Abstract
Micromix combustion is introduced in premixed injector designs to develop burners allowing the combustion of fuels ranging from natural gas to pure hydrogen by controlling the micromix fuel ratio (MFR), which can lead to premixed, partially-premixed, and micromixed combustion with different stability mechanisms. A multi-injector configuration, consisting of five (5) injectors placed in a cross pattern, is used to investigate the combustion of pure methane to pure hydrogen. Stability and combustion dynamic maps are obtained at atmospheric temperature and pressure for fuel-lean mixtures of H2/CH4 ranging from 0/100, 70/30, 90/10, to 100/0%, by volume, with the same adiabatic flame temperatures. An increase in blowoff limit is observed for the multi-injector array compared to a single nozzle, while flashback occurs more rapidly for dominantly-premixed conditions with high-hydrogen-content fuel. In addition to extending the flashback limit, micromixed flames are generally quieter for high-hydrogen-content fuels. Laser diagnostics are performed on a selection of eight stable cases at a constant bulk inlet velocity to highlight the impact of hydrogen content and MFR on the flame shape. Two-dimensional (2D) PIV, OH and acetone planar laser-induced fluorescence (PLIF), as well as acoustic measurements, are performed simultaneously. The planar measurements show that the OH-PLIF signal becomes thinner and non-axisymmetric as MFR is increased from 0 to 100%, with the flames gradually transitioning from V-shaped to M-shaped, before stabilizing as jet flames in crossflow.
