The recent advancements in vehicle powertrain and aerodynamics have led to an
increase in the production of faster passenger cars, where high-speed driving
scenarios demand equally efficient and safe braking systems to ensure the safety
of both passengers and surrounding vehicles and pedestrians. At high speeds,
aerodynamics can significantly impact overall vehicle braking performance due to
the interaction between downforces and lift forces, which, in turn, affects the
vehicle’s overall dynamic weight, directly contributing to the maximum
attainable deceleration or braking force. Accordingly, the braking performance
can be maximized by generating more downforce by means of rear spoilers, while
taking into consideration their inevitable drag, which adds to the total vehicle
motion resistance. Therefore, this proposed work aims to investigate the
effectiveness of employing an active rear spoiler to enhance the vehicle’s
braking performance, without introducing remarkable drag that could impair the
driving performance and its accompanying fuel consumption. For aerodynamics
analysis, a two-dimensional computational fluid dynamics (CFD) model has been
developed in ANSYS-Fluent®, and its results have been fed into an integrated
7-DOF vehicle body dynamics model equipped with a nonlinear pneumatic tire model
developed in MATLAB®. The investigation has been conducted for different
combinations of braking initial speed, tire–road adhesion, and rear spoiler
angle. The findings show that the existence of the optimal angle of the rear
spoiler remarkably enhances the overall braking performance and reduces the
distance needed to make the car come to a complete stop. Ultimately, this shows
the effectiveness and necessity of implementing an active rear spoiler to
optimize the performance of both braking (reduction in the needed braking
distance) and driving (reduction in the inevitable accompanying aerodynamic
drag).
