Kick-off “Greener-RQL” Project

TUM.PtX News |

The “Flightpath 2050” report documents Europe’s vision for aviation to achieve a drastic reduction in pollutant emissions of CO2 and NOx, as well as emitted noise. The fuel change from kerosene to hydrogen is considered as a step closer towards the goal of decarbonization. The project “Greener-RQL” which started at the Professorship of Sustainable Future Mobility in July 2022 supports the development of new hydrogen aircraft engines by focusing on the causes for the Growl/Rumble-phenomenon.

The Growl/Rumble-phenomenon describes a low frequency noise, which can be perceived in the aircraft cabin as unpleasant and risks to damage the engines. Entropy and equivalence ratio waves are suspected as possible causes for this phenomenon. However, well-founded research is still lacking, especially in the context of hydrogen use.

To address this shortcoming “Greener-RQL“ investigates the convection of entropy waves and equivalence ratio waves as well as their feedback mechanism with acoustic waves inside an aero engine combustion chamber with air-staging (RQL).

RQL combustion chambers are a concept which traditionally reduce nitrogen oxide emissions. This type of chamber divides combustion into two stages. In the first stage, combustion occurs with excess fuel in the rich regime. While in the second stage, additional air is added and combustion occurs under excess air in the lean regime. This allows to evade combustion near the stochiometric regime, high temperatures, and associated nitrogen oxides production.

 “Greener-RQL”, supported by the Bavarian aviation research program “BayLu25”, contributes to the environmental protection objectives of “Flightpath 2050” with respect to its noise reduction and environmental compatibility objectives of aircraft engines supporting the development of hydrogen engines.