Ironing out the wrinkles: development and utilisation of a V-shaped flame burner for measuring the burning velocity of iron dust flames

The use of carbon-based fuels has been a boon to many countries, allowing for fast development and increased quality of life. The price? The release of large amounts of greenhouse gasses, leading to climate change and resulting in extreme weather and rising sea levels. With global energy demands ever increasing, alternative ways of obtaining, storing and releasing this energy at the right times and locations are vital. The solutions of obtaining sustainable energy are already underway - solar panels, wind turbines and hydro-electric dams are some examples of sustainable energy and electricity generation. The challenge of storage, however remains unsolved. The aforementioned methods of sustainable energy generation tend to be seasonal and intermittent with no guarantee of meeting energy demands at a given moment. The technology to capture energy in times of excess, and store it long-term for release in times of need is not yet available on large scales. Long-term, bulk energy storage is where iron powder has potential. The oxidation reaction (combustion) of iron with air releases heat and no greenhouse gasses. That iron may be combusted has been known for a long time - metals have been used in the past in fireworks and in rocket fuels. However the idea of iron powder being burned in bulk for controlled energy release is a relatively new one. There are, therefore, still quite some questions to be answered on the fundamentals of iron powder combustion. To address (some of) these questions is the aim of this work. This work focuses on investigating the burning velocity, a parameter studied extensively for gas flames which aids in understanding the mechanisms of combustion, as well as being a vital component in numerical simulations. While the burning velocity of iron-air flames has been studied and reported on previously, there is significant variation within these results when using very similar combustion systems. For the measurement of this parameter, a new burner was built - the inverted Bunsen-flame burner, also referred to as the v-shaped flame burner. A prototype of this burner was tested for consistency with values available in the literature and to identify any areas of improvement. Initial results were a success with a reasonable match to the results in the literature. Improvements were made in the form of two optical diagnostics systems: particle image velocimetry for measuring the local velocity of the iron powder and laser attenuation/extinction for a non-intrusive, real-time measurement of particle concentration in the flame. Data was obtained in the form of images from a high-speed camera. The burning velocity of v-shaped flames may be evaluated using several different methods. These methods were applied to the same data to determine any differences between them and the reasons for these differences. The burning velocity was found to be in the range of 3-22 cm/s, depending on the method of evaluation. This reduces to ~ 3-9 cm/s when considering only the most suitable method, which combines the angle method with the local velocity. While quite different to the previously report values of ~ 15-20 cm/s, the values obtained from this work match well with independently obtained numerical work.