Optimal Design of Squeeze Film Supports for Flexible Rotors

1983 ◽  
Vol 105 (3) ◽  
pp. 487-494 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Optimal Design ◽  
Vibration Amplitude ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Rotor Vibration ◽  
Design Constraints ◽  
Supply Pressure ◽  
Flexible Rotors ◽  
Wide Range ◽  
Film Lubrication

Assuming central preloading, operation below the second bending critical speed, and full film lubrication, this paper presents a theoretical model which allows one, with minimum computation, to design squeeze film damped rotors under conditions of high unbalance loading. Closed form expressions are derived for the maximum vibration amplitudes pertaining to optimally damped conditions. The resulting vibration amplitude and transmissibility data of design interest are presented for a wide range of practical operating conditions on a single chart. It can be seen that for a given rotor, the lighter the bearing the more easily one can satisfy design constraints relating to allowable rotor vibration levels and lubricant supply pressure requirements. The data presented are shown to be applicable to a wide variety of rotors, and a recommended procedure for optimal design is outlined.

scholarly journals Optimal Design of Squeeze Film Supports for Flexible Rotors

1982 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Optimal Design ◽  
Vibration Amplitude ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Rotor Vibration ◽  
Design Constraints ◽  
Supply Pressure ◽  
Flexible Rotors ◽  
Wide Range ◽  
Film Lubrication

Assuming central preloading operation below the second bending critical speed and full film lubrication, this paper presents a theoretical model which allows one, with minimum computation, to design squeeze film damped rotors under conditions of high unbalance loading. Closed form expressions are derived for the maximum vibration amplitudes pertaining to optimally damped conditions. The resulting vibration amplitude and transmissibility data of design interest are presented for a wide range of practical operating conditions on a single chart. It can be seen that for a given rotor, the lighter the bearing the more easily one can satisfy design constraints relating to allowable rotor vibration levels and lubricant supply pressure requirements. The data presented are shown to be applicable to a wide variety of rotors, and a recommended procedure for optimal design is outlined.

scholarly journals Cooling Performance of Arrays of Vibrating Cantilevers

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Mark Kimber ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Vibration Amplitude ◽  
Past Research ◽  
Resonant Mode ◽  
Operating Conditions ◽  
Infrared Thermal Imaging ◽  
Practical Applications ◽  
Wide Range ◽  
Piezoelectric Fans

Piezoelectric fans are vibrating cantilevers actuated by a piezoelectric material and can provide heat transfer enhancement while consuming little power. Past research has focused on feasibility and performance characterization of a single fan, while arrays of such fans, which have important practical applications, have not been widely studied. This paper investigates the heat transfer achieved using arrays of cantilevers vibrating in their first resonant mode. This is accomplished by determining the local convection coefficients due to the two piezoelectric fans mounted near a constant heat flux surface using infrared thermal imaging. The heat transfer performance is quantified over a wide range of operating conditions, including vibration amplitude (7.5–10 mm), distance from heat source (0.01–2 times the fan amplitude), and pitch between fans (0.5–4 times the amplitude). The convection patterns observed are strongly dependent on the fan pitch, with the behavior resembling a single fan for small fan pitch and two isolated fans at a large pitch. The area-averaged thermal performance of the fan array is superior to that of a single fan, and correlations are developed to describe this enhancement in terms of the governing parameters. The best thermal performance is obtained when the fan pitch is 1.5 times its vibration amplitude.

scholarly journals Experimental Evaluation of Squeeze Film Supported Flexible Rotors

1982 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Theoretical Model ◽  
Experimental Evaluation ◽  
Measurement Errors ◽  
Vibration Amplitude ◽  
Squeeze Film ◽  
Experimental Investigations ◽  
Flexible Rotors ◽  
The Mean ◽  
Lubricant Viscosity ◽  
Theory And Experiment

This paper describes the experimental investigations which were conducted to verify existing theoretical vibration amplitude predictions for centrally preloaded, squeeze film supported flexible rotors. The influence of measurement errors and operating condition uncertainties are quantified. The agreement between theory and experiment was excellent, and it is shown that any discrepancy can be explained in terms of errors in determining the mean lubricant viscosity and the orbit magnitudes. Hence, for the range of parameters investigated, the theoretical model and predictions therefrom are validated.

