Tailpipe gas sensors
Emissions from automobiles are an important worldwide source of pollutants. Improvements in technology have helped reduce emissions on a per automobile basis, but the total number of automobiles in use continues to increase and counteracts this improvement. Emitted pollutants include carbon dioxide (which contributes to global climate change), oxides of nitrogen and hydrocarbons (which combine to form photochemical smog), carbon monoxide and other harmful substances. When changes in engine efficiency (to reduce fuel consumption), fuel composition (e.g. reformulated gasoline, biofuel, natural gas, hydrogen energy, etc.), or other potential improvements are implemented, engineers require a method to evaluate the results. This can be performed in a controlled environment using a dynamometer (akin to a treadmill for a car), but it is best to perform such measurements in real-world operating conditions - on the road. A group of European companies, including several high profile automobile manufacturers (Fiat, Renault and Volvo), participated in the ECONOX II Project to develop an industrial grade gas sensor prototype. The sensor examines the chemical composition of the engine exhaust at the tailpipe for carbon monoxide (CO), oxides of nitrogen (NOx) and hydrocarbons (HC). Mass production of the sensor was achieved using screen-printing technology, meeting industry standards for reproducibility and stability in performance. Testing of the sensor revealed good sensitivity to CO, HC and NO2, but unsatisfactory detection of NO. The microelectronics organisations involved in ECONOX II look to extend the innovative screen-printing technology to other, non-automotive sensor applications. On the other hand, the other partners look to exploit the simple planar structure employed that allows the sensors to operate directly in the exhaust flow, which is normally impossible due to the high operating temperatures. Further research support is also sought to improve the response of the sensor (e.g. to NO).
