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1 air resistance coefficient
Introduction:
drag coefficient (drag coefficient), by a unit surface area calculation feature, air a kind of progress in the form of car reverse force. Air resistance is proportional to the square of the velocity with the relationship, that is to say: speed doubled, car by the resistance will increase 4 times. Thus affecting the high-speed traveling of the automotive air resistance is very clear, high vehicle speed, the engine will be a significant portion of the power, energy or fuel to overcome air resistance. In other words, the air resistance is small can not only save fuel, under the same power condition of the engine, but also to achieve higher speed.
by improving aerodynamic performance of the car, such as changes in the tail, the chassis cover, the front air inlet portion and the hub cap, can reduce the drag coefficient. Body height is reduced, the reduced cross-sectional area equal to, or covering the vehicle body more wheels, also help to reduce air resistance.
Cd drag coefficient is a measure of the influence of air resistance of a car by a standard size. Drag coefficient is smaller, it is subject to the influence of air resistance, and vice versa. Drag coefficient and fuel consumption is proportional to the relationship, the lower the lower the drag coefficient of the car, fuel consumption. And has a formula: W = Cdtimes; V is quadratic, W representative of vehicle fuel consumed, Cd is the drag coefficient of the vehicle, V is the vehicle speed. Seen from the formula, any slight change in drag coefficient, are to be amplified speed, and fuel consumption for the power loss which would adversely. There is also indicated a test, when the car is traveling at 80km / h, which is 60 percent power to overcome windage.
In automobiles running due to air resistance, while producing three longitudinal, lateral and vertical center of gravity of the car and the like around the aerodynamic forces, which is the largest longitudinal air power air resistance, about the overall air resistance of 80% or more. Air resistance coefficient values areGet out of the wind tunnel test. As the air resistance and air resistance coefficient proportional, modern cars in order to reduce air resistance would have to consider reducing the air resistance coefficient. From the 1950s to the early 1970s, car air resistance coefficient is maintained between 0.4 to 0.6. After the 1970s energy crisis, countries in order to further save energy and reduce fuel consumption, are committed to reducing air drag coefficient. Now car air resistance coefficient is generally between 0.28 to 0.4.
test showed air resistance coefficient every 10 percentage, the percentage of fuel savings of about 7. Some of the two cars has the same mass, the same size, but with different air resistance coefficient (0.44 and 0.25, respectively) compared to the travel speed per hour 88kin 100km, fuel consumption saving than the former 1.7L.
windage of the vehicle:
from the drag resistance of the air when the vehicle is running, air resistance generally has three forms a first resistance to gas flow is generated in the vehicle frontal collision – like a piece of wood against the wind and the line, the resistance experienced by almost all the impact resistance generated by the airflow. The second is the friction, air and across the body will produce the same friction, however, with the fastest speed of the vehicle can travel in general, the friction is small to negligible. The third is the shape resistance, in general, high-speed driving, the appearance of resistance is the main source of air resistance. Exo vacuum zone created by the resistance from the rear of the vehicle, the greater the vacuum zone, the greater the resistance.
In general, the appearance of San Xiangshi RV resistance will be lower hatchback RV. The vehicle is traveling, to overcome the resistance of the organic member resistance loss, rolling resistance of tires produced (generally referred to as road resistance) and air resistance. With increasing vehicle speed, the air resistance is becoming the main traveling resistance, when the speed of 200km / h or more, the air resistance accounts for almost 85 percent of all of the traveling resistance. Usually the vehicle is forward, the wind resistance generally suffer from the front, unless large side wind speed. Or will not have much impact on the vehicle, even if it has, it can be corrected by the steering wheel. Effects of drag on the performance of the car is very large. According to the test, when a car forward at 80 km / h, 60 percent of the fuel is used to overcome wind resistance. Cd drag coefficient is a measure of aA car by the influence of air resistance of the standard size. Drag coefficient is smaller, it is subject to the influence of air resistance, and vice versa, therefore said that the smaller the better drag coefficient. Generally, the stronger the linear flow cars, smaller drag coefficient. Drag coefficient can be determined by wind tunnel. When the vehicle is tested in a wind tunnel by the vehicle speed at the wind speed to simulate the cars, and then to test equipment to measure how much force needs to know the car took to resist the wind speed, the car will not retreat in the wind. After the measured force required, after deducting the wheel friction with the ground, the rest is a drag, then a so-called drag coefficient of a formula can be calculated from the aerodynamic. = Drag coefficient of a front wind resistance times; 2divide; (air front frontal projection area x density x speed squared). Drag coefficient of a car is stationary, the vehicle suffered at various speeds can be calculated from the resistance of the drag coefficient.