Automobile Diffuser Downforce via Convex Bump and Inverted Wing
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Solution Overview
Problem
Existing automobile diffusers, particularly in road cars, struggle to effectively generate substantial downforce due to high ride height, resulting in reduced aerodynamic drag and fuel efficiency, whereas racing cars benefit from low ride height and enhanced tire traction.
Innovation Solution
Incorporating a convex-shaped bump and an inverted low-speed/high-lift/flat-bottomed airfoil-shaped wing within the diffuser, positioned near the exit, to enhance pressure recovery and increase downforce by accelerating airflow and creating a pressure gradient, while maintaining modest aerodynamic drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a smooth underbody and diffuser section are used in road cars with high ride height, then aerodynamic drag is reduced and fuel economy is improved, but downforce generation is insufficient
Solution Approach 1:
The patent applies local quality by introducing specific aerodynamic features (convex bump and inverted wing) at particular locations within the diffuser rather than modifying the entire underbody. The convex bump is positioned on the diffuser ramp surface while the inverted wing is mounted above it, creating localized flow manipulation zones that generate downforce without disrupting the overall smooth underbody design intended for drag reduction.
Solution Approach 2:
The convex-shaped bump introduces curvature to the diffuser ramp surface, altering the airflow path and creating favorable pressure gradients. This curved surface accelerates the boundary layer and delays flow separation, while the inverted wing above it creates a corresponding curved flow path, together generating downforce through pressure differential while maintaining compatibility with the smooth underbody configuration.
2Force
If aerodynamic devices are added to enhance downforce, then downforce generation is improved, but aerodynamic drag increases
Solution Approach 1:
The patent employs partial action by using a modest-sized convex bump (5-7mm length) and a relatively thin inverted wing (5-6mm thickness) that provide sufficient downforce enhancement without creating excessive drag. The devices are positioned strategically within the diffuser where they can generate downforce through pressure recovery enhancement rather than through large-scale flow deflection that would increase drag.
Solution Approach 2:
The convex bump acts as an intermediary element between the diffuser ramp surface and the inverted wing above it. This intermediate structure modifies the boundary layer characteristics and creates a pressure gradient that enhances the downforce-generating capability of the inverted wing while minimizing the overall drag penalty of having two aerodynamic devices in close proximity.
3Force
If the convex-shaped bump and inverted wing are positioned close together within the boundary layer, then pressure recovery is enhanced and downforce is increased, but manufacturing precision requirements increase
Solution Approach 1:
The patent segments the downforce-generating structure into two distinct but closely spaced components: the convex bump mounted on the diffuser ramp and the inverted wing mounted above it. This segmentation allows each component to be manufactured and positioned independently, with the convex bump serving as a reference feature for positioning the inverted wing at the optimal 9-15mm spacing within the boundary layer.
Solution Approach 2:
The patent specifies parameter ranges rather than fixed dimensions to accommodate manufacturing tolerances. The gap between the convex bump and inverted wing is defined as 9-15mm, the convex bump length as 5-7mm, and the inverted wing thickness as 5-6mm. These parameter ranges provide sufficient tolerance for manufacturing and assembly while maintaining the critical spacing needed for effective boundary layer interaction and downforce generation.
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 solution significantly increases downforce generation with a minimal increase in aerodynamic drag, improving driving performance and fuel efficiency in road cars, similar to racing cars.
Implementation Method 1
the start of the elevating ramp surface of the diffuser further accelerates and also lowers the pressure of the airflow travelling through the diverging area of the diffuser
Implementation Method 2
enhance pressure recovery and increase downforce by accelerating airflow and creating a pressure gradient
Implementation Method 3
The diverging expansion of the diffuser area then acts as a region where the airflow expands, thereby reducing its speed and increasing its pressure
Implementation Method 4
The gap between the top surface of the suspended inverted wing and the convex-shaped bump thickest point is within the approximate boundary layer thickness of the diffuser ramp surface
Data Source
AI summary
An automobile diffuser is the upwardly-ramped surface at the rear of the vehicle's underbody. Aerodynamic downforce and drag are generated as airflow travels underneath and along the ramped surface of the diffuser. However, with a moderate drag penalty, the downforce-producing effect of the diffuser can be further enhanced by an arrangement of aerodynamic devices along the ramp surface and within the diverging flow channel of the vehicle's diffuser.