The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform
Alan Palazzolo - One of the best experts on this subject based on the ideXlab platform.
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long duration Blade Loss simulations including thermal growths for dual rotor gas turbine engine
Journal of Sound and Vibration, 2008Co-Authors: Alan Palazzolo, Andy Provenza, Charles Lawrence, Kelly S CarneyAbstract:This paper presents an approach for Blade Loss simulation including thermal growth effects for a dual-rotor gas turbine engine supported on bearing and squeeze film damper. A nonlinear ball bearing model using the Hertzian formula predicts ball contact load and stress, while a simple thermal model estimates the thermal growths of bearing components during the Blade Loss event. The modal truncation augmentation method combined with a proposed staggered integration scheme is verified through simulation results as an efficient tool for analyzing a flexible dual-rotor gas turbine engine dynamics with the localized nonlinearities of the bearing and damper, with the thermal growths and with a flexible casing model. The new integration scheme with enhanced modeling capability reduces the computation time by a factor of 12, while providing a variety of solutions with acceptable accuracy for durations extending over several thermal time constants.
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an efficient algorithm for Blade Loss simulations using a high fidelity ball bearing and damper model
ASME 2003 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 2003Co-Authors: Nikhil Kaushik, Alan Palazzolo, Andy Provenza, Charles Lawrence, Kelly S CarneyAbstract:This paper presents a novel approach for Blade Loss simulation of an aircraft gas turbine rotor mounted on rolling element bearings with squeeze film dampers. The modal truncation augmentation (MTA) method provides an efficient tool for modeling this large order system with localized nonlinearities in the ball bearings. The gas turbine engine, which is composed of the power turbine and gas generator rotors, is modeled with 38 lumped masses. A nonlinear angular contact bearing model is employed, which has ball and race degrees of freedom and uses a modified Hertzian contact force between the races and balls. This combines a dry contact force and an equivalent viscous damping force. Prediction of the maximum contact load and the corresponding stress on an elliptical contact area between the races and balls is made during the Blade Loss simulations. A finite-element based squeeze film damper (SFD), which determines the pressure profile of oil film and calculates damper forces for any type of whirl orbit, is developed, verified, and utilized in the simulations. The new approach is shown to provide efficient and accurate predictions of whirl amplitudes, maximum contact load and stress in the bearings, transmissibility, the maximum and minimum damper pressures and amount of unbalance force for incipient oil film cavitation.Copyright © 2003 by ASME
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Transient analysis of plain and tilt pad journal bearings including fluid film temperature effects
Journal of Tribology-transactions of The Asme, 1996Co-Authors: R. K. Gadangi, Alan PalazzoloAbstract:The paper considers vibration response of spinning shafts supported by flexible fluid film bearings to sudden mass imbalance (Blade Loss). A time transient study of the plain journal bearing with thermal effects is performed. A comparison between three transient analyses is performed. The three transient analyses studied are, the full nonlinear analysis, linear analysis using dynamic coefficients, and pseudo transient analysis using static application of dynamic loads. The validity of the nonlinear transient analysis is checked by matching the lower unbalance results with the linear analysis and the static equilibrium position results with Newton-Raphson iterative scheme. A nonlinear transient analysis of the tilt pad journal bearing is also performed, and a comparison is drawn between the three approaches.
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Transient Analysis of Tilt Pad Journal Bearings Including Effects of Pad Flexibility and Fluid Film Temperature
Journal of Tribology-transactions of The Asme, 1995Co-Authors: R. K. Gadangi, Alan PalazzoloAbstract:The paper considers vibration response of spinning shafts supported by flexible tilt pad journal bearings, to large mass imbalance (Blade Loss). A time transient study of the tilt pad journal bearing with thermal effects and without pad deformations, and with pad deformations and without thermal effects, is performed. Influence of the inclusion of thermal effects on the jurnal center's orbit, the minimum film thickness, and the maximum film temperature is evaluated, and also the influence of pad deformations due to the fluid film forces on the journal center's orbit and the minimum film thickness is studied. Inclusion of thermal effects had little effect on the orbit, while the inclusion of pad deformations had considerable effect on the journal orbit and the minimum film thickness. Three cases are studied in this paper; static load without imbalance, static load with low imbalance, and static load with high imbalance
Jie Hong - One of the best experts on this subject based on the ideXlab platform.
