bearing Damper for Turbomachinery: Part I—Theoretical Model and Predictions

1995 ◽  
Vol 117 (4) ◽  
pp. 742-749 ◽  
Author(s):  
P. Sundararajan ◽  
J. M. Vance
Keyword(s):  
Theoretical Model ◽  
Squeeze Film ◽  
Working Fluid ◽  
Previous Theory ◽  
Damping Characteristics ◽  
Squirrel Cage ◽  
Theoretical Predictions ◽  
Current Design ◽  
Gas Damper ◽  
Hardware Designs

This is the first (Part I) of two papers describing recent results of the research program directed at developing a vibration damper suitable for high-temperature turbomachinery applications. It is expected that such dampers will replace squeeze-film dampers, which use oil as the working fluid and have limitations at higher temperatures. A novel gas-operated bearing damper has been evaluated analytically and experimentally for its damping characteristics. A theory based on the isentropic assumptions predicts the damper performance characteristics reasonably well. A maximum damping level of 2311 N-m/s (13.2 lb-s/in.) at a frequency of 100 Hz was measured with a single actuator of the gas damper. Since many such actuators could be placed circumferentially around the squirrel cage, considerable damping levels can be realized. The study also shows that significantly higher damping levels can be achieved by modifying the current design. Part I describes the theoretical model that has been developed based on isentropic assumptions. This model is an improved version of the previous theory (Vance et al., 1991) and includes the supply groove effects, dynamic area changes of the inlet feeding holes, and the effects of flow choking on damper behavior. The governing equations are derived and theoretical predictions using these equations have been made for two hardware designs that were experimentally investigated (see Part II for experimental results).

scholarly journals REINFORCED AND PRESTRESSED CONCRETE HOLLOW BEAMS UNDER TORSION

2014 ◽  
Vol 19 (Supplement_1) ◽  
pp. S141-S152 ◽  
Author(s):  
Luis F. A. Bernardo ◽  
Jorge M. A. Andrade ◽  
Luiz A. Pereira-De-Oliveira
Keyword(s):  
Theoretical Model ◽  
Prestressed Concrete ◽  
Experimental Results ◽  
Membrane Model ◽  
Global Behaviour ◽  
Theoretical Predictions ◽  
Hollow Beams

Recently a new rational theoretical model for beams under torsion has been proposed. This model, called Softened Membrane Model for Torsion (SMMT), is able to predict well the global behaviour of reinforced and prestressed concrete solid beams under torsion. This paper presents a study in order to check the SMMT for reinforced and prestressed concrete hollow beams under torsion. Theoretical predictions from SMMT are compared to some experimental results of hollow beams available in the literature and also with the predictions of another theoretical model previously proposed from the authors. It is shown that SMMT, with some corrections, is able to predict satisfactorily the overall behaviour of reinforced and prestressed concrete hollow beams under torsion.

ELECTRON-PHONON INTERACTION WITHIN THE FRAMEWORK OF THE FLUCTUATING VALENCE OF COPPER ATOMS — A THEORETICAL MODEL FOR HIGH TEMPERATURE SUPERCONDUCTIVITY

1990 ◽  
Vol 04 (05) ◽  
pp. 325-331
Author(s):  
SURESH V. VETTOOR ◽  
V. M. NANDAKUMARAN
Keyword(s):  
High Temperature ◽  
Theoretical Model ◽  
Green's Function ◽  
High Temperature Superconductivity ◽  
Experimental Results ◽  
Function Technique ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Good Agreement ◽  
Quasiparticle Excitations

Electron-phonon interaction is considered within the framework of the fluctuating valence of Cu atoms. Anderson's lattice Hamiltonian is suitably modified to take this into account. Using Green's function technique the possible quasiparticle excitations are determined. The quantity 2∆k(0)/k B T c is calculated for T c = 40 K . The calculated values are in good agreement with the experimental results.

Contact Force Measurements Under a Brush Seal

1995 ◽  
Author(s):  
Christopher A. Long ◽  
Yannis Marras
Keyword(s):  
Theoretical Model ◽  
Contact Force ◽  
Experimental Results ◽  
Experimental Techniques ◽  
Force Measurements ◽  
Rotating Shaft ◽  
Simple Theoretical Model ◽  
Brush Seal ◽  
Torque Measurements ◽  
Theoretical Predictions

This paper discusses results of experiments carried out to measure the bristle contact force of a brush seal on a shaft. Two separate experimental techniques were used: i) indirectly through torque measurements and ii) directly using a force blade located under the bristle tips. The tests were conducted on a non-rotating shaft having a nominal diameter of 122 mm, with static radial interferences of 0.4, 0.2, 0.1 and 0.05 mm; and for the range of pressure ratios 1 to 4.5. The experimental results obtained from these measurements are compared with predictions from a simple theoretical model. Although there are some large differences, the experimental results do show some agreement with the theoretical predictions. However, both this current simple theoretical model and the experiments have their limitations. Despite these shortcomings, the experimental results are considered to support the qualitative value of the current theoretical model.

