Optical diagnostics
At NCCAT, advanced optical diagnostics deliver precise, non-contact measurements under real-world conditions—providing critical insights into thermo-fluid processes within modern aerospace gas turbines.
Optical diagnostic measurements at NCCAT are highly applied and target non-contact measurements under conditions of direct relevance to the thermo-fluid processes occurring within modern aerospace gas turbines. The measurement capability is focused around imaging: providing spatially resolved data optimised for specific measurement requirements. Given the central role of the research at NCCAT in delivering reactants to combustion processes, many of these measurements directly target fuel/air preparation and flame structure. The majority of optical techniques developed and applied therefore specialise on the physical processes underpinning the mixing of fuel and air and the subsequent combustion reaction.
Velocimetry
Understanding the structure and time evolution of velocity fields is central to describing the behaviour of engineering relevant thermo-fluid systems due to the inherent coupling with fluid turbulence. Measurements which are able to provide instantaneous pictures of the complex structure of the flow and accurately recover turbulence statistics are particularly valuable. Due to wide applicability, particle image velocimetry (PIV) has become the front-runner in this area. The optical team at NCCAT have developed a particular specialism in the application of both conventional and novel PIV methods applicable to gas turbine applications.
Multiphase flow
Modern aerospace gas turbines rely upon the combustion of liquid fuel to raise core gas path temperature and generate thrust. Fuel is introduced into the combustor and initially mixed by a fuel injector, which provides the foundation for combustor performance. Very small changes in fuel preparation, or fuel/air interaction, leads to significant differences in stability and pollutant emissions production. Fuel measurements are typically performed “isothermally” – without combustion of the injected fuel. This simplification allows understanding of how the liquid and gas are prepared prior to combustion and to develop models to predict fuel placement inside the combustor. Measurements typically seek to determine the size, structure, placement and velocity of the liquid phase. Determining this presents significant challenges for imaging and the techniques developed are applicable to other multiphase flow problems, for example cavitation within bulk liquids.
Combustion
Modern gas turbine combustion systems are extremely efficient, producing enormous propulsive power with low fuel consumption and minimal pollutant emissions. Efficiency is achieved by operating at high pressures and high combustor inlet temperatures and emissions managed through careful design of the combustion system. Optical measurements at these conditions are extremely difficult. They seek to determine where in space the combustion reactions are taking place and how these interact with the combustion hardware and delivered gas streams.