This is the hero behind the key technology of the car maker.

Technology hero car

zhike· 2016-07-16 23:24:39

style= " Zhike =



public number: vehicle aerodynamics, ID:Auto-Aerodynamics


in automotive wind tunnel, wind speed at 300km/h is how to produce? What kind of equipment drives the whole wind tunnel to run? Known as the most expensive man-made wind is how to blow? This issue of "automotive wind tunnel advanced equipment" series, we will introduce you to the car in the wind tunnel behind the hero - fan system.


wind tunnel is based on the similarity principle, the car will be fixed on the ground, through the surface of the car through the high speed airflow simulation test equipment, automobile driving state of the actual pavement aerodynamic characteristics.


can simulate the change from the speed of 0-300km/h in automotive wind tunnel, the speed and the control precision can reach 0.03%, so the high speed range, accelerating effect of wind tunnel contraction on the one hand, but more important is the core in the wind tunnel equipment - fan system played a key role.



automotive wind tunnel fan principle

wind tunnel fan system with us in the daily lives of similar, mainly composed of a motor and a blade, also called axial flow fan Machine.



, we usually feel the size of the wind is the wind speed, the electric fan used as we all know, stalls of different wind speeds are different, different stalls in different power is corresponding to the fan, fan power is greater, so the wind speed is higher.


, but we also know that standing in front of a small fan, even if the electric fan is again big, also can not blow blow head to foot, feet can blow to blow out, this is caused by the size of the fan blade diameter, the difference is the volume.



automotive wind tunnel fan size

so much wind fan size in the end? For modern vehicle aerodynamics wind tunnel fans, the diameter is usually around 9m! The wind turbine is slightly smaller, and the diameter is usually around 4m.



wind turbine hub center usually accounted for about half of the diameter of the fan, the electric machine is huge hidden in them. The axial length of the fan, usually ranging from 5m to 7m, mainly depends on the design of the motor and the size of the tail vertebra.


automotive wind tunnel fan power

fan mainly depends on the maximum wind speed and wind tunnel design from the static to the most rapid acceleration, maximum speed of modern cars are usually more than 200km/h, one hundred kilometers acceleration time is also very easy to reach within 10 seconds, the With the motor rated power requirements will be improved. In order to ensure the wind speed simulation of the test vehicle in the wind tunnel, the wind turbine motor often needs to have a power rating of thousands of kilowatts.


automotive wind tunnel fan control precision
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wind tunnel fan can follow real time simulation of the vehicle driving speed, speed follow the deviation can be controlled within one second, no matter how you add speed, can guarantee the wind blowing with the shadow Form, you fast it also fast, you slow it also slow. Wind speed control accuracy of the wind turbine can be up to 0.03%. For example,


, if your speed is 100km/h, then the wind blowing machine is about 100 + 0.03km/h, taking into account the rounding, then is 100km/h. In practical engineering applications, it can be considered that the two speeds are exactly the same, of course, the actual use of the problem also need to consider the calibration. This is also the main reason for the wind tunnel to accurately simulate the automobile driving environment on the external road.

automotive wind tunnel fan efficiency

general household fan is about 50%, half of the electricity by waste heat Off. And the efficiency of the wind tunnel can reach more than 90%, taking into account the huge power of the wind turbine, so high efficiency will save a lot of electricity, which in today's context of energy-saving emission reduction, it is particularly important.


wind tunnel fan to achieve such a high efficiency requires special design, a large number of fan blade for example, select suitable hub ratio and special optimization, leaves usually requires the use of carbon fiber material, between the blade and the casing does not exceed 1/1000 of the diameter of the fan. Through this series of design in order to meet the high efficiency of the wind turbine.


world advanced automotive wind tunnel fan
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now we generally understand the basic situation of wind tunnel fan, below let us look at what the fan used the world famous automobile manufacturers and their tunnels.

GM
 
wind tunnel fan; built in 1980, GM ESAL aerodynamic wind tunnel, and West spruce made by the fan blade, a blade length of 12 feet (about 3.6 meters), weighing about 1 tons, driven by a variable speed DC motor 4500 HP, the test area high speed can reach 222km/h.



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  the latest automotive wind tunnel
Mercedes Benz cars put into use in 2013, the aerodynamics of wind tunnel fan diameter 9m, maximum power 5300kw, consists of 18 pieces of carbon fiber blades with high speed test up to 265km/h.
 
TOYOTA of Japan in 2013 built the most advanced automotive wind tunnel, the wind power machine at 8MW, diameter 9m, carbon fiber blades used.
 
in the construction of the China Bari aero acoustic wind power of the fan diameter was about 4000kW. 9m, maximum wind speed of more than 250km/h, with 18 pieces of carbon fiber blades.
with the Mercedes



is a nouveau riche to you. 25 thousand yuan per hour for the wind tunnel test!


this paper selected since WeChat No. automobile aerodynamics ID:Auto-Aerodynamics



auto aero acoustic wind tunnel test is known as the automobile test in the highest on a test, the test cost 25 thousand yuan per hour, also let the automotive wind tunnel wind blowing become the most expensive wind. Style= line-height: "23.2727px




automotive wind tunnel is in accordance with the design requirements of the pipeline system, the use of the power device drives a controllable airflow, according to the movement relativity and similarity principle of aerodynamics test equipment.


Benz GLA in the wind tunnel test


Benz automotive wind tunnel aerodynamic force measurement test of

break-word! "In the aerodynamic measurement, aerodynamic drag coefficient, aerodynamic lift coefficient (including front and rear axle lift coefficient measurement) is an important test project. They have a great influence on the fuel economy of the automobile and the high speed stability of the automobile.


in aerodynamic measurement, the general need according to the wind tunnel structure size and installation of model test results correction. In order to obtain accurate test results, such as the wind tunnel blockage ratio correction, the nozzle disturbance correction, the axial static pressure gradient correction, the support interference correction, the ground boundary layer correction.

in the six component of aerodynamic force measurement test, measuring equipment mainly includes force balance, turntable, mobile belt system, boundary layer suction system. In the modern automotive wind tunnel, these measuring devices are generally integrated in the rotary table.

FKFS automotive wind tunnel balance where mobile belt equipment

distributed automotive wind tunnel boundary layer suction system

test in the wind tunnel but also through the method of rotation, crosswind generator carry out crosswind stability, driving stability of vehicles in the crosswind conditions.

FKFS automotive wind tunnel generator in



< /section>
< > acoustic measurement test The development of section>
automobile wind noise performance has become the following after another drag car enterprises focus on the development of the field, the wind noise has become an important factor affecting the performance of automobile driving experience.

artificial head acoustic measurement equipment

Benz car noise measurement using microphone array

< /section>
[img! " 24]
Porsche wind tunnel frame type microphone array

Porsche Mike array acoustic measurement results of wind tunnel



flow measurement test flow measurement test can be divided into qualitative and quantitative flow visualization test of air flow parameter measurement test.

, a

< section>
flow measurement test flow visualization measurement test was used to observe the flow of air around the vehicle and the surface. There are four main methods: the ribbon method, oil film method, smoke flow method and particle image velocimetry (PIV).

ribbon
 
wire band is a common method used to observe the surface flow of the car. By observing the movement of the ribbon adhered on the surface of the body to determine the flow pattern of the body surface.


is usually used to soft and fine silk ribbon. Ribbon length and spacing is determined according to the model of location and the complex situation in the flow field, flow field of complex parts, such as the front window near, use short thread, spacing is smaller. On the contrary, in some of the structural changes in the smaller, more simple flow of the surface of the ribbon is longer, the spacing is larger.


ribbon method can also be used to display the spatial flow pattern. The ribbon stick around the model with space frame of fine woven wire, you can clearly see the flow around the model, especially the air flow model in the wake region.



 
< section>
oil film method; oil film method is mixed with a certain color less volatile, the viscosity of the oil liquid is uniformly sprayed on the car the surface. According to the oil film, the direction of airflow and the velocity of flow can be seen. />


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