An optical fibre sensor for the measurement of hydrocarbons and oxides of carbon emissions in the exhaust of land vehicles.

This work describes the investigation and development of an optical fibre gas sensor based on mid infra red absorption spectroscopy. The sensor is suitable for monitoring the gases present in the exhaust emissions of a motor vehicle. The need for a sensor to be able to perform this task has emerged from increasingly stringent European Union legislation regarding emissions from automotive vehicles. Existing commercially available automotive gas sensors based on other technologies fail to meet these requirements and therefore a sensor capable of performing this task is required. The sensor of this investigation is able to monitor the exhaust gases can be made low cost and is compact and very robust. The sensor is designed for direct integration into the exhaust of the vehicle and therefore has to withstand a very hostile environment, The infrared emitter and detector used in the sensor are compact and inexpensive when compared to many components used in other optical fibre gas sensors e.g. Quantum Cascade Lasers (QCLs). The sensor was initially developed in the laboratory of the Optical Fibre Sensors Research Centre and tested using cylinder gases using CO2 as the test gas. The initial sensor design was enhanced such that it could be used to accurately measure the concentration of other exhaust gases such as hydrocarbons and carbon monoxide. Finally, optimised sensors based on optically transmissive and reflective type gas cell designs were tested in a diesel engine in CRF in Italy. Detailed analyses of the results are included and comparisons are made with theoretically predicted values.