Comparison of a Conventional and an Additively Manufactured Burner Nozzle for Technically Premixed Turbulent Combustion

Decarbonized fuels such as green hydrogen (H2) or its blends with methane become increasingly important in modern combustion technologies. Here, changed combustion characteristics, e.g., an increased flame speed in comparison to hydrocarbon fuels can result in instabilities, especially for technically relevant turbulent flames. An optimized burner design is therefore crucial to prevent critical conditions such as flame flashback, lift-off or pronounced pollutant formation. A greatly improved design freedom for burners can nowadays be achieved through additive manufacturing such as laser powder bed fusion. However, this often comes on cost of surface roughness quality, whose impact on flame stability needs to be investigated in comparison to conventional manufactured burner parts. We present a diagnostic study on the distribution of the hydroxyl (OH) radical to provide a comparison between a nozzle design that was once conventionally manufactured vs. once by an additively manufacturing technique. The nozzle design is based on a technical premixing shortly before the nozzle outlet with an internal flow body and a conically tapered outlet similar to that presented in. A flexible test bench was designed that allows for a simultaneous operation of two nozzles. Chemiluminescence measurements of the hydroxyl radical are used to assess the flame stability and planar laser-induced fluorescence is applied to visualize the reaction front in the flame. A discussion on flame structures and behavior related to surface roughness and the manufacturing technique is provided.