Theoretical investigation into balancing high-speed flexible shafts, by the use of a novel compensating balancing sleeve

2013 ◽  
Vol 228 (13) ◽  
pp. 2323-2336 ◽  
Author(s):  
Grahame Knowles ◽  
Antony Kirk ◽  
Jill Stewart ◽  
Ron Bickerton ◽  
Chris Bingham
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Low Cost ◽  
Full Range ◽  
Bending Moment ◽  
Operating Conditions ◽  
Drive Shaft ◽  
Practical Applications ◽  
Simply Supported ◽  
Shaft Deflection

Traditional techniques for balancing long, flexible, high-speed rotating shafts are inadequate over a full range of shaft speeds. This problem is compounded by limitations within the manufacturing process, which have resulted in increasing problems with lateral vibrations and hence increased the failure rates of bearings in practical applications. There is a need to develop a novel strategy for balancing these coupling shafts that is low cost, robust under typically long-term operating conditions and amenable to on-site remediation. This paper proposes a new method of balancing long, flexible couplings by means of a pair of balancing sleeve arms that are integrally attached to each end of the coupling shaft. Balance corrections are applied to the free ends of the arms in order to apply a corrective centrifugal force to the coupling shaft in order to limit shaft-end reaction forces and to impart a corrective bending moment to the drive shaft that limits shaft deflection. The aim of this paper is to demonstrate the potential of this method, via the mathematical analysis of a plain, simply supported tube with uniform eccentricity and to show that any drive shaft, even with irregular geometry and/or imbalance, can be converted to an equivalent encastre case. This allows for the theoretical possibility of eliminating the first simply supported critical speed, thereby reducing the need for very large lateral critical speed margins, as this requirement constrains design flexibility. Although the analysis is performed on a sub 15 MW gas turbine, it is anticipated that this mechanism would be beneficial on any shaft system with high-flexibility/shaft deflection.

Application of computational fluid dynamics for thermohydrodynamic analysis of high-speed squeeze-film dampers

2019 ◽  
Vol 43 (3) ◽  
pp. 306-321 ◽  
Author(s):  
Maxime Perreault ◽  
Sina Hamzehlouia ◽  
Kamran Behdinan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Base Line ◽  
Squeeze Film Dampers ◽  
Shaft Deflection ◽  
Whirl Speed

In high-speed turbomachinery, the presence of rotor vibrations, which produce undesirable noise or shaft deflection and losses in performance, has brought up the need for the application of a proper mechanism to attenuate the vibration amplitudes. Squeeze-film dampers (SFDs) are a widely employed solution to the steady-state vibrations in high-speed turbomachinery. SFDs contain a thin film of lubricant that is susceptible to changes in temperature. For this reason, the analysis of thermohydrodynamic (THD) effects on the SFD damping properties is essential. This paper develops a computational fluid dynamics (CFD) model to analyze the THD effects in SFDs, and enabling the application of CFD analysis to be a base-line for validating the accuracy of analytical THD SFD models. Specifically, the CFD results are compared against numerical simulations at different operating conditions, including eccentricity ratios and journal whirl speeds. The comparisons demonstrate the effective application of CFD for THD analysis of SFDs. Additionally, the effect of the lubricant THDs on the viscosity, maximum and mass-averaged temperature, as well as heat generation rates inside the SFD lubricant are analyzed. The temperature of the lubricant is seen to rise with increasing whirl speed, eccentricity ratios, damper radial clearance, and shaft radii.

Modeling Hydrocarbon Processing

2006 ◽  
Vol 3 (1) ◽  
Author(s):  
Teh C Ho
Keyword(s):  
Low Cost ◽  
Petroleum Industry ◽  
Operating Conditions ◽  
Process Models ◽  
Market Demand ◽  
Practical Applications ◽  
Hydrocarbon Processing ◽  
Minimum Capital ◽  
Microscopic Interactions ◽  
The Way

Driven by the global competition and market demand, the petroleum industry is under increasing pressure to produce clean, high-value products from low-cost feedstocks with minimum capital outlays. This has triggered an urgent need to develop robust process models capable of predicting the effects of feedstock composition, operating conditions, and catalyst properties on product quality. To develop such models, one generally splits the reaction mixture at the molecular level, examines microscopic interactions among individual reactions, and then works all the way up to the macroscopic level. Along the way one performs lumping to keep the size and complexity of the problem at bay. This is not only crucial for practical applications, but also important for fundamental understanding, since one does not want to lose sight of the forest for too many trees. This paper gives an overview of new and emerging theoretical tools for building kinetic models for hydrocarbon processing. While the emphasis is on reaction kinetics, the question of reducing hydrodynamic complexities is addressed as well.

