Stability evaluation of rotor/bearing system

A stability study of rotor/bearing systems is presented. Even though it was limited to study of a fully lubricated bearing subject to oil whirl, and further limited to low eccentricity region for linearity and with only one type of lubricant, it can be seen that the perturbation methodology, together with the sorting of the impedance terms into direct and quadrature with respect to input force can be very useful to the general study of stability. Further, the concept of active feedback should assist to increase knowledge in rotor system stability. While there remains a large amount of study to be accomplished, perhaps some more tools are available to assist this field of analysis

Comments on Frequency Swept Rotating Input Perturbation Techniques and Identification of the Fluid Force Models in Rotor/bearing/seal Systems and Fluid Handling Machines

Perturbation techniques used for identification of rotating system dynamic characteristics are described. A comparison between two periodic frequency-swept perturbation methods applied in identification of fluid forces of rotating machines is presented. The description of the fluid force model identified by inputting circular periodic frequency-swept force is given. This model is based on the existence and strength of the circumferential flow, most often generated by the shaft rotation. The application of the fluid force model in rotor dynamic analysis is presented. It is shown that the rotor stability is an entire rotating system property. Some areas for further research are discussed

The parameters and measurements of the destabilizing actions of rotating machines, and the assumptions of the 1950's

The measurability of destabilizing actions is demonstrated for a rotor built to produce a forward circular, self excited malfunction (gas whip). It is argued that the continued use of past modeling technqiues is unfortunate in that it has led to the use of inappropriate words to express what is happening and a lack of full understanding of the category of forward circular whip instability mechanisms

Why have hydrostatic bearings been avoided as a stabilizing element for rotating machines

The advantages are discussed of hydrostatic, high pressure bearings as providers of higher margin of stability to the rotor/bearing systems. It is apparent that deliberate use of hydrostatic bearing high pressure lubricated (any gas or liquid) can easily be used to build higher stability margin into rotating machinery, in spite of the thirty years bias against high pressure lubrication. Since this supply pressure is controllable (the Direct Dynamic Stiffness at lower eccentricity is also controllable) so that within some rotor system limits, the stability margin and dynamic response of the rotor system is more readily controllable. It may be possible to take advantage of this effect in the various seals, as well as the bearings, to assist with stability margin and dynamic response of rotating machinery. The stability of the bearing can be additionally improved by taking advantage of the anti-swirling concept. The high pressure fluid supply inlets should be located tangentially at the bearing circumference and directed against rotation. The incoming fluid flow creates stability by reducing the swirling rate

Privilege and Property. Essays on the History of Copyright

Copyright law is the site of significant contemporary controversy. In recent years copyright history has transformed as a subject from being one of interest to a few books historians to the focus of sustained historical investigation attracting the attention of scholars from across the humanities. This book comprises a collection of essays on copyright history by leading experts drawn from a range of countries and disciplinary perspectives. Covering the period from 1450 to 1900, these essays engage with a number of related themes. The first considers the general movement, from the sixteenth century onwards, from privilege to property-based conceptions of copyright protection. The second addresses the relationship between the protection provided for literary and print materials and that provided for other forms of cultural production. The third concerns the significance and relevance of these various histories in shaping and informing contemporary policy and academic practice. Essays include: 0. The History of Copyright History, by Kretschmer, Deazley & Bently; 1. From Gunpowder to Print: The Common Origins of Copyright and Patent, by Joanna Kostylo; 2. A Mongrel of early modern copyright: Scotland in European Persepctive, by Alastair Mann; 3. The Public Sphere and the Emergence of Copyright: Areopagitica, the Stationers’ Company, and the Statute of Anne, by Mark Rose; 4. Early American Printing Privileges: the Ambivalent Origins of Authors’ Copyright in America, by Oren Bracha; 5. Author and Work in the French Print Privileges System: Some Milestones, by Laurent Pfister; 6. A Venetian Experiment on Perpetual Copyright, by Maurizio Borghi; 7. Les formalités son mortes, vive les formalities! Copyright formalities in nineteenth century Europe, by Stef van Gompel; 8. The Berlin Publisher Friedrich Nicolai and the reprinting sections of the Prussian Statute Book of 1794, by Friedemann Kawohl; 9. Nineteenth Century Controversies relating to the protection of Artistic Property in France, by Frédéric Rideau; 10. Maps, Views and Ornament. Visualising Property in Art and Law: The Case of pre-modern France, by Katie Scott; 11. Breaking the Mould? The Radical Nature of the Fine Art Copyright Bill 1862, by Ronan Deazley; 12. ‘Neither bolt nor chain, iron safe nor private watchman, can prevent the theft of words’: The birth of the performing right in Britain, by Isabella Alexander; 13. The Return of the Commons: Copyright History as a Common Source, by Karl-Nikolaus Peifer; 14. The Significance of Copyright History for the Publishing History and Historians, by John Feather; 15. Metaphors of Intellectual Property, by William St Clair. The volume is a companion to the digital archive Primary Sources on Copyright (1450-1900), funded by the UK Arts and Humanities Research Council (AHRC): www.copyrighthistory.or

Role of circumferential flow in the stability of fluid-handling machine rotors

The recent studies of the dynamic stiffness properties of fluid lubricated bearing and seals by the authors have yielded most of the generalized characteristics discussed and used in this paper. They include bearing and seal nonlinear fluid film properties associated with stiffness, damping, and fluid average circumferential velocity ratio. Analytical relationships yield the rotor system's dynamic stiffness characteristics. This paper shows the combination of these data to provide the fluid-induced rotor stability equations

Rotor internal friction instability

Two aspects of internal friction affecting stability of rotating machines are discussed. The first role of internal friction consists of decreasing the level of effective damping during rotor subsynchronous and backward precessional vibrations caused by some other instability mechanisms. The second role of internal frication consists of creating rotor instability, i.e., causing self-excited subsynchronous vibrations. Experimental test results document both of these aspects

Copyright, Translations, and Relations between Britain and India in the Nineteenth and Early Twentieth Centuries

This paper examines the tension between trade and development, and its handling in multiple layers of law-making through an historical case study concerning copyright in India in the late-nineteenth and early-twentieth century. The paper explains the emergence of views in the Government of India of what copyright law should cover that reflected longstanding but not unproblematic assumptions about India\u27s need for European knowledge and learning. The belief that India needed access to European knowledge informed resistance to the desires of British publishers that copyright owners should be able to control the making of translations of their works. These divergences between what are broadly described as British and Indian views as to the desirability of translation rights emerged towards the end of the nineteenth century in a complex legal environment in which international copyright arrangements were added to those of imperial and local Indian copyright. After two cases in which the Bombay High Court denied the existence of a translation right (under both Indian and the imperial Copyright Act), the British government and the Government of India came under pressure from publishers to adopt such a right. The paper describes how the Government of India resisted such attempts and the deference the British Government was willing to offer it. However, specifically Indian desires were neglected when Britain negotiated copyright matters on the international stage. Instead, Britain committed itself to an increasingly full translation right in the various revisions of Berne Convention, and following the 1908 Revision, sought to legislate a new Imperial Code that reflected these commitments. While India complied with British wishes, and introduced the imperial copyright regime, it utilized the residual powers granted to it to modify and limit the duration of the translation rights. However, the limited application of the modified translation right to works published in India meant that it was an unsuitable means for facilitating the acquisition of European knowledge. Rather, the modifications must be understood symbolically as a proclamation of autonomy, and instrumentally, as a mechanism for the production of an Indian national culture. The case study of the translation right in India highlights the critical importance of social, economic, and cultural context to the operation of copyright and simultaneously resonates with contemporary discussions as to how to accommodate local difference in the context of globalized norms

Dynamic stiffness characteristics of high eccentricity ratio bearings and seals by perturbation testing

The complex behavior of cylindrical bearings and seals that are statically loaded to eccentricities in excess of 0.7 are examined. The stiffness algorithms as a function of static load are developed from perturbation methodology by empirical modeling

Measurement of rotor system dynamic stiffness by perturbation testing

Specific aspects of the application of Modal Analysis to rotating machines are discussed. For lowest mode analysis, the circular force perturbation testing gives the best results. Examples of application are presented