Experiments on Oil-Film Dampers for Turbomachinery

1976 ◽  
Vol 98 (3) ◽  
pp. 393-399 ◽  
Author(s):  
M. Botman
Keyword(s):  
Dynamic Responses ◽  
Maximum Speed ◽  
Test Results ◽  
Oil Film ◽  
Outer Race ◽  
High Speeds ◽  
Typical Test

Oil-film dampers are used in turbomachinery to suppress undesirable shaft dynamic responses. They are located at the nonrotating outer race of selected main bearings. A rig is described that was designed to evaluate the effect of damper geometry on the rotor responses. Typical test results are shown which indicate that cavitation limits the maximum speed at which dampers should be used. Below cavitation speed the effect of the damper appears predictable with existing theory. More tests are required to substantiate this. At high speeds the damper generates nonsynchronous motion. The damper may have a significant effect on the stiffness of the support felt by the rotor.

Experiments on the Transient Response of Oil-Film Dampers

1978 ◽  
Vol 100 (1) ◽  
pp. 30-35 ◽  
Author(s):  
M. Botman ◽  
R. K. Sharma
Keyword(s):  
Transient Response ◽  
Data Reduction ◽  
High Speed ◽  
Dynamic Responses ◽  
Oil Film ◽  
Outer Race ◽  
Synchronous Behavior ◽  
Blade Loss

Oil-film dampers are used in turbomachinery to suppress undesirable shaft dynamic responses. They are located at the nonrotating outer race of selected main bearings. Experiments on the synchronous behavior of oil-film dampers under steady unbalance loads were reported previously [1]. In this paper results are presented of experiments on the transient response of dampers which are subject to simulated blade-loss loads at high speed. The tests were performed on the rig used for the synchronous tests. A method of data reduction was developed. Results are shown for a number of different masses released at various speeds and dampers with several clearances.

The Mechanism of Rapid Running in the Ghost Crab, Ocypode Ceratophthalma

1973 ◽  
Vol 58 (2) ◽  
pp. 327-349 ◽  
Author(s):  
MALCOLM BURROWS ◽  
GRAHAM HOYLE
Keyword(s):  
High Speed ◽  
Effective Length ◽  
Maximum Speed ◽  
Ghost Crab ◽  
High Speeds ◽  
Intact Crab ◽  
Leg Movements

1. Ocypode ceratophthalma has a maximum speed of 2.1 m/sec when running on a measured track with a base of hard-packed sand. Speed increases linearly with the width of the carapace up to a certain size, beyond which larger crabs run slower than smaller ones. 2. The crab does not run at these high speeds by making extremely rapid movements as these data seemed to require. The highest frequency of leg movements observed was 20 Hz. 3. Electromyographs of muscles used in running, made from the freely running, intact crab, showed asymmetry in the motoneurone discharges. Extensors and flexors in the meropodites of legs on the leading side frequently showed only a maintained tonus and could not have contributed to the running movements. Those on the trailing side showed alternation synchronous with stepping. 4. It is concluded that the crab mainly pushes itself along rather than using a push-pull combination. 5. Three pairs of legs are commonly used in running. Legs 2 and 4 of one side move together with leg 3 of the opposite side and provide a tripod of support. At the highest speeds only legs 2 and 3 of one side are used to provide thrust alternately. 6. The high speed is achieved by the crab leaping through the air as it steps, thereby increasing the effective length of the steps.

Galloping response of sector-shape iced eight bundle conductors

2020 ◽  
Vol 47 (10) ◽  
pp. 1201-1213
Author(s):  
Meng-qi Cai ◽  
Lin-shu Zhou ◽  
Qian Xu ◽  
Xiao-hui Yang ◽  
Xiao-hui Liu
Keyword(s):  
Transmission Lines ◽  
Theoretical Basis ◽  
Wind Tunnel Test ◽  
Dynamic Responses ◽  
Test Results ◽  
The Finite Element Method ◽  
Aerodynamic Coefficients ◽  
Aerodynamic Loads ◽  
Natural Modes ◽  
Wind Velocities

Wind tunnel test results of the aerodynamic coefficients of sector-shape iced eight bundle conductors varying with wind attack angles are presented. Then, by means of the user-defined cable elements, the aerodynamic loads are applied on the cable elements of each sub-conductor through the finite element method (FEM). In addition, the galloping responses of sector-shape iced eight bundle conductors are discussed. Finally, galloping responses, including dynamic responses (natural modes and frequencies), galloping orbits, and amplitudes of typical sector-shape iced eight bundle conductor transmission lines in the cases of different span lengths, wind velocities, and angles of wind attack are studied, respectively. These results provide useful references for a theoretical basis for the study of galloping and the technique of anti-galloping in cold regions.