BEHAVIORS OF PHOTOCONDUCTIVE DETECTORS BASED ON MAPbI3 PEROVSKITE FILMS

2018 ◽  
Vol 25 (02) ◽  
pp. 1850057
Author(s):  
GENYUAN YU ◽  
LISHA FENG ◽  
LU MENG ◽  
ZHIZHEN YE ◽  
JIANGUO LU
Keyword(s):  
High Speed ◽  
Low Cost ◽  
Solution Process ◽  
Light Illumination ◽  
Practical Applications ◽  
Fundamental Knowledge ◽  
Photoconductive Detectors ◽  
Similar Appearance ◽  
Relaxation Time Constants ◽  
Fast Rise

The CH3NH3PbI3 films were synthesized by a facile low-cost solution process and were used to fabricate photoconductive detectors. The perovskite photodetector is very sensitive to light, with a high responsivity of 5.51[Formula: see text]mA/W and a sensitivity of 50 at 5[Formula: see text]V under 350[Formula: see text]nm light illumination. The device exhibits the fast rise and decay processes with similar appearance, and the relaxation time constants are 270 and 300[Formula: see text]ms, respectively. The photo-current shows an evident saturation, without further increase for prolonging the illumination period. The perovskite photodetectors display high responsive performances to short-wavelength lights. This study is expected to provide a fundamental knowledge of perovskite photodetectors with high speed and repeatability for practical applications.

Dynamic Stability Analysis of High Speed Axially Moving Bands With End Curvatures

1991 ◽  
Vol 113 (1) ◽  
pp. 62-68 ◽  
Author(s):  
K. W. Wang
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Equilibrium Configuration ◽  
Equilibrium States ◽  
Operating Conditions ◽  
Multiple Equilibrium ◽  
Global Dynamic ◽  
Trivial Equilibrium ◽  
Axially Moving ◽  
Moving Band

Measurements of vibration on continuous bands driven by rotating wheels show that the end curvature of the spans can greatly affect the system dynamic characteristics [1,2]. Significant error in the predicted response of a span can occur if the end curvature is neglected. To understand the global dynamic behavior of such systems under high speed operating conditions, a nonlinear model of axially moving bands with finite end curvatures is developed and analyzed in this paper. It is shown that a pitch-fork bifurcation from the trivial equilibrium state will occur at the critical speed of a perfectly straight, axially moving band and the original trivial equilibrium configuration will become unstable. However, for bands with finite end curvatures, the classical critical speed theory does not apply. The equilibrium configuration will continuously change with increasing band speed, but will remain stable. Multiple equilibrium states will occur at sufficiently high band speed, and the minimum speed for this phenomenon to happen increases with the end curvature of the band. Large oscillation coupling the multiple equilibrium states will be induced by large enough initial disturbance. The disturbance required for this to occur varies with the band end curvature and transport speed. The study provides us with new insight and guidelines toward optimizing this class of high speed mechanical systems.

CFD Study Exploring Jet Configurations and Jet Pulsing for an Aeroengine Scoop-Based Oil Delivery System

2018 ◽  
Author(s):  
Kathy Simmons ◽  
Luke Harrison ◽  
Evgenia Korsukova ◽  
Paloma Paleo Cageao
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Operating Conditions ◽  
Capture Efficiency ◽  
Direct Access ◽  
High Speed Imaging ◽  
Ansys Fluent ◽  
Practical Applications ◽  
Single Jet ◽  
Oil Jet

With reduction of gas turbine core size, clearances between internal components are reduced and directing oil jets for bearing lubrication becomes more difficult. If direct access to the bearings or scallops is impeded, the inclusion of oil scoops becomes highly desirable for lubricant supply. With a scoop-based system oil is targeted at a scooped rotor, collected and fed along axial passages and delivered at a different axial location thus enhancing design opportunities. The proportion of oil from the supply jet retained by the scoop system is an important design parameter that can be characterised by the concept of capture efficiency. Previous investigations have focussed on a proposed scoop device’s operating conditions and oil jet configurations; this study proposes new methods of utilising the jets to improve scoop capture efficiency. A parametric study of a 2D scoop geometry was conducted using the Computational Fluid Dynamics (CFD) software ANSYS Fluent. The simulation utilised the Volume of Fluids (VOF) approach for multiphase modelling and the k-ω SST model to account for turbulence. In the configuration studied the oil was supplied via two nozzles separated by 10 degrees circumferentially. An uneven flow rate between two oil jets in tandem allowed for the identification of jet interaction effects. A transition in capture efficiency responses was also highlighted between shallow and steep jet angles. The knowledge of individual jet behaviour may immediately improve existing tandem jet configurations. Further, the concept of pulsing the jets was investigated, the idea being initiated following observation of high speed imaging of a scoop system tested experimentally. The imaging shows that most of the uncaptured oil is deflected or splashed following interaction with the scoop. Turning the oil off for part of the cycle potentially reduces or eliminates this. By defining and implementing an optimised time scheme for the pulsation of a single jet, the capture efficiency was improved by 10%. Compensating for the associated flow rate reduction by increasing the jet velocity resulted in a further 5% increase in capture efficiency. The development of pulsed jets for practical applications has the potential to significantly improve oil scoop capture efficiency.

