2004 IRISH SCIENTIST YEAR BOOK

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University of Limerick
Jim Mulrooney, Colin Fitzpatrick & Elfed Lewis
An optical fibre sensor based intelligent system for monitoring and control of exhaust emissions from road vehicles – coming to a dashboard near you soon!!

As the number of vehicles on our roads increases annually, so too does the level of exhaust emissions accumulating in the atmosphere. To assist car manufacturers in reducing these emissions to acceptable levels and to make drivers aware of their own emissions, it is necessary to develop an intelligent monitoring system. In order to address this issue, the Optical Fibre Research Group at the University of Limerick is co-ordinating a collaborative research project called Opto-Emi-Sense, funded by the European Commission, with five other partners from three different countries. These partners are City University (London) and the University of Liverpool (both in England); Fibreware GmbH and the University of Rostock (both in Germany); and Centro Ricerche Fiat (Italy).


Exhaust gas emissions from automobiles are an increasing environmental concern

Optical fibre sensors will be used to monitor these emissions. Exhaust fumes comprise a complex mixture of hot gases and particulates including CO (carbon monoxide), NO x (nitrogen oxides), SO x (sulphur oxides), and HC (hydrocarbons), and therefore present any prospective monitoring system with a highly challenging problem. Optical fibre sensors are particularly suited to the exhaust system of a car as they can withstand high temperature, are lightweight and small, and are unaffected by mechanical vibration. The use of glass and ceramics in the construction of optical fibres guarantees their immunity to the corrosive elements present in the exhaust.

It is further proposed to interface and fully integrate the novel sensor network systems into the existing data network of the vehicle, thus providing the driver with clear and unambiguous in-car information on contaminant levels of exhaust emissions. Furthermore information from the sensors is input to the engine management system for controlling and further limiting the pollutant levels emitted from the engine.

To detect the analyte gases, it is proposed to use an optical absorption technique. Each gas absorbs infrared radiation at a signature wavelength, and an analysis of the infrared indicates what gases are present. To date, practically all optical fibre gas sensing has taken place in the near-infrared region of the electromagnetic spectrum, as components at these wavelengths (<1500nm) have been optimised for use in the communications industry. However the absorption lines, which exist at these wavelengths, are overtones and are generally an order of magnitude weaker than the fundamental absorption lines in the mid-infrared region (wavelengths greater than 2µm). A sensor with higher sensitivity could be produced if these mid-infrared absorption lines could be probed. Recent technological advances in mid-infrared components have indicated that it should be possible to develop an optical fibre sensor based on mid-infrared absorption for the gases of interest.

The project started in January 2004 and continues until December 2006. The initial work is being conducted in the Optical Fibre Sensors Laboratory at UL and the sensors developed here will be tested in Centro Ricerche Fiat's Research Laboratories in Turin in the latter stages of the project.

Contact: Dr Elfed Lewis, Optical Fibre Sensors Research Group,
Department of Electronics and Computer Engineering,University of Limerick;
E-mail: [email protected]