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Complex geometry provides formula for better auto air conditioning
It's a little more complicated than high-school geometry, but geometric principles are adding up to improved climate control systems in automobiles.
Researchers at the Mississippi State University/National Science Foundation Engineering Research Center for Computational Field Simulation are designing Better climate control systems with the help of an advanced geometric process called unstructured grid technology.
"A vehicle's climate control system plays a big part in the level of customer satisfaction," explained mechanical engineering professor David Marcum. "You don't want the passenger compartment to have hot spots in the summer or places that never get quite warm enough in the winter."
Marcum is leading the effort to apply unstructured grid technology to automotive design. The technology, which is not at haphazard as the name implies, is based on an advanced form of geometry.
"It's easy to calculate air flow in a rectangular box with perfectly smooth sides," he said. "The interior of a car, however, has an irregular shape and is filled with obstacles that prevent the even distribution of air."
Using a computer model, Marcum and other scientists at the ERC can fill the Interior of a car design with a grid made up of triangular-shaped cells. They can then use computer generation to predict airflow and other factors important in keeping the temperature of the passenger compartment comfortable. The same process can be used to measure temperatures in the engine compartment.
The unstructured grid technology research is one part of the computational Field simulation work conducted at the ERC. Field problems are those in which some physical phenomenon occurs in a two- or three- dimensional space in a complex way. Engineers in many industries, ranging from shipbuilding to chemical processing, must solve such problems.
Scientists at the ERC have been solving field problems since the center was founded in 1990. The center's first director, Joe Thompson, began working with grid generation in the early 1970s.
"The first work in the field was done with structured grids, which look like a net in which each cell has four sides in two dimensions," Thompson explained. He and other ERC scientists pioneered the use of structured grid technology for military and industrial applications in this country.
Using a computer, a structured grid can be "wrapped" around an object, such as an aircraft fuselage, to simulate airflow and other data. Advantages of unstructured grid technology include significantly less person-time for setup and its application to objects with more irregular dimensions, such as the interior of a car.
"Each cell in an unstructured grid is triangular and that gives it more versatility," Thompson said. "Dave Marcum, along with Nigel Weatherill, pioneered the use of unstructured grids in solving field problems and are world leaders in the technology."
Marcum joined the mechanical engineering faculty at MSU in 1991. Nigel Weatherill is a member of the faculty of the University of Wales in the United Kingdom and also an adjunct professor of aerospace engineering at MSU.
The ERC's initial work in unstructured grid technology was sponsored by the Department of Defense and focused on the search for improved designs for naval Vessels and military aircraft. In 1995, however, Ford Motor Company provided the center a three-year, unrestricted grant for unstructured grid technology research. The ERC researchers are working in conjunction with Ford engineer Thomas Gielda, a pioneer in the use of unstructured grid technology for heating and cooling system design.
"The support from Ford has helped us adapt the technology for commercial use," Marcum said. "There are thousands of engineers who use the technology developed here at the ERC on a regular basis and the current work is helping make it even more available."
He added that one of the benefits of unstructured grid technology for car Manufacturers is that they can determine heating and cooling requirements of a vehicle much earlier in the design process.
"The use of unstructured grid technology allows carmakers to design a vehicle in the computer that will have even air distribution both under the hood and in the passenger compartment," Marcum explained. "In the past, they had to build physical models to test air distribution. This severely limited their design flexibility due to time and cost constraints."
He noted that with the previous design process manufacturers sometimes had to make last minute modifications to the heating and cooling system and under the hood after a new design was already in production. The design modifications could be costly and reduce customer satisfaction.
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