AdHyBau2: Development of an approvable hydrogen-electric propulsion system for aircraft and testing of the cryogenically cooled electric motor

Project description

Several challenges must be overcome in order to fly electrically over long distances. In addition to saving energy, reducing mass, and increasing the efficiency of the overall system, suitable energy sources are needed as an alternative to kerosene in order to enable environmentally friendly aviation.

The consortium is developing a powertrain with liquid hydrogen (LH2) as the primary energy source and a cryogenically cooled electric drive. With >30 kWh/kg, liquid hydrogen has three times the gravimetric energy density of kerosene (12 kWh/kg) and is stored at approximately -250°C. When used appropriately, this combination can have a very beneficial effect on the overall system. Among other things, the cryogenic temperature range enables the use of superconductivity without additional energy consumption, but at the same time poses major challenges in terms of design and materials. Efficiencies of up to 98% have already been achieved in stationary applications of superconducting generators. A study on the applicability of superconductivity will show whether this efficiency can also be achieved in aviation applications within the power class under investigation. The overall system will be examined for scalability using digital methods and then evaluated for transferability to other power classes.

To further increase the potential for lightweight construction, Work Package 2 will develop novel additive processes and construction methods to increase geometric freedom in the design of disruptive approaches and enable components that were previously impossible to produce. The focus here is on copper and aluminum, which are important materials in electrical engineering. The latter is to be made suitable for low temperatures through further development of the process chain. The extreme environmental conditions of liquid hydrogen have disadvantages that can have a negative effect on elastic-plastic properties. Common databases, data sheets, and literature sources contain very little to no information about material properties at cryogenic temperatures and in a hydrogen atmosphere. With this database, aviation certification of the materials and manufacturing processes is not possible.

In a first step, the LuFo project "AdHyBau" was able to fundamentally investigate selected, additively manufactured metallic materials and clarify their suitability for these boundary conditions. However, the material data required for aviation certification is not yet complete. In addition, a complete description of the elastic-plastic properties of the materials is also required for the development of hardware that can be constructed and tested. This is the only way to ensure safe design and, consequently, safe test operation. In addition to structural materials, an electric drive requires functional materials, e.g., for electrical insulation or magnetic flux guidance. There are serious gaps in the data for the environmental conditions. Fundamental research into these materials by the participating institutes and universities is therefore essential in order to achieve the joint goal of proving the functionality of the electric drive through experimental investigations. The necessary research into the materials will be carried out based on the test strategy in work package 3, which is tailored to aviation certification. The results will form the basis for future aviation certification.

The digital twin of an electric drive, which was prepared in the LuFo project "AdHyBau" using a continuous design and simulation process, forms the basis for the digitalization of R&D activities. In work package 4, model order reduction is used to reduce the complexity of the models while maintaining the same quality of results in order to significantly reduce resource requirements and computing time. This makes studies on acoustics and scalability as well as a novel method for multi-criteria optimization of structural and functional components possible for the first time.

The construction, commissioning, and experimental testing of the drive under laboratory conditions are an essential part of the project. This work will be carried out in work package 5. The electric drive is expected to reach TRL 4. The findings from the experimental testing will provide important conclusions for the further development of the demonstrator.

Fraunhofer IWM subproject: Investigation of additively manufactured materials and substructures under the influence of hydrogen and cryogenic temperatures; development of mechanism-based service life models

Fraunhofer IWM is a development partner in the field of reliability, safety, service life, and functionality of components and systems. In particular, numerical modeling and simulation of material behavior under a wide variety of loads is used to make statements about the performance of components. The latest testing technology is used to analyze issues relating to hydrogen embrittlement. Models that take into account the influence of hydrogen on mechanical properties are developed, used, and continuously expanded at Fraunhofer IWM.

In the project, Fraunhofer IWM is investigating additively manufactured metals regarding their susceptibility to (combined) hydrogen and low-temperature embrittlement in order to ensure their suitability for use under the conditions mentioned. Fraunhofer IWM is coordinating work package 3 on analyzing the influence of hydrogen on material behavior at different temperatures. Within this framework, Fraunhofer IWM will conduct its own tests for material qualification. To this end, Fraunhofer IWM is adapting existing testing techniques to the necessary test conditions and helping to make these methods of material qualification usable. Fraunhofer IWM will use the results to further develop material models for predicting service life. In other work packages, Fraunhofer IWM is involved in transferring the knowledge gained to components and substructures. The research at Fraunhofer IWM forms the basis for future aviation certification and industrialization of the technology.