Enhancement of Mixing by Inclined Jet Impingement in Partially Premixed Hydrogen-Oxygen Combustion

The characteristics of a novel partially premixed pure hydrogen-oxygen combustion triple nozzle cluster unit are investigated by direct numerical simulation using a detailed chemical mechanism, mainly focusing on the mixing progress. Reactants are injected into the computational domain through a triple nozzle unit, with twin lateral oxidizer nozzles inclined inwards to impinge on a central fuel jet downstream of the inlets, creating a zone of intense turbulent mixing and heat release ignited by hot recirculated burnt products. The mixture fraction, normalized flame index and product-based reaction progress variable are analyzed to systematically describe reaction characteristics and the formation of premixed flame branches in the downstream neighborhood of the impingement point. Analysis of the transport budgets of elemental mixture fraction suggests that the improved overall mixing from jet impingement is due to an intensification of convective transport dispersing the fuel and oxidizer jets resulting in a larger diffusive interface. Turbulent combustion characteristics are explored for impingement angles of 60 degrees and 75 degrees, revealing a dominant effect on mixing intensity, heat concentration, flame length and alignment across premixed and non-premixed combustion regimes. These results shed light on the underlying reaction dynamics and parametric dependencies of the proposed multi-cluster configuration, providing a numerical reference for the development of advanced hydrogen partially premixed combustion systems utilizing jet impingement mixing.