Flame dynamic insights into pollutant production characteristics of NH<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si193.svg" display="inline" id="d1e1530"><mml:msub><mml:mrow/><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:math>/H<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si188.svg" display="inline" id="d1e1538"><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>/air combustion during turbulent flame–wall interaction
Cheng Chi
Abstract
A turbulent premixed NH 3 /H 2 /air flame with Damköhler number Da = 0.004 has been simulated using direct numerical simulations (DNS) with detailed chemistry. The flame is propagating in a fully-developed turbulent channel flow with friction Reynolds number Re τ = 313. The global and local production speeds of NO, N 2 O and NH 3 have been analyzed. Special attention is paid on the flame dynamic insights into the pollutant production characteristics during the flame–wall, flame–turbulence and flame–flame interaction process. Finally, important findings have been concluded: (1) The unburned NH 3 is reduced in the turbulent case due to the smaller quenching distance; (2) The N 2 O consumption speed would decrease just before flame quenching on the wall in the turbulent case, due to the thickened flame thickness, which is contradictory to the laminar case; (3) Effect of flame curvature on pollutant production speeds should be combined with the effect of flame surface density; (4) Low Damköhler number flame tends to produce more N 2 O and less NO, due to the more frequent flame–flame interaction events. These findings would help to better understand the pollutant production characteristics of turbulent premixed NH 3 /H 2 /air flames in lab-scale burners with strong flame–wall interactions. Novelty and Significance Statement The novelty of this research is summarized into 3 points: (1) It is, to our knowledge the first time, pollutant production characteristics are investigated in detail for the premixed NH 3 /H 2 /air flame propagating in a fully developed turbulent boundary layer; (2) The effects of flame–wall, flame–turbulence and flame–flame interactions, the underlying reasons and controlling mechanisms are investigated in detail, which has not yet been (comprehensively) done in previous studies; (3) Novel and important findings have been concluded for the wall effects, turbulence effects (including flame curvature and surface density function effects) and flame–flame interaction effects. Some of these findings have never been reported before, but important for the comprehensive understanding of the pollutant production characteristics. It is significant because understanding the turbulence and wall effects on NO, N 2 O and NH 3 production characteristics in the premixed NH 3 /H 2 /air flames is crucial for the future clean combustion energy system design.