Fuel effects on interacting triple flame propagation velocities

Triple flame propagation velocities have been characterized in the literature as a function of equivalence ratio gradient and flame curvature to better understand flame propagation through a single fuel–air mixing layer. Turbulent partially-premixed flowfields, however, can produce regions which have multiple stoichiometric locations, and therefore multiple edge flames. Previous work with partially-premixed ethylene has shown that these multiple flames can interact resulting in even larger propagation speeds. In this paper, propagation velocities for interacting triple flames of partially-premixed methane and propane were measured with different levels of triple flame interaction. For both fuels, the interacting triple flames propagate faster than a single triple flame with similar equivalence ratio gradients. The interacting triple flames can be described with an effective curvature, allowing the linear relationship between propagation speed and curvature from single triple flames to be used to describe the interacting flame speed. The aerodynamic effects of the interaction maximize the propagation speed and achieve the theoretical maximum velocity for single triple flames. For all fuels studied, the interacting flames reach this asymptotic limiting propagation speed and no significant effects are observed due to the variations in fuel diffusivity.