NOx Scaling of Syngas H2/CO Turbulent Non-Premixed Jet Flames

Abstract

NOx emission characteristics and EINOx scaling of hydrogen and H2/CO syngas non-premixed jet flames under turbulent condition are investigated. Flame length and NOx concentration were measured simultaneously for four different syngas compositions (100/0, 75/25, 50/50, and 25/75 H2/CO% vol.) and three different fuel nozzle diameters (2.5, 3.0, and 3.5 mm). The jet flames were in the buoyancy-momentum transition regime. NOx emission is reduced with increased Reynolds number and increased CO content in the syngas fuel, which result from a decreased flame residence time. The previous EINOx scaling correlation, which is based on flame residence time (flame volume divided by volume flow rate of fuel), does not apply to a hydrogen jet flame in the buoyancy-momentum transition region. The previous scaling applies only to momentum-dominated jet flames. A modified scaling based on a simplified flame residence time (flame length divided by fuel jet velocity) considered the buoyancy effect as proposed. This scaling aligns the 1/2-power with the jet flame in both momentum-dominated and transition regions. The modified scaling also satisfies the 1/2 slope with H2/CO syngas jet flames. Furthermore, the proposed modified scaling adopts the nitrogen amount as a reference, instead of the fuel amount. Finally, the modified scaling collapses the all syngas compositions into a single line.