Heavy & Commercial Vehicles Manufacturers Strive to Optimize Their Designs For Efficiency with PowerFLOW: From Fuel Economy to Tier 4 Standards

Economically Engineering Trucks of the Future Today

Heavy and Commercial Vehicle manufacturers have been finding ways to economically and accurately optimize their vehicles long before the recent economic conditions presented themselves. Making 'greener' vehicles to meet government emissions standards made early-stage product computer-aided simulation for design optimization not just necessary, but critical to be successful at meeting government deadlines.

Above and beyond emission regulations, optimizing for efficiency has been key for trucks and commercial vehicles. From HVAC and engine fans to minimizing soiling and drag - areas throughout these heavy vehicles may now be simulated and analyzed using Exa's suite of software products, and design optimization variations evaluated long before a truck or agricultural vehicle is in its final stages of development. Customers who integrate Exa's offerings into their processes find their investment pays for itself in short order by finding ways to optimize designs early in the development process and by delivering more competitive products to the market....faster.

Global Industry Leaders Look to Exa to Reach Their Efficient Design Goals

Leading Global Heavy Truck and Commercial/Agricultural Vehicle Manufacturers choose Exa's suite of simulation software products to economically address efficient design goals and government regulation requirements while trying to make vehicles that adhere to company styling standards and customer demands. With Exa, these customers are simulating their designs early in the process to 'virtually optimize economically via simulation rather than wait for physical prototypes to be built. Industry customers currently using Exa software or services include:

Truck Aerodynamics

The benefits of PowerFLOW for passenger vehicle development apply equally well for commercial vehicles.  The design process for heavy highway trucks is significantly influenced by aerodynamic drag performance within the constraints of cooling flow requirements.  Bumper, fascia, fender, hood, cab, roof fairing, and side fairings are designed to meet fuel economy targets for the truck.  PowerFLOW provides a digital process for vehicle development to design the truck.  Simulations provide diagnosis of pressure distributions that contribute to drag – flat forward-facing areas produce high pressure that increase drag, but curved forward edges can produce low-pressure peaks that reduce drag.  Other regions such as the hood and roof require optimization of panel angles, radii and curvature profiles in order to direct the flow appropriately with minimum pressure drag.  Separations off of rear-facing edges can be optimized to minimize low pressure associated with vortices and wakes.  Deflection of flow around components under the vehicle, especially the wheels and axles, is critical for minimizing drag.  Finally, the impact of flow circulation in the large wake behind the truck on the base-pressure drag of the vehicle can be assessed.

Aerodynamic simulations of heavy trucks using Exa PowerFLOW. Top Left: Streamlines & slices demonstrate flow movement above and around truck; Top Right: Airflow through engine compartment shown using streamribbons help determine optimal grille and fan size for proper cooling. Bottom. Airflow at yaw angle demonstrated in PowerFLOW animation. Images courtesy of Freightliner & Kenworth.

Diagnosis of the aerodynamic shape leads to ideas for design changes.  Some design changes are related to the proportions of different regions and panels.  Others are described by parametric angles and radii, while others are presented as alternative styling designs.  All of these design changes can be accomplished using Exa’s PowerCLAY as the primary design test tool.  PowerCLAY allows rapid modification of vehicle geometry to support design process timelines.  Pin-point analysis of pressure distributions from one change to the next provides immediate feedback about design changes, and PowerCLAY provides the tool to modify the geometry in the direction of drag improvement.

Thermal Management

For heavy trucks, the aerodynamic performance requirements are significant but are secondary to cooling performance.  A large grille opening, heat exchangers and cooling fan are the prominent features of the truck front-end, and are optimized for maximum cooling flow into the underhood.  Cooling flow is also managed to control temperatures of underhood components which are heated by the engine, exhaust and hot flow through the heat exchangers. 

For low-speed or stationary commercial vehicles, the thermal management requirements are met by design of the cooling flow path, heat exchangers and cooling fans, and placement of hot components and heat shields.

The applications of PowerFLOW for automobile thermal management apply equally well to heavy trucks and other commercial vehicles, and provide support of the complete design process for managing thermal requirements.

CASE STUDY: AGCO - Engineering the Engines of the Future
AGCO's challenge, like many of today's agricultural machinery manufacturers, is to find a way to design and fit engines within a small underhood compartment while balancing optimal performance, new space demands required for Tier 4 emissions-reducing equipment, and styling requirements. With the larger farms growing at an average of 30% per year, the market potential for heavy equipment sales is enormous, and companies that can offer reliability and efficiency will get the orders.

MOVING TO VIRTUAL DESIGN
Traditionally, AGCO had used a series of physical tests to map out and analyze engine airflow and thermal management issues, often running up to twenty iterations for each proposed design. In the end, hundreds of thousands of dollars and thousands of man hours were required to run, analyze, redesign and run again each physical model test.

With multiple platforms and numerous variations of engines and cooling packages to support for each platform, Dave Bloch, AGCO's Chief Engineer of Engine Installations, quickly realized that CAE would be required to make his deadlines, streamline the process and reduce his budget. He began researching commercial computational fluid dynamics (CFD) packages. Unfortunately, Bloch was immediately disappointed. “The first software application I investigated was not user-friendly, and in our numerous attempts to run thermal and airflow simulations, we never got acceptable results; often, no results,” Bloch stated. “That’s when I began to work with Exa.”

SERVICES & AN ON DEMAND SOLUTION
After evaluating the extensive list of simulations required, and with his team already being pulled in many directions, Bloch quickly came to the conclusion to try Exa’s services and its On Demand option. “I was pleased to finally find a one stop solution that not only handled both our underhood cooling and airflow management demands, but also virtually extended my engineering staff,” commented Bloch. “The ability for AGCO to use our fully-detailed geometry, with Exa’s PowerFLOW and PowerCOOL applications, was very reassuring, as we knew for the first time the results would reflect the extremely complex underhood geometry. We’ve found Exa’s results to be fast and consistently accurate.” Bloch also discovered great value in Exa’s On Demand servers where PowerFLOW and PowerCOOL simulations can be turned around in record time as CPU hours can be picked up as needed. David Bloch commented, “To have CPU-capacity ready and waiting is a luxury most companies cannot afford. Exa has made it easy for us to perform geometry iterations in record time.”

	AGCO Corporation's use of Exa's thermal simulations helped them stay on budget to meet Tier 4 standards. Left: AGCO external airflow image demonstrating heat loss as it exits the engine compartment. Below, left column: Exa PowerCOOL® simulation of underhood/engine compartment demonstrating thermal flow. (Heat exchanger hidden to show effect.) Below, right column, Exa PowerFLOW simulation of underhood/engine compartment to analyze airflow movement. Flow is colored by velocity magnitude (red-fastest/blue-slowest).