On the quality of micromixing in an oxy-fuel micromixer burner for gas turbine applications: A numerical study

The study examines numerically the non-reacting flow and mixing characteristics inside a single tube of a micromixer burner for potential zero-emission premixed oxy-fuel combustion applications, such as gas turbines. The aim is to investigate how the geometrical parameters can affect the mixing quality in an oxy-fuel reactant mixture consisting of CH₄, O₂, and CO₂. The ranges of design parameters are fuel inlet diameter (from 0.2 to 1.0 mm), number of fuel holes (4 and 6), and tube length (from 5D to 15D). It was found that the mixing quality is significantly improved by increasing the tube length. The results also showed that mixing quality is not directly dependent on fuel hole size but on the ratio of main flow to jet flow momenta. At fixed total fuel mass flow rate, the mixing quality depreciates when the number of fuel holes is increased from four to six for all hole diameters, except for the smallest one of 0.2 mm. The peak mixing quality was achieved with fuel hole diameters of 0.25 mm and 0.2 mm for the micromixer tubes with four and six inlet holes, respectively. The results showed that micromixers can achieve high mixing quality at a reasonable burner height.