Stabilization characteristics and mechanisms in a novel tubular flame burner with localized stratified property

Abstract

The combustion characteristics in a localized stratified tubular flame burner (LSTFB) were experimentally studied under lean conditions. The stability limit and pressure fluctuation were obtained under various global equivalence ratios and fuel flow rates. The mechanisms driving the combustion instability were analyzed with the combination of numerical simulation. Results show the lean stability limit of the burner can be as low as 0.12 of the global equivalence ratio. On the basis of the local stratification of species, a kind of unique binary tubular flame is formed with both the premixed and non-premixed flame properties. Meanwhile, the internal recirculation heats the incomplete combustion gases distributed inside the tubular flame, thereby guaranteeing the balance between the flow velocity and the local flame speed. The amplitudes of pressure fluctuation are less than 4 kPa in the entire experimental range because of the flow laminarization caused by the large body force and density gradient. The pressure fluctuation characteristics depend on the relative magnitude of viscous force, inertial force, body force, and density gradient. The Taylor number Ta and stratification parameters Ri∗ are key parameters in evaluating the flame stability in the LSTFB.