汽车风洞试验.pdf

Road Loads
Chapter 4 – Road Loads n Aerodynamic drag (in –X direction)
n Aerodynamic lift (in –Z direction)
n Tire rolling resistance
n Road gradient (hills)
Drag Coefficient, C D Density of Air, r
1
D = ρV 2C A Eqn. 4-2 Air pressure
A 2 D
Drag force Frontal area
of vehicle æ P öæ 519oF ö lbf × sec2
ρ= ç r ÷ç ÷
Drag ç ÷ç o ÷ 4
Density of Vehicle è inHg øè 460 F + Tr ø ft
air velocity coefficient
Air temperature
kg
Eqn. 4-4 ρ= (*** Automotive Handbook, p. 339)
m3
1
Frontal Area of Vehicle, A Typical Frontal Areas
Vehicle Frontal Area
2 2
For passenger cars, GM 1-Ton full size van m ft
2 2
A ~ * Height * Track Ford Minivan m ft
2 2
Chrysler Minivan m ft
(*** Automotive 2 2
Height Typical . Sedan m ft
Handbook, p. 338) 2 2
5 passenger Volvo ECC m ft
2 2
1991 Honda Civic DX m ft
2 2
GM Experimental Ultralite m ft
2 2
Track Renault VESTA II m ft
From: /handbook/
Drag Coefficient, C D Typical Drag Coefficients
Drag Coefficients Cd for a range of Vehicles
Average 1975 . Estate Wagon
Average 1979 . Car
Figure GM 1-Ton full size van
Average 1987 . Car
Average 1992 . Car
Chrysler T-115 1990 Minivan
1986 Subaru XT Coupe