The performance of several aerodynamic technologies and approaches, such as trailer skirts, trailer boat tails, gap reduction, was evaluated using track testing, model wind tunnel testing, and CFD simulation, in order to assess the influence of the design, position and combination of various aerodynamic devices.
The track test procedure followed the SAE J1321 SAE Fuel Consumption Test Procedure - Type II. Scale model wind tunnel tests were conducted to have direct performance comparisons among several possible configurations. The wind tunnel tests were conducted on a 1/8 scale model of a tractor in combination with a 53-foot semi-trailer.
Among others, the wind tunnel tests and CFD simulations confirmed the influences of trailer skirts' length observed during the track tests and that the wider skirt closer to the ground offer better results.
The differences in the shape, dimensions and position of rear deflectors and trailer skirts on the trailer are reflected in the test results. Track testing and CFD simulation confirmed that the approach to reduce the tractor-trailer gap can result in improved fuel efficiency.
The tests showed that combinations of aerodynamic devices can bring additional benefits. The results obtained by combining trailer skirts and trailer rear deflectors are better than those obtained by the trailer skirts or gap deflector alone. This can be explained by the additional reduction in aerodynamic drag at the rear of the trailer, or in the gap between the tractor and trailer.
