Optical Fibre Sensors for Gas Sensing in Extreme Environments

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This project revolves around the use of optical fibre sensor systems for gas species sensing. The ability of optical fibres to withstand extreme environments such as high temperature and high pressure as well as exposure to magnetic fields and radiation leads to use in a variety of applications. Fibre sensors can typically withstand temperatures up to 1000 degrees C, but sapphire fibre can be used for operating at temperatures above this limit. The sensors are also unaffected by electrical interference and do not conduct electricity, hence they can be used in places with a high voltage electricity supply or flammable material. These areas would be otherwise inaccessible with conventional sensors. The project is motivated by the many benefits to the use of these systems in extreme environments as it allows for improved control systems, with better safety and efficiency. The technology has many potential applications. For example, in aero engines to detect the gas composition of the emission coming from the engine in close to real time. This allows the emissions to be monitored and operating conditions adapted to reduce them. The ability for detectors to be able to do this is exciting as it has many implications such as contributing to the development of improved efficiency of burning fuels for energy and propulsion systems. This of course has environmental impact which is something that is of great importance to society. The overall aim of this project is to develop current optical fibre sensor technologies for applications in real-time gas detection. The objectives are to develop gas species detection systems with (i) higher sensitivity; (ii) the ability to operate remotely; (iii) the ability to operate in extreme environments. The novelty of the proposed research lies in that the gas species detection will be performed in new types of hollow-core optical fibre (such as anti-resonant fibres and photonic bandgap fibres). The idea is to inject gases into the hollow fibre core, where it will interact with guided light. The concentration of individual gas species can be determined by measuring the light absorption at specific gas absorption lines. This interaction will be enhanced using precision laser micromachining to modify the optical fibre properties. This allows for much quicker sensing and hence close to real-time feedback which provides many advantages in the applications of this technology. Further novelty will come from the development of new optical fibre interrogation systems to further enhance the detection sensitivity. This may allow for use of lower cost components and components which will be able to withstand harsh environments themselves. The project falls within the EPSRC engineering research area. Within this theme, it is within the topic areas of Optical Devices and Subsystems, as well as Sensors and Instrumentation. However, being multidisciplinary there are also numerous links to applications of the technology. The collaborators on the project will be the Department of Chemistry at the University of Oxford and Rolls-Royce plc. The Department of Chemistry will provide guidance on species detection at elevated temperatures and experimental calibration. Rolls Royce will provide input on requirements for nitrogen oxide and nitrogen dioxide detection in aero engines for emission reduction.