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 and operators’ demands for ever improving fuel economy is driving the need for more efficient power trains, continuous improvement in aerodynamic efficiency, and reductions in vehicle weight. Operators also require improved quality and durability, and increasingly want more innovative and emotionally expressive external designs. Power train supplier warranty contracts require strict operational temperature ranges within ever tighter underhood packaging. in addition, soiling and water must be managed to avoid safety issues.
These goals often conflict, requiring truck manufacturers to make careful trade-offs of competing values. The commercial vehicle engineer’s task is to create a truck that sufficiently satisfies the customers’ design preferences, and quality and comfort expectations; offers fuel efficiency within a desired target range; provides sufficient cooling; meets safety targets; and can be brought to market on time at an acceptable profit. This need to optimize the balance of industrial design, performance factors, cost, and process efficiencies is a continual challenge for the industry.
The old methods of product development are no longer sufficient. Building prototypes to test performance and assess quality is not only very expensive, but the engineering team needs to understand the design trade-offs very early in the product development process — months or years before any prototype could be built. Simulation-driven design not only provides feedback earlier and in a more useful form than traditional approaches, but is critical for success at meeting government regulatory deadlines. In many areas, simulation has reached a level of accuracy and robustness that is sufficient to enable a manufacturer to rely solely on simulation results for design decisions and tooling sign-off — without prototype testing.
Aerodynamic simulations of heavy trucks using Exa PowerFLOW.
Many of these design challenges including aerodynamics, thermal management, noise, and cabin comfort are heavily influenced by the complex fluid flows over and through the vehicle. Exa has the solution. Exa PowerFLOW’s unique, inherently transient Lattice Boltzmann-based physics enables it to perform simulations that accurately predict real-world transient conditions on the most complex geometry. PowerFLOW imports fully detailed vehicle geometry, and accurately and efficiently performs transient aerodynamic, aeroacoustic, and thermal management simulations. Exa’s solutions enable you to rapidly create, evaluate, and propose alternative designs that meet all the requirements. Using the PowerFLOW suite, you can evaluate product performance early in the design process — when change has the smallest impact on both the design process and engineering budget. Customers who integrate Exa's offerings into their processes find their investment pays for itself in short order. PowerFLOW applications have been fully validated and are in deep productive use at many of the leading global commercial vehicle manufacturers. Industry customers currently using Exa software or services include Scania, MAN, Volvo Trucks North America, Kenworth Truck Company, Peterbilt, Navistar, and Dong Feng Motor Corporation.
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 to direct the flow appropriately with minimum pressure drag. You can optimize separations off rear-facing edges 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, you can assess the impact of flow circulation in the large wake behind the truck on the base pressure drag of the vehicle.
For heavy trucks, cooling performance is critical. A large grille opening, heat exchangers, and a 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 that are heated by the engine, exhaust, and hot flow through the heat exchangers. PowerFLOW simulations provide accurate predictions of temperature distributions in the airflow, top-tank temperature, and rise over ambient at the intake port. Because PowerFLOW handles the detailed underhood geometry with ease, design challenges such as exact placement of heat exchangers and hot air recirculation problems can be identified and addressed easily.
Exa offers solutions for the following commercial vehicle applications:
AEROACOUSTICS — Greenhouse wind noise, including propagation to the interior; underbody wind noise; side window buffeting; gap and seal noise; high-frequency whistles; community noise; and cooling fan noise