Introduction
Optimizing a
turbofan is always a challenging task, especially because it needs to deal
with both aerodynamics and structural performance. While designing a fan with
high performance and efficiency is important, the strength and reliability
of structure is also critical. Furthermore, integrating parametric CAD, CFD
and stress analysis is not a trivial task and usually takes extensive effort.
In this issue
of SmartDO eNews, we will introduce how SmartDO and ANSYS was utilized to
optimize a turbofan. The technical team of FEA-Opt technology helped the customer
build a parametric model with DesignModeler, construct the CFX and mechanical
analysis block, and integrate SmartDO with ANSYS Workbench. SmartDO was able
to increase the mass flow of the fan by almost 14%, and slightly reduced
the maximum stress under aero and structural loading. The result shows promising
possibilities for further advanced development.
Building Integrated CAD/CAE Workflow with ANSYS Workbench
Figure 1 shows the geometry of an existing turbofan. The model
was built on legacy data for an existing product. The product has been serving
for years with proved reliability, but it was desired to increase the aerodynamics
performance without sacrificing the strength of the blade.
Figure 1. Geometry of the Existing Fan
ANSYS DesignModeler
(DM) was invoked to re-build the parametric CAD model of the fan with the
help from FEA-Opt Technology. The result was a CAD model with around 90 meaningful
controlling parameters, which was able to fit the existing design accurately.
The DM model was than
linked with CFX and Mechanical analysis block to form a complete CAD/CAE
workflow, as shown in Figure 2. Figure 3 shows the ¡§Parameter Set¡¨ list in
ANSYS Workbench, which can be linked directly with SmartDO/SmartLink to perform
design optimization directly.
Figure 2 Integrated CAD/CAE Workflow
in ANSYS Workbench
Figure 3 List of Parameter Set in Workflow
After the workflow in ANSYS Workbench is done, it can be easily
link with SmartDO to performance Direct Global Optimization (see, for example,
our previous newsletter of "Structural
Optimization with SmartDO and its Direct Link to ANSYS Workbench" and
"Using SmartDO and ANSYS Workbench/CFD
for Design Optimization").
Defining the Optimization Task with SmartDO
Although there
are around 90 design parameters in the model, the customers¡¦ experience has
led them to focus on airfoil sectional shape on the tip, middle and root of
the blade, as shown in Figure 4. And few design variables are considered more
important than others, namely
- Attack angle and curvature
of the airfoils, which governs the aerodynamics performance.
- Thickness distribution of the
airfoils, which governs mechanical properties.
Figure 4 Focusing on Tip, Middle and Root of the Airfoil Sectional
Shape
Figure 5 shows
the imported WB parameters in SmartDO for setting up design optimization problems.
The model was formulated to toggle the following design problem.
- Design Variables :
- Attack Angles, Curvatures and
Thickness Distribution of the airfoils (totally 9 independent Design Variables)
- Objective :
- Maximize the mass flow under
specific rotational speed
- Design Limitation :
- Maximum stress should be lower
than the original design
- Radial displacement should
be lower than the original design
Figure 5 Imported WB Parameters and Setting in SmartDO
SmartDO Global Optimizer Provides Promising Improvement
The optimization
problem was solved by SmartDO and ANSYS. Using its global optimizer, SmartDO
was able to overcome the local minimums, and produce a new design with 14%
increase in mass flow, with maximum stress slightly smaller than the original
design (from 1884 to 1820 MPa).
Figure 6 shows the stress distribution of the initial and optimal design.
The radial deformation was reduced from 3.5mm to 3.0mm. Figure 7 to Figure
9 shows the comparison of pressure distribution at the airfoil of tip, middle
and root sections. Finally, Figure 10 shows the comparison of airfoils at
different sections.
Figure 6 Stress distribution of Initial
(left) and Optimal (right) design
Figure 7 Comparison of Fluid Pressure
Distribution on the Airfoil at the Root Section
Figure 8 Comparison of Fluid Pressure
Distribution on the Airfoil at the Middle Section
Figure 9 Comparison of Fluid Pressure
Distribution on the Airfoil at the Tip Section
Figure 10 Comparison of Airfoil Sections
Although further study is still necessary
for the final product revision, the optimal result from SmartDO shows promising
improvement over the current design. The return of investment for SmartDO
is significant and obvious.
More Information
FEA-Opt Technology is an international
RD/Consultancy/CAE and Software firm. We provide superior RD/consultancy services
to our customers, and customized solutions for each customer's special need.
SmartDO, our flagship
product, is the leader of Smart Global Optimization Technology. Capable of
Direct Global Search for both Gradient-Based and GA-Based methodology. For
details about SmartDO, please visit our web site at http://www.SmartDO.co/
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