Flame blow-off correlation for lean direct injection hydrogen burners

Abstract

Hydrogen is a promising zero-carbon fuel to achieve decarbonisation targets. Its broad flammability range com- pared to hydrocarbons allows fuel-leaner operations, which can help to mitigate thermal nitrogen oxides emissions. The Lean Direct Injection Combustor (LDIC) design is used to mitigate flame flashback arising under fully pre- mixed conditions. For the LDIC used for this study, the hydrogen is injected transversely through two opposed jets into a cross-flowing air and the flame is stabilised using pilots. The global equivalence ratio of this main flame is varied by gradually changing the hydrogen mass flow rate until the lean blow-off (LBO) of the main flame occurs. The LES of these flames are conducted using flamelet based models for partially premixed combustion. The com- puted velocity statistics for non-reacting flow compare well with measurements. The computed flame attributes and LBO over a range of operating conditions are observed to agree well with the corresponding measurements. The physical insights obtained from the LES analyses are used to derive a correlation for the LBO, which agrees well with the measurements and LES results for two burner configurations