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Theoretical and experimental investigation on the sudden unbalance and rub-impact in rotor system caused by Blade off
Mechanical Systems and Signal Processing, 2016Co-Authors: Cun Wang, Yanhong Ma, Dayi Zhang, Zhichao Liang, Jie HongAbstract:Abstract Blade Loss from a running turbofan rotor will introduce sudden unbalance into the dynamical system, and as a consequence leads to the rub-impact, the asymmetry of rotor and a series of interesting dynamic characteristics. The paper focuses on the theoretical study on the sudden unbalance and rub-impact caused by Blade Loss, in particular investigates the response of the rotor on a rotor test rig with sudden unbalance and rub-impact device designed respectively. The results reveal that the sudden unbalance will induce impact effect on the rotor, and critical speed frequency is excited in frequency spectrum. Meantime, the impact effect is more obvious for the rotor operating above critical speed. The influence of rub-impact is considered as additional constraint to the rotor, analyzed by the theory of time-varying system for the first time, and the results are evaluated by experimental tests. The study shows that great attention should be paid to the dynamical design for the overhung rotor system, additional constraint and corresponding analysis method in rub-impact need to be intensively studied.
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Experimental Investigation on Dynamical Response of an Overhung Rotor due to Sudden Unbalance
Volume 7B: Structures and Dynamics, 2015Co-Authors: Yanhong Ma, Dayi Zhang, Zhichao Liang, Jie HongAbstract:Blade Loss is a typical extreme load in the turbo machinery, which can cause intense vibration in rotor and huge loads in supporting system due to the sudden unbalance applied on the disk. An overhung rotor-support system is built to study the dynamic characteristics of rotor and support experimental system under the sudden unbalance excitation. The responses due to a mass Loss are tested respectively both in subcritical state and in supercritical state, further the orbits of the rotor and load transmitting process on the stator are obtained and investigated. Moreover, the impact effect of response achieved by a mechanical model is presented to compare with the test result. The results show that sudden unbalance can induce an impact effect on the rotor system with response containing rotational speed frequency and natural frequency in frequency domain. The impact effect is more evident for flexible rotor than the rigid rotor, and the vibration response exhibits local effect. As a consequence the paper provides a reference and basis for the dynamical design and analysis for flexible overhung rotor system suffering sudden unbalance.Copyright © 2015 by ASME
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Safety design method of fan rotor system in aeroengine due to extreme loadings
2015 First International Conference on Reliability Systems Engineering (ICRSE), 2015Co-Authors: Jie Hong, Dayi Zhang, Meiling Xu, Zhichao LiangAbstract:Fan Blade Loss is the most serious condition of typical extreme working conditions in turbofan engines. The transient huge unbalance force leads to the complicated and destructive vibration response of the rotor system. The paper proposed a set of safety design method for the rotor system, which ensured the engine to stop safely after the fan Blade lost. The variable stiffness supporting structure at the rear of the fan was presented and its parameters were optimized through dynamic characteristics calculation. The results revealed that the vibration response of the rotor system could be suppressed during the speed reduction process. The spherical matching surface between the bearing ring and the rotation shaft could reduce the impact of the large shaft deformation, and enhanced the bearing's safety.
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Study of Transient Characteristic of a Simple Rigid Rotor Supported on a Squeeze Film Damper With Valvular Metal Rubber Squeeze Film Ring
Volume 5: Turbo Expo 2007, 2007Co-Authors: Yanhong Ma, Jie Hong, Dayi Zhang, Hong WangAbstract:An efficient oil film damper known as a squeeze film damper with valvular metal rubber squeeze film ring (SFD/VMR) was developed for more effective and reliable vibration control, and especially for improving the Blade Loss dynamics of high-speed rotors based on the conventional squeeze film damper (SFD). The immobile squeeze film ring of the SFD was replaced by the elastic squeeze film ring with the valvular metal rubber subassembly (VMR) of the SFD/VMR. The squeeze film force properties of the SFD/VMR was improved, because it can passively adjust the squeeze film clearance by taking advantage of the elastic deformation of the VMR and can control the squeeze film clearance in a suitable range. The characteristics of squeeze film stiffness and damping coefficients, as well as the steady-state unbalance response of a simple rigid rotor supported on SFD/VMR and SFD, were reported in a previous literature[1]. In this paper, the transient response of the rigid rotor supported on SFD/VMR and SFD subjected to sudden unbalance of Blade Loss are inverstigated. Time transient simulation and experimental results indicated that SFD/VMR can operate effectively under much greater unbalance compared with SFD, especially under relative large impact loads of Blade Loss. The SFD/VMR can suppress the occurrence of the nonlinear vibration phenomenon markedly, such as the bistable jump up phenomenon. Furthermore, the effective eccentricities of SFD/VMR with small transfer ratio (T
