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

•The performances of a helical-fin-assisted micro-step combustor are numerically investigated.•Helical-fin-anchored and step-stabilized flame modes are found in the proposed combustor with increasing inlet velocities.•Helical fins improve the radiant energy conversion ratio and combustion efficiency of the micro-step combustor.•The effects of helical fins are analyzed in terms of conjugate heat transfer, flame-flow interactions, and reactants transport and reactions.