A passive ventilation opening system for aircraft engines
With aviation looking to reduce its carbon footprint, aircraft engines are getting another look. While the latest engine designs represent a step change in efficiency, they create new challenges in thermal management. “As next-generation propulsion systems become increasingly efficient, it becomes crucial that we find ways to optimise the ventilation of the engine’s core compartment,” says Nicolas Baillot d’Etivaux, practice manager – system and data modelling at EPSYL-ALCEN. With the support of the EU-funded PALOMA project, EPSYL-ALCEN, together with Nimesis, Akkodis and Atherm, are working to do exactly that. “Our goal is to optimise engine ventilation as a means of improving the cooling of the core compartment depending on its temperature,” adds Baillot d’Etivaux, who served as the project coordinator.
Replacing electronics with shape memory alloy
In most aircraft, the ventilation of the core compartment is sized to avoid flammable vapour concentration. It is also designed to ensure sufficient cooling of various components during the most critical phases of a flight. “Standard ventilation systems are not optimised for the less critical flight phases, such as cruise, which represent the most flight time and lead to unnecessary fuel consumption,” explains Baillot d’Etivaux. To improve this situation, the project designed an adaptive ventilation system that can adjust the cooling of the core compartment based not on flight phase, but on actual temperature. Instead of relying on electronics, the solution uses the heat released by the engine to trigger the opening of the flap. A heat pipe then transports the captured heat to a shape memory alloy placed frontward in the compartