Effect of wall boundary conditions on flame propagation in Microchambers
2015 (English)In: American Society of Mechanical Engineers, Power Division (Publication) POWER, American Society of Mechanical Engineers (ASME) , 2015Conference paper (Refereed)
Flame dynamics in micro-pipes have been observed to be strongly affected by the wall boundary conditions. In this respect, two mechanisms of flame acceleration are related to the momentum transferred in these regions: 1) that associated with flame stretching produced by wall friction forces; and 2) when obstacles are placed at the walls, as a result of the delayed burning occurring between them, a jet-flow is formed, intensively promoting the flame spreading. Wall thermal conditions have usually been neglected, thus restricting the cases to adiabatic wall conditions. In contrast, in the present work, the effect of the boundary conditions on the flame propagation dynamics is investigated, computationally, with the effect of wall heat losses included in the consideration. In addition, the powerful flame acceleration attained in obstructed pipes is studied in relation to the obstacle size, which determines how different this mechanism is from the wall friction. A parametric study of two-dimensional (2D) channels and cylindrical tubes, of various radiuses, with one end open is performed. The walls are subjected to slip and non-slip, adiabatic and constant temperature conditions, with different fuel mixtures described by varying the thermal expansion coefficients. Results demonstrate that higher wall temperatures promote slower propagation as they reduce the thermal expansion rate, as a result of the post-cooling of the burn matter. In turn, smaller obstacle sizes generate weaker flame acceleration, although the mechanism is noticed to be stronger than the wall friction-driven, even for the smaller sizes considered.
Place, publisher, year, edition, pages
American Society of Mechanical Engineers (ASME) , 2015.
Other Mechanical Engineering
IdentifiersURN: urn:nbn:se:umu:diva-122446ISBN: 978-079185660-4OAI: oai:DiVA.org:umu-122446DiVA: diva2:938985
ASME 2015 Power Conference, POWER 2015, collocated with the ASME 2015 9th International Conference on Energy Sustainability, the ASME 2015 13th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2015 Nuclear Forum; San Diego; United States; 28 June 2015 through 2 July 2015