Experimental Investigation of NO_x Emission from a Sequential Combustor with the Kinetic Second Zone

Abstract

This is the fourth paper in a series of publications on the experimental investigation of fuel-air mixture combustion in a combustion chamber (CC) with two combustion zones set in a series with an outlet temperature ranging from 1550 to 1700°C and meeting the requirements for NO_x and carbon oxide emissions. The results of the experimental investigation into combustion of gaseous fuel CS comprising two combustion zones set it a series, each with its own burner unit, are presented. The first burner unit (BU1) is typical for low-emission combustors. It has swirlers, a premixing zone, and pilot and main burners. The premixed fuel-air mixture (FAM) is fed to the BU1 inlet. The second burner unit (BU2) is located downstream of the first combustion zone and is fed with FAM with a fuel concentration equal to or higher than the fuel concentration in the first combustion zone. The kinetic fuel combustion whose rate depends on the kinetics of the fuel oxidation reaction rather than on the rate of migration of the reacting components to the flame surface by molecular or kinetic diffusion (as in case of diffusion combustion) occurs in the first and second zones. The second burner unit has its own premixer. In the second zone, the fuel burns in a high-temperature environment at a reduced oxygen content. Four CS configurations with different lengths of the first and second combustion zones were investigated experimentally. The first configuration with single-zone fuel burning is the base one. In the other three configurations, the length of the first and the second zone varied (with the total length of the liner being the same). The results of optimization of the FAN between two sequential combustion zones are presented. The best length of the second zone minimizing NO_x and CO emissions at a CC outlet temperature from 1550 to 1700°С was found.