Controllable Squeeze Film Damper: An Application of Electro-Rheological Fluid

1991 ◽  
Author(s):  
Shin Morishita ◽  
Jun’ichi Mitsui
Keyword(s):  
Apparent Viscosity ◽  
Vibration Mode ◽  
Squeeze Film ◽  
Damping Capacity ◽  
Flexible Rotor ◽  
Rotor Vibration ◽  
Squeeze Film Damper ◽  
Rotating Speed ◽  
Wide Range ◽  
Er Fluid

Abstract A notable characteristic of Electro-Rheological (ER) fluid is the variation of its apparent viscosity with the application of an electric field. The application of this characteristic to the performance of squeeze film damper of a flexible rotor is investigated in this paper. It is shown experimentally that by controlling the supporting damping capacity continuously, rotor vibration can be reduced remarkably in a wide range of rotating speed. Moreover, the study indicates experimentally that there exists an optimum supporting damping for every vibration mode.

Onset of 12X Vibration and Its Prevention

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
John J. Yu
Keyword(s):  
Parametric Excitation ◽  
Vibration Amplitude ◽  
Operating Conditions ◽  
Experimental Results ◽  
Rotating Machines ◽  
Supply Pressure ◽  
Upward Shift ◽  
Oil Whirl ◽  
Multiple Orders ◽  
Spectrum Data

This paper discusses real cases on three different machines where subsynchronous vibration occurred suddenly at a frequency exactly equal to one-half (12X) of the operational speed of 3600 rpm. In two cases, vibration amplitude increased from around 2 mils (51 μm) pp to over 12 mils (305 μm) pp, causing the machine to trip unexpectedly. The 12X vibration was even sustained during shutdown at speed below 3600 rpm after trip. Unlike other reported experimental results, shaft orbit measured by proximity probes was fairly circular and dominantly composed of the 12X component without significant components at multiple orders of the 12X. The onset of the subsynchronous 12X vibration was sometimes triggered by changes in bearing lube oil temperature and supply pressure, which would typically be believed to be caused by oil whirl that could occur at close to the 12X frequency. An upward shift in shaft centerline plot was observed to occur prior to the onset of the subsynchronous vibration. The 12X vibration was successfully prevented by changing bearing clearance or adjustment of bearing oil temperature and supply pressure. Parametric excitation analysis on 12X vibration is also given in this paper. The main purpose of this paper, unlike previously published papers on analytical or experimental results, is to show shaft orbital and centerline plots as well as spectrum data due to the 12X vibration, including effects of operating conditions in real rotating machines.

A bubbly oil-lubricated squeeze film damper. Part 1: A finite-element model

2008 ◽  
Vol 222 (11) ◽  
pp. 2191-2201 ◽  
Author(s):  
W S Ng ◽  
M C Levesley ◽  
M Priest
Keyword(s):  
Finite Element ◽  
Homogeneous Model ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Air Bubbles ◽  
Eccentricity Ratio ◽  
Squeeze Film Damper ◽  
Finite Element Software ◽  
Supply Pressure ◽  
Non Linear

The non-linear vibration of a squeeze film damper (SFD) supported rotor assembly is closely linked to the presence of air bubbles in the lubricant, due to cavitation, where the discrete gas phase influences the squeeze film pressure profile and gives rise to a non-linear stiffness force. The aim of this paper is to assess the ability of a computational model for homogeneous bubbly oil to predict the influence of air bubbles on the film reaction forces under various operating parameters. The numerical model which considers the solubility of gas and the growth of gas bubbles was developed using the finite-element software, FEMLAB™. Parametric studies of eccentricity ratio, whirling frequency, and supply pressure were conducted to evaluate the influences of air bubbles on the pressure field and hence the squeeze film forces. Results show that an increase in eccentricity ratio and whirling frequency enhances the growth of air content in lubricant and hence increases the radial (stiffness) to tangential (damping) force ratio in an SFD, whereas an opposite effect is gained by applying higher supply pressure. Compared with the classical theoretical half-film model predictions, the bubbly oil model provides a more realistic estimation with respect to different damper operating conditions. From the simulation findings, it can be concluded that the homogeneous two-phase flow model reasonably describes the bubbly oil behaviour in SFDs and effectively shows the rise in stiffness force due to the growth of air bubbles. The homogeneous model can be easily applied to the well-established lubrication equation and solved with efficiency. However, any possible interfacial effects between the liquid and gas phases are inevitably concealed. The success of the current model allows its subsequent coupling with a structural rotor to form a multi-disciplinary model for unbalance analysis.

