Date of Award

5-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Committee Chair

Monika Ivantysynova

Committee Member 1

Andrea Vacca

Committee Member 2

Farshid Sadeghi

Committee Member 3

Karthik Ramani

Abstract

The piston cylinder interface of axial piston machines of swash plate type is one of three critical lubricating interfaces that are responsible for proper machine operation. The interface must simultaneously bear large time changing external loads while preventing excessive leakage or friction. For long term machine reliability, a full fluid film must be maintained between the piston and cylinder surfaces. The goal of this work is to further the understanding of the phenomena contributing to fluid film behavior. A novel multi-body non-isothermal fluid-structure-thermal-interaction piston cylinder interface model is introduced that considers compressible fluid flow, squeeze due to transient deformation, as well as realistic surface profiles based on profilometer measurements. Piston force balance and correction forces are examined in instances where the fluid pressure build up numerically calculated on the standard coarse grid does not fully support the required load. Results of the piston cylinder model are verified by comparison to measurements made using a special purpose test pump. Small areas of collapsed film due to insufficient calculated load support are further investigated through a novel High Definition model that individually refines the analysis of each area of collapsed film. Dynamic grid refinement and a linear half space pressure-deformation model are employed to show the potential for full film load support in these areas. Combining the developed dynamic grid refinement method with the full piston cylinder model and comparing to measurements confirms full film lubrication is occurring.

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