Automatic shape variations for optimization and innovation - IFIP

2nd IFIP Working Conference on Computer Aided Innovation October 8 - 9, 2007 Delphi Corporation, Technical Center Brighton Product Development IT - Chrysler LLC

Automatic shape variations for optimization and innovation Shape Optimization of Cylinderhead Gasket using CFD Noel León, José Cueva, César Villarreal, Sergio Huitrón, Germán Campero Tecnologico de Monterrey, CIDYT-CIII Ave. Eugenio Garza Sada # 2501 Col. Tecnológico, Monterrey, NL, CP. 64839, Mexico http://cidyt.mty.itesm.mx

Automatic shape variations for optimization and innovation: Shape Optimization of Cylinderhead Gasket using CFD

N. León, J. Cueva, C. Villarreal, S. Huitrón, G. Campero

Agenda 1. Introduction 2. Splinization and Mesh Morphing 2.1. Mesh morphing 3. Case Study: Shape Optimization of CylinderHead Gasket using CFD 3.1. Optimization of the engine cooling process 3.2. Preliminary results

4. Future work 5. Conclusions Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC

2nd IFIP Working Conference on Computer Aided Innovation October 8-9, 2007

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1. Introduction • The available CAD-CAE tools and methods are not always adapted to satisfy design requirements that are increasingly more focused on potential creativity enhancement. • This paper focused on the innovation of shape and topology using proven and mature methods that has been used successfully for parametric optimization, extending its application to design automation and Computer Aided Innovation. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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1. Introduction (2) • Commonly, performance improvement is first obtained through quantitative changes in parametric design in search for optimization. • When the resulting improvements reach the limits of performance improvements, new searches must be carried on through qualitative changes or paradigm shifts.

Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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1. Introduction (3) • Qualitative changes and paradigm shifts lead to innovation. • Optimization looks for the most advantageous state of equilibrium before a contradictory situation is faced: The improvement of one or several performance characteristics, deteriorates others. • In order to get out of this deceptive goal, innovative concepts are needed by changing not only parametric values, but also shapes, topologies and physical principles. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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1. Introduction (4) • Parametric CAD and CAE systems were originally conceived for facilitating only parametric variations on modeled parts. • In recent times, topology optimization methods have been also introduced in meshing environments.



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1. Introduction (5) • Topological optimization functions are currently used to find optimum topologies and shapes for given parts under prearranged conditions. • Shapes and topologies obtained this way are not models with a CAD structure, and require manual post processing or even a complete redesign Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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1. Introduction (6) • Topological optimization:





1. Introduction (7) • The splinization concept was presented during the 1st IFIP Working Conference on Computer Aided Innovation in Ulm, Germany in November 2005 for implementing methods that may be integrated into conventional CAD/CAE systems for executing shape and topology changes that transcend parametric values. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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2. Splinization and Mesh Morphing • Performance enhancements are searched with the aid of genetic algorithms and shape and topology variations at both CAD and mesh models that may be converted in both directions. • Now a new way of combining the splinization approach with the meshing software, for integrating the shape variation method to the CAE analysis method is presented. • This method has special advantages as it allows shape variations at mesh level that may be later translated into direct modification for a previously “splinized” CAD feature. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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2. Splinization and Mesh Morphing • In this case mesh morphing in existing commercial finite element meshing software was used. • The way the mesh surrounding the shape is modified depends on a bias value (so called a “handle”) that is equivalent to the tension of a Bezier curve. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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2. Splinization and Mesh Morphing • The use of the “morphing” became advantageous because: – It allows shape variations to a model without remeshing it. – The interpolation of previous results can save computational time enormously in FEM simulations. – Previously converged simulation results (or interpolated new results) can be used as an initial guess and speed up the simulation process. – It takes advantage of converged solution – It is good to have a mesh model that remains consistent



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2. Splinization and Mesh Morphing • The final goal is to integrate in an automatic manner. – CAD/mesh shape optimization process through splinization – CAE Thermal simulations – Genetic algorithms

• The splinization approach and mesh morphing are connected by positioning the morphing handles at the control points that define the spline.



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2. Splinization and Mesh Morphing 2.1. Mesh morphing

• Because it is sometimes desirable to modify only a certain feature within a mesh model, manipulating node coordinates must be done in a very controlled manner to maintain model consistency and quality of the mesh elements. • The best way to modify a certain shape at mesh level is to alter the nodes defining it. • Smoothing the node displacements allows that the perturbation of the elements is minimized and mesh topology is preserved. • This effect is known as mesh morphing, which is a tool included in some meshing software. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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2. Splinization and Mesh Morphing 2.1. Mesh morphing

• For each modifiable shape, edge domains are formed in the shape that defines the mesh boundaries. • Several stepped regions allow defining a bigger region than would be allowed by mesh quality criteria when performing the variation in a big region. • Within a domain, handles allow the actual node manipulation. • Even though this kind of variations has major limitations because of mesh quality constraints, it is very practical when only small changes in shapes need to be made. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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3. Case Study: Shape Optimization of CylinderHead Gasket using CFD • Simulations for the performance enhancement of the cooling water jacket of cylinder engines involves: – Geometry

– Meshing tools

– Computational Fluid Dynamics (CFD).

• It is a highly time consuming process and is usually performed manually modifying the gasket holes dimensions based on the results of CFD simulations subject to manufacturing, packaging and material constraints. • Each of the iterations takes about 1/2 week (mesh generation and analysis). • Under these conditions the possibilities of variations of shapes and topologies are very limited and therefore only changes of the holes diameters are commonly introduced. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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3. Case Study: Shape Optimization of CylinderHead Gasket using CFD • Water jackets are designed for peak power condition that is representative of the worst case scenario with respect to heat rejection to coolant with the flow rate specified at peak pump output. – Predominant design variables • Number of gasket holes. • Dimension of each gasket hole. • Location of each gasket hole.

– Restrictions • Gasket holes should reside inside of intersection of block and head water jackets. • Flow-distribution near critical areas such as exhaust valve bridge, • Spark plug and peak velocity zones that are prone to metal erosion. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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3. Case Study: Shape Optimization of CylinderHead Gasket using CFD • The first goal is to significantly reduce the time for finishing a design, by providing a methodology that integrates the engineering concept and the geometry restricted to manufacturing, packaging and material constraints. • Additionally performance increments beyond those achieved by traditional manual methods may be expected as not only changes in diameter values but also shape and topology variations. • Thermal analyses are performed to predict heat transfer coefficients (HTC).

• Thermal analyses provide the coolant flow rate from the water pump performance, heat fluxes corresponding to the peak power condition in different regions of the water jacket. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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3. Case Study: Shape Optimization of CylinderHead Gasket using CFD 3.1. Optimization of the engine cooling process

• Holes in a cylinder head gasket are the only available passage for cooling fluid between the cylinder head and cylinder block.



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• The pattern of gasket holes defines the flow conditions • Changes in their pattern can positively impact heat transfer coefficients for the cylinders, thus improving engine cooling. • In this case the objective of gasket holes optimization is to maximize heat transfer coefficient as well as to minimize the difference among heat transfer coefficients among cylinders. • With the help of the mesh morphing process explained earlier, in the DOE step re-meshing is avoided while boundary conditions are changed. • The optimization step uses mesh morphing to achieve a new mesh in a reasonable time.



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• Overall procedure of DOE and optimization process of gasket holes.



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• The main benefit is the reduction of manhours required for set-up and post processing by eliminating routine tasks that are now implemented automatically. • The implemented procedure allows closing this shape optimization process by feeding the shape variations of the mesh morphing controlled by the handles to the CAD environment as control points of a spline.



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3. Case Study: Shape Optimization of CylinderHead Gasket using CFD 3.2. Preliminary results

• The investigation has been conducted in a simplified model, in which six holes perform a scale factor, without shape and/or topology variations yet. Top View

Inlet/Outlet

1

3 5 6 2

4

• The process integration for performance optimization in the software applications has been already achieved. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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• The objective is to maximize the minimum heat transfer coefficient (HTC) as well as to minimize the maximum difference of HTC among cylinders. • To perform the DOE analysis the objective function is defined as follows: •

f = HTC1+HTC2+HTC3-3(|HTC1- HTC2 |+|HTC1-TC3 |+|HTC2 HTC3|)



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• Results of the DOE analysis

• The tendency is having bigger holes while they are farther from the inlet. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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• The results of the DOE analysis



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4. Future work • Taking advantage of the automatic shape variation presented in this paper, it is being working in applying this technique looking for innovative shapes of Savonius tye rotors for wind generators. • The Savonius wind turbine – Drag type vertical axis wind turbine. – Developed in the early 20’s of last century. – Has been undermined because of its low efficiency in comparison with traditional wind turbines of horizontal axis.



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4. Future work • Research work has been done for finding new shapes of the Savonius rotor making subtle changes to its profile shape, but the traditional geometrical features such as arcs and lines have remain unchanged. • By using splines in the rotors design it is possible to create forms never explored before, which may be analyzed trough the techniques described in this paper for the Shape Optimization of CylinderHead Gasket using CFD. Delphi Corporation, Technical Center Brighton Product Development IT, Chrysler LLC


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4. Future work • Known rotor designs:

Banesh (1994) Patent 1996

Traditional Rotor (1922) Patent 1924

Rahai (2005) Patent App. 2007



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4. Future work • Possible rotor designs variations:



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5. Conclusions • CAI may benefits from mature optimization methods for performing shape and topologic variations in CAD/CAE environments leading to innovative shapes and topologies that allow achieving higher performance when parametric optimization faces technical contradictions. • Using “splinization” techniques together with mesh morphing and genetic algorithms facilitates the search for higher performance exploring innovative shapes that avoid expensive manual trial and search methods.



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6. Acknowledgments • The authors acknowledge the support received from Tecnológico de Monterrey through Grant number CAT043 to carry out the research reported in this paper. • Authors acknowledge collaboration effort with Vamshi Korivi, Surendra Gaikwad and Su Cho working from Aerothermal Center of Competence and Product Development IT, Chrysler LLC.



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Automatic shape variations for optimization and innovation - IFIP

Automatic shape variations for optimization and innovation - IFIP

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