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You searched for subject:(Rotor bearing vibration). Showing records 1 – 3 of 3 total matches.

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Cranfield University

1. Preciado Delgado, E. Mixed modal balancing of flexible rotors without trial runs.

Degree: PhD, 1998, Cranfield University

The subject of this thesis is about the balancing of large flexible rotors which exhibit mixed modal characteristics. The objective of the research was to develop a balancing procedure to determine correction masses without trial runs. This required the determination of(a) the modal vibration vectors for each resonance, (b) the modal damping ratios,(c) the mode shapes and(d) the equivalent mass of the rotor for each mode. It was made clear from the beginning that trial runs are unavoidable either, when the mode shapes cannot be determined using an analytical or numerical method, or when there is dual vibration at normal operating speed, produced by the influence of higher unbalanced modes, is too high to allow continuous operation of the machine. Therefore, the scope of the project was limited to the possible determination of correction masses without trial runs for the vibration modes included within the normal operating range. Some studies about the minimisation or complete elimination of trial runs have been published by several authors, but a literature search revealed no reports of systematic application of these procedures to field balancing of large turbo generators. This suggested that some practical difficulties had still to be overcome, opening the possibility for further research on this area. Analysis of the rotor response demonstrated the necessity of considering the angular position of the transducers when registering the rotor vibration. It was shown that measuring in a direction other than those of the principal axes of stiffness introduces errors when determining the magnitude and phase of the correction masses. That is to say, failing to consider the effects of the transducer angular position eliminates the possibility of balancing the rotor without trial runs. This is the first time that this problem has been recognised. The procedure developed was verified using an experimental rotor rig. The successful application of the procedure to the balancing of this rotor demonstrates that balancing withouttrialrunsisnotonlyatheoreticalbutalsoapracticalpossibility. The dynamic characteristics of the rotor rig, however, were some what limited and did not cover all the possibilities considered during the project. Therefore, a more complete numerical example was also successfully solved using the computer model of a rotor with characteristics similar to those of a real turbine, and whose unbalanced distribution was not initially known by this author.

Subjects/Keywords: 621.8; Turbogenerators; Rotor bearing vibration

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APA (6th Edition):

Preciado Delgado, E. (1998). Mixed modal balancing of flexible rotors without trial runs. (Doctoral Dissertation). Cranfield University. Retrieved from http://dspace.lib.cranfield.ac.uk/handle/1826/10638 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266988

Chicago Manual of Style (16th Edition):

Preciado Delgado, E. “Mixed modal balancing of flexible rotors without trial runs.” 1998. Doctoral Dissertation, Cranfield University. Accessed October 28, 2020. http://dspace.lib.cranfield.ac.uk/handle/1826/10638 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266988.

MLA Handbook (7th Edition):

Preciado Delgado, E. “Mixed modal balancing of flexible rotors without trial runs.” 1998. Web. 28 Oct 2020.

Vancouver:

Preciado Delgado E. Mixed modal balancing of flexible rotors without trial runs. [Internet] [Doctoral dissertation]. Cranfield University; 1998. [cited 2020 Oct 28]. Available from: http://dspace.lib.cranfield.ac.uk/handle/1826/10638 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266988.

Council of Science Editors:

Preciado Delgado E. Mixed modal balancing of flexible rotors without trial runs. [Doctoral Dissertation]. Cranfield University; 1998. Available from: http://dspace.lib.cranfield.ac.uk/handle/1826/10638 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266988


Cranfield University

2. Al Mandhari, Nasr. Influence of centrifugal compressor system components on its general rotordynamic characteristics.

Degree: MSc by Research, 2015, Cranfield University

Nowadays most countries are depending on Oil and Gas for their energy supply. In such operations, centrifugal compressors are dominating most of the used critical machines hence it is important to give these turbomachines more consideration in terms of their technical performance and reliability. Centrifugal compressors are one of many turbomachines that require technical solutions for Enhanced Oil Recovery (EOR). The oil and gas fields have different production environments which require adequate selection of compressors to handle the variance in gas and oil specifications and this in turn force the equipment manufacturers to revise their currently used design specifications. This research presents different types of compressors and their work principles with an emphasis on centrifugal compressor components The literature review carried in this research describes different cases in turbomachinery rotordynamics where failures were encountered at the commissioning and operation stages. Also the literature shows how these machines are improved technically by improving the compressor components performance such using Pocket Damper seals and tilting type bearings. The aim of this research is to study the factors affecting Rotordynamic behaviour of large natural gas centrifugal compressors. The study will review the influence of various conditions of rotor components such as bearings, seals, impellers, etc on the overall Rotordynamic stability at various process conditions ... [cont.].

Subjects/Keywords: Labyrinth Seals; Unbalance; Rotor; Bearing; Instability; Cross coupling forces; Torsional vibration; Lateral vibration; Damping; stiffness; Critical Speed

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Al Mandhari, N. (2015). Influence of centrifugal compressor system components on its general rotordynamic characteristics. (Doctoral Dissertation). Cranfield University. Retrieved from http://dspace.lib.cranfield.ac.uk/handle/1826/12326

Chicago Manual of Style (16th Edition):

Al Mandhari, Nasr. “Influence of centrifugal compressor system components on its general rotordynamic characteristics.” 2015. Doctoral Dissertation, Cranfield University. Accessed October 28, 2020. http://dspace.lib.cranfield.ac.uk/handle/1826/12326.

