Department of Hydraulics and Pneumatics, Faculty of Mechanical Engineering, Gdansk University of Technology, Gdansk, Poland

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FLUID POWER RESEARCH CENTRES WORLD-WIDE

General Information

Fig. 1: Gdansk University of Technology - main building

The GUT, whose academic community currently comprises 17000 students and 2500 staff, has 10 faculties:

Applied Physics and Mathematics, Architecture, Chemical Faculty, Civil Engineering, Electrical and Control Engineering, Electronics Telecommunication and Informatics, Hydro and Environmental Engineering, Management and Economics, Mechanical Engineering, Ocean Engineering and Ship Technology.The GUT uses 30% of its financial resources on research and development. Approximately 70% of the funding comes from the state budget and 30% from non-government sources, including 1% from the European Union funds.

Faculty of Mechanical Engineering

• Mechanics and Mechanical Engineering,
• Automatics and Robotics,
• Materials Engineering.

The Faculty's research activities include: optimisation of manufacturing processes with special emphasis put on energy efficient and environmentally friendly processes; computer aided product development; production and utilization of machines; modelling, simulation and expert reports in the area of interest.

Faculty students can choose one of the following study profiles:

• Production Engineering,
• Machinery Design Engineering,
• Robotics and Automation,
• Flexible Manufacturing Engineering,
• Power and Thermal Engineering,
• Automotive Engineering,
• Engineering and Marketing,
• Production Engineering and Marketing,
• Computer Aided Production Engineering.

Membership of FEANI organisation enables the graduates of the Faculty to apply for the European Engineer Diploma.

Department of Hydraulics and Pneumatics

Fig. 2: The Department's staff (first row, third from the left - Prof. A. Balawender, fourth from the left - Prof. L. Osiecki)

The laboratory facilities comprise main hydraulic research laboratory (250 m2) and four didactic laboratories for teaching hydraulics and pneumatics (total area 150 m2 ).

The main research laboratory (Fig. 3), built in 1992-99, is equipped with 7 specialized stands, among them:

• the universal test stand for high-power hydraulic components and systems, especially pumps, motors and hydrostatic transmissions. The main engine has 70 kW of power, in recuperative mode it enables to test machines up to 200 kW. The available speed range 200 to 4000 rpm, both directions,
• the low-power test stand for pumps, motors and transmissions up to 30 kW, variable speed 100 to 3000 rpm,
• the recuperative stand for high-torque hydraulic motors (100 kW, max. 500 rpm ),
• two test stands (currently modernized) for testing hydraulic sealing components,
• special stand for researching air-in-oil phenomena and de-aeration devices.

Fig. 3: The hydraulics research laboratory

The research stands are equipped with high-accuracy transducers (accuracy class 0.1 to 0.25) and connected to central computer data acquisition and oil temperature stabilization systems. To improve accuracy of measurements some new devices were invented and developed, among them the whole range of flow meters: piston (class 0.2 to 0.25, pressure 40 to 60 MPa, up to 1000 l/min ) and gear (class 0.25, pressure 25 MPa). Special devices allow oil contamination monitoring (HYDAC) and noise intensity measurements using two microphone method (BRUEL&KJAER).

Three hydraulic didactic laboratories are equipped with 5 stands, which allow students to assembly and test the whole range of hydraulic, electrohydraulic and proportional circuits. The pneumatic didactic laboratory with it's several stands covers the whole range of pneumatic and electropneumatic systems with modern electronic controllers. Computer simulation of hydraulic and pneumatic systems is also available.

Education

The graduates with MSc degree may continue their education on PhD courses. The department currently employs 5 PhD students, who conduct a research under the supervision of Prof. A. Balawender.

In June 2002 R. Jasinski completed his PhD thesis on starting-up the cooled hydraulic motors fed by a hot oil. The thesis contains the results of an extensive experimental research, theoretical analysis and computer simulation of the motors heating-up process which enables to establish the allowable parameters of the start-up in such conditions (Fig. 4).

Fig. 4: Computer simulation of the heating-up process of the cooled motor

Co-operation with Industry

• Since 1995 the seminars DRIVES AND CONTROL SYSTEMS have been organised by Prof. A. Balawender every February. The seminars accompany the fairs under the same title taking place in the Gdansk International Fair and are a forum where scientists and industry representatives can meet and exchange information.
• The department's laboratories are used to train industry workers.
• The research and expertises of hydraulic systems are performed for ship and power industries and for hydraulic components manufacturers.
• The industry engineers and academic teachers are members of the Hydraulic Drive and Control Section which is one of the divisions of the Polish Mechanical Engineering Association.

Research Projects

Several prototypes of the new pump, their size ranging from 17 up to 68 cm3/rev, were built and tested in laboratory. Results of tests confirmed theoretical expectations and showed some exceptionally good features of the new design:

• high working pressure (continuous 50 MPa, peak pressure 56 MPa),
• extremely high torque efficiency reaching 98 to 99 % - well beyond today's pumps,
• high overall efficiency - 92 to 94%,
• high speed and power density,
• extremely low dead volume - less than 10 % of stroke volume.

The new cam-driven commutation unit, fully discharged from hydrostatic forces, allows also to control pump's displacement directly by a low-energy actuator, like proportional electromagnet or stepping motor. Heavy and costly hydraulic servomechanism, necessary in today's machines, may be eliminated. Thanks to reduced pressure drop in internal channels, pump is self-sucking in wide range of working parameters. Another unique feature of the new pump is it's piston-slipper units, equipped with screw throttles to improve performance of the hydrostatic support in slippers. The new machine can work bi-directionally, as a pump or as a hydraulic motor (Fig. 5).

Fig. 5: New design of axial pump

Production of the new pumps is now being prepared in cooperation with Polish company Hydrotor S.A.

Satellite Hydraulic Motors with Axial Clearance Compensation The satellite hydraulic gear motors without compensation have been known in Poland since mid seventies. Some of them were extensively researched in the Department's laboratories. The search for a further development of satellite motors has lead to a conception of HS motor with a new satellite mechanism with the 6/8 of teeth curvatures, which gives 48 work cycles per one shaft revolution (Fig. 6).

The essential novelty lies in applying a special solution of clearance compensation to reduce the leakages in the working chambers. This can ensure the motors performance also for very low viscosity fluids and achieving low speeds (below a few revolutions per minute) while using mineral oils.

Fig. 6: : Satellite motor type HS with axial clearance compensation
a) satellite working mechanism: 1-stator, 2-rotor, 3-satellite, 4-inlet
b) Motor: 1-stator, 2-rotor, 3-satellite, 4-shaft, 5-compensation plate, 6-front cover, 7-back cover, 8-screw

The applied in the motors additional compensation plates contain commutation channels. The working fluid under pressure is delivered to compensation spaces and counteracts deforming the plates outside. Thus, the clearance is kept the same or even decreased, which limits the increase of leakages.

The whole series of types of the new concept of satellite motors has been developed. They are marked with letter symbols HS and number symbols from 0.4 to 6.3 defining the volumetric displacement in dm3/min. Thanks to the carburizing of all the motors working parts, the nominal pressure may be up to 20 MPa.

High versatility of HS motors design makes it possible to apply them in many drive systems e.g. closed cycle hydrostatic transmissions, multi-speed drives, synchronic drives etc.