T/CSAE 111-2019 in English
VALIDThe terms and definition related to aerodynamics performance for passenger car
- Issued on:2019-07-10
- Implemented on:2019-07-10
- File Format:PDF
- Delivery:Via email within 5 business days
$495.00
Introduction
Standard Background and Technical Evolution
This standard was developed by the Automotive Aerodynamics Branch of the China Society of Automotive Engineers and co-drafted by seven units including SAIC and Tsinghua University. As the first terminology standard for passenger car aerodynamic performance in China, its release fills the gap in standardization in the field of automotive aerodynamics. As the competition for electric vehicle range intensifies, aerodynamic optimization has become a key means to reduce the drag coefficient. This standard provides a unified technical language for the industry.
Analysis of the core terminology system
| Term category | Key parameters | Calculation formula | Engineering significance |
|---|---|---|---|
| Aerodynamic force | Drag coefficient CD | D/(q∞·A) | Influence on cruising range and fuel consumption |
| Aerodynamic moment | Pitching moment PM | q∞·A·WB·CPM | Determines driving stability |
| Coordinate system | Yaw angle ψ | Positive when the front of the vehicle is facing right | Crosswind Condition Analysis |
Key Technical Points
1. Aerodynamic Coordinate System
The standard clearly defines that the origin is located at the intersection of the wheelbase center and the track center, and establishes the XYZ three-axis coordinate system:
- X-axis: points to the rear of the vehicle and is used to measure aerodynamic drag
- Y-axis: points to the right and is used for lateral force analysis
- Z-axis: points upward and corresponds to lift measurement
2. Key Coefficient Calculation
The aerodynamic lift coefficient CL is calculated using formula (4), where:
q∞=1/2ρV∞² is the dynamic pressure, ρ is taken as 1.184kg/m³ (standard atmospheric pressure at 25℃)
In practical applications, attention should be paid to the impact of front/rear axle lift distribution on handling, as shown in formulas (5)(6).
Implementation suggestions
- Wind tunnel test specifications: The model vehicle must meet the wheel speed stability requirements, and it is recommended to use a 1:1 or 3:8 ratio
- Data correction: The scaled-down test needs to be converted to equivalent speed according to Article 3.4.12
- Development process: Phased verification from clay model to engineering prototype
Technical extension
The definition of Reynolds number (3.4.13) in the standard is the basis for judging flow characteristics. It is recommended that Re be controlled within the range of 2×10⁶～7×10⁶ when developing electric vehicles. When measuring the boundary layer thickness (3.4.10), attention should be paid to the selection of the judgment point of 99% free flow speed.
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