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Several practical devices to reduce aerodynamic drag on a typical class 8 line-haul tractor-trailer application were evaluated last year by this author and Fongloon (Peter) Pan in SAE 2007-01-1781 [Reference 1]. Those evaluations were conducted via reduced scale wind tunnel testing and focused on three areas within the tractor-trailer system: tractor-trailer gap, trailer sides and trailer aft body. This paper builds on our previous work, and presents the results of full scale, on-road fuel economy tests of a select sub-set of those devices. The on-road fuel economy testing was accomplished in accordance with SAE Type II (J1321) test procedure [Reference 2]. An 11.5% improvement in highway fuel economy was demonstrated for a select combination of devices.

This paper presents the impact of a number of practical add-on devices on reducing aerodynamic drag for tractor/semi trailer combination trucks. The evaluations were conducted via reduced scale wind tunnel testing. Sub-scale testing is a very efficient and accurate method to conduct trade studies and evaluate alternate shapes. The test focused on three areas within the tractor-trailer system: tractor-trailer gap, trailer sides and trailer wake. A 23% aerodynamic drag reduction was demonstrated by utilizing trailer skirts, base plates and lengthened side extenders and air fairing. A 20% drag reduction was also demonstrated for several combinations of devices.

The need of upfront modeling, simulation and design optimization has been ever increasing during full vehicle product development process. The overall vehicle system and component subsystem performances remain critical considerations for making final product release decision. With these challenges in mind, the work of this paper discusses the development of feasible CAE methods, tools, and processes for multi-objective design optimization. A full integrated tractor trailer truck vehicle is used as an example to demonstrate this capability. The proposed approach allows several design objectives to be simultaneously optimized, which might otherwise be extremely difficult to achieve with experimental methods.