P. Verrier - One of the best experts on this subject based on the ideXlab platform.
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A Method for Assessing the Turbine Generator Set Shaft-Line Behavior in Accidental Situations
Proceedings of the 9th IFToMM International Conference on Rotor Dynamics, 2015Co-Authors: Nicolas Guilloteau, Ionel Nistor, Nabila Sellali-haraigue, Pierre Yves Couzon, P. VerrierAbstract:Ensuring the operating safety of electrical power plants is a major issue for operators. Regarding turbine generator sets, a risk was identified due to the potential Loss of one or more low pressure last stage Blades of the turbine which could lead to a large unbalance, and then to an accident. This kind of accident is generally avoided using several means among which robust design, condition monitoring and periodic non destructive inspections. Nevertheless, safety studies must be undertaken. This led researchers to develop realistic numerical methods to predict the effects of such an accident. In this framework, EDF R&D has developed its own method to describe the most accurately the dynamic behavior of a shaft-line in an accidental situation caused by a Blade Loss. The objective is to evaluate the loads on the bearings in these conditions and compare them to the maximum design loads provided by the manufacturers. This methodology is composed of two phases. The first one focuses on the study of the shaft-line behavior before the Blade Loss considering the linear behavior of the bearings oil film: a preliminary static computation is made under gravity loads considering the altimetry of the bearings. Loads on the bearings resulting of this calculation are used by a bearing code in order to compute the dynamic coefficients associated with the oil film. Then, the harmonic response to unbalance is calculated for different unbalance positions. The objective is to find the critical positions, critical rotational speeds and the most loaded bearings, for which a nonlinear modeling of the oil film is to be considered. The second phase starts at the instant which follows the Blade Loss and simulates the shutdown of the turbine. The simulation of the transient response under unbalance is performed taking into account the nonlinear behavior of the most loaded bearings oil films. The aim is to estimate the maximum loads that the bearings have to support, especially when the rotor to stator contact occurs. In this paper, the steps described above are detailed and applied on an industrial study. Results and performances are presented as well.
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A method for assessing the turbine generator set shaft-line behavior in accidental situations
Mechanisms and Machine Science, 2015Co-Authors: Nicolas Guilloteau, Ionel Nistor, Nabila Sellali-haraigue, Pierre Yves Couzon, P. VerrierAbstract:© Springer International Publishing Switzerland 2015. Ensuring the operating safety of electrical power plants is a major issue for operators. Regarding turbine generator sets, a risk was identified due to the potential Loss of one or more low pressure last stage Blades of the turbine which could lead to a large unbalance, and then to an accident. This kind of accident is generally avoided using several means among which robust design, condition monitoring and periodic non destructive inspections. Nevertheless, safety studies must be undertaken. This led researchers to develop realistic numerical methods to predict the effects of such an accident. In this framework, EDF R&D has developed its own method to describe the most accurately the dynamic behavior of a shaft-line in an accidental situation caused by a Blade Loss. The objective is to evaluate the loads on the bearings in these conditions and compare them to the maximum design loads provided by the manufacturers. This methodology is composed of two phases. The first one focuses on the study of the shaft-line behavior before the Blade Loss considering the linear behavior of the bearings oil film: a preliminary static computation is made under gravity loads considering the altimetry of the bearings. Loads on the bearings resulting of this calculation are used by a bearing code in order to compute the dynamic coefficients associated with the oil film. Then, the harmonic response to unbalance is calculated for different unbalance positions. The objective is to find the critical positions, critical rotational speeds and the most loaded bearings, for which a nonlinear modeling of the oil film is to be considered. The second phase starts at the instant which follows the Blade Loss and simulates the shutdown of the turbine. The simulation of the transient response under unbalance is performed taking into account the nonlinear behavior of the most loaded bearings oil films. The aim is to estimate the maximum loads that the bearings have to support, especially when the rotor to stator contact occurs. In this paper, the steps described above are detailed and applied on an industrial study. Results and performances are presented as well.
Qihan Li - One of the best experts on this subject based on the ideXlab platform.
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Development of porous squeeze film damper bearings for improving the Blade Loss dynamics of rotor-support systems
Journal of Vibration and Acoustics, 1992Co-Authors: Shiping Zhang, Qihan LiAbstract:An efficient oil film damper known as porous squeeze film damper (PSFD) is developed based on conventional squeeze film damper (SFD) for more effective and reliable rotor vibration control and especially for improving the Blade Loss dynamics for rotor support system. The permeability of the outer race of PSFD could remarkably improve the squeeze film damping properties. The transient response of a simple rigid rotor and flexible Jeffcott’s rotor supported on PSFD and SFD subjected to sudden unbalance of Blade Loss are investigated. Time transient simulation show that PSFD could operate effectively under much greater unbalance as compared with SFD, especially under relative large impact loading of Blade Loss. Furthermore, the effective eccentricities of PSFD with small transmissibilities (T
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development of porous squeeze film damper bearings for improving the Blade Loss dynamics of rotor support systems
Journal of Vibration and Acoustics, 1992Co-Authors: Shiping Zhang, Qihan LiAbstract:An efficient oil film damper known as porous squeeze film damper (PSFD) is developed based on conventional squeeze film damper (SFD) for more effective and reliable rotor vibration control and especially for improving the Blade Loss dynamics for rotor support system. The permeability of the outer race of PSFD could remarkably improve the squeeze film damping properties. The transient response of a simple rigid rotor and flexible Jeffcott’s rotor supported on PSFD and SFD subjected to sudden unbalance of Blade Loss are investigated. Time transient simulation show that PSFD could operate effectively under much greater unbalance as compared with SFD, especially under relative large impact loading of Blade Loss. Furthermore, the effective eccentricities of PSFD with small transmissibilities (T<1.0) extend to a range of e<0.9, and optimum film stiffness and damping distribution within the whole film clearance could be achieved.
