Given the limited reserves of fossil fuels and the environmental ramifications of their burning; a transfer to new energy resources is all but inevitable. Hydrogen-blended fuel is a promising resource for future generations of Gas Turbine Engines (GTE), due to its high reactivity and ability to reduce carbon emissions. However, several limitations prevent its application, especially for swirl configurations. The literature does not account for the hydrogen-swirl-equivalence ratio interaction at high turbulence levels, a shortcoming this dissertation addresses. The main objective of this research is to numerically investigate the effects of hydrogen addition (to methane) and swirl intensity on the combustion process under relevant GTE conditions. A numerical study is conducted to assess Hydrogen-Enriched Combustion (HEC) in a lab-scale burner operating at a high turbulence level (Rein = 36,000 and u'/Sl L up to 45), under lean and stoichiometric burning conditions. A wide range of H2 (up to 90%) is used for enriching CH4-air lean combustion, in combination with a high swirl level (S up to 1.3). The study reveals the feasibility of using H2-CH4 blends with 25% H2 to replace CH4 in the primary stages of GTE operation, and of using up to 90% and 60% H2 to enrich lean and stoichiometric combustion, respectively, without any design modification. Under the studied conditions, it is found that H2 addition raises the reaction zone temperature, reduces the size of the Inner Recirculation Zone (IRZ), responsible for stabilizing the flame, and results in longer flames, due to the interaction between the high reactivity of H2 with a high turbulence level. Conversely, the swirl intensity is found to reduce the flame surface area and associated heat release, increase the IRZ size, in addition to resulting in shorter flames, due to an increased turbulent intensity. Hence, increasing the swirl intensity is favoured when using H2-blended fuel with high H2 concentrations. Radiation is considered for all simulations and found influential, as it yields a reduction of the outlet temperature by not less than 100 K, thus reducing emissions by half. A moderate H2 concentration (up to 50%) and swirl intensity up to 1.3 are found to slightly increase NOx; however, such an increase is not deemed significant, for as long as NOx levels are generally in the order of a few ppm at the burner’s outlet. H2 results in reducing CO, as it promotes CO conversion into CO2, which was also reduced as the H2 concentration increased. Overall, hydrogen-blended fuel is highlighted as an encouraging resource towards a carbon-free fuel and HEC is deemed as a clean combustion approach.
Elbayoumi, M. (Author),
Seers (Supervisor),
Garnier (Co-supervisor) &
Moustapha (Co-supervisor),
13 Apr 2022Student thesis: Doctoral thesis › Doctorate in Engineering: Engineering