Abstract:
In this thesis, the compressor part of a turbocharger system is examined. In the turbocharger
compressor performance map provided by the supplier, the efficiencies are not at the
desired levels. For this reason, it has been tried to increase the efficiency of the operating
points selected on the compressor map under the same conditions. The first step of the study
is to analyze the compressor side geometries (compressor wheel, diffuser and volute). In
order to perform the analysis, three different operating points (OP1-OP2-OP3) are selected
from the critical regions of the performance map. The numerical analysis of the existing
compressor is performed at these three points. It is seen that the efficiency error rates
between the analysis and the experiment data are %1.6 (OP1), %0.9 (OP2) and %3.1 (OP3).
This proves that our CFD model is validated based on the experimental data. The second part
of the study is started with an examination of the impeller. Literature studies on increasing
the performance of the compressor system are examined in detail. As a result of the literature
research, it has been seen that the centrifugal compressor backsweep angle at the outlet of
the blade (β2) and total blade number of blades (z) design parameters have significant
effects on turbocharger compressor performance. A total of 45 different CFD models are
defined for a total of 15 different designs (including the original design) at three different
operating points and analyzed on the validated CFD model in order the examine the effect of
the blade backsweep angle (β2) at compressor wheel outlet and total blade number
combination on performance. For the total number of blades, a total of twelve (six – six (main
blades– splitter blades)), a total of fourteen (seven – seven) and a total of sixteen (eight –
eight) (original compressor wheel) are examined. In addition, 5 different trailing edge
backsweep angles (20°, 22.5°, 25°, 27.5° (original angle of compressor wheel), and 30°) are
considered.
Within the scope of this thesis, efficiency gains at levels where pressure variation is
negligible are taken into account. Efficiency and pressure variations of all designs, including
the current impeller design, are evaluated on the same graphs for the same operating points,
and the blade backsweep angle is reduced 2.5°, while the total number of blades is reduced
from 16 to 14. The results of the analyzes performed with the existing impeller design are
compared in terms of compressor outlet pressure and compressor isentropic efficiency. At
the first operating point, an increase of 0.78% is achieved in the isentropic efficiency of the
compressor when the total outlet pressure variation is 0.58%. In the case where the total
outlet pressure change at the second operating point was 0.68% an efficiency increase of
1.98% is achieved. Finally, when the third operating point is examined, a 2.34%
improvement in the isentropic efficiency of the compressor is obtained when the total
pressure change at the compressor outlet is 0.35%. The greatest efficiency increase is seen
in OP2 and the greatest pressure change is observed in OP3.