As the demand for greenhouse gas neutral transportation and power generation solutions is growing, alternative carbon-free fuels such as hydrogen (H2) and ammonia (NH3) are gaining more attention. Mixtures of both fuels allow the adjustment of combustion properties. With future fuels also the vision of very clean combustion can be taken into the focus, being for instance based on lean premixed combustion for gas turbines. For the utilization of such concepts, however, flame stability is essential. In this study the upper stability limits, i.e. lean blowout of turbulent hydrogen/ammonia/air flames is experimentally investigated in a generic non-swirl premixed burner at atmospheric conditions. Special focus is laid on a measurement setup with fully automatized measurement procedure, to reach the stability limits, as these limits tend to depend for instance on the approach speed towards the limit. The ammonia content was varied from 0 vol% to 50 vol% in 10 vol% steps. The lean blowout limit is determined by decreasing the fuel-air-equivalence ratio for given starting velocity.It is found that the lean blowout velocity limit is increasing almost linearly with increasing fuel-air-equivalence ratios, or, in other words that the limit fuel-air-equivalence ratio is increasing for increasing velocity. For increasing ammonia content the blowout velocity limit is decreasing. Quantitative limits are determined. Additionally, chemical kinetic analyses are conducted. Most relevant species and elementary reactions are identified. For the lean blowout limits the correlation with the laminar burning velocity is found to be strong. Some first results on flashback limits of these mixtures will be reported as well.

Experimental Study on Lean Blowout Limits of Turbulent Premixed Hydrogen/ammonia/air Mixtures

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

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