International Science Index


Impact of Different Fuel Inlet Diameters onto the NOx Emissions in a Hydrogen Combustor


The Advisory Council for Aeronautics Research in Europe (ACARE) is creating awareness for the overall reduction of NOx emissions by 80% in its vision 2020. Hence this promotes the researchers to work on novel technologies, one such technology is the use of alternative fuels. Among these fuels hydrogen is of interest due to its one and only significant pollutant NOx. The influence of NOx formation due to hydrogen combustion depends on various parameters such as air pressure, inlet air temperature, air to fuel jet momentum ratio etc. Appropriately, this research is motivated to investigate the impact of the air to fuel jet momentum ratio onto the NOx formation in a hydrogen combustion chamber for aircraft engines. The air to jet fuel momentum is defined as the ratio of impulse/momentum of air with respect to the momentum of fuel. The experiments were performed in an existing combustion chamber that has been previously tested for methane. Premix of the reactants has not been considered due to the high reactivity of the hydrogen and high risk of a flashback. In order to create a less rich zone of reaction at the burner and to decrease the emissions, a forced internal recirculation flow has been achieved by integrating a plate similar to honeycomb structure, suitable to the geometry of the liner. The liner has been provided with an external cooling system to avoid the increase of local temperatures and in turn the reaction rate of the NOx formation. The injected air has been preheated to aim at so called flameless combustion. The air to fuel jet momentum ratio has been inspected by changing the area of fuel inlets and keeping the number of fuel inlets constant in order to alter the fuel jet momentum, thus maintaining the homogeneity of the flow. Within this analysis, promising results for a flameless combustion have been achieved. For a constant number of fuel inlets, it was seen that the reduction of the fuel inlet diameter resulted in decrease of air to fuel jet momentum ratio in turn lowering the NOx emissions.

[1] D. Dunn-Rankin. Lean Combustion, Technology and Control. Elsevier, 2007.
[2] I. Glassman and R.A. Yetter. Combustion. Elsevier, 2008.
[3] Andreas Züttel. Hydrogen storage methods. Springer, 2004.
[4] J. Ziemann , F. Shum, M. Moore, D. Kluyskens, D. Thomaier, N. Zarzalis, H. Eberius. Low-NOx combustors for hydrogen fueled aero engine. International Journal of Hydrogen Energy, 1998.
[5] G. Dahl, F. Suttrop. Engine control and low-NOx combustion for hydrogen fuelled aircraft gas turbines. International Journal of Hydrogen Energy, 1998.
[6] J. A. Wünning and J. G. Wünning. Flameless Oxidation to Reduce Thermal NO-Formation. Prog. Energy Combustion Science, 23:81–94, 1997.
[7] H. Malli, K. Eckerstorfer, O. Borm, and P. Leitl. Experimental and Numerical Investigation of a Hydrogen Combustion Chamber under Various Inlet Conditions. Proceedings of ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, 2014.
[8] A. Veríssimo, A. Rocha, and M. Costa. Experimental Study on the Influence of the Thermal Input on the Reaction Zone under Flameless Oxidation Conditions. Fuel Processing Technology.
[9] Arianna Mastrodonato. Impact of the Air to Fuel Jet Momentum Ratio on the NOx Emissions. Institute for Thermal Turbomachinery and Machine Dynamics,TU Graz,2015.
[10] N. Peters. Fifteen Lectures on Laminar and Turbulent Combustion. Ercoftac Summer School September 14-28, 1992, RWTH Aachen.
[11] H. Schlichting and K. Gersten. Grenzschicht-Theorie. Springer, 2006.
[12] Joseph. E. Shepherd. Hydrogen-Steam Jet-Flame Facility and Experiments. Sandia National Laboratory. February 1985.
[13] Liñán A. On the structure of laminar diffusion flames. Aeronautical Engineering Thesis, California Institute of Technology, Pasadena, 1963
[14] Funke, Harald H W. Experimental and numerical study on optimizing the dry low NOx micromix hydrogen combustion principle for industrial gas turbine applications. Journal of Thermal Science and Engineering Applications. June 2017.
[15] Cavaliere.A, “Mild combustion”, Prog. Energy Combust. Sci., 30: 329-366, 2004.