Stabilization mechanisms of an ammonia/methane non-premixed jet flame up to liftoff

Abstract

Ammonia is a promising alternative fuel for CO2 emission mitigation. The use of ammonia blends allows for more flexibility compared to pure ammonia fuel and is often considered for immediate CO2 emission reduction in existing facilities running on natural gas. However, fundamental studies on these fuel mixtures remain scarce. This study thus focuses on ammonia/methane blend fuels. The effect of ammonia on methane jet flame stabilization is investigated using a non-premixed jet flame configuration to observe the flame stabilization mechanisms, the flame-burner interactions and how ammonia addition affects the attached flame stabilization up to liftoff. The flame tip position was observed using CH* chemiluminescence. Heat transfer to the burner was monitored by temperature measurement at the burner lip and inside the burner to observe the impact of ammonia addition on thermal interactions. The main stabilization regimes described for the methane non-premixed jet flame are still observed in the case of ammonia addition. However, the transition between those regimes appeared to be shifted toward larger velocities relative to the methane case due to ammonia addition. Those changes could be related to the change in the mixture combustion properties which affects both flame position, heat transfer to the burner and in turn the transition between the identified stabilization regimes. The dynamic leading to liftoff was further analyzed to highlight how ammonia addition perturbated the stabilization balance up to liftoff.