Ongoing Research: H2 Combustion Chambers with low NOx Emissions (H2-LoNOCS)

Contact	Maximilian Aubel Adrian Hochmuth
Funding	Bundesministerium für Wirtschaft und Klimaschutz

Compared to RQL combustion in hydrogen-fueled aero engines, the state of knowledge for technically premixed combustion with hydrogen in aircraft engines is still far behind. This applies to the conceptual level as well as to the optimization of promising concepts. However, the further development of premixed hydrogen combustion is expected to bring several benefits especially regarding the reduction of NO_x emissions. This project therefore investigates the behavior of an innovative, premixed injection and combustion concept which is suitable for the use of hydrogen. Therefore, steady-state (mixture formation and heat release distribution) and transient (ignition, start-up and shutdown) behavior will be evaluated and thermoacoustic investigation of premixed combustion with lowest NO_x emissions will be conducted. GE Aerospace will design the injection and combustion system and deliver them to TUM where the above-mentioned experiments will be performed.

In addition, a novel axially staged system will be developed at TUM and first functional tests will be performed. This system is intended to apply the developed technology for staged hydrogen combustion from stationary gas turbines to aircraft engines, thus paving the way for new approaches to emission reduction. The staged system has an increased reduction potential compared to the non-staged one. To meet the demands in various flight conditions and thus different load requirements, the stages are tailored to different operating points in various configurations. This concept is first designed through simulation and then experimentally tested, with measurements focusing on emissions.

Ongoing Research: SAFMech - Combustion Mechanisms for Industry Applications

Funding

Bayerisches Staatsministerium für Wirtschaft, Landesentwicklung und Energie

Due to the ever-more urgent problem of global warming, the aviation industry is looking towards using Sustainable Aviation Fuel (SAF). While using SAF leads to a reduction in CO₂ emissions, and might even result in net carbon neutrality, the problem of non-CO₂ emissions, like nitrogen oxides (NO_x) and soot, is not directly tackled.

The SAFMech project aims to investigate the chemical-physical processes involved in the combustion of Fischer-Tropsch (FT) and Alcohol to Jet (ATJ) type SAF surrogates, using innovative computational/numerical methods and making the advances usable for industrial application.

The work involves the generation of detailed chemical kinetic mechanisms for SAF surrogates using the Reaction Mechanism Generator (RMG) software, followed by the development of software for mechanism reduction and optimization while maintaining the accuracy of the detailed mechanism as best as possible. These reduced kinetic mechanisms, along with fluid dynamics models, are used to predict essential combustion characteristics. Furthermore, due to their role in soot nucleation and growth, the study also aims to provide a more detailed insight into the formation of polycyclic aromatic hydrocarbon (PAH).

 “SAFMech”, 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.

Ongoing Research: The GreenerRQL Project

Contact	Ángel Brito Gadeschi Thuy An Do
Funding	Bayerisches Staatsministerium für Wirtschaft, Landesentwicklung und Energie

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.

Ongoing Research: Hydrogen Conditioning and Safety (WAKOS)

Contact	Benjamin Kölbl Jannes Papenbrock
Funding	Bundesministerium für Wirtschaft und Kimaschutz

Compared to the combustion of kerosene-fueled aero engines, the degree of knowledge on hydrogen combustion in the aviation sector is still significantly low. This applies both for the conceptual level and also the optimization of promising approaches. In this project, the strategy of air staging with RQL (Rich-Quench-Lean) combustion, which is common in kerosene operation, is to be built upon. This approach is used to reduce pollutant emissions significantly by means of multi-step combustion. Due to the highly different physical and chemical properties of hydrogen compared to kerosene, the behavior of innovative injection and staging scenarios suitable for hydrogen combustion will be investigated. In this context, the steady-state behavior, such as mixture formation and heat release distribution, as well as the transient behavior with respect to ignition, start-up and safe shutdown are examined. In addition, a high degree of attention will be paid to possible thermoacoustic combustion instabilities. The project is part of a larger research network in order to progress towards the safe and reliable combustor technology of the future for hydrogen propulsion.

Ongoing Research: HydrogEn combuSTion In Aero engines (HESTIA)

Contact Katharina Meinecke Cooperation and Funding European Commission: Climate, Energy and Mobility Motivation To reduce the climate impact of aviation, decarbonisation is a major challenge. Current combustion chambers are burning hydrocarbon fuels, such as kerosene or more recently emerging SAF products. Hydrogen is also considered today as a promising energy carrier but burning hydrogen creates radically new challenges which need to be understood and anticipated. HESTIA focuses on increasing the scientific knowledge on hydrogen fuelled aero-engines. The related physical phenomena will be evaluated through fundamental experiments. This experimental work will be closely coupled to numerical activities by project partners who will adapt or develop models and progressively increase their maturity so that they can be integrated into industrial CFD codes. To this end, HESTIA gathers 17 universities and research centres as well as the 6 European aero-engine manufacturers to significantly prepare in a coherent and robust manner for the future development of hydrogen combustion chambers. (Source: European Comission) Experimental Setup The experimental measurements are going to be carried out on the LaBreVer test rig at TUM. The rig allows for testing diffusive, perfectly premixed, and technically premixed combustion conditions with gaseous and liquid fuels. Pressure data can be gathered by several static and dynamic pressure sensors spread along the channel. Besides, chemiluminescence measurements are going to be used for flame visualization. The flame topology will provide valuable insights into flame dynamics.