MLA Handbook (7th Edition):

Al Mandhari, Nasr. “Influence of centrifugal compressor system components on its general rotordynamic characteristics.” 2015. Web. 28 Oct 2020.

Vancouver:

Al Mandhari N. Influence of centrifugal compressor system components on its general rotordynamic characteristics. [Internet] [Doctoral dissertation]. Cranfield University; 2015. [cited 2020 Oct 28]. Available from: http://dspace.lib.cranfield.ac.uk/handle/1826/12326.

Council of Science Editors:

Al Mandhari N. Influence of centrifugal compressor system components on its general rotordynamic characteristics. [Doctoral Dissertation]. Cranfield University; 2015. Available from: http://dspace.lib.cranfield.ac.uk/handle/1826/12326


Virginia Tech

3. Alsaeed, Ali A. A Study of Methods for Improving the Dynamic Stability of High-Speed Turbochargers.

Degree: PhD, Mechanical Engineering, 2010, Virginia Tech

The turbocharger industry is booming recently, and there is an urgent need for new evaluations of the overall design. As the oil prices continue to rise, along with the new emissions regulations strictly enforced for the in-road as well as the off-road vehicles, the transition to turbocharged engines, and especially for diesel engines, has become irresistible. Higher power, smaller engines, reduced emissions, and overall better efficiency are the main concerns. By means of the recent development in the computational tools, a new era of the product development has emerged. Most diesel engine turbochargers incorporate floating-ring bearings that use the engine's oil for lubrication. The high-speed turbocharger is known to have subsynchronous vibrations at high amplitudes for a wide speed range that could reach 150,000 rpm. The bearing fluid-film whirl instability is the main source of the subsynchronous vibration. The nonlinear reaction forces inside the bearings are usually causing the rotor to whirl in a limit cycle but may become large enough to cause permanent damages. Additionally, the lubrication oil may leak at higher rates through the seals into the engine or the exhaust emissions. This dissertation investigates methods for improving the dynamic stability of the high-speed automotive turbochargers, especially designed for heavy-duty diesel engines that are used for example in heavy machinery, trucks, tractors, etc. The study utilizes the available modern computational tools in rotor-dynamics in addition to the locally developed supportive computer codes. This research is a major part of the turbocharger dynamic analysis supporting the current extensive experimental tests in the Virginia Tech Rotor Dynamics Laboratory for the product development of different high-speed diesel engine turbochargers. The study begins with the method of enhanced-performance hydrodynamic bearings. The aim is to modify the inner surface of the bearing for better dynamic characteristics. The finite-element model of the turbocharger rotor shaft with linearized bearing dynamic coefficients is developed. The system is solved for eigenvalues and eigenvectors in order to evaluate the dynamic stability. The first phase of the study demonstrated that there are two modes of instability that persist during much of the operating speed range, and one of the modes exhibits serious subsynchronous vibration levels at the higher speeds. The first unstable mode builds up at very low speeds forming a conical shape, where both rotor shaft ends whirl forward out-of-phase. The second unstable mode has a cylindrical shape with slight bending, where both rotor ends whirl forward in-phase. The outcome of the study is that the inner surface of the bearing has direct influence on the turbocharger dynamic stability. However, a fixed hydrodynamic bearing may not give total linear stability of the system if it is used without additional damper. The second method is to analytically design flexible damped bearing-supports in order to improve the dynamic… Advisors/Committee Members: Kirk, R. Gordon (committeechair), Vick, Brian L. (committee member), Taheri, Saied (committee member), Kraige, Luther Glenn (committee member), Kasarda, Mary E. F. (committee member).

Subjects/Keywords: turbocharger; vibration; stability; fluid-film bearing; unbalance; rotor-dynamics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Alsaeed, A. A. (2010). A Study of Methods for Improving the Dynamic Stability of High-Speed Turbochargers. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26664

Chicago Manual of Style (16th Edition):

Alsaeed, Ali A. “A Study of Methods for Improving the Dynamic Stability of High-Speed Turbochargers.” 2010. Doctoral Dissertation, Virginia Tech. Accessed October 28, 2020. http://hdl.handle.net/10919/26664.

MLA Handbook (7th Edition):

Alsaeed, Ali A. “A Study of Methods for Improving the Dynamic Stability of High-Speed Turbochargers.” 2010. Web. 28 Oct 2020.

Vancouver:

Alsaeed AA. A Study of Methods for Improving the Dynamic Stability of High-Speed Turbochargers. [Internet] [Doctoral dissertation]. Virginia Tech; 2010. [cited 2020 Oct 28]. Available from: http://hdl.handle.net/10919/26664.

Council of Science Editors:

Alsaeed AA. A Study of Methods for Improving the Dynamic Stability of High-Speed Turbochargers. [Doctoral Dissertation]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/26664

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