Prediction of Vibration Behaviour of Large Turbo-Machinery on Elastic Foundations Due to Unbalance and Coupling Misalignment

A computational assessment of the vibrational behaviour of turbo-sets on elastic foundations is of significance with regard to the design and optimization of the complete installation. Using modern computer programs, for example, MADYN, and refined modelling techniques, the natural and response behaviour of even large systems can be calculated reliably, but there does remain some uncertainty, especially with regard to vibration excitement. The present contribution develops possibilities of how to handle these problems.

Statics of Gas-Lubricated Slider Bearings in Magnetic Recording Disk Files

This paper presents theoretical and experimental analyses of the static characteristics of gas-lubricated slider bearings. An implicit scheme, based on the Patankar-Spalding method, which is commonly utilized in the numerical heat transfer and fluid flow, is developed for the numerical solution of the Reynolds equation. Further investigations on the steady static minimum flying height and the pitch angle are presented by use of a transient response analysis. Theoretical results are experimentally verified to be correct and reliable. By comparing a grooved slider with a non-grooved one in the surface of bearing rails, it is concluded that the grooves in the surface of bearing rails may effectively improve statics of gas-lubricated slider bearings in magnetic disk storages.

Kinetostatic Modelling of an Unconventional Motion Conversion Mechanism in Application of a Plunger Pump System

The development of a mathematical model of Stiller-Smith mechanism for the application of a four-cylinder plunger pump system is presented. The magnitude and direction of the internal dynamic load are obtained by solving a set of equations using the overall geometric parameters, prescribed motions, inertia distribution and applied torques on the system. The simulation presented here yields the history of the internal loads, which are then normalized with respect to the required peak output load on the plungers, through an entire rotary cycle. The approach allows for the development of further design criteria through parametric sensitivity studies.

In-Grasp Robotic Fine Motion with Frictionless Elastic Point Contacts

This paper discusses the form-closure robotic grasping of a rigid object and shows how fine motion of the grasped object may be induced. Preloads are applied along point contacts, a knowledge of whose elastic properties are necessary to overcome statical indeterminacy in the grasp, and whose properties can be exploited to allow the induced fine motion. Appropriate values of these preloads can be derived so as to maintain the grasp against external loads and to induce predefined fine motion to the object. Where a defined fine motion cannot be exactly induced, a best approximation can be found. The analytical approach is supported with examples.

Parametric Minimum Film Thickness Performance of an Elastic Big-End Bearing under Inertial Load

Big-end bearing design has, in the past, been well served by design charts. However, in more recent times, simple design-level information has not kept pace with developments in bearing analysis. This paper presents simple parameterizations of the effects of con-rod distortion on dynamic big-end minimum film thickness performance. Non-dimensionalization of cyclic minimum film thickness, film mechanism transitions, bearing flexibility and inertial load enabled quantitative tribological measures of elastic geometry to be developed. This characterization, ratified against corresponding full analyses, provides a useful new insight into elastic con-rod bearing design, something hitherto based on experience and intuition.

Computer Simulation of a Variable Fill Hydraulic Dynamometer: Part 2: Steady State and Dynamic Open-Loop Performance

Part 1 of this paper presented a theoretical model for the torque absorption and energy dissipation processes in a variable fill Froude-type hydraulic dynamometer. Effects of working compartment geometry changes on steady state running full torque absorption performance were also shown. Part 2 presents both steady state and dynamic computer simulations of an engine-dynamometer system under open-loop control. Comparisons between model simulations and test bed data show that the dynamic model reproduces both the negative torque-speed dynamometer characteristics and other transient phenomena that occur under real open-loop partial fill conditions. Requirements of control systems to modify this behaviour and ensure stable set point holding are introduced. Part 3 of the paper will deal with the simulation of the engine-dynamometer system under closed-loop control.

Alias Errors in Precision Rotary Encoder Calibration

Discrepancies between errors measured by back-to-back tests on rotary encoders and the errors quoted by the manufacturers led to investigation of the causes for the difference. An error that was apparently at 96 cycles per revolution was found to be due to a much higher frequency which was well outside the normal operating range for transmission error work.