Effect of Hydrogen Injection on Combustion Instability in Hydrogen Arrayed Microtube Burner

The influence of hydrogen injection configuration on combustion instability in arrayed microtube burners is investigated through experiments and large-eddy simulations. Three injector configurations, namely, baseline radial injection (nozzle A), upstream-shifted radial injection (nozzle B), and 45 deg inclined injection (nozzle C), are examined under different equivalence ratios and pressure-drop conditions. Chemiluminescence imaging and simulations show that nozzle A maintains a stable diffusion flame with a fixed heat-release region, whereas nozzle B enhances fuel–air premixing, increases flame liftoff, and strengthens the coupling between heat-release fluctuations and flow disturbances, leading to reduced stability. Nozzle C modifies flame anchoring through additional radial momentum and mitigates pressure oscillations relative to nozzle B. Pressure measurements, flame dynamics, recurrence analysis, and flame transfer function results consistently indicate that nozzle B and nozzle C are more sensitive to inlet velocity perturbations than nozzle A. Overall, the results demonstrate that hydrogen injection configuration plays an important role in regulating flame dynamics and thermoacoustic stability in arrayed microtube hydrogen combustors.