Active Rear Diffuser Panel for Vehicle Aerodynamic Drag Reduction
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Solution Overview
Problem
Conventional rear diffusers are limited by design restrictions and aesthetic considerations, failing to provide optimal aerodynamic benefits without compromising vehicle styling or legal compliance.
Innovation Solution
An active diffuser assembly with a fixed panel and a movable active panel that deploys to create a gap between the rear bumper and the active panel, allowing airflow over both surfaces and balancing downwash and upward flows, thereby reducing lift force and increasing downward force on the rear axle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional fixed rear diffuser is used, then aerodynamic benefits are provided, but the vehicle styling and legal compliance are compromised
Solution Approach 1:
The diffuser panel is designed to be movable rather than fixed, allowing it to change position between a deployed state (providing aerodynamic benefits) and a retracted state (maintaining vehicle styling). The panel can be actuated to extend rearward and downward to create the desired airflow management, then retracted to follow the vehicle's contour lines and not interfere with styling.
Solution Approach 2:
The diffuser system is divided into a fixed portion and a movable active panel. The fixed portion remains attached to the vehicle body while the active panel can independently move to the deployed position. This segmentation allows the aerodynamic function to be separated from the styling requirements, as only the movable portion needs to be retractable.
2Loss of energy
If a conventional fixed rear diffuser is used, then aerodynamic benefits are provided, but legal requirements for ground clearance and vehicle dimensions are violated
Solution Approach 1:
The diffuser panel transitions from a static extension that permanently increases vehicle length to a dynamic component that only extends when needed for aerodynamic performance. When retracted, the panel follows the vehicle's contour and does not interfere with legal ground clearance or overall length requirements.
Solution Approach 2:
The diffuser panel is designed to move in multiple dimensions - extending both rearward (length dimension) and downward (vertical dimension). This multi-dimensional movement allows the panel to create the necessary aerodynamic gap without permanently increasing the vehicle's ground clearance requirements, as the downward component of movement compensates for the rearward extension.
3Loss of energy
If the active panel is deployed to create aerodynamic benefits, then airflow is improved, but the device complexity increases
Solution Approach 1:
The system uses a movable active panel that can be actuated between deployed and retracted positions. This dynamic component adds complexity compared to a fixed diffuser, but the complexity is localized to the movable panel mechanism rather than requiring a completely active system, providing a balance between aerodynamic performance and system simplicity.
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 active diffuser assembly improves aerodynamic drag by balancing airflow, reducing lift force, and increasing downward force on the rear axle, while maintaining vehicle styling and compliance with design and legal requirements.
Implementation Method 1
allowing airflow over both surfaces and balancing downwash and upward flows
Implementation Method 2
balancing downwash and upward flows
Implementation Method 3
improves aerodynamic drag
Implementation Method 4
reducing lift force and increasing downward force on the rear axle
Data Source
AI summary
A vehicle having a vehicle body including a front portion, an opposing rear end portion and an underbody portion configured to face a road surface; and an active diffuser assembly disposed on the underbody portion and configured to control ambient airflow passing under the vehicle body. The active diffuser assembly includes a fixed panel disposed on the vehicle underbody; a movable active panel disposed adjacent the fixed panel and configured for selective movement to be deployed away from the vehicle body and to be retracted toward the vehicle body for stowage; and an actuator configured to deploy and retract the movable active panel, the fixed panel and the movable active panel defining a continuous plane when the movable panel is in the stowed position.