Downstream air dilution and biomass pulverisation into bluff-body and swirl stabilised confined turbulent jets

Bluff-body and swirl-stabilised turbulent annular flows (single phase and multi-phase) find broad practical utility, especially in high-power non-premixed combustion applications. Their significance stems from features like their characteristic recirculation zones and intense upstream turbulence, both of which promote air-fuel mixing and aid in flame stabilisation. Moreover, in response to the push for low-emission and carbon-neutral fuel sources, there's a growing emphasis on integrating biomass, especially in its pulverised form, into major power generation systems. In practical gas turbine combustors featuring bluff-body and swirl stabilised flame burners, the incorporation of (air) side dilution jets plays a crucial role. These jets influence downstream reactant mixing by introducing cooler dilution air, effectively controlling combustion temperature and mitigating pollutant emissions, particularly oxides of Nitrogen. Whilst literature reports investigations exploring bluff-body and swirl-stabilised annular turbulent annular flows, as well as others which separately look into the influence of dilution air in a crossflow, this thesis addresses the clear lack of fundamental insight that exists regarding (i) the interplay between turbulent side dilution jets and underlying flow behaviour of both swirling and non-swirling bluff-body stabilised annular jets in geometries typical of industrial combustors. This project also studies (ii) particle dispersion and the overall flow field associated with using pulverised raw biomass over a wide range of conditions spanning differing (particle phase) loadings, Reynolds numbers of both the (air) side dilution jets and annular jets as well as swirl numbers. The outcomes therefore not only progress our fundamental understanding of such complex two-phase flows but can ultimately assist in assessing and applying pulverised biomass to replace or reduce reliance on solid fossil fuels (coal) in power generation. To achieve the above