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Biphasic Heat Transport integration for efficient heat exchange within Composite materials Nacelle

Periodic Reporting for period 2 - BISANCE (Biphasic Heat Transport integration for efficient heat exchange within Composite materials Nacelle)

Reporting period: 2021-01-01 to 2022-03-31

The project intends to test in icing wind tunnel (IWT) one demonstrator of engine air intake integrated in a nacelle and equipped with an innovative biphasic heat transport system for regenerating the energy from the oil of the engine. The objective, by testing the technology in a representative environment, is to reach TRL5. At the end of the project the technology will be able to be further developed towards TRL6 to 9 with the final aim to be transferred to the aeronautic value chain.

The ambition of the project is to demonstrate the possibility to use the energy from the engine oil for protecting the engine air intake against the ice accretion. To make sure that the oil is sufficiently cooled down in all the environmental conditions, even the warmest ones, aircraft on the ground for example, a significant area of the nacelle will be used as a heat exchange surface additionally to the ice protected surface.
The perspective of this heat exchange concept is to optimize the existing system architecture by removing the active cooling system for the oil, removing the active ice protection system, and to harvest the energy from the oil to regenerate it for the ice protection purpose.

Modifying an aluminium structure into a composite nacelle would decrease the weight by 50% for a similar structural resistance.
Replacing the classical Air Cooling Oil Cooled System and the active ice protection system will lead to another weight saving.
Substituting the active systems (oil cooling and ice protection systems) by the biphasic passive system will permit to save around 100kW of power per A/C.
Globally, combining all the above effects, the objective is to save 25kg and 889 000kg of CO2 emissions per A/C along its life.

The promising environmental benefits listed above will directly enhance the competitiveness of the European companies proposing and operating these new technologies. The fuel saving will decrease the operational costs by 200 000$ for each A/C compared to a similar A/C with a metallic nacelle and active systems.
Conceptual and preliminary phases were completed on the system and its integration into the engine nacelle structure. will be frozen in Q3 2022. For the final selection of the system concepts integration, various specimens were manufactured and analyzed. Finally, testing on reduced scale specimens has started and the final testing in icing wind tunnel is expected in February 2022.

Along the first phase of the project, various system integration concepts into the structure were proposed.
Three integration concepts were proposed:

✓ Metallic panels for the nacelle featuring channels for the biphasic system
✓ Metallic additive manufacturing process for the front lip of the air intake integrating channels for the biphasic system
✓ Composite material for the rear parts of the air intake integrating tubes for the the biphasic system

The selection of the design and manufacturing process for the various heat exchangers was done through theoretical considerations but also following small specimens manufacturing.

✓ For the metallic panels, chemical milling, metallic sheet rolling and welding are the processed used to have the final shaped panel featuring tight channels.
✓ For the additive manufacturing lip, a small specimen was built to test the compatibility of the material with the system fluid.
✓ For the composite part, specimens were manufactured to define precisely the layup of carbon fiber plies to consider

Several biphasic system architectures were proposed and a trade off was done. The needed heat transfer to comply with both functions of the biphasic system was widely investigated (oil cooling and ice protection). All the flight phases were considered and the most critical conditions for both functions were highlighted.
One of the main conclusions on the power analysis is that the current active oil cooling system cannot be fully removed because the amount of heat to be extracted is too significant.
For optimization reasons, a selection of fluids was investigated to find out the one providing the best heat exchange performance and considering the constraints such as flammability, pressures, ...

Reduced scale tests were prepared to anticipate the behaviour of the complete biphasic loop and to limit the risk of failure during the final demonstration in icing wind tunnel. The system loop was tested on a bench and the amount of heat exchanged was measured and found to be promising for the final test. Also, the system loop was qualified to check its adequate operation like simulating the rolling and the pitching effects of the aircraft.
The next stage is the testing of the reduced scale specimen using a small wind tunnel (with no icing) to simulate the cold source on the heat exchanger.

After the assessments performed so far concerning the system development as well as its integration into the nacelle structure, the critical design review should be completed by Q3 2022 and will allow the manufacturing of the specimens for being ready in early 2023 to start the icing wind tunnel characterization expected in February 2023. The last 3 months of the project will be dedicated to the analysis of the results.
The biphasic system will be developed and will propose a unique passive solution in terms of ice protection of the air intake.
Since the initial phases of the project, the amount of energy available for the passive heat transport and the technology foreseen for the system provide good hope that the ice protection will be efficient.
Also, the first investigation showed goood results for the thermal efficiency of the system and it is reasonnable to think that the current active oil cooler system will be downsized using a biphasic system resulting in significant power savings.

On top of the activities linked to the system itself, a huge effort is brought to the integration of the system into the structure of the nacelle. Three concepts of integration are investigated:

- An additive manufacturing process for the air inlet, allowing a full integration of the system tubing within the inlet structure. Such a technology enables the optimisation of the system integration design leading to the realization of complex architecture and the optimization of the overall weight. This technology will first be investigated through the manufacturing of coupons before implementing it on the full scale specimen.

- An advanced metallic structure for the side panels of the nacelle, featuring channels for the fluid circulation. The metallic sheets will be chemically machined to create the channels, covering the entire surface of the panels. To ensure the airtightness of the channels, the metallic sheets will be welded together using an advanced electron beam welding process.

- A composite structure for the rear side of the air intake. Aluminium tubes will be cured together with carbons fiber plies. Also, a metallic mesh will be located inside the laminate for improving the heat conductivity through the material and to enhance the thermal performance of the system.

Once all the coupons and reduced scale specimens are tested and analysed, the risks associated to the innovative system and structure will be cleared such as the activities for the full scale specimen can start, leading to the final test in icing wind tunnel.