|
Fluid Power
Research Group
Department of Industrial Engineering
Faculty of Engineering
University of Parma, Italy
|
 |
| Location |
Parma, Italy |
| Responsible Leader: |
Dr. Andrea Vacca |
| Address |
via G.P. Usberti 181/A
43100 Parma (Italy)
|
| Telephone number |
+39 0521 905866 |
| Fax number |
+39 0521 905705 |
| Email |
andrea.vacca@unipr.it
|
| Internet Site |
http://ied.unipr.it
|
From Editor
International Journal of Fluid Power would like to introduce the fluid
power research and education centres with their expertise and
particular interests in this column. Jumping from continent to
continent we like to offer every research centre the opportunity to
present itself.
FLUID POWER RESEARCH CENTRES WORLD-WIDE
1 General information
The University of Parma
is one of the oldest univer-sities in the world, founded in the 11th
century. Cur-rently it is organised in twelve faculties and has about
30,000 students. The University of Parma is one of the very few Italian
universities provided with a Campus, equipped with many facilities for
students and aca-demic staff (libraries, canteens, sport equipments,
etc.). The Campus is in the outskirts of Parma, at a distance of about
130 km from Milan and 100 km from Bolo-gna.
The Faculty of Engineering was established in 1986, and consists of an
Educational Centre and a De-partmental Area (Fig. 1), both of which
located inside the Campus. After his birth, the number of students and
of academic staff grew rapidly; nowadays the Faculty has a student
population of approx. 4,200. This has stimulated the development of
applied research activity valued at international level in the main
fields of Engi-neering (Civil, Environmental, Electronic,
Telecom-munication and Industrial), thus combining research and
education in a binomial which is the basis of aca-demic training.
Fig. 1: Campus of the University
of Parma. Frames at Educational (A) and Departmental centres (B),
Faculty of Engineering
The
Department of Industrial Engineering
The Department of Industrial Engineering (IED) is the benchmark for the
research activities in the fields of Mechanics and Management
Engineering. At present the staff is comprised of almost 50 people, the
greater part being academic. The research is often based on
academic-industrial joint programs and involves many master degree
theses, PhD students (currently 31) and Research Associates.
IED is organized in different areas, according to main research
subjects:
•
Applied Physics;
• Industrial Plants (Mechanical);
• Fluid Machinery and Energy
Systems;
• Applied Mechanics;
• Machine Design;
• Manufacturing Technology;
• Food Technology;
• Industrial Management.
Research activities in
the field of Fluid Power are carried out by the Fluid Power Group at
the Fluid Ma-chinery and Energy Systems area, as concerns the study of
hydraulic systems and components. Some research in the ambit of
tribology and pneumatics are also car-ried out by the Applied Mechanics
Group.
The Fluid Power
team
The first works in the field of Fluid Power started 20 years ago, i.e.
since the foundation of IED. However from 1996, when Prof. G.L. Berta
became head of the Fluid Machinery and Energy Systems area, all the
ac-tivities were rearranged and all the topics related to Fluid Power
systems and components acquired more and more importance. During the
last few years, the number of people involved in the group has grown,
the test facilities has been enlarged, while cooperation with
industries and funding significantly increased. At pre-sent, the team
is formed by a permanent group:
−
Gian Luigi Berta – Full Professor;
− Paolo Casoli –
Associate Professor;
− Andrea Vacca –
Assistant Professor,
- Lecturer in Fluid Power
Systems;
− Germano Franzoni –
PhD;
− Michele Greco – PhD
Student.
plus an average number of 7 people involved in the research, as
collaborators or students developing their project works.
2 Research fields
Research topics in the field of hydraulics could be divided into two
areas (Fig. 2): analysis of components and systems. In both cases the
research is focused on the development of new designs, the optimization
of current ones and the definition of proper test methods. All the
research projects involve both experimental and numerical
computer-aided analyses. In most cases the development of each project
evolves through the fol-lowing five-step procedure:
i.
Problem screening and shifting analysis to the mathematical
domain (definition of design variables and simulation targets);
ii. Selection of the most suitable
approach for simula-tion (lumped parameter, 1D, 3D, etc.) and
develop-ment of the numerical model using proper software
(AMESim®, MATLab®-Simulink®, C++ or For-tran).
iii. Experimental analysis focused on
model validation;
iv. Review of the model, if necessary.
v. System/component optimization and
improvement proposal.
vi. Development of optimized
prototypes/system and testing.
