This paper presents a systematic experimental study on the lift-off behavior of jet flames impinging on a cylindrical surface by conducting horizontal jet fire experiments. In the tests, the fuel exit velocity was varied between 8.5 and 73.1 m/s, while the internal diameter of the nozzle was 2.0, 3.0, and 4.2 mm. The nozzle-to-surface spacing was set to be infinite (corresponding to free jet flame), 15, 20, and 25 cm. The flame lift-off distance was observed to be between 0.46 and 20.97 cm. This distance was accurately calculated by using an image visualization technique to reconstruct the image frames of a camera. It was found that the lift-off distance depends on not only the exit velocity but also on the nozzle diameter of the free jet flame. The proportionality of lift-off distance to exit velocity increases as the nozzle diameter increases. It is also indicated that the exit velocity, nozzle diameter and nozzle-to-surface spacing have a complex coupled effect on the jet flame lift-off behavior. For the 2.0 mm diameter nozzle, the lift-off distance of a jet flame impinging on a cylinder increases more remarkably than that of free jet flame. The lift-off distance first increases and then remains the same as the exit velocity increases for all nozzle-tosurface spacings. For the 3.0 mm diameter nozzle, the lift-off distance is only affected at a nozzle-tosurface spacing of 15 cm. For the 4.2 mm diameter nozzle, the cylinder has no effect on the lift-off distance regardless of the nozzle-to-surface spacing. The dimensionless flow number expression for the lift-off distance of free and impinging jet flames in the subsonic regime provides the best fit, after consideration of four different available correlations that are evaluated against the experimental measurement in this paper.

International Seminar on Fire and Explosion Hazards (9; 2019; Saint Petersburg, Russia). Proceedings of the Ninth International Seminar on Fire and Explosion Hazards [Электронный ресурс]: 21-26 April 2019, Saint Petersburg, Russia. Vol. 2 / Peter the Great St. Petersburg Polytechnic University, Autonomous Non-Profit Organization "Fire and Explosion Safety", Gefest Holding Ltd ; [edited by A. Snegirev [et al.]. — Электрон. текстовые дан. (1 файл : 98,7 Мб). — Saint Petersburg, 2019. — Загл. с титул. экрана. — Свободный доступ из сети Интернет (чтение, печать, копирование). — Adobe Acrobat Reader 7.0. — <URL:http://elib.spbstu.ru/dl/2/k19-97.pdf>. — <URL:http://doi.org/10.18720/SPBPU/2/k19-97>.