Application of Ultrasound in the measurement of Lubricant Fluid Film Thickness in the Piston-Cylinder Interface of an Axial Piston Pump

In this paper a feasibility study has been conducted to determine a technique for the measurement of lubricant fluid film thickness in the piston-cylinder interface of an axial piston pump. The thickness of the lubricant film has a significant impact on the efficiency of the piston pump yet it still remains an uncertainty. If the lubricant film is too thin then friction will cause excessive damage resulting in deformation of interacting surfaces resulting in further uncertainty in thickness measurement. If the lubricant film is too thick then there is excessive leakage which will compromise the efficiency of the system. Acoustic, inductive, capacitive and optical techniques were investigated through literature review and it was decided to investigate further into acoustic techniques. Experimental procedures using ultrasound to measure the lubricant fluid film thickness are investigated and an experimental procedure is explored further into in this paper. The governing factors of measuring fluid film thickness were determined. The effect of surface deformation on lubricant thickness is also investigated and a technique of imaging using ultrasonic sensors is presented. A CAD model displaying sensor locations and mounting apparatus in piston-cylinder interface is also presented. A feasible method for the measurement of lubricant fluid film thickness is proposed. These measurements will be used to validate existing models which predict the behavior of lubricant fluid film.