Magnetic damping system to limit blade tip vibrations in turbomachines

Abstract

A system that provides reliable blade damping with the capability to limit vibration in the blade tips to inconsequential amplitudes. A preferred embodiment of the invention comprises configurations of stationary electromagnets placed on a turboengine in three groups of three magnets, each separated circumferentially by 120 degrees, and each being powered and controlled by one central electronics module. The module can turn on the magnetic fields when the rotor is at a known critical speed or passing through a range of speeds that are known to cause large vibrations. Each blade tip enters the magnetic field of each electromagnet which is turned on once in a complete rotation. The electromagnets are located on or embedded in the casing surrounding the blade disk assembly. The blades may be of either magnetic or nonmagnetic material, but must be able to conduct an electrical current. As the blades cut through the lines of force of the electromagnets, bi-circulating eddy currents are set up in conformance to Faraday's Law of Magnetic Induction. The vibratory motions in the blades are dampened by the forces of the eddy currents. The preferred application of this invention is to gas turbine engines used to power passenger, cargo and military aircraft. Other possible applications include damping steam turbine blades for power stations and nuclear reactor systems.