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Experiments on the Blade Loss Transient Response of Rotor with Flexible Damped Support
Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education; IGTI Scholar, 1991Co-Authors: Qihan Li, Shiping Zhang, Fuan ZhaoAbstract:The purpose of this paper is to present some experimental results on the transient response dynamics of a rotor system with flexible damped support due to the event of simulated Blade Loss.Experiments under different sudden unbalances applied on the rotor system with various SFD film clearances at different rotational speeds were performed. The instability conditions characterized by limiting circle orbits for large amplitude at damper location were determined and some special phenomena such as lock up, bistable jump and subharmonic etc. have been observed. The effectiveness and the capability of SFD for suppressing instability are analyzed.Copyright © 1991 by ASME
R. K. Gadangi - One of the best experts on this subject based on the ideXlab platform.
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Transient analysis of plain and tilt pad journal bearings including fluid film temperature effects
Journal of Tribology-transactions of The Asme, 1996Co-Authors: R. K. Gadangi, Alan PalazzoloAbstract:The paper considers vibration response of spinning shafts supported by flexible fluid film bearings to sudden mass imbalance (Blade Loss). A time transient study of the plain journal bearing with thermal effects is performed. A comparison between three transient analyses is performed. The three transient analyses studied are, the full nonlinear analysis, linear analysis using dynamic coefficients, and pseudo transient analysis using static application of dynamic loads. The validity of the nonlinear transient analysis is checked by matching the lower unbalance results with the linear analysis and the static equilibrium position results with Newton-Raphson iterative scheme. A nonlinear transient analysis of the tilt pad journal bearing is also performed, and a comparison is drawn between the three approaches.
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Blade Loss Simulation of Multi Mass Rotor Model With Nonlinear Tilt Pad Journal Bearings
Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education; IGTI Scholar, 1995Co-Authors: R. K. Gadangi, A. B. PalazzoloAbstract:Prediction of rotor vibrations due to large imbalance requires nonlinear solution of the supporting bearings. This paper presents a methodology and results for the effects of large, sudden imbalance on the response of a multi mass rotor model supported on tilt pad journal bearings. For a given imbalance, response is obtained for rotor speeds below, above and at the rotor natural frequency. The maximum peak to peak amplitude is larger at the critical speed than at a speed above or below the critical. The imbalance response is compared with two other methods used for predicting the transient response of a rotor bearing system. The rigid rotor and nonlinear bearing model shows a response similar in shape to that obtained with a flexible rotor and nonlinear bearing model, but the magnitude is different, which reached a limiting value as the imbalance was increased. The flexible rotor and linearized bearing model predicts a similar trend as the flexible rotor and nonlinear bearing model, with increasing speed for a given imbalance, but the shape and magnitude of the orbit is completely different. The motion of rotor to static equilibrium location for the flexible rotor and nonlinear bearing model showed oscillations which diminished with time, while the rigid rotor and nonlinear bearing model does not show any oscillations.
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Transient Analysis of Tilt Pad Journal Bearings Including Effects of Pad Flexibility and Fluid Film Temperature
Journal of Tribology-transactions of The Asme, 1995Co-Authors: R. K. Gadangi, Alan PalazzoloAbstract:The paper considers vibration response of spinning shafts supported by flexible tilt pad journal bearings, to large mass imbalance (Blade Loss). A time transient study of the tilt pad journal bearing with thermal effects and without pad deformations, and with pad deformations and without thermal effects, is performed. Influence of the inclusion of thermal effects on the jurnal center's orbit, the minimum film thickness, and the maximum film temperature is evaluated, and also the influence of pad deformations due to the fluid film forces on the journal center's orbit and the minimum film thickness is studied. Inclusion of thermal effects had little effect on the orbit, while the inclusion of pad deformations had considerable effect on the journal orbit and the minimum film thickness. Three cases are studied in this paper; static load without imbalance, static load with low imbalance, and static load with high imbalance
