Tracer-free, non-intrusive, time- and space-resolved temperature and scalar measurements

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The growth in air transport, and the need for base and balance thermal power in an electricity-powered future centres creates a pressing need for low emission, high efficiency gas turbines, particularly regarding NO, CO and soot. The key variables determining the production of these pollutants in the product gases are the local instantaneous product gas temperature and the local fuel fraction. The large fluctuations in gas temperature, and the exponential dependence of pollutant production on temperature means that predictions of NO, CO and soot in combustion are not possible without suitable accurate statistics of instantaneous local temperature measurements. Yet there are very few such measurements in practical devices to validate models. Local instantaneous temperature measurements in high pressure radiant devices require optical techniques which are rather complex for industrial laboratories. This proposal aims to extend a much simpler technique for the purpose to allow tracer free local measurements of temperature, pressure and water vapour. Laser-induced grating spectroscopy (LIGS) has been shown to work even in highly radiant, soot-prone environments, and may also enable local measurements of additional target scalars (water vapour, pressure) using the easily accessible Nd:YAG laser wavelength of 1064 nm. The technique uses both the electrostrictive mode and weak absorption spectral lines in this wavelength range to enable measurements of both temperature and relative water concentrations in realistic devices. The signal to noise of the technique improves with pressure, a significant advantage for realistic devices, especially in environments such as gas turbines, which are prone to large amounts of radiant luminosity. The project will extend the current capabilities of the technique from point measurements to spatially resolved line measurements. Finally, it will extend the pump laser wavelength into near infrared, which will unlock the ability of the technique to use strong absorption lines for a range of widely available species (water, carbon dioxide and hydrocarbons), using industrial lasers at high repetition rates. The final outcome of the project will be the development of an instrument and method for non-intrusive temperature and species measurements in high temperature, high pressure practical reacting flows, requiring only a fraction of the cost of previous techniques of comparable precision. Demonstration measurements will be produced in a high pressure, high temperature, realistic industrial facility. Data produced during these measurements will also allow researchers and developers to review and validate robust reacting flow models for industry and open up the possibilities for optimisation of clean energy conversion devices. The plan for technology transfer is ensured by partnering with a company (Dantec) that has already packaged and commercialised similar instruments. An extension of the validation measurements to other industrial facilities at Rolls-Royce is planned once the instrument development and demonstration has been successfully concluded. Finally, the project will also offer opportunities to PhD students associated with the Energy CDT at Cardiff.