This approach includes the development of numeri-cal tools with a high
predictive capacity, preferably easy to use since they are composed
within platforms specifically designed for hydraulic systems analysis.
The research group always assigns a primary impor-tance to the first
screening phase: the correct under-standing of the research targets is
necessary for the development of a numerical model suitable for the
analysis of the real problem. Usually, simulation mod-els for
components focus on the detailed modelling of the main aspects
characterizing the component opera-tion (e.g. leakages inside pumps,
flow forces on a valve spool, etc.), while models for systems are often
focused on the interactions between parts (e.g. pump / engine
matching), using simplifying assumptions for the sub-model pertinent to
each element.
As represented in Fig. 2, experimental tests are per-formed by the
research engineers directly on site or in the R&D facilities of
the cooperating industries; but, for the most advanced investigations,
in the Fluid Power Laboratory of IED.
Fig. 2: Research areas and main
industrial engagements
So far, the components analysis has focused on volumetric
pumps and motors (gear and piston) and on flow and pressure control
valves. Research on hydrau-lic systems has involved analysis and
optimization (from the energy saving and motion control points of view)
of hydrostatic transmissions. Details of some relevant studies are
given in the following paragraphs.
2.1 Modelling and design of hydraulic pumps
In the last few
years, the activity of the group has been focusing mainly on the
numerical modelling of hydraulic positive displacements machines. In
particu-lar, the analysis of the fluid-dynamic effects in gear and
axial piston pumps and motors represented the most outstanding topic.
The research led to the development of two simula-tion tools:
i.
Simulpompa is a simulation tool for axial piston pumps. The software
core is written in FOR-TRAN®, and a customized graphic
interface has
been developed in VISUALBASIC® environment. The software is
focused on
the simulation of phe-nomena through pump ports (suction and delivery):
a 1D model accounts for the main fluid dynamic ef-fects (pressure
peaks, backflows, momentum ef-fects, leakages) in the piston chambers,
through the port-plate and in the suction and delivery volumes.
Fig.
3a shows how the user can interact with the software; the port-plate
shape can be easily defined and modified. Different solutions can be
tested in particular operating conditions. Results (such as pressure,
flow rates, geometrical features, etc.) are given as a function of time.
ii. HYGESim (Hydraulic Gear machines
Simulator, Fig. 3b): is a deeply detailed simulation software for
external gear pumps and motors. The tool has been developed in the
AMESim® environment. The model accurately analyzes the
fluid-dynamic effects inside the pump through specific sub-models
writ-ten in C++® language. Geometrical features are
automatically calculated through a further PRO-E® based module
which uses the 3D geometrical mod-els of the machine. Different
geometries can be eas-ily tested and compared in different operating
con-ditions. Taking advantage of an accurate definition of the internal
geometry (shape of the gears and side bearings, inner volumes, etc.)
the software is able to calculate the detailed course of flow and
pressure at the inlet and outlet ports, inside the internal cham-bers
(such as the inter-teeth pressure), the forces acting on each tooth and
the instantaneous shaft torque. Latest version of HYGESim accounts for
the interaction between gears and bearings, thus predicting the actual
position of the gears’ centre during operation, determining
also the actual teeth-casing gaps for a correct evaluation of leakages.
A further module can perform an estimation of casing wear.
Double-click the images to
enlarge them
and click once to make them thumbnail size again.
Fig. 3: Simulation model for
hydraulic pumps and motors developed by the Fluid Power group at IED:
a) Simulpompa (the
graphic interface) and an example of a pump simulated using the software
b) HYGESim: a sketch of a AMESim system
with a gear pump and an example of pump simulated using the
software
Both simulation models have been developed dur-ing joint projects
between the Fluid Power Research group and Casappa S.p.a. (which
headquarters are a few kilometres far from IED), one of the most
impor-tant manufacturer of gear and axial piston machine in Europe.
Both models are currently used by the Casappa R&D engineers to
support the development of new prototypes and the optimization of
existing products.
Results obtained with both models led to several
technical papers, which have been successfully pre-sented and
appreciated in the most important Fluid Power Conferences worldwide.
Currently, the research group is working on further developments of
HYGESim in order to improve the potential of the model.
2.2 Modelling and design of hydraulic valves
The activity related to
this topic involves two im-portant aspects: the development of accurate
numerical models and the application of advanced optimization
techniques.
Recently, the analysis concerns two particular ele-ments (represented
in Figs. 4 and 5): a special anti-shock, pressure control, cartridge
valve and a load-sensing priority valve. In both cases dedicated lumped
parameters models have been developed in AMESim® environment.
