Some flows associated with premixed laminar flame propagation in a rotating tube flow

Abstract

The influence of fluid rotation on the propagation of a laminar premixed hydrogen flame in a cylinderhas been investigated with the use of numerical simulations. The flow patterns are a strong function of the tube rotation rate, and intense flame stretch along with large increases in fuel consumption rates have been observed. The primary factors driving the flow patterns are the centrifugal pressure gradients and the convergence of burned products toward the tube centerline. An interesting property of the flow is spin-up of the swirl velocity as the fluid particles pass through the flame, and this characteristic can be directly related to approximate conservation of fluid angular momentum. Although the spin-up process is rather exotic, it does not appear that it plays a significant roll in the flame propagation process. The interaction between the centrifugal pressure gradients and the density gradient in the flame generates vorticity, and this flow is a good example of generation of vorticity associated with the term baroclinic vorticity generation. The basic flame propagation in the rotating flow appears to be fundamentally unsteady above a minimum tube rotation rate. At high rotation rates, the flame tip propagates down the tube at such a rapid rate that a major part of the flame propagates almost directly into the wall. The basic process also appears to occur for non-reacting flows, where temperature and density gradients are created by hot wall boundary conditions. The most straightforward explanation of the processes can be gained from the centrifugal pressure gradients that are created in the cold and hot regions of the flow.