Rapid exhaust measurements

Emission standards in Europe are constantly being tightened. In the quest to improve engines, carmakers measure the concentration of several gases simultaneously. A device used by Volkswagen gives particularly rapid results - not only because of its infrared lasers.

Statutory requirements for vehicle emissions are being tightened even further: The new EU4 emission standard comes into force in 2005 for all vehicles in Europe. Gasoline and diesel engines will have to halve their emissions of toxic gases by comparison with the present EU3 standard, established only three years ago. Car manufacturers have long since adapted their development processes to the production of compliant (and tax-reduced) engines with catalytic converter systems. One example is the lean-burning engine already incorporated in many Volkswagen models. To reduce the emission of pollutants still further, engineers in Wolfsburg are using a device called DEGAS IV to measure the composition of exhaust gases. Jörg-Dieter Baronick, a department manager at VW, describes the advantages of the new device, developed at the Fraunhofer Institute for Physical Measurement Techniques IPM: Infrared spectroscopy has advanced to such a high level that we were convinced by the cost-efficiency of the new device. In particular, the tenfold increase in data recording speed persuaded us to venture into what in our field of metrology is new. Engineers working on the test rig are now better able to identify the timing of peak output levels of specific gases.
The ability to capture ten reliable values per stroke of the engine, i. e. about one hundred per second, is primarily due to the technique employed. Infrared laser spectroscopy produces fast results, emphasizes marketing officer Dr. Karsten Sassenscheid. But its not the laser alone that makes the difference. My colleagues at the Institute have optimized all of the devices components to operate at the highest possible speed. This applies particularly to the laser control circuits, the sampling method, and the miniaturization of the test cells.
Since up to three diode lasers can operate simultaneously in DEGAS IV, it can measure the concentration of three gases simultaneously. By using lasers working at different wavelengths, data can be obtained from various gases including carbon monoxide, nitrogen monoxide and dioxide, ammonia and methane. Engine designers can gain greater insights through the fact that the system is capable of supplying measurements from four different points in an exhaust system at the same time. The design team also paid particular attention to ease of use, to allow even less highly trained persons to obtain reliable measurement results. Customers nowadays expect a modern measuring equipment to be compatible with computers and other peripheral electronic devices.
,For further information:
Dr. Karsten Sassenscheid ,Telefon +49/ 7 61 / 88 57-3 12 ,Fax +49/ 7 61 / 88 57-2 24 ,[e-mail]
Fraunhofer-Institut fur Physikalische Messtechnik IPM ,Heidenhofstra?e 8 ,79110 Freiburg ,http://www.ipm.fraunhofer.de/
Links: ,IPM: Presseinformation ,http://www.ipm.fhg.de/presseordner/pressemit_akt/degas_iv.html
Kfz-Technik: Entwicklung von Abgas und Verkehr ,http://www.kfztech.de/kfztechnik/motor/abgas/abgas1.htm
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