Water hydraulics are used for applications which require an environmental safety standard for the fluid. In comparison to oil, lubrication with water is a challenging aspect because of the fluid’s lower viscosity. Wear and leakage in water lubricated contacts require lower pressure loads. In order to estimate the possible load carrying capacity in water hydraulics, the tribological contact between the piston slipper and swash plate in axial piston machine and respectively eccentric shaft in radial piston machines is investigated. For this purpose simulations based on the Reynolds-Equation are carried out and analysed.

Digital pumps using high speed on/off valves to control fluid entering and leaving the piston cylinder displacement chamber can increase efficiency by eliminating the leakage and friction associated with the port plate. Leakage scales with the displacement because the displacement chamber is only pressurized during a portion of the piston stroke. This work investigates the modeling, prototyping, and testing of two prototype digital pumps. The first prototype actuated on/off valves using electrical solenoids; the second configuration used mechanical cams. The mechanical actuation improved the repeatability and accuracy of the valves, matching or exceeding the performance of the electrically actuated prototype while eliminating all transducers and electronics. The mechanically actuated pump operated at 86% efficiency (full displacement) and 58% efficiency (25% displacement).

A new-born design and construction of a mini gerotor metering pump with trochoidal-teeth is presented. The
technical innovation in this new-born design is to study the fluid dynamic effects of interteeth and lateral
clearances by using OpenFOAM toolbox, an open source CFD software. This work is based on two critical
aspects, the deforming of the mesh following the solid gears rotation, a complex interaction between mesh and
gear profile surface that has to maintain a moderate quality of the mesh, and the simulation by means of a new
boundary condition of the interteeth contact, reproducing actual contact points between the rotors. The posibility
of contact point simulation by means of a proper mesh motion model is also suggested.

The proportion of churning losses increases significantly with the increasing speed, thus churning losses reduction has a significant influence on the efficiency improvement in axial piston pumps. In this paper, a test pump with nano-coating is proposed, and analyzed in details. The analysis shows that the surface energy and friction coefficient on the outside surface of cylinder block are reduced due to the decrease of surface roughness and wettability on the nano-film. Experimental results indicate that energy losses of the proposed nano-coated test pump are reduced by 12~37%. Some of the conclusions in this paper may provide a suitable novel guidance for improving the friction-reducing abilities in axial piston pumps.

The objective of this work is to design and investigate the aerodynamic performance of a novel integrated motor-compressor. The integrated motor-compressor integrates the axial-flow compression into the electromagnetic function by designing the airfoil-shaped rotor of the electric machine to provide compression. Hence, the integrated motor-compressor is both an axial-flow compressor and an electric machine. It is capable of providing axial flow compression and electromagnetic torque at the same time. In this work, the aerodynamic design of the proposed machine is done and evaluated by both analytical method and computational fluid dynamics (CFD). The effect of attack angle to the blade lift and drag forces are investigated. The effect of solidity to the axial-flow compressor performance is also evaluated. The electromagnetic performance of the proposed machine is investigated by motor sizing equations and finite element analysis (FEA).