Spray Automated Balancing of Rotors: Concept and Initial Feasibility Study

This paper describes a new balancing concept: Spray Automated Balancing Of Rotors (SABOR). The Fuel Air Repetitive Explosion (FARE) process of metal film deposition is used to apply discrete amounts of metallic or ceramic particles to a spinning rotor at a controlled angular location on the rotor. In this way, without stopping the rotor, its mass eccentricity is changed in a manner designed to reduce the vibration sensed by a balancing machine. The system design and control for implementing SABOR are described. Preliminary results are presented from a demonstration rig that confirm the ability of the method to control both angle of application and rate of application to the extent necessary for effective automated balancing. The method is used to balance a spinning disk without stopping it. Results are presented which show that the bond strengths of materials deposited by the FARE process for use in small gas turbine engines are acceptable for the level of centrifugal stresses expected. Fatigue tests of sprayed samples show the data to be indistinguishable from those available for specimens hand-ground according to current balancing practice.