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By Lin-Jie Huang, PhD, Delphi Harrison Thermal Systems, Lockport, NY
View the pdf of this article
Delphi Automotive has reduced the time needed to develop automotive heating,
ventilation, and air conditioning (HVAC) modules by providing design engineers
with an automated CFD tool that helps them optimize designs prior to prototyping.
For many years, Delphi has been using CFD to determine the flow and thermal
characteristics of their HVAC systems. Traditionally, CFD experts have
done CFD work during the late stages of the product life cycle. Unfortunately,
this strategy allows little opportunity for designers to understand the
performance of any given concept early on. In an effort to shorten and
improve the efficiency of the product design cycle, Delphi initiated an
effort to use CFD in the early stages of the cycle, by handing certain
CFD tasks to the design engineer. Doing so greatly reduces the need for
design changes late in the process, which are expensive and time-consuming.
The graphical user interface of the guided template for an HVAC module
Delphi researchers worked to
develop a tool that would guide the
design engineer step-by-step through
the process of analyzing a product or
part through an examination of airflow
and thermal performance. They
began by drawing on the expertise of
resident analysts who understood the
physics of the HVAC system, had validated
many CFD models in the
past, and had developed a set of best
practices for CFD modeling that
could be incorporated into the automated
CFD tool.
A guided template was created that was built upon GAMBIT and FLUENT.
An interface was created using the GUI customization functionality available
in GAMBIT. This made it possible for design engineers to input the geometry
from their latest concept design, enter information specific to the design,
and do flow simulation in a very short period of time. The interface limits
the entry of design parameters to the range for which the model has been
validated, ensuring its accuracy. To date, interfaces have been created
for design engineers to set up an HVAC module, powertrain cooling system,
or heat exchanger for analysis in a matter of minutes.
Velocity contours (top) and temperature contours (bottom) on a plane through
the HVAC module
The template walks the designer
through the entire CFD process.
After the CAD geometry is imported,
GAMBIT automatically performs
the modifications to the geometry
required for efficient analysis. The
designer is then asked to graphically
identify key components of the
geometry along with the corresponding
boundary conditions. The mesh
building routine includes guidelines
for the size of the mesh in different
areas of the problem. Throughout the
process, a model is created that takes
advantage of the best practices and
design guidelines developed by
Delphi product experts.
Because this tool is so easy to use,
requiring minimum CFD knowledge
and training, over 50% of the design
engineers at Delphi Thermal Systems
use it to support their product
research efforts, leaving CFD experts
to devote their time to advanced
research and modeling. More than
ten product programs have now been
completed using the new tool. By providing
engineers with answers in the
early phase of the product development
cycle, the tool has shortened the
cycle by 30%, resulting in substantial
cost savings. Besides reducing the
design cycle, the automated template
tool has also reduced the model shop
and testing expenses for each development
project by about 25%
because fewer prototypes are needed.
In the future, Delphi plans to expand
the automated tool to cover even more
items in their product line.
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