NONLINEAR IMPACT DYNAMIC ANALYSIS AND COMPARISON WITH EXPERIMENTAL DATA FOR THE SKID GEAR

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1403-1408 ◽  
Author(s):  
DONG-HYUN KIM ◽  
YU-SUNG KIM
Keyword(s):  
Three Dimensional ◽  
Element Model ◽  
Landing Gear ◽  
Gear System ◽  
Dynamic Responses ◽  
Test Results ◽  
Dimensional Finite Element ◽  
Nonlinear Transient ◽  
Skid Landing Gear ◽  
Three Dimensional Finite Element

In this study, nonlinear crash analyses have been conducted for the skid landing gear of helicopter. The realistic configuration of skid landing gear system is considered. Detailed three-dimensional finite element model with variable thickness and material nonlinearity is constructed for required impact design conditions. Advanced computational approach is used to conduct nonlinear transient impact dynamic analyses for different collision models. Characteristics of impact dynamic responses due to the ground crash are practically investigated in detail. It is also shown that the exact consideration of friction effect is very important to accurately predict the crash behavior of the skid type landing gear system. Finally, two typical landing conditions are analyzed and correlated with drop test results.

Fluid-Structure Dynamics With a Modal Hybrid Method

1992 ◽  
Vol 114 (2) ◽  
pp. 133-138 ◽  
Author(s):  
B. Brenneman ◽  
M. K. Au-Yang
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Hybrid Approach ◽  
Dynamic Responses ◽  
Test Results ◽  
Strongly Coupled ◽  
Large Structures ◽  
Modal Synthesis ◽  
Loss Of Coolant ◽  
Thermal Shields

Large structures in nuclear power plants are often separated by very thin fluid-filled cavities. For example, core support structures, thermal shields, and reactor vessels are usually large concentric cylindrical shells with annuli between them as small as 2 percent of the shell diameter. Such thin cavities cause the structures to be very strongly coupled, and such coupling must be accurately modeled to predict the dynamic responses of new designs to turbulence, pump acoustic loading, loss-of-coolant accidents, and seismic events. This paper summarizes a very versatile and efficient method of solving these problems with small personal computers. Among other things, this method uses component modal synthesis with the hybrid approach, and the solution of the resulting unsymmetric eigenvalue problem for the coupled vibration modes. System responses are then found in terms of “right” and “left” eigenvectors. Comparisons with test results are also presented.

Paper 10: Lubrication of Air Compressors

1969 ◽  
Vol 184 (18) ◽  
pp. 93-105
Author(s):  
E. M. Evans ◽  
A. Hughes
Keyword(s):  
High Pressure ◽  
Test Method ◽  
Test Results ◽  
Process Industries ◽  
Air Compressors ◽  
Operating Instructions ◽  
Very High ◽  
Lubricant Performance ◽  
Pneumatic Equipment ◽  
Typical Test

There is an increasing use of pneumatic equipment in production and process industries and reliability of equipment in these industries is of paramount importance. The failure of an air compressor due to deficiencies in the lubricant can be very costly. In this paper important aspects of lubricant performance are discussed. The differences between the requirements of lubricants for rotary oil-cooled air compressors and for reciprocating air compressors are highlighted. Some of the requirements are conflicting and can cause problems if an oil is used in a type of compressor for which it is not designed. Mechanisms by which oil can cause failures are analysed. Some of the failures are common to certain types of compressor. Guidance is given which can reduce the risks of failures. This includes both design and operating instructions. Finally, full-scale methods of test for rotary oil-cooled and reciprocating air compressors are given, including a test method for very high-pressure reciprocating compressors; typical test results are supplied.

Nonlinear Dynamic of a Geared Rotor System With Nonlinear Oil Film Force and Nonlinear Mesh Force

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Yahui Cui ◽  
Zhansheng Liu ◽  
Yongliang Wang ◽  
Jianhuai Ye
Keyword(s):  
Numerical Integration ◽  
Dynamic Model ◽  
Rotational Speed ◽  
Nonlinear Dynamic ◽  
Journal Bearing ◽  
Rotational Frequency ◽  
Rotor System ◽  
Dynamic Responses ◽  
Oil Film ◽  
Gear Mesh

To investigate the effect of oil film force on a geared rotor system, a short journal bearing model was applied to represent nonlinear oil film force. A dynamic model of the geared rotor oil journal bearing system was presented. The nonlinear gear mesh force and nonlinear oil film force were considered in the model. The nonlinear dynamic responses of the system were investigated by numerical integration method. This article shows that when the rotational speed is relatively low, the vibration of the system is mainly affected by nonlinear mesh force. With the increase of rotational speed, the influence of nonlinear oil film force also increases gradually, and the subsynchronous forward precession phenomena appear. When the speed increases to a certain value, the amplitude of the subsynchronous forward precession exceeds the amplitude of the rotational frequency, and the nonlinear mesh force is greatly affected by the nonlinear oil film force. However, the linear oil film force does not affect the nonlinear mesh force. The subsynchronous forward precession is difficult to be predicted by linear oil film force which was previously applied. This experiment is performed to validate the correctness of the dynamic model presented, and the numerical integration results of low speeds are validated by the experimental data.

