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@PHDTHESIS{Tiefers:723872,
author = {Tiefers, Rüdiger},
othercontributors = {Bührig-Polaczek, A. and Friedrich, Karl Bernhard},
title = {{D}esign- und {G}ießprozessoptimierung von near-net-shape
{N}iederdruckturbinenschaufeln aus dem
{H}ochleistungswerkstoff {T}itanaluminium},
volume = {22 (2018)},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {Gießerei-Institut der RWTH Aachen},
reportid = {RWTH-2018-224377},
isbn = {978-3-944601-11-3},
series = {Ergebnisse aus Forschung und Entwicklung},
pages = {1 Online-Ressource (xviii, 194 Seiten) : Illustrationen},
year = {2018},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen University, 2018},
abstract = {The present work describes deeper investigations on the
castability of TiAl blades. For this purpose, a
process-specific test methodology was developed to determine
the casting properties of two -TiAl cast alloys (GE 48-2-2
and 45-2-2 XD) already certified for aviation. In addition,
the first design limitations for the design of cast turbine
blades have been demonstrated using test specimens. With
these designed test specimens, it has been possible during
the course of the investigations to characterize the above
mentioned alloys in detail in their casting-specific
properties (shape filling and flow properties as well as
cavity behavior). Thus, in a comparative comparison, a
generally better shape filling and flowability for the GE
48-2-2 alloy is indicated. In addition to the shape and the
design of real low-pressure turbine blades, various sample
body geometries have been developed, which on the one hand
are designed and dimensioned as realistically as possible,
but on the other hand permit a relatively simple
mathematical description. The results of the experiments
with such simplified turbine blades show that, in
particular, the rear edge of a blade is to be regarded as a
critical area because of its filigree dimensioning for the
mold filling. However, the extent of an incomplete form
filling depends decisively on the type of design. Thus, the
rear edge thickness of the blade profile has a significantly
greater effect on the reject rate than the profile
parallelism at the rear edge. As a result, the almost
parallel running length section at the rear edge of a blade
profile section is not to be regarded as critical, but
rather the absolute thickness at the rear edge. During the
experimental investigations, a calibration of the internal
simulation software STAR-Cast took place with the help of
the real casting results. An optimized parameterization of
the initial and boundary conditions during the simulation
was considered for both investigated alloys. The numerical
simulation for the alloy GE 48-2-2 appears to have been
parameterized successfully in the course of the work. For
the alloy 45-2-2 XD, on the other hand, it is difficult to
predict defects on the basis of simulation results.
Furthermore, important and interesting results concerning
the blade geometry and its influence on the castability
could be determined during the course of this work. It was
found that the determined parameters (area, camber line
length, etc.) of almost all the investigated blades lie in a
similar order of magnitude and tend to vary in a similar
manner with increasing blade height. A correlation between
the geometric parameters and the occurring cold runs in the
cast vanes could partially be found. The results are of
great uncertainty, since the statistical total quantity of
blades was very low and the casting experiments were rather
random. Furthermore, the alloy influences (GE, XD, TNM) were
not considered. The different alloys have a great influence
on the casting of a defect-free component due to their
different casting properties, such as mold filling and flow
properties. Nevertheless, geometrical limits for the
castability of NDT blades could be determined. These values
refer to the parameters trailing edge radius, maximum
profile thickness, wedge size, parallelism, bulge and
twisting of the blade or the blade profile. In addition, the
various courses of the profile thickness along the camber
line were shown. The limits determined in the course of this
work can be taken into account in the future design of new
low-pressure turbine blades, to shorten the time of
development. A shorter development time of the NDT blades
made of titanium aluminide is in this case, for example,
desirable from an economic point of view. On the other hand,
it increases the attractiveness of the material TiAl for use
in turbine blade production. This is again desirable for
environmental protection reasons, since TiAl is almost half
as heavy as the nickel base alloys commonly used in turbine
construction. A reduction in the turbine weight leads to a
lower fuel consumption, which is economically useful again.
The consideration of the developed casting limits is already
taken into account in the developed design tool and provides
good results with regard to the castability of a profile.
The consideration of twisting and bulging of a blade profile
during the design process is planned. With the networked
design tool for the production of low-pressure turbine
components from the high-performance material TiAl, it is
possible to automatically generate a blade geometry which is
the optimum of efficient aerodynamics, economical
production, material suited construction and long service
life. Up to now, this aero-thermodynamic and
structure-dynamic design of turbine blades, in particular
for the material TiAl, has been decoupled from the
production processes due to the separation of turbine and
component manufacturers. This holistic view leads to a
maximization of the economy during the whole life cycle.
With the design tool, the optimization of the components is
achieved faster and more efficiently taking into account all
aspects. Due to the early use, the number of iterations
between design and production can be decisively reduced.},
cin = {526110 / 520000},
ddc = {620},
cid = {$I:(DE-82)526110_20140620$ / $I:(DE-82)520000_20140620$},
typ = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2018-224377},
url = {https://publications.rwth-aachen.de/record/723872},
}
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