Effect of helical fins on the combustion performance in a micro-step combustor

Abstract

This study proposed a novel helical-fin-assisted micro-step Helix combustor to improve the performance of micro-combustors under high flow rates. The effects of the helical fins on the flow and combustion characteristics were analyzed with the aid of detailed hydrogen-air chemistry and a conjugated heat transfer mode. The performance of the proposed Helix combustor and the conventional micro-step combustor was compared. With the increase of the inlet velocity, two flame stabilization modes can be identified, i.e., the helical-fin-anchored flame and the traditional step-stabilized flame. The intensified heat transfer conjugation between the flame and helical fins enables the ignition and stabilization of the premixed flame before the inlet velocity reaches 34 m/s. The swirl flow induced by the helical fins reduces the length of the recirculation zones behind the step while augmenting the mixing between the hydrogen and the high-temperature products, which finally improves the combustion efficiencies. The helical-fin-anchored flame is preferred for thermo-electric/photovoltaic systems due to the uniform yet high wall temperature, as well as higher thermal efficiency. Meanwhile, the step-stabilized flame in the proposed combustor shows advantages of higher combustion efficiency and higher exhaust temperature for micro- engines under higher inlet velocities.