September 2008 Edition

simulation software

No more trial and error

CAD-embedded CFD helps save months in automotive valve design

The Ventrex CO2 valve needs to operate at pressures seven to 10 times higher than previous generation systems.

Ventrex Automotive GmbH, of Graz, Austria, saved four months in the design of an automotive valve by taking advantage of Flomeric’s EFD.V5 for Dassault Systèmes CATIA V5-embedded computational fluid dynamics (CFD) simulation software.

"In the past, we would have had to build and test at least 50 valves in order to get the design right," says Peter Pfaffenwimmer, project manager for Ventrex Automotive GmbH.

"CAD-embedded CFD made it possible to determine simulation results nearly as fast as we changed the design," says Daniel Gaisbacher, also a project manager for Ventrex. "The result is that we were able to improve the flow rate of our new valve by 15 percent while eliminating about 50 prototypes and reducing time to market by four months."

Automotive air conditioning systems are beginning to use CO₂ as the refrigerant because it does not damage the ozone layer and also has a low impact on global warming. But CO₂-based systems need to operate at pressures seven to 10 times higher than previous generation systems, and this requires redesign of many components.

‘By using CFD software that is embedded into our CAD software, we could evaluate the performance of each new design iteration almost as fast as we could conceive it.’ — Daniel Gaisbacher

This view shows a part of an a/c-line with Ventrex’s valve body and the assembled valve core.

Among the components most affected by the change is the valves used to evacuate and charge the system. Most important, the pressure drops seen in existing valves are too high to enable the required flow rates. But reducing the pressure drop of valves is challenging because of the complexity of internal flow passages caused by the presence of components used to open and close the valve.

In the past, engineers would make design changes based on educated guesses. For each design change they had to build and test a prototype of the valve. This process was time-consuming and expensive, and the test results did not provide diagnostic information that would help engineers determine whether or not the design change had the intended effect.

CFD makes it possible to build a software prototype of the valve that can be solved to determine the pressure drop of any particular design iteration without having to build a prototype. A drawback to its use has been that traditional CFD codes require the user to understand deeply the computational aspects of fluid dynamics in order to be certain of obtaining accurate results.

But EFD.V5 eases the simulation process by extending CATIA V5 functionality to include fluid flow and heat transfer simulation within a single-user environment.

An embedded computational fluid dynamics (CFD) simulation tool helped Ventrex to improve the flow rate of its new valve by 15 percent.

"We selected EFD.V5 because it simplifies the process of performing fluid flow analysis to the point where it can be accomplished by any engineer," Gaisbacher says. "By using CFD software that is embedded into our CAD software, we could evaluate the performance of each new design iteration almost as fast as we could conceive it. This made it possible to quickly improve the performance of the design."

He says the company reduced pressure drop to the point that flow rate improved by about 15 percent in the
final design at any given pressure.

"We reduced the number of prototypes that were required during the design process by about 50, which saved a considerable amount of money, but most importantly let us bring the product to market faster," Gaisbacher says.

Flomerics Group PLC

Dassault Systèmes

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