SmartDO eNews Feb. 19, 2014 : Optimizing Aero and Structural Performance of Turbofans with SmartDO and ANSYS
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
1. Attack angle and curvature of the airfoils, which governs the aerodynamics performance.
2. 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.
FEA-Opt Technology Co. Ltd. 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/