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Over recent years ionic liquids have gained in importance, causing a growing number of scientists and engineers to investigate possible applications for these liquids because of their unique physical and chemical properties. Their outstanding advantages such as nonflammable liquid within a broad liquid range, high thermal, mechanical, and chemical stabilities, low solubility for gases, attractive tribological properties (lubrication), and very low compressibility, and so forth, make them more interesting for applications in mechanical engineering, offering great potential for new innovative processes, and also as a novel hydraulic fluid. This paper focuses on the outstanding compressibility properties of ionic liquid EMIM-EtSO4, a very important physical chemically property when IL is used as a hydraulic fluid. This very low compressibility (respectively, very high Bulk modulus), compared to the classical hydraulic mineral oils or the non-flammable HFDU type of hydraulic fluids, opens up new possibilities regarding its usage within hydraulic systems with increased dynamics, respectively, systems' dynamic responses.

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In the field of hydraulic drive technology various power supply systems are used within different power unit set-ups. The both of two mostly used drive concepts in modern electrohydraulic systems, a variable displacement pump driven by constant speed electric motor and fixed displacement pump driven by a variable speed electric motor, have some disadvantages, especially regarding the increasing demand for maximum efficiency of the entire power unit without lowering the high dynamics. The combination of a variable pump and speed-controlled electric motor, offers the option of setting two parameters of the drive, the rotational speed of the motor and the pump flow-rate.Such a combination allows all power unit components to operate within the areas of their maximum efficiencies, the so-called maximum efficiency drive. A prerequisite for designing suitable controllers that would ensure the operations of individual components within the areas of maximum efficiency, regardless of the current operating point, is certainly knowledge about the efficiency area of the entire power unit. This paper presents a procedure for determining areas of efficiency, first on the basis of simulation and detailed models of each component, and later verification of the model using an experiment.

Hydraulic power units are one of the most commonly used power sources in industry. The progress in recent years has offered high efficiency and reliable hydraulic components, yet the hydraulic tank design is often neglected part of the development.The paper presents the development of industrial 400 litre hydraulic tank. In order to reduce oil swirling and improve stability of fluid flow, CFD simulations of oil flow inside hydraulic tank were made. Several variations of new hydraulic tank designs are compared with standard industrial tank. Furthermore, to achieve steady flow through the entire reservoir and reduce the phenomenon of oil swirling, newly-developed diffuser is used. Consequently a full scale hydraulic power unit was built according to obtained results.