Heat flux mapping of oxyacetylene flames and their use to characterise Cf-HfB₂ composites

† Now at Alstom (Switzerland) Ltd.

Abstract

Cost effective and fast ultra-high-temperature testing methods such as oxyacetylene torch testing are extremely useful for the rapid screening of ultra-high-temperature ceramic (UHTC) materials for hypersonic applications. There is no report in the literature, however, of an organised study to measure the heat flux and how it varies with gas flow rate, gas flow ratio and distance from the nozzle tip for an oxyacetylene flame. In this paper, the authors report for the first time the heat flux mapping of an oxidising, neutral and reducing flame. The measured heat flux was as high as ∼17 MW m⁻² at a distance of 10 mm from the nozzle, which is much higher than that previously reported in the literature. Torch testing was carried out for Cf-HfB₂ UHTC composites at this heat flux and the results are presented along with detailed microstructural characterisation.

Keywords:

• Heat flux
• Oxyacetylene
• Ultra-high-temperature ceramics
• Ablation

Acknowledgements

The authors thank the Defence Science and Technology Laboratory (DSTL), UK, for providing the financial support for this work under contract number DSTLX-1000015267.

ORCID

A. Paul http://orcid.org/0000-0003-4473-0104

Notes

† Now at Alstom (Switzerland) Ltd.

‡ Now at the University of Birmingham, UK.

§ The peak flame temperature at the tip of the inner cone depends on the nature of the flame. The following values were reported in Fundamentals of Gas Cutting and Welding, Bhatia A., cedengineering.com: reducing flame, 3150°C; neutral flame, 3260°C and oxidising flame, 3480°C. Whilst the absolute values may be disputed, it is very clear that the flame temperature increases with the increasing oxygen content leading to a higher heat flux value.