Conceptual, preliminary, detailed and testing phases were completed on the system and its integration into the engine nacelle structure. For the final selection of the system concepts integration, various specimens were manufactured and analyzed. Finally, tests on reduced scale specimens were performed for the assessment of the system prior to the final test done on a full-scale specimen in early 2023.
Along the first phase of the project, various system integration concepts into the structure were proposed.
Three integration concepts were proposed:
✓ Metallic panels
✓ Metallic additive manufacturing process
✓ Composite
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.
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. Also, the system loop was qualified to check its adequate operation like simulating the rolling and the pitching effects of the aircraft.
Following the preliminary analysis and the reduced scale tests, the detailed design of the full-scale specimen was completed. The test article was manufactured featuring both ALM metallic and composite heat exchangers. The system loop was fully integrated into the mock-up nacelle, featuring the lines, for the fluid transportation as well as the heat exchanger between the oil and the fluid inside the loop. Outside of the test article, an oil test bench was manufactured to reproduce the engine hot oil of an operating engine. The oil was used as the hot source of the system. The equipment was sent to the icing wind tunnel where the specimen was confronted to extreme icing conditions down to -30°C and strong winds of 350 km/h.
The analysis of all tests and investigations concluded that the ice protection of the engine inlet using the developed passive system loop is efficient and that the use of the system to cool down the engine oil is efficient but does not allow to remove completely the existing active cooling system. Beyond the test analysis, the project was concluded with the establishment of a final system design as well as a thermal model. The promising results have conducted to a new project to test the integration of such a system into a real engine environment that will allow to increase even more the maturity level of the capillary loop. The interesting results and analysis done along the project were disseminated to a targeted audience through various conferences (ILA Berlin, IHPC conference or the Coock fighting icing project).
