Project Leaders: Paul Michael, Research Chemist & Ashlie Martini, Professor of Mechanical Engineering
Institutions: Milwaukee School of Engineering & University of California, Merced
Viscosity modifiers are used in most hydraulic fluid formulations and are known to positively impact efficiency through three mechanisms: (i) reducing leakage flow by thickening, (ii) reducing viscous friction through beneficial shear thinning, and (iii) reducing traction via formulation with lower molecular weight base oils. We explored the first mechanism in our previous CCEFP project and showed direct correlations between thickening as a function of shear rate and leakage flow. However, the second two mechanisms remain unexplored, despite being critical to the mechanical efficiency of pumps. In the proposed project we will disentangle the effects of beneficial polymer shear thinning and base oil traction effects on pump torque. In collaboration with Afton Chemical and Evonik Oil Additives, we will focus on two widely used viscosity modifiers, polyisobutylene and polymethacrylate. The outcome will be new understanding of how polymer-enhanced hydraulic fluids improve efficiency which in turn will enable selection of optimized polymer/base fluid combinations for a given application to maximize mechanical efficiency.