A Review of Shielding Performance for Anechoic Chamber

2015 ◽  
Vol 793 ◽  
pp. 600-604
Author(s):  
Hafizah Mustapha ◽  
K.H. Ismail ◽  
T.J. Daim ◽  
S.F. Jamil
Keyword(s):  
Random Noise ◽  
Operation Mode ◽  
Good Condition ◽  
Anechoic Chamber ◽  
Test Results ◽  
Electronic Components ◽  
Specific Test ◽  
Different Types ◽  
Anechoic Chambers ◽  
Typical Test

Anechoic chambers are widely used in performing EMC measurements according to the established EMC standards. As in space area, EMC measurement is critically important to ascertain all of electrical and electronic components in the satellite body will function correctly without fail during launching and operation mode. Recognizing the needs and importance of performing the EMC measurements, the shielding performance of the chamber should be prioritized to ensure the interference of electromagnetic wave from outside going to inside the constructed chamber does not exist. As to maintain the shielding element, periodic checking and inspection should be well planned by conducting a specific test. This paper outlines a series of procedures that are developed while running the test. The test will characterize the shielding performance at four (4) frequency ranges using different types of antenna set. Typical test results are gathered and presented at the measured frequencies. Based on the results, it is concluded that the shielding performance of anechoic chamber is standing in good condition at three (3) ranges of frequencies except for frequency of 10 kHz to 200MHz. Several steps are recommended to remove or eliminate the random noise.

Development of an Efficient Oil Film Damper for Improving the Control of Rotor Vibration

1991 ◽  
Vol 113 (4) ◽  
pp. 557-562 ◽  
Author(s):  
Shiping Zhang ◽  
Litang Yan
Keyword(s):  
High Speed ◽  
Porous Metal ◽  
Porous Matrix ◽  
Squeeze Film ◽  
Oil Film ◽  
Squeeze Film Damper ◽  
Outer Race ◽  
Typical Experiment ◽  
Stiffness And Damping ◽  
Film Stiffness

An efficient oil film damper known as a porous squeeze film damper (PSFD) was developed for more effective and reliable vibration control of high-speed rotors based on the conventional squeeze film damper (SFD). The outer race of the PSFD is made of permeable sintered porous metal materials. The permeability allows some of the oil to permeate into and seep out of the porous matrix, with remarkable improvement of the squeeze film damping properties. The characteristics of PSFD oil film stiffness and damping coefficients and permeability, and also, the steady-state unbalance response of a simple rigid rotor and flexible Jeffcott’s rotor supported on PSFD and SFD are investigated. A typical experiment is presented. Investigations show that the nonlinear vibration characteristics of the unpressurized SFD system such as bistable jump phenomena and “lockup” at rotor pin-pin critical speeds could be avoided and virtually disappear under much greater unbalance levels with properly designed PSFD system. PSFD has the potential advantage of operating effectively under relatively large unbalance conditions.

System to Measure the Pressure Distribution on Fan Aerofoil Surfaces During Flutter Conditions

1980 ◽  
Vol 102 (4) ◽  
pp. 427-432
Author(s):  
John W. H. Chivers
Keyword(s):  
Surface Pressure ◽  
High Speed ◽  
Cross Correlation ◽  
Test Results ◽  
Blade Surface ◽  
Pressure Data ◽  
Pressure Transducers ◽  
Induced Stress ◽  
Blade Tip ◽  
Typical Test

In order to assist in the understanding of high speed flutter, a series of tests has been conducted on a research fan in which the blade surface pressures have been measured by means of miniature silicon diaphragm pressure transducers embedded in selected fan blades. Prior to this investigation a program of rig tests was conducted to examine the effects of centrifugal force and vibration on the transducer performance and a transducer mounting technique was developed to minimize blade induced stress in the transducer. Instantaneous measurements of the tip stagger angles of the pressure instrumented fan blades have enabled a cross correlation to be performed on the blade surface pressure data and the blade tip angles. Some typical test results are shown.

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