Engine Oil Condition Monitoring Using High Temperature Integrated Ultrasonic Transducers

High temperature integrated ultrasonic transducers (IUTs) made of thick piezoelectric composite films have been coated directly onto the lubricant oil supply and sump lines of a modified CF700 turbojet engine. These thick piezoelectric films are fabricated using a sol-gel spray technology. The center frequencies of these IUTs are in the range of 10 to 12 MHz. The top electrodes, electrical wires, conducing adhesive bond, connectors and cables have been tested for temperatures up to 500\ub0C. By operating these IUT in transmission mode, the amplitude and velocity of transmitted ultrasonic waves across the flow channel of the lubricant oil in supply and sump lines were mea sured during engine operation. The results have shown that the strength of the ultrasonic waves is sensitive to the presence of air bubbles in oil and the ultrasound velocity is linearly dependent on oil temperature. Based on the sensiti vity of ultrasound velocity to oil temperature, a method for real-time monitoring of engine oil degradation is proposed.Peer reviewed: YesNRC publication: Ye