These models focused, in particular, on the detailed analysis of the
fluid-dynamic aspects and on the evaluation of the forces on the moving
elements. Various and accurate test campaigns and sometimes CFD 2D or
3D simulations supported the development of these lumped parameter
models, permitting their validation over a wide range of design
parameters.
For both the components of Figs. 4 and 5 the simu-lation models have
been utilized to formulate new design features. For this purpose,
MATLAB® scripts which directly communicate with the
AMESim® mod-els have been developed, to implement particular
RSM (Response Surface Methodology) optimization proce-dures based on
DOE (Design Of Experiments) algo-rithms. These scripts are able to run
the simulations, analyze the results and modify the design parameters
until the required optimum design is found.
As a result of the optimization, new design solu-tions were suggested
to the industries for both valves. Experimental tests on prototypes
confirmed the poten-tial of the developed numerical tools.
These research projects were carried out in coopera-tion with important
Italian fluid power industries, namely Casappa S.p.a., Walvoil Spa. and
Oleostar S.p.a..
Double-click the images
to
enlarge them
and click once to make
them thumbnail size again.
Fig. 4: Optimization of a two-way
load sensing spool valve. The AMESim model and representation of the
implemented RSM-based procedure
Double-click the images to
enlarge them
and click once to make them thumbnail size again.
Fig.
5:
Optimization of a special relief, anti-cavitation and anti-shock
cartridge valve:
a)
the most influencing parameters considered in the analysis;
b) map of velocity inside the
valve: this is an example of CFD- 2D (Fluent® 6.3) simulation
per-formed to develop and set the AMESim® model;
c) experimental activity on
proto-types of the valve at IED.
2.3 Modelling and analysis of hydraulic
systems
Recently, as a consequence of newest
industrial-academic joint projects, the interest in the analysis of
complete hydraulic systems has grown. At present, some important
industries cooperate in this research, as reported in Fig. 2: CNH (Case
New Holland) Italy and Airo lifts, all of which operate in the field of
mobile hydraulics.
The systems have been studied through the simula-tion software
AMESim® or Simulink®, both of them suited for this
application. Key issues of the research are represented by:
•
the identification of the critical elements in the sys-tem, as concern
the steady and transient performance;
• the analysis of the
interactions between different parts of the systems (i.e. internal
combustion engine, pumps, valves, motors and other actuators);
• the proposal of improvements
or alternative sys-tem(s);
• the study of the proper
control strategy in order to increase performance and energy
efficiencies.
Fig. 6 shows some examples of the activity carried out by the research
group.
Double-click the images to enlarge them
and click once to make them thumbnail size again.
Fig.
6: Modelling of hydraulic system:
a) hydraulic transmission of an articulated boom lift
b) hydraulic system of a crane for small
trucks
3. The
IED Laboratory
IED is provided with a Laboratory for both educa-tional and scientific
use, equipped with the fundamental machinery for mechanics machining
and with the basic measurement systems. Test rigs were purposely
erected for measurements in the field of hydraulics (Fig. 7). In
particular, a new test rig for hydraulic components (Fig. 7a) was
recently (Aug. 2006) installed at the laboratory of IED, that supports
the research activities of the Fluid Power group. Funding for the new
equipment were provided by Casappa S.p.a., whose engineers contrib-uted
also in its design.
The test rig has a total installed power of 160 kW and allows for a
high flexibility of use and its design in view of several extensions.
As a matter of fact it allows several measurements to be performed:
steady state and transient performance tests on pumps and motors, on
valves, and on simple hydraulic systems. For example, Fig. 8a
illustrates the graphical interface of the control software developed
for one of the tests; while Fig. 8b depicts the test on a gear pump for
measuring the deliv-ery pressure ripple: a piezo-electric sensor is
used, the pressure pulsations are monitored through real time spectral
analysis.
The current activity is focused on the design and in-stallation of a
fully instrumented gear pump in order to measure the real course of the
inter teeth pressure. In order to achieve these results, miniaturized
sensors and telemetry systems are used. The special pump will also
allow the tracking analysis to be performed, monitoring each variable
as a function of the shaft angular position with a definition of
1/3600th rev.
Fig.
7: Relevant
facilities at IED Labs:
a)
the 160 kW test rig for hydraulic component
b) lubrification measuring
machine
Fig.
8: a)
The graphical interface of the control system of the hydraulic test
rig, during one of performed tests
b) picture of the apparatus utilized for
the measurement of pressure ripple in gear pumps
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