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North American on-highway tractor fuel efficiency has evolved significantly from its 1950’s roots to today’s Department of Energy SuperTruck prototypes and current Original Equipment Manufacturer production models. Innovating tomorrow’s Environmental Protection Agency Green House Gas compliant and economically efficient designs require understanding and manipulating the complex interactions between multiple systems in the context of both how the vehicles are formally evaluated and how and where they are actually used. This SAE L. Ray Buckendale Lecture paper provides an in depth overview of fuel economy and freight efficiency evaluation methods, their contexts and limitations, especially with respect to comparisons between the different methods.

Modern aerodynamic Class 8 freight tractors can improve vehicle freight efficiency and fuel economy versus older traditional style tractors when pulling Canadian style A- or B-Train double trailer long combination vehicles (LCV's) at highway speeds. This paper compares the aerodynamic performance of a current generation aerodynamic tractor with several freight hauling configurations through computational fluid dynamics evaluations using the Lattice-Boltzmann methodology. The configurations investigated include the tractor hauling a standard 53′ trailer, a platooning configuration with a 30′ separation distance, and an A-Train configuration including two 48′ trailers connected with a dolly converter. The study demonstrates CFD's capability of evaluating extremely long vehicle combinations that might be difficult to accomplish in traditional wind tunnels due to size limitations.

On-highway tractor-trailer vehicles operate in a complex aerodynamic environment that includes influences of surrounding vehicles. Typical aerodynamic analyses and testing of single vehicles on test track, in wind tunnel or in computational fluid dynamics (CFD) do not account for these real world effects. However, it is possible with simulation and on-road testing to evaluate these aerodynamic interactions. CFD and physical testing of multiple vehicle interactions show that traffic interactions can impact the overall drag of leading and trailing vehicles. This paper will discuss results found in evaluating the effects of separation distances on tractor-trailer aerodynamics in on-road and CFD evaluations using a time-accurate Lattice Boltzmann Method based approach and the ramifications for improving real world prediction versus controlled single vehicle testing.

Comparison of computation fluid dynamics (CFD) analysis of physical testing on curved test tracks highlights that simplifications in both methods can lead to significant error in predicting real world fuel economy performance for heavy duty tractor/trailer vehicles. The importance of understanding the differences in and the accuracy of these test methods have increased recently due to North American greenhouse gas (GHG) regulations and similar developments in other regions requiring manufacturers to assess aerodynamic performance of nearly every tractor sold. This paper discusses lessons learned in enhancing the accuracy of CFD and track predictions of real world aero performance by quantifying the effects of test track curves and challenging simplifying assumptions.

A web-based, enterprise-wide system management tool integrating a hierarchical product structure with purchasing, engineering and accounting databases can significantly improve the organization's ability to adapt to change and ultimately, attain project financial goals. This paper describes the fundamental elements of the PCS WEBTRACK tool developed at PACCAR for a systems approach to managing the evolving nature of part costs.