Rotating Machines Featuring New Rotor Topologies, Internal Actuation and Magnetic Bearings for Active Control

Abstract

Rotating machines underpin many aspects of modern technology, from the sector of energy with flywheels and gas turbines, transport with aircraft jet engines, to manufacturing with spindles. These rotors generate vibrations that are detrimental to the performance of the machines. Reducing these vibrations has been a rich research topic, but to enable extremely high performance a transformative breakthrough is required.

This project presents the design, modelling, and experimental validation of the concept of an active rotor with onboard hydraulic bending, supported by Active Magnetic Bearings (AMBs). Two lead screw actuators inside a hollow shell, which forms the centre of the rotor, pressurise four hydraulic lines. This results in moments that are used to control the bend of the rotor. The hydraulic jack principle is used to multiply the actuator force. A battery and radio signal are used to communicate between the external control computer and an onboard Arduino controller.

A finite element model is used to predict the amount of bend generated by a pressure difference of 100bar between opposite lines of the hydraulic system. The location of the critical speeds is also investigated, with the main one being triggered by the rotor vertical vibration interacting with the base plate at 800RPM. The achievable amount of vibration reduction is predicted in relation to the rotor unbalance.

The technique used to measure the oil pressure without the use of pressure sensors via strain gauges positioned on the structure is presented. Additionally, all the steps taken to ensure minimal leakage and low air content in the hydraulic lines are given.

A laser tracker was used to measure targets distributed along the length of the rotor, and the response to pressure variations of the internal hydraulic lines was studied. The maximum bending amplitude achievable with one control axis was 23µm. Rotating tests between 500RPM and 2200RPM were then carried out to study the dynamic response. Once identified, the optimal bending phase leads to 50% to 75% of decrease in the vibration orbit. Bending actuation was also used with the rotor on rolling elements bearings to cancel the vibration induced by an unbalance of 900gmm up to 1400RPM and 360gmm up to 2000RPM.

Date of Award	13 Sept 2023
Original language	English
Awarding Institution	University of Bath
Supervisor	Patrick Keogh (Supervisor) & Nicola Bailey (Supervisor)