High-Temperature Dielectric Properties Measurements of Ceramics

1992 ◽  
Vol 269 ◽  
Author(s):  
Shane Bringhurst ◽  
Octavio M. Andrade ◽  
Magdy F. Iskander
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Frequency Band ◽  
Perturbation Technique ◽  
Measurement Techniques ◽  
Coaxial Line ◽  
Experimental Results ◽  
Experimental Measurements ◽  
Insulating Materials ◽  
Made In

ABSTRACTThis paper dicusses experimental arrangements, describes measurement techniques and presents experimental results for hightemperature broadband dielectric properties measurements of ceramics. The cavity perturbation technique and the open-ended coaxial line method are used in these experimental measurements. The design and construction details of cavities and probes are described and representative results of measurements on zirconia and alumina samples (green and sintered) are presented. Results of measurements made on insulating materials are shown. In general measurements are made in the frequency band 1 to 10 GHz and temperatures up to 1000°C.

scholarly journals Rotor Instability Induced by Radial Clearance in Ball Bearing Supports

1993 ◽  
Author(s):  
Yao-Qun Lin
Keyword(s):  
Experimental Investigation ◽  
Internal Friction ◽  
Natural Frequency ◽  
Computer Simulations ◽  
Ball Bearing ◽  
Rotor Dynamics ◽  
Experimental Results ◽  
Radial Clearance ◽  
Speed Range ◽  
Theoretical Predictions

In rotor dynamics, the rotor nonsynchronous natural frequency vibration, or rotor instability, has been mainly ascribed to two mechanisms, i.e., internal friction effects and fluid actions. It is shown, however, in this paper that the radial clearance in ball bearing supports can also induce rotor instability through an internal-impacts mechanism. The behavior of the rotor with radial clearance in its ball bearing supports is simulated numerically. The computer simulations show that there is a speed range in which the rotor will vibrate at both the synchronous frequency and the natural frequency. Below or above this speed range, the rotor has only the synchronous response and its harmonics. An experimental investigation was conducted to verify this analysis. The experimental results agree well with the theoretical predictions.

A Theoretical and Experimental Investigation of a Gas Operated Bearing Damper for Turbomachinery: Part I — Theoretical Model and Predictions

1993 ◽  
Author(s):  
Padmanabhan Sundararajan ◽  
John M. Vance
Keyword(s):  
Theoretical Model ◽  
Squeeze Film ◽  
Working Fluid ◽  
Previous Theory ◽  
Damping Characteristics ◽  
Squirrel Cage ◽  
Squeeze Film Dampers ◽  
Theoretical Predictions ◽  
Current Design ◽  
Gas Damper

Abstract This is the first (Part I) of two papers describing recent results of a research program directed at developing a vibration damper suitable for high temperature turbomachinery applications. It is expected that such dampers will replace squeeze-film dampers that use oil as the working fluid and have limitations at higher temperatures. A novel gas operated bearing damper has been analytically and experimentally evaluated for its damping characteristics. Theory that is based on the isentropic assumptions predicts the damper performance characteristics reasonably well. A maximum damping level of 13.2 lb-s/in at a frequency of 100 hz was measured with a single actuator of the gas damper and, since many such actuators can be placed circumferentially around the squirrel cage, considerable damping levels can be realized. The study also shows that significantly higher damping levels can be achieved by modifying the current design. Part I describes the theoretical model that has been developed based on isentropic assumptions. This model is an improved version of the previous theory [1,2] and includes the supply groove effects, dynamic area changes of the inlet feeding holes and the effects of flow choking on damper behavior. The governing equations are derived and theoretical predictions using these equations have been made for the three hardwares that were experimentally investigated (see Part II).

A Theoretical Prediction of Natural Frequency of a Ferromagnetic Beam Plate With Low Susceptibility in an In-Plane Magnetic Field

1998 ◽  
Vol 65 (1) ◽  
pp. 121-126 ◽  
Author(s):  
You-He Zhou ◽  
Kenzo Miya
Keyword(s):  
Magnetic Field ◽  
Theoretical Model ◽  
Natural Frequency ◽  
Magnetic Force ◽  
Damping Ratio ◽  
Theoretical Models ◽  
Energy Functional ◽  
Magnetoelastic Interaction ◽  
Magnetic Damping ◽  
Theoretical Predictions

In order to simulate the experimental phenomenon of increase of natural frequency to a cantilevered ferromagnetic beam plate in in-plane magnetic fields, a theoretical model for behaving the magnetoelastic interaction is proposed in this paper based on the variational principle of energy functional of the system. It is found that the expression of magnetic force is distinctly different from those of the existing theoretical models in publications, and the experimental phenomenon is successfully simulated by this theoretical model. After the increase of natural frequency is quantitatively considered in the predictions of magnetic damping, the theoretical predictions of magnetic damping ratio are agreement with the corresponding experimental data well.

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