The work started with the definition of the technological assumptions for year 2035, followed by the definition of the reference 2020 and baseline 2035 TRL6 engines. The baseline engines were developed for short-, medium-, and long-range applications and are based on geared turbofan architectures featuring low-NOx combustion systems. Additionally, the short-range engine is based on a hydrogen recuperative cycle. In parallel, aircraft models for entry into service at year 2040 were developed for each one of the aforementioned engines. For a comprehensive evaluation of the global fuel consumption impact of MINIMAL technology, aircraft fleet models were developed for a number of techno-economic and social scenarios up to year 2050. This supported the creation of reference year 2019 and baseline year 2050 emission inventories that were used to estimate the climate impact from aviation using baseline (conventional) technology. Finally, the inventories were used to create climate response functions that estimate global temperature variations as a function of emission species at the engine exhaust. These can be directly employed into the engine design optimisation loops, allowing to optimise each one of the CCE configurations for minimum climate impact.
The maturation of intercooled CCE technologies to TRL2 is progressing well. Models have been created at the component and system level, to predict the performance of all three topping cycles (crankshaft-based, free-dual, opposed), including hydrogen combustion models, and heat-transfer performance. Emission models for NOx have been integrated into the design loops allowing to investigate efficiency vs emission trades for varying design parameters. Additionally, NOx mitigation strategies such as exhaust gas recirculation (EGR), and steam injection, have been investigated showing promising NOx reduction potential. This work is supported by parallel studies ranging from 0D/1D to CFD modelling of thermal loads, secondary cooling flows, intake and exhaust manifold flows, as well as thermochemistry performance in combustion chambers. With the aim of developing the most effective cooling strategies for CCE concepts.
The down-selection of the novel hydrogen intercooler design is following the established plan and several TRL2 activities are ongoing, leading to the initial preliminary system design. Several piston cooling strategies are also currently being evaluated at TRL2. This work is supported by the creation of new or tailored heat-exchanger design tools. Regarding the low-NOx combustion rig, the activities were focused on the design and work towards the commission of the oppose-piston test facility. The project acquired a fully operational opposed piston assembly from Libertine, which has been instrumented for NOx and performance studies at Cranfield University. The rig will be located in a new combustion test facility that was design for usage during project MINIMAL. The new facility will be tailored for hydrogen combustion (PCCI and potentially HCCI) and aims at demonstrating low-NOx operation. To support the upcoming experimental activities different models with increased fidelity were developed. The models range from simple spreadsheet models to high-fidelity CFD and aim at predicting NOx formation at different operating modes. The models were further used to map out the anticipated performance of hydrogen powered operation to predict piston loads and develop motion control strategies.
