Exploring the contest with air Chang ‘an Auchan wind tunnel test

　　　　[XCAR Technology Original]

　　　　I believe that card friends are no strangers to the "wind resistance coefficient". When the vehicle is driving at a low speed, the resistance mainly comes from the friction between the tire and the ground. When it reaches a certain speed, for example, when the speed exceeds 110km/h, about 70% of the resistance of the vehicle comes from the impact of airflow, which is what we often call air resistance. The magnitude of resistance is generally measured by wind resistance coefficient. The drag coefficient of our common cars is mainly between 0.28 and 0.4, so how to design the body shape and chassis to achieve the most reasonable drag coefficient has become one of the biggest problems faced by many car companies.

　　　　For family cars, low drag coefficient is particularly important, because it directly affects the fuel consumption and noise level of vehicles at high speed. Therefore, sometimes even the performance and appearance of some vehicles are sacrificed in pursuit of lower drag coefficient.

　　　　So how is the drag coefficient measured? After all, we can’t consider the data published by car companies, especially the "illusory" data like drag coefficient. To this end, we came to the Shanghai Ground Vehicle Wind Tunnel Center in Jiading Campus of Tongji University in Shanghai to reveal the whole process of this experiment. The brand-new 7-seat MPV Auchan of Changan is our test vehicle. Judging from the officially announced drag coefficient of 0.334, it is definitely at the top level in the same class, even far exceeding some joint venture brands.

　　　　Shanghai Ground Vehicle Wind Tunnel Center can be said to be the most advanced vehicle wind tunnel center in China, which cost 500 million yuan to build and has been tested by hundreds of enterprises. I have to ridicule here that it is absolutely extravagant to "blow the wind" in the experimental room. According to the staff, their charging standard is in minutes, and it takes 400 yuan RMB to blow for one minute. Under normal circumstances, it takes nearly 8 hours for a car to complete all the test processes, and the total cost is about 250,000 to 300,000 yuan. Of course, this has not calculated other additional costs such as transportation and labor. Normally, a new car needs to do three wind tunnel tests, and through the process of improvement and retest, it can reach the most perfect state.

　　　　We should know that not all car companies will choose wind tunnel test when developing new models, and some of them will use computer simulation to simulate the test process. Although the cost is relatively low, the accuracy of the measured data remains to be discussed.

　　　　Changan Automobile is not "spending money like water". They reasonably combine the two testing methods. In the early development, they used computer simulation technology to improve the design of the body and chassis as much as possible to achieve lower drag coefficient and quiet cabin space. In the final stage, the real wind tunnel test was used to improve the shortcomings of the vehicle and improve it. It can also be seen that Changan Automobile has invested heavily in this brand-new home MPV and has high expectations.

　　　　Through this reasonable development process, the drag coefficient of Auchan finally reached 0.334. Because of the demand of interior space, this MPV model can not achieve the streamlined structure like a car, so it is necessary to make up for its disadvantages as much as possible through scientific treatment of some details. Because the positioning of MPV models is completely family-oriented, who can achieve lower fuel consumption and noise while ensuring space can be more popular.