Experimantal study of stationary flame propagation in a tube under conditions of weight lessness

Abstract

The development of detailed concepts of the effect of gravitational conditions on a wide class of combustion phenomena has been hindered by the lack of a sufficient amount of experimental data on combustion under conditions of weightlessness. The present study investigates the changes in form of a laminar flame under the influence of natural thermal convection with stationary propagation in a vertical tube under normal gravitational conditions and under conditions of weightlessness, in which case convection is absent. Lean propane/CO/air mixtures were ignited in a reaction tube suspended in a weightlessness simulation chamber. High speed photographic recording of the flame front revealed that for flame propagation from an open lower end under normal gravitational conditions the flame front is more convex than under weightless conditions. Under conditions of weightlessness the form of the flame front is the same for propagation from either end. Equations are derived describing the change in flame front convexity produced by convection. Some divergence of the calculation results from the experimental data may be explained by the fact that the equations do not consider factors such as thermal expansion and viscosity of the combustion products, and the peculiarities of convective ascent of these products.