Thesis Abstract

Abstract
This research project focuses on the design and construction of a Michell tilting pad apparatus. Michell tilting pad bearings are widely used in various rotating machinery applications due to their ability to provide stable operation, high load capacity, and reduced power consumption. The project aims to develop a test apparatus that can simulate the operating conditions of Michell tilting pad bearings to study their performance characteristics. The design process involves developing a compact and versatile apparatus that can accurately replicate the tilting pad bearing's behavior under different load and speed conditions. The construction of the apparatus includes selecting appropriate materials for the bearing pads, housing, and support structure to ensure durability and reliability during testing. Special attention is given to the tilting mechanism to allow for precise control of pad movement and tilt angles. The apparatus is equipped with sensors and data acquisition systems to monitor various parameters such as pad temperature, pad deflection, and oil film thickness. These measurements provide insights into the bearing's performance under different operating conditions and help validate theoretical models and simulations. The experimental data obtained from the apparatus can be used to optimize the design of Michell tilting pad bearings for specific applications. The construction process involves machining precision components and assembling them with care to ensure proper alignment and fit. The apparatus is tested for functionality and calibration to ensure accurate and repeatable results during experiments. The final apparatus design is compact, user-friendly, and capable of accommodating different pad configurations to study various bearing designs. Overall, the design and construction of the Michell tilting pad apparatus provide a valuable tool for researchers and engineers to study the performance of tilting pad bearings in a controlled laboratory environment. The apparatus can be used to investigate the effects of different operating conditions on bearing performance, optimize bearing design parameters, and validate numerical models. The insights gained from these experiments can lead to the development of improved Michell tilting pad bearings with enhanced performance and reliability for a wide range of industrial applications.

Thesis Overview

INTRODUCTION

The Michell tilting pad apparatus is a hydrodynamic measuring instrument developed in the early 1880’s in the laboratory of Beauchamp Tower in England. Tower was employed to study the friction in railway journal bearings and come up with the best method of lubricating them. The Michell tilting pad apparatus is used broadly in two different experiments namely;
1) Determination of the load carrying capacity of the slider bearing.
2) Confirming the theory of the hydrodynamic lubrication.
Tilting pad journal bearings are a source of both static support and dynamic stiffness and damping. Tilting pad journal bearings have a number of pads, typically four or five. Each pad in the bearing is free to rotate about a pivot and cannot support a moment. As a result, the destabilizing forces are greatly reduced or eliminated, and the bearings are no longer a potential source of rotordynamic instability. This feature has made tilting pad journal bearings the standard fluid-film bearing for most high-speed applications. High-speed rotordynamic applications often have rotors that pass through one or two bending critical speeds as the machines are accelerated to the operating speed. The damping from the fluid film bearings is required to safely pass through these bending critical speeds as the rotating element is accelerated. The damping also helps suppress potentially destabilizing forces from sources such as radial seals, balance pistons, impeller eye seals, internal friction fits, and unbalanced electromagnetic forces.

1.1 AIMS AND OBJECTIVES OF THE PROJECT

The project designing, constructing and testing on the Michell tilting pad apparatus is aimed at achieving the following objectives:
1) To verify the hydrodynamic theory of lubrication as it was propounded by Beauchamp Tower in 1880 AD.
2) To determine the load carrying capacity of the tilting pad slider bearing
3) To provide the fluid mechanics laboratory of the Mechanical Engineering Department with a hydrodynamic fluid analyzing apparatus.
4) To activate and motivate the students potentials into practically solving problems facing mankind.
5) To run tests with the apparatus and compare the results obtained with the established or ideal standards.

1.2 PROJECT JUSTIFICATION

Engineering is known to be to be practice-oriented discipline. In Other Words, no useful Engineering endeavor can exist in theory only, it must be applied to touch and transform life through meaningful practice. Therefore, this project task given to us is to ensure the knowledge we students gained throughout our five year degree programme and channeled towards the construction of Mechanical Engineering equipments.

1.3 APPLICATIONS AND USES

The Michell tilting pad apparatus is applicable in experiments which does not require;
3
1) Hydrostatic lubrication
2) Boundary lubrication
3) Solid lubrication
4) Elastohydrodynamic form of lubrication.
It only finds its application useful in full film or fluid lubrications in motion, in which there is a situation that the load carrying surfaces of the bearing are separated by an adequate supply at all times of a relatively thick film of lubricant, so as to prevent metal to metal contact and that the stability thus obtained can be explained by the laws of fluid mechanics. The Mitchell tilting pad is a Mechanical Engineering apparatus with the above aims and objectives.

1.4 LIMITATIONS

The Michell tilting pad apparatus is limited to use with the specified oil viscosity (SAE20W/50) or White oil which is typical automobile engine oil. The Michell tilting pad apparatus is also limited to operation when there is power failure or insufficient supply of power that drives the electric motor, other limitations are stipulated below;
1) The use of lubricants that do not obey Newton’s law of viscous flow.
2) The use of compressible lubricants
3) Fluid pressure varying in the axial direction.
From the limitations stated above, it is necessary to identify the Newton’s viscous effect, which states that the shear stress in the fluid is proportional to the rate of change of velocity with respect to ‘y’.