Clean Propulsion Technologies
As part of the national civil aviation research programme (LuFo), the Environmentally Friendly Propulsion Technologies department supervises research projects relating to alternative, mostly hydrogen-based and/or (hybrid) electric propulsion systems as well as conventional propulsion technologies in the field of aircraft gas turbines.
The focus here is particularly on increasing drive efficiency and reducing climate-relevant emissions as well as avoiding non-CO2 effects. This is to be achieved, for example, through the use of new types of energy sources such as hydrogen and through increasing hybridisation and electrification of propulsion systems. In the field of conventional aircraft engines, efficiency increases are to be achieved through the use of new (high-temperature-resistant) materials and the research and development of advanced cycle processes, among other things. In addition, the department is working on new simulation, manufacturing and repair processes for climate-friendly aircraft engines.
Reasons for the research
In order to fulfil the requirements and objectives of the EU Commission's Green Deal and the German government's Climate Protection Act and to strengthen social acceptance, intensive efforts to avoid climate-damaging emissions and to further reduce the consumption of materials and resources in production are necessary in coordination with the EU's funding programmes (Horizon Europe, Clean Aviation). The expected increase in air traffic and the integration of new unmanned aerial vehicles into the airspace will only be possible in future with more efficient and climate-friendly air transport and production systems. New types of circular processes, e.g. with the supply and recovery of water or the increasing hybridisation of classic aircraft engines, offer significant potential for increasing efficiency and thus enable the reduction of both climate-damaging greenhouse gas emissions and non-CO2 effects. In particular, the use of alternative energy sources in the form of fuel cell-based or hydrogen combustion concepts represent key aspects for the timely realisation of sustainable and climate-friendly propulsion systems.
Current research priorities
Research into alternative, climate-friendly propulsion systems is a key element in achieving international and national climate targets. The focus here is on the use of new energy sources and the implementation of new processes that are specifically aimed at reducing the climate impact caused by aviation. The current research priorities in the field of alternative propulsion systems can be summarised as follows:
- Improving the performance parameters of fuel cells
- Cooling circuit/thermal management of fuel cell-based drive systems
- Fuel cell and cooling system integration
- Hydrogen direct combustion and technologies for multi-fuel capability
- Methods for water recovery and separation
- Development of suitable volume- and weight-saving energy storage systems with pumps, valves or distribution systems for LH2
- Material ageing processes, especially under the influence of H2
- Energy management of (hybrid) electrical systems
- Superconducting technology and cryogenic systemsyogenic systems
In the field of conventional aircraft engines, topics in the areas of reducing fuel consumption and increasing efficiency in the design, development and overhaul of propulsion systems are funded. The following research priorities are addressed:
- Efficient propulsors (open fan, counter-rotating open rotor (CROR), boundary layer ingestion (BLI), electric distributed propulsion (eDP), etc.).
- Increasing power density through compact core engines as well as lightweight and efficient low-pressure systems (gearbox, low-pressure turbine, variable nozzle)
- Measures to reduce noise and actively improve aerodynamics
- Low-emission combustion chambers
- New thermodynamic cycle processes
- Innovative cooling concepts (intermittent, transpiration cooling)
- Hybridisation concepts
- Qualification of high-performance materials (ceramic / metallic high-temperature materials, fibre-plastic composites)
- Advanced manufacturing processes (additive manufacturing, ECM, automation, joining processes, repair processes, etc.)
- Improvement of numerical design and evaluation tools in method development (optimisation, scale-resolving simulation CFD/FEM, ROM, pre-design tools, multiphysics simulation)
- - Utilisation of big data, virtual engine, digital twin (predictive maintenance, AI-based simulation, design feedback)
In addition to the technologies mentioned above, the Environmentally Friendly Propulsion Technologies department of the Project Management Agency for Aviation Research is involved in projects from the context of the UpLift programme of the Federal Ministry for Economic Affairs and Climate Protection to accelerate the development of climate-friendly technologies using the test platforms set up for this purpose. The main areas of research are, for example
- Testing and validation of fuel cell-based drive systems under realistic operating conditions
- H2 storage integration, H2 distribution systems
- H2 direct combustion
- Thermal management system including cooling system integration
- Validation of condenser/water separator, water handling
- Control and avionics
- Material ageing processes and testing of sustainable materials
Goals
The central goal of the national civil aviation research programme is to significantly reduce the climate impact of aviation through aviation-induced greenhouse gases and non-CO2 effects. The path to climate-neutral aviation means completely dispensing with fossil fuels such as paraffin in aircraft. As alternative energy sources based on hydrogen are expensive to produce and have a lower energy density, there are two key research approaches. Firstly, energy sources must be used as sparingly as possible and secondly, technologies must be optimised for the most economically and ecologically sensible use of alternative energy sources. The aviation industry is therefore facing a significant transformation process.
Against this backdrop, technological developments are being supported that will make flying sustainably climate-neutral by 2045 while maintaining and expanding safety standards. The technical solutions and concepts developed make a significant contribution to sustainable air transport and thus strengthen the competitive position of Germany as a centre of aviation.
In line with the European targets, technologies are to be developed in an intermediate step by 2035 that enable fuel consumption to be reduced by up to 30% and thus emissions (greenhouse gas and non-CO2 effects) to be reduced by over 80% for medium-haul routes.
The availability of climate-neutral technologies for medium-haul flights is required by 2045. In order to achieve this, the following primary targets are being pursued:
- Use of sustainable fuels
- Reduction of energy requirements by up to 50%
- Significant reduction in development, production and operating costs by up to 30%
- At the same time, a reduction in perceived noise is to be achieved so that the number of people affected by noise is halved.
In the context of environmentally friendly drive technologies, research focuses on the introduction of new energy sources such as hydrogen in connection with direct combustion or a fuel cell-based hybrid-electric system in conjunction with the necessary distribution and tank systems for conditioning and storing the mostly liquid hydrogen. In addition, significant fuel savings are expected through aerodynamic optimisation of the gas turbine blading and the implementation of innovative cycle processes, among other things, which will enable a significant reduction in greenhouse gas emissions. Advanced development, production and repair methods such as additive manufacturing also contribute to a reduction in resources for the production and operation of aircraft engines.
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Adrian Klassen