Retractable Side Skirts for EV Downforce Without Drag Penalty
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Solution Overview
Problem
High-performance electrically-propelled passenger cars face a conflict between maximizing range and maintaining high vertical aerodynamic load (downforce) without increasing aerodynamic drag, and the use of skirts is impractical due to road surface irregularities and regulatory constraints.
Innovation Solution
A road-use motor vehicle with retractable side skirts that adjust dynamically based on vehicle speed, road conditions, and other parameters to maintain optimal downforce while preventing air disturbances, using an electronic drive system and elastic counteracting assemblies to manage impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If skirts are used to prevent air disturbances and maintain downforce, then aerodynamic performance is improved, but the skirts are destroyed by road surface asperities after just a few kilometres of travel
Solution Approach 1:
The side skirts are made retractable and adjustable in position, allowing them to dynamically adapt to different driving conditions. The skirts can be retracted when encountering road asperities to avoid damage, and extended when smooth roads are detected to maintain aerodynamic performance. This dynamic adjustment resolves the contradiction between maintaining aerodynamic performance and ensuring skirt durability.
Solution Approach 2:
The position and configuration of the side skirts are changed based on detected road conditions and driving parameters. The system monitors variables such as vehicle speed, ground clearance, and road surface quality to determine optimal skirt positions, transforming the static skirt design into a parameter-adjustable component that optimizes both performance and durability.
2Reliability
If skirts are installed to maintain downforce, then aerodynamic performance is improved, but the passenger car cannot be sold in some countries where minimum ground clearance regulations apply
Solution Approach 1:
The retractable side skirts allow the vehicle to dynamically adjust ground clearance by retracting the skirts when encountering rough terrain or when regulatory minimum ground clearance is required. This dynamic capability enables the vehicle to comply with various regulatory requirements across different markets while maintaining aerodynamic performance on smooth roads.
Solution Approach 2:
The side skirt system serves multiple functions: it maintains aerodynamic performance on smooth roads, provides protection against road asperities, ensures compliance with minimum ground clearance regulations in various countries, and can be adjusted for different driving conditions. This multi-functionality resolves the contradiction between aerodynamic performance and regulatory adaptability.
3Force
If flat floor underbody is used to generate downforce, then vertical aerodynamic load is increased, but aerodynamic drag coefficient increases
Solution Approach 1:
The side skirts are strategically positioned to address specific local airflow problems along the lateral sides of the underbody. By locally modifying the airflow control in the regions where air disturbances occur, the skirts prevent harmful vortices from reducing downforce, without requiring a complete redesign of the entire underbody geometry, thus minimizing the increase in aerodynamic drag.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The retractable side skirts enhance aerodynamic performance by maintaining downforce while protecting against road impacts and complying with regulatory ground clearance requirements, thus optimizing energy consumption and range.
Implementation Method 1
the flat shape of the underbody generates, beneath the passenger car, a depression (low-pressure air zone) which, in turn, generates a vertical force that tends to press the passenger car to the ground (downforce)
Implementation Method 2
extend parallel to the longitudinal axis of the vehicle, along the right and left sides of the underbody, and are fixed to the underbody so as to extend cantilevered downwards up to graze the ground, so as to prevent the disturbed airflows that flow along the lateral sides of the passenger car from gliding underneath it
Data Source
Figure 1
Figure 2~3
AI summary
A road-use motor vehicle (1) comprising: a vehicle-vehicle body (2) provided with a plurality of ground-resting wheels (3, 4); a powertrain adapted to drive into rotation at least one of said ground-resting wheels (3, 4); an underbody (5), which is arranged to cover, or is integrated into, the lower part of the vehicle-vehicle body (2) so as to directly face the ground; at least one pair of side skirts (10), which have a ribbonlike structure, are flag-hinged to the underbody (5) on opposite sides of a vehicle vertical midplane (M) so as to vary their incline with respect to the vertical, and are adapted to prevent the airflows that flow along the lateral sides of the vehicle from reaching the central area of the underbody (5); and an electronic drive system (11), which is adapted to rotate said side skirts (10) so as to vary the ground distance (d) of the distal longitudinal edges (10a) of the same side skirts (10).