The paper presents possible use of Ionic Liquids as a lubricant suitable for use as a hydraulic fluid. After a short presentation of ionic liquids and their interesting properties, the paper focuses on very low compressibility (resp. very high Bulk modulus) of ILs compared to the common hydraulic mineral oils and investigates the effects of their high bulk modulus on pressure pulsation and flow ripple of hydraulic pump.
Two most adequate ionic liquids for hydraulic application with highest bulk modulus where chosen and a special test rig was built using bent axis 7-piston pump powered by a servo motor. Results show change of resonance frequencies of entire hydraulic system due to higher bulk modulus and higher density of the ionic liquids. On the other hand, there is no significant change in pump pressure pulsation in non-resonance frequency range below 2500 rpm.

With pressure levels rising for applications such as compression-ignition engines and numerical design approaches are used to optimise fluid power components, rheological properties of the fluid in the according operation points gain interest. The measurement of viscosity under high-pressure has been subject to research for many years. However, to this day, it still bears uncertainty. This paper presents typical errors for high-pressure measurements and strategies to minimise uncertainty. With a focus on material combinations, geometric parameters and the measurement principle, the errors are explained, and an improvement proposal is given based on the findings.

Utilizing accumulators in hydraulic systems with the purpose of energy storage, temporal changes in state of the storage medium must be considered during design and prospectively also monitored during operation. High efficiency aside, the reduction of weight and size is of high interest, especially in mobile applications. Regarding these objectives, accumulators with sorbent material are an innovative and promising development. The herein introduced generic physical model enables the consideration of sorption processes in the description of such accumulators. The results are discussed by means of time response analysis and compared to the behaviour of conventional accumulators. Potential use cases are investigated and the model application to a practical duty cycle is shown.

High pressures and harsh working conditions in hydraulic systems has made us sceptical about suitability of
plastics for its components. Nevertheless in some cases it can become a sufficient substitute for expensive steels.
In water hydraulic components, where demanding surface contacts are slowing its development, polymers can be
a solution. Focus of our research is on implementing polymers into a moving contact in high speed water
hydraulic on/off valve where high friction and wear occur. In this article we are presenting friction coefficient
and wear rate of some engineering polymers immersed in water for different time periods. PEEK and POM
showed comparable results regardless their price difference.

To reduce turbine mass, maintenance requirements, complexity, and thus the Levelized Cost of Energy (LCOE) for offshore wind, the Delft Offshore Turbine (DOT) concept combines individual hydraulic drive train wind turbines with a centralized generator system. In 2015 DOT built and tested a large-scale prototype, by retrofitting a 600kW wind turbine with a hydraulic drive train using commercial off-the-shelf components. The goal was to showcase a proof of concept from a technological and controllability point-of-view. This paper presents the results of building and testing the DOT500. Its drive train has an oil-hydraulic stage and a water-hydraulic stage. The method of rotor torque control with spear valves is novel and proves to be a substitute for conventional implementations.