Low-NOx Emissions Over an Enlarged Range of Overall Equivalence Ratios by Staged Lean Premixed Tubular Flame Combustion

One of the inherent problems of lean premixed combustion is a narrow range of combustion-zone fuel-air ratios where low NOx emissions and complete combustion can be simultaneously achieved. The use of the reaction of lean to ultra-lean mixtures injected into the hot burned gas produced in the upstream lean-burn combustion zone can alleviate the abovementioned problem. The combustion characteristics of staged model gas turbine combustors with arranging two or three cylindrical swirl combustion chambers in series were investigated at atmospheric pressure. Tubular flame was stabilized in the primary stage and homogeneous mixture was injected into the burned gas from the upstream stage. It is shown that the lean multi-staged premixed tubular flame combustion has a potential to extend the range of gas turbine operation where both complete combustion and ultra-low NOx emissions can be achieved.