Short-flame/quick-quench: A unique ultralow emissions combustion concept for gas turbine combustors

Abstract

This paper describes the emission characteristics of model combustors employing a unique low-emissions gas turbine combustion concept named short-flame/quick-quench combustion . Its potential for ultralow NO x emissions and complete combustion has previously been successfully demonstrated by testing in an engine. This concept combines lean premixed combustion in a short reaction zone generated by many small flames stabilized on a perforated plate flame holder, and quick quenching of NO x formation by injecting dilution air immediately downstream of the reaction zone. Multiple tubes penetrate through the flame holder and extend into the combustion chamber, and dilution air is injected from holes on the tubes at an axial position where major combustion reactions have been completed, to achieve both ultralow NO x emissions and complete combustion. Measurements of gaseous emissions from the model combustors were made for natural gas at combustor inlet air temperatures ranging from 300 to 900°C and pressures of 0.1 to 0.7 MPa. Modulation of combustion and dilution air split resulted in NO x emissins of 3–4 ppm (corrected at 15% O 2 ) or 0.3–0.4 EINO x (g NO 2 /kg fuel) over the range of overall equivalence ratios required in simple- and regenerative-cycle gas turbine operations. The NO x concentrations in parts per million correlated well by the Arrhenius expression with the adiabatic flame temperature in the reaction zone, T p , over a wide range of pressure, temperature, and air split between combustion and dilution. It is shown that NO x ∞ exp(−(50±2)×10 3 / RT p ), where R is the universal gas constant in cal/mol K.