The reactivity of hydrogen enriched turbulent flames

Abstract

The use of hydrogen enriched fuel blends, e.g. syngas, offers great potential in the decarbonisation ofgas turbine technologies by substitution and expansion of the lean operating limit. Studies assessingexplosion risks or laminar flame properties of such fuels are common. However, there is a lack of exper-imental data that quantifies the impact of hydrogen addition on turbulent flame parameters includingburning velocities and scalar fluxes. Such properties are here determined for aerodynamically stabilisedflames in a back-to-burnt opposed jet configuration featuring fractal grid generated multi-scale turbu-lence (Ret= 314 ± 19) using binary H2/CH4and H2/CO fuel blends. The binary H2/CH4fuel blend is variedfrom ̨ = XH2/(XH2+ XF) = 0.0, 0.2 and 0.4–1.0, in steps on 0.1, and the binary H2/CO fuel blend from ̨ = 0.3 − 1.0 also in steps of 0.1. The equivalence ratio is adjusted between the mixture specific lowerlimit of local flame extinction and the upper limit of flashback. The flames are characterised using PIVmeasurements combined with a flame front detection algorithm. The study quantifies the impact ofhydrogen enrichment on (i) turbulent burning velocity (ST), (ii) turbulent transport and (iii) the rate ofstrain acting on flame fronts. Scaling relations (iv) that correlate STwith laminar flame properties areevaluated and (v) flow field data that permits validation of computational models is provided. It is shownthat CH4results in a stronger inhibiting effect on the reaction chemistry of H2compared to CO, that tur-bulent transport and burning velocities are strongly correlated with the rate of compressive strain andthat scaling relationships can provide reasonable agreement with experiments.