Design of a Heat Recovery Steam Generator

1984 ◽  
Author(s):  
David R. Logeais
Keyword(s):  
Steam Generator ◽  
Heat Recovery ◽  
Size Range ◽  
Operating Conditions ◽  
Heat Recovery Steam Generator ◽  
Construction Work ◽  
Design Constraints ◽  
Innovative Design ◽  
Wide Range ◽  
Steam Production

A gas turbine in the size range of 20,000 hp (14.9 MW) was retrofitted with a heat recovery steam generator (HRSG). The HRSG produces high pressure superheated steam for use in a steam turbine. Supplementary firing is used to more than double the steam production over the unfired case. Because of many unusual constraints, an innovative design of the HRSG was formulated. These design constraints included: 1. A wide range of operating conditions was to be accommodated. 2. Very limited space in the existing plant. 3. A desire to limit the field construction work necessary in order to provide a short turn-around time. This paper will discuss the design used to satisfy these conditions.

scholarly journals An Improved Squeeze Film Damper for Rotor Vibration Control: Theoretical Results

1994 ◽  
Author(s):  
J. Y. Zhao ◽  
I. W. Linnett ◽  
E. J. Hahn
Keyword(s):  
Operating Conditions ◽  
Outer Ring ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Constant Stiffness ◽  
Wide Range ◽  
Squeeze Film Dampers ◽  
Secondary Support ◽  
Stiffness And Damping ◽  
Theoretical Results

This paper proposes an improved squeeze film damper which will prevent the bistable operation associated with conventional squeeze film dampers at large unbalances and/or at small bearing parameters. It consists of a conventional squeeze film damper with a flexibly supported outer ring. This secondary flexible support is considered to be massless, and to have a constant stiffness and damping. The effectiveness of this damper in preventing bistable operation is investigated over a wide range of operating conditions for a rigid rotor supported on a centrally preloaded squeeze film damper. It is shown that depending on relevant parameters such as the stiffness ratio between the secondary support and the retaining spring, the damping coefficient of the support, and the mass ratio between the damper outer ring and the rotor, this proposed damper is very effective in preventing bistable operation even for high unbalance conditions.

scholarly journals A Driving and Control Scheme of High Power Piezoelectric Systems over a Wide Operating Range

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4401
Author(s):  
Tianyue Yang ◽  
Yuanfei Zhu ◽  
Zhiwei Fang ◽  
Haoyu Wu ◽  
Wanlu Jiang ◽  
...  
Keyword(s):  
High Power ◽  
Vibration Amplitude ◽  
Operating Conditions ◽  
Phase Detector ◽  
Displacement Sensor ◽  
Operating Range ◽  
Control Scheme ◽  
Wide Range ◽  
And Control ◽  
Wide Operating

Significant variation in impedance under a wide range of loads increases the difficulty of frequency tracking and vibration control in high-power piezoelectric systems (HPPSs). This paper proposed a wide operating range driving and control scheme for HPPSs. We systematically analyzed the impedance characteristics and deduced the load optimization frequency. In order to provide sufficient drive capability, the inverter combined with an LC matching circuit is configured. With the aid of a transformer ratio arm bridge (TRAB) combined with a proposed pulse-based phase detector (PBPD), the proposed scheme can control the vibration amplitude and keep parallel resonance status under a wide range of loads. Experiments conducted under actual operating conditions verify the feasibility of the proposed scheme under the modal resistance range from 7.40 to 500 Ω and the vibration range from 20% to 100%. Moreover, with the aid of a laser displacement sensor, our scheme is verified to have a vibration amplitude control accuracy better than 2% over a tenfold load variation. This research could be helpful for the driving and control of HPPSs operating in a wide range.

Experimental Evaluation of Squeeze Film Supported Flexible Rotors

1983 ◽  
Vol 105 (3) ◽  
pp. 495-503 ◽  
Author(s):  
M. D. Rabinowitz ◽  
E. J. Hahn
Keyword(s):  
Theoretical Model ◽  
Experimental Evaluation ◽  
Measurement Errors ◽  
Vibration Amplitude ◽  
Squeeze Film ◽  
Experimental Investigations ◽  
Flexible Rotors ◽  
The Mean ◽  
Lubricant Viscosity ◽  
Theory And Experiment

This paper describes the experimental investigations which were conducted to verify existing theoretical vibration amplitude predictions for centrally preloaded, squeeze film supported flexible rotors. The influence of measurement errors and operating condition uncertainties are quantified. The agreement between theory and experiment was excellent, and it is shown that any discrepancy can be explained in terms of errors in determining the mean lubricant viscosity and the orbit magnitudes. Hence, for the range of parameters investigated, the theoretical model and predictions therefrom are validated.

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