Whirl and Friction Characteristics of High Speed Floating Ring and Ball Bearing Turbochargers

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Matthew D. Brouwer ◽  
Farshid Sadeghi ◽  
Craig Lancaster ◽  
Jamie Archer ◽  
James Donaldson
Keyword(s):  
High Speed ◽  
Ball Bearing ◽  
Full Range ◽  
Operating Conditions ◽  
Friction Characteristics ◽  
Frictional Losses ◽  
Synchronous Motion ◽  
Displacement Sensors ◽  
Air Supply ◽  
Compare And Contrast

The objective of this experimental investigation was to design and develop a high speed turbocharger test rig (TTR) in order to critically examine the whirl and frictional characteristics of floating ring and ball bearing turbochargers. In order to achieve the objective, a high speed TTR was designed and developed with the capability of reaching speeds in excess of 100,000 rpm and was equipped with speed and displacement sensors to obtain the necessary results for comparison between the two turbocharger models. The TTR was used to compare and contrast the whirl and friction characteristics of two identical turbochargers differing only by the support structure of the rotor system: one containing a floating ring bearing turbocharger (FRBT) and the other a ball bearing turbocharger (BBT). The TTR is driven by an industrial compressor powered by a six cylinder 14 liter diesel engine. This configuration closely resembles turbocharger operation with an actual engine and was able to operate in both nominal and extreme operating conditions. A pair of displacement sensors was installed to measure the whirl of the rotor near the end of the compressor. Whirl results indicated that the BBT was significantly more rigid and stable than the FRBT. Waterfall plots were used to compare the frequency response of the two turbochargers over the full range of operating speeds. The majority of motion for the BBT was the whirl of the synchronous excitation due to a negligible inherent imbalance with some larger motions caused by vibrational modes. The whirl of the FRBT consists of not only the synchronous motion but also subsynchronous motions as a result of oil film instabilities throughout the entire operating range of speeds. The TTR was also used to compare frictional losses within the bearings. A study of the run-down times after the pressurized air supply was removed indicated that the BBT has significantly lower frictional losses under all operating conditions tested.

scholarly journals Nonlinear Response and Stability of an Experimental Overhung Compressor Mounted With a Squeeze Film Damper

2020 ◽  
Author(s):  
William J. Gooding ◽  
Matthew A. Meier ◽  
Edgar J. Gunter ◽  
Nicole L. Key
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Test Facility ◽  
Squeeze Film ◽  
Stable Operation ◽  
Static Structure ◽  
Squeeze Film Damper ◽  
Inertial Interaction ◽  
Rolling Element ◽  
Shaft Deflection

Abstract This paper presents rotordynamic data obtained within a test facility studying the aerodynamics of a high-speed centrifugal compressor for aero-engine applications. The experimental overhung compressor is supported by two rolling element bearings. The compressor-end ball bearing is supported by an oil-fed squeeze film damper. After some period of operation, the compressor began to exhibit a unique nonlinear increase in the rotordynamic response followed by an unexpected subsynchronous whirl instability as the speed continued to increase. Finally, as the rotor speed was increased further, the rotor re-stabilized. A numerical model of the compressor system was created using a commercially available software suite. This model indicates the effective weight of the damper support has a significant effect on the frequency of the second critical speed. Increasing this weight causes the second critical speed, originally predicted at 35,200 RPM, to shift down to 15,650 RPM. This increase in the support weight is due to inertial interaction between the damper support and the surrounding static structure. The increased shaft deflection that occurs as the rotor passes through this shifted critical speed causes the damper to lockup, resulting in the increased response observed experimentally. At a slightly higher speed, Alford-type aerodynamic cross-coupling forces excite the two subsynchronous critical speeds. Finally, as the rotor departs from the second critical speed, the damper unlocks and is able to effectively suppress the Alford-type instabilities, allowing the rotor to return to stable operation.

scholarly journals Transmissibility Analysis of a Regenerated Rotor System

2021 ◽  
Vol 9 (8) ◽  
pp. 1102-1107
Author(s):  
Akanksha Dhurvey
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Rotor System ◽  
Jet Engines ◽  
Simply Supported ◽  
Rotor Bearing ◽  
Unbalance Force ◽  
Force Transmissibility ◽  
Very High ◽  
Bearing System

Abstract: The aim of this paper is to represents a dynamic behavior of rotor bearing system wirth simply supported beam for three different position disc. rotating machinery such as compressors, turbines, pumps, jet engines, turtobo chargers, etc. are subject to vibrations. rotating machines are operated in very high speed and they are subjected to some unbalance force due to vibration from that machine pass to the foundation of machine.so the analysis of the dynamics parameter of rotor it is important to determine force transmissibility, natural frequency, critical speed and amplitudes of rotor system. Keywords: force transmissibility, vibration, critical speed, rotor bearing system etc.

The Vibration Analysis of a Simply Supported Plate Excited by Piezoelectric Actuators

2009 ◽  
Vol 419-420 ◽  
pp. 41-44
Author(s):  
Shiuh Chuan Her ◽  
Chun Yen Liu ◽  
Bo Ren Yao ◽  
Shien Chin Lan
Keyword(s):  
Opposite Sign ◽  
Numerical Study ◽  
Piezoelectric Materials ◽  
Low Cost ◽  
Bending Moment ◽  
Piezoelectric Actuators ◽  
Structural Vibration ◽  
Simply Supported ◽  
Bending Effect ◽  
Exciting Frequency

Piezoelectric materials have the advantage of being lightweight, temperature insensitivity low-cost, easy of implementation that can be utilized for passive and active control of structural vibration. They can be surface bonded or embedded in the structures with slight modifications and without significantly changing the structural stiffness of the system. In this investigation, two piezoelectric actuators are symmetrically embedded in a simply supported plate. Electric voltages with the same amplitude and opposite sign are applied to the two symmetric piezoelectric actuators, resulting in the bending effect on the plate. The bending moment is derived and applied to the simply supported plate. The harmonic response of the simply supported plate excited by the piezoelectric actuators is derived and compared with the finite element solution to show the validation of present approach. The effects of the location and exciting frequency of the piezoelectric actuators on the response of the plate are presented through a numerical study.

scholarly journals Generalised analysis of compensating balancing sleeves with experimental results from a scaled industrial turbine coupling shaft

2017 ◽  
Vol 232 (19) ◽  
pp. 3453-3468 ◽  
Author(s):  
Grahame Knowles ◽  
Antony Kirk ◽  
Chris Bingham ◽  
Ron Bickerton
Keyword(s):  
Engineering Design ◽  
High Speed ◽  
Critical Speed ◽  
Simulation Analysis ◽  
Experimental Measurements ◽  
Safe Operation ◽  
Scaled Model ◽  
Simply Supported ◽  
Reaction Ratio ◽  
Industrial Gas Turbine

The paper furthers the analysis of a recently proposed balancing methodology for high-speed, flexible shafts. This mechanism imparts corrective balancing moments, having the effect of simulating the fixing moments of equivalent double or single encastre mounted shafts. This is shown to theoretically eliminate/nullify the first lateral critical speed, and thereby facilitate safe operation with reduced lateral critical speed margins. The paper extends previously reported research to encompass a more generalised case of multiple, concentrated, residual imbalances, thereby facilitating analysis of any imbalance distribution along the shaft. Solutions provide greater insight of the behaviour of the balancing sleeve concept, and the beneficial implications for engineering design. Specifically, (1) a series of concentrated imbalances can be regarded as an equivalent level of uniform eccentricity, and balance sleeve compensation is equally applicable to a generalised unbalanced distribution, (2) compensation depends on the sum of the applied balancing sleeve moments and can therefore be achieved using a single balancing sleeve (thereby simulating a single encastre shaft), (3) compensation of the second critical speed, and to a lesser extent higher orders, is possible by use of two balancing sleeves, positioned at shaft ends, (4) the concept facilitates on-site commissioning of trim balance, which requires a means of adjustment at only one end of the shaft, (5) the Reaction Ratio, RR, (simply supported/encastre), is independent of residual eccentricity, so that the implied benefits resulting from the ratio (possible reductions in the equivalent level of eccentricity) are additional to any balancing procedures undertaken prior to encastre simulation. Analysis shows that equivalent reductions in the order of 1/25th, are possible. Experimental measurements from a scaled model of a typical drive coupling employed on an industrial gas turbine package, loaded asymmetrically with a concentrated point of imbalance, are used to support the analysis and conclusions.

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