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New Methodology: Intercooler Integration Space & Efficiency Optimization

magneti marelli

Figure 1 - CAE Team

Topic Introduction (Issue & Solution), Industry
Automotive industry is one of the fastest evolving industries when it comes to Passion, Expectation and Demand. Continuous addition of new techniques and technologies in the vehicle has shown exponential improvements in the past and this growth rate is increasing exponentially. With the introduction of electronics and its fine integration with mechanics there has been more evolution in the last 20 years than in a century.
There is a highly progressive expectation of improvement in overall efficiency, a vision for global system’s size reduction along with the strictness towards the environmental impact. Optimized use of resources and precise crafting of technology is of utmost importance.

Magneti Marelli Powertrain is Magneti Marelli business line dedicated to engines and transmissions components production for cars, motorbikes and light vehicles. With an vision for the future of technology Nazario Bellato, Simulation Manager, Magneti Marelli Powertrain, Italy along with Vijay Raj Gupta, HOD, Magneti Marelli Powertrain, Mechanical, India are determined to work together and develop competencies in the Off-Shore development center at Manesar, India.

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magneti marelli

Figure 2 - ANSYS 2015 Italian User
Conference: Massimiliano Di Paola

An Indo – Italian Magneti Marelli team under their guidance is working to develop an integrated Air Intake System for Internal Combustion Engine (ICE) that will improve the performance at the vehicle level by reducing overall energy losses and will open the room to provide more technological alternatives for psychological comfort of the end users. Involvement of young engineers filled with passion for the technology in the team has given Magneti Marelli a vision to create and give hope for more challenging windows for the better future of technology. The team is working with the support of ANSYS to use special 3-D Computational Fluid Dynamics (CFD) features to simulate physically and numerically complex Thermo-Fluid Dynamic behavior to evaluate the overall system’s response and hence confidently analyze many virtual prototypes using DOE strategy in the time that would be required to build a single physical prototype.

Analysis Description & what we were trying to accomplish
Integration of the intercooler with Air Intake Manifold involved several benefits such as reduction of overall pressure loss, the possibility to use Air to Liquid Intercooler which has higher heat capacities compared to Air to Air Intercooler. In house manifold design flexibility gave us the opportunity to make air flow lines uniform, and hence optimize the heat exchange.
The prime objective of this approach was to design the Air Intake Manifold and optimize the fluid dynamic behavior of the air inside it. For this, the first and probably the biggest challenge was to understand the fluid dynamics inside the component and find innovative ways to numerically calculate the thermal, static and dynamic parameters of the integrated system.

magneti marelli

Figure 3 - The new approach, Intercooler integrated with Air intake manifold

Developing the integrated system configuration through conventional process involving several iterations of design – analysis and testing was not the preferred choice because this project particularly involved large number of parameters in its Design of Experiment (DOE). An extensive use of numerical analysis in the system’s development cycle seemed to be the best compromise to optimize Quality – COST – TIME.
For a CFD analysis, to adequately capture flow behavior on regions which will experience abrupt change in key variables such as pressure, velocity or temperature, it is necessary to have a refined mesh. This is done by generating inflation/boundary layer in those regions. This boundary layer preferably involves Hexa - Hedral prismatic elements as it is considered to be a better representation of the numerical domain for a CFD model. Quality of the boundary layer profile can be best understood in terms of y+ parameter which is a non-dimensional variable representing the distance from the wall to the first node away from it. It follows the following correlation:

 

Boundary layer mesh generation on one hand is basic criteria for an acceptable CFD analysis but for complex geometries (usualy the case in powertrain components) creation of a very high quality boundary layer mesh requires long time and large resources. From the lesson learned in the past, here in Magneti Marelli we use a Hibrid meshing approach for CFD analysis as a trade off between QUALITY and TIME. The number of prismatic/hexa-hedral layers are decided uniquely for each analysis and component depending on the design and design change.

magneti marelli

Figure 4 - The boundary layer approach

CFD analysis for this integrated system configuration was a mammoth task because of the presence of irregular fluid domain that comprised of micro channels of the intercooler. Modeling the air passage domain of the intercooler was a very complex task as they were too small to be meshed with a good quality hybrid mesh. Even the Hex-Dominant approach was not the preferred one because of the presence of flow hindrances that were designed to create turbulence and improve the heat transfer along the flow direction. Even after neglecting the presence of flow hindrances and meshing the micro channels as regular fluid passages the approach remained very complex as it led to very high element count, non-uniformity in the mesh density and hence long solution times.
The numerical analysis team overcame these challenges by using special ANSYS features. Small sizes of the air passages in the intercooler domain were assumed to be the porosity in a porous medium. The directional loss model in ANSYS CFX that corresponds to the Darcy’s momentum loss equation for the fluids flowing in a porous medium was used for the analysis. The possibility to alter the linear and quadratic loss coefficients gave us the opportunity to study intercooler’s porosity levels based on its design and control the air pressure drop across the intercooler based on the experimental data.
This special feature in ANSYS CFX proved to be a tool that substantially reduced the complexity of the numerical model. Not only a reduction of approximately 12 million elements and 24 working hours was observed for each simulation, we were also able to use the numerical and experimental results to study and develop an approximated correlation between design and porosity levels of the intercooler.

magneti marelli

Figure 5 - Definitions for Darcy’s Law and its application for the Intercooler simulation

Now, as a next step towards further improvements in the system, our team is determined to study several other complex phenomena through numerical analysis such as the Condensation effect inside the air intake manifold, the water hammer effect in the intake system during the engine cranking. Studying and understanding these phenomena’s could help the team to suggest design improvements and reduce the present losses substantially. These physical phenomena’s are industry specific and hence it is quite uncommon to have the related codes and models in the regular ANSYS package. For this reason ANSYS has agreed to provide a direct support to our Magneti Marelli team which would involve a series of learning sessions and discussions one on one with ANSYS’s top researchers.

magneti marelli

Figure 6 - Images Illustrates the Velocity profile of air for the Momentum Loss Model

Outcome description & Helpful ANSYS feature
ANSYS tool once again proved to be a very useful platform for us to analyze some of the complex phenomena which once became a bottleneck in the component development process. Rational understanding of phenomena’s such as the flow uniformity, intercooler permeability not just from the fluid dynamic point of view but also from point of design and structural stability of the system was studied. Further, with the use of ANSYS we were able to iteratively alter the system’s configuration and optimize the physical phenomena such as heat exchange through the intercooler and reduce the overall pressure loss.

Direct one on one support from the ANSYS team has given a lot of confidence and a vision to our engineers to solve highly complex physical problems numerically.

 

 

 



Articolo pubblicato sulla Newsletter EnginSoft Anno 12 n°3

Massimiliano Di Paola, Nicola Mundo
Magneti Marelli Powertrain

Bhartendu Tavri
Magneti Marelli India

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