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

Parameter identification of a rotor supported in a pressurized bearing lubricated with water

A rig for testing an externally pressurized (hydrostatic), water-lubricated bearing was developed. Applying a nonsynchronous sweep frequency, rotating perturbation force with a constant amplitude as an input, rotor vibration response data was acquired in Bode and Dynamic Stiffness formats. Using this data, the parameters of the rotor/bearing system were identified. The rotor/bearing model was represented by the generalized (modal) parameters of the first lateral mode, with the rotational character of the fluid force taken into account

Influence of rubbing on rotor dynamics, part 1

The results of analytical and experimental research on rotor-to-stationary element rubbing in rotating machines are presented. A characterization of physical phenomena associated with rubbing, as well as a literature survey on the subject of rub is given. The experimental results were obtained from two rubbing rotor rigs: one, which dynamically simulates the space shuttle main engine high pressure fuel turbopump (HPFTP), and the second one, much simpler, a two-mode rotor rig, designed for more generic studies on rotor-to-stator rubbing. Two areas were studied: generic rotor-to-stator rub-related dynamic phenomena affecting rotating machine behavior and applications to the space shuttle HPFTP. An outline of application of dynamic stiffness methodology for identification of rotor/bearing system modal parameters is given. The mathematical model of rotor/bearing/seal system under rub condition is given. The computer program was developed to calculate rotor responses. Compared with experimental results the computed results prove an adequacy of the model

Influence of rubbing on rotor dynamics, part 2

Rotor dynamic behavior depends considerably on how much the specific physical phenomena accompanying rotor rubbing against the stator is involved. The experimental results of rotor-to-stator rubbing contact are analyzed. The computer code is described for obtaining numerical calculations of rotor-to-stator rubbing system dynamic responses. Computer generated results are provided. The reduced dynamic data from High Pressure Fuel Turbo Pump (HPFTP) hot fire test are given. The results provide some significant conclusions. Information is provided on the electronic instrumentation used in the experimental testing

Forward Subrotative Speed Resonance Action Of Rotating Machinery

PaperPg. 103-114.A wide variety of mechanisms can create net effective forces on those rotor systems which follow the rotor around in its rotation direction. While whatever dampening the rotor system has always exists, it is frequently the nature of these forward acting forces to act effectively opposite to the system damping. Once any one or a combination of these forces matches or exceeds the existing rotor damping the rotor system responds by excitation of resonances which lie below rotative speed. To show this general category of machinery malfunction mechanisms, first the oil whirl and oil whip behaviors are shown in graphical non-mathematical forms. To show that its relationship to oil whip is more than symptom-deep, the next presentation is the internal friction malfunction. Following this, a series of other known energy transformers are shown to exhibit the behavior and relationship of this class of rotor malfunction mechanisms. The relationships between the forward acting mechanisms, the non-directional mechanisms, and reverse mechanisms are discussed, and demonstrations of some of the forward mechanisms are performed. Recent classical cases of some of the destructive mechanisms are presented, and the general category of malfunction is summarized

From the Author to the Proprietor: Newspaper Copyright and The Times (1842-1956)

The article examines a major transformation in newspaper copyright and the existence of modern media markets in Great Britain. It explores the legal foundation of news copyright under the Copyright Act 1842 and depicts the difficulty in reconciling the reporter's right with newspaper management practices. It also examines the creative role played by managers as well as key legal personnel at "The Times" newspaper