Development of an Ultrasonic Sensing Technique to Measure Lubricant Viscosity in Engine Journal Bearing In-Situ

This thesis presents a novel ultrasonic instrument for non-invasive and in-situ characterization of journal bearing lubricant viscosity. In particular, the application to journal bearings is described by non-invasively measuring the viscosity and localized power losses throughout operation. 

This ultrasonic viscometer is based on the reflection of polarized shear waves from a thin resonating coating layer to increase the measurement sensitivity, in comparison to conventional ultrasonic methods. This instrument allows for a full engine oil viscoelastic characterization in-situ. 

The book investigates the effects of temperature, pressure and shear rate, and describes in detail the ultrasonic setup and method. Further, it demonstrates that the same technique can be applied similarly to monitor the lubrication of other engine components. As such, it offers a unique instrument that can drive the research of oil formulations to improve engine performance and fulfill the requirements of international fuel economy regulations. 

Michele Schirru graduated as Mechanical Engineer at the University of Cagliari (Italy) in 2012. The same year, he joined the Leonardo Center for Tribology at the University of Sheffield for a PhD course in Tribology and graduated in 2016. His research focuses on the development of novel ultrasonic viscometer techniques and instrumentations for in-situ monitoring of lubricant performances in engines. He obtained the first circumferential viscosity measurement in an operating journal bearing using a novel matching layer viscometer. This technique is now employed by different lubricant manufacturers to design novel fully formulated engine oils. He won the 23^rd Mission for Tribology IMechE Prize for the novelty of his research  and also he won the 'Innovation in Tribology Prize' 2016 of the Institute of Physics Tribology Group.