A Novel Swirled Tri-Channel Injector for Hydrogen Combustion

Abstract Decarbonization is driving the development of various technologies to reduce the environmental impact across multiple fields. In aerospace and other sectors, hydrogen is envisioned as an alternative fuel for carbon-free combustion. As a result, many different combustion technologies are being developed to adapt processes to hydrogen operations. In the context of combustion in an aircraft turbine, new hydrogen combustion technologies have to comply with stability and low emission requirements, as the higher reactivity and flame temperature raise concerns about flashback and nitrogen oxide emissions. This work focuses on one specific combustion technology derived from the conventional Rich-Quench-Lean (RQL) technology in wide use in current aircraft engines. It is based on the injection of a rich premix followed by air injection in order to achieve globally lean conditions and finish combustion. To accommodate this new injection technology, an injector was developed to leverage the unique properties of rich premixed hydrogen flames, particularly their high resistance to strain. To do so, the injector was designed around a concentric arrangement of three channels, with hydrogen being injected in the intermediate channel in order to benefit from two shear layers surrounding the flame. This setup aims to reduce flame temperature and NOx emissions while ensuring a stable flame through the injection of a rich mixture. To increase control over the flame structure, each channel of the injector was fitted with a swirler. The individual and combined effects of these swirlers were investigated to yield an inventory of the flame types possible on the injector. To do so, OH* chemiluminescence imaging was employed. In addition, using a gas analyzer, we monitor NOx emissions in various conditions to evaluate the effects of the different parameters of this new injector.