Examining the burning velocity of iron-air flames with a V-shaped flame burner
Helen Prime defended her PhD thesis at the Department of Mechanical Engineering on December 4th.
Solar, wind, and hydropower tend to be seasonal and intermittent, with no guarantee of meeting energy demands at a given moment. Technology capable of capturing excess energy and storing it long-term for later use is not yet available at large scales. Iron powder is an attractive candidate because its oxidation with air releases heat without producing greenhouse gases. Although metals have historically been used in fireworks and rocket fuels, the idea of burning iron powder in bulk for controlled energy release is relatively new. This raises fundamental questions about the mechanisms of iron-powder combustion, including the burning velocity of iron–air flames which Helen Prime investigates in her research.
Building a v-shaped flame burner
While the burning velocity of iron-air flames has been studied previously, reported results vary significantly - even when using very similar combustion systems. For this research, a new burner was built: the inverted Bunsen-flame burner, also referred to as the V-shaped flame burner. A prototype was tested against values reported in the literature to ensure consistency and identify areas for improvement. The initial results were successful, showing a reasonable match with the results in the literature. The system was then enhanced with two advanced optical diagnostics: particle image velocimetry, for measuring the local velocity of the iron powder, and laser attenuation/extinction, for real-time, non-intrusive measurement of particle concentration in the flame.
Replicating combustion conditions
Prime used images from a high-speed camera to capture flame behavior. In addition, several evaluation methods were applied to the same dataset to compare results. The burning velocity of V-shaped flames was found to lie 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. Although these values differ substantially from previously reported results of ~15–20 cm/s, they match well with independently obtained numerical findings.
Title of PhD thesis: . Supervisors: Prof. Philip de Goey, Dr. and Dr. Yuri Shoshyn.