Waiblingen, 25 February 1998 - The Research Institute for Vehicles and Automotive Engines in Stuttgart (FKFS) as a private law foundation in accordance with its articles of association, has the task of serving technical progress with highly qualified personnel and high-tech equipment as a partner of the automotive and automotive supplier industry. The research results gained by the FKFS during the past few years have contributed greatly to the German automotive aerodynamics being able to hold a top international position in the second half of this century.

Automotive aerodynamics researches the multi-facetted interaction between the vehicle shape and the air flow which have a lasting effect on all kinds of different qualities of the vehicle and has tried to determine these theoretically and via practical experiments. Major goals include the reduction of fuel consumption, the reduction of pollution and noise emissions as well as the increase of road safety and comfort.

Since September 1988 FKFS has been contracted by the University of Stuttgart to operate two of the most modern automotive wind tunnels for industrial development work, as well as for the basic research purposes of the University: a vehicle wind tunnel with a nozzle opening of 22.45 square meters for real size cars and vans, as well as a model wind tunnel with an area of 1.65 square meters for model cars to a scale of 1:4 to 1:5. The vehicle wind tunnel became one of the most modern aero-acoustic vehicle tunnels in Europe in 1993, thanks to the installation of fibre-free acoustic insulation between the fan and the conduit, as well as the lining of the measurement area with absorbent material. The highly developed traversing technology for all types of sensors enables a fast and complete examination of the circulation of and flow-through of air around the vehicles in the near field and far field in both wind tunnels.

To establish and optimise the performance data of radiators in cars, the flow-through of the radiator has to be measured. For this purpose, eight vane wheel flow sensors type TSR 26/16 GE 40 m/s/125 °C from Höntzsch were used by FKFS. They were installed alongside each other on a cross bar which can be traversed on two axes parallel to the surface of the radiator, directly in front of or behind the radiator. Due to the cramped conditions in the engine compartment the fact that the sensors in the flow direction are only 16 mm wide proves to be a great advantage in this case.

The volume flow which is present in front of and behind the radiator is determined by allocating each sensor position to an area with an assumed constant flow speed. As the protective sensor ring has an external diameter of only 26 mm, the travelling distance between the individual measurements can be selected so small that a high measure-ment resolution is attained.

As reflux effects can also arise on the radiator, additional information about the +/- flow direction is required which is obtained by scanning the vane wheel direction of rotation in the TSR sensor head. The specific measurement accuracy can in this case be specified with 0.15 m/s for speeds lower than 10 m/s and with 1.5% of the measured value for speeds higher than 10 m/s.

Thanks to the constant temperature resistance of the TSR sensors from +125°C upwards, tests can also be made whilst the vehicle is being driven.

The frequency signals of the flow sensors are fed to an eight-channel evaluation unit type µP-ASD-R and converted into voltage signals. An additional V24/RS232 port enables connection to a PC on which the data can be digitally and graphically depicted in seconds.

By using the configuration of measurement equipment described above, FKFS has succeeded in making fast accurate statements about the com-plex flow-through of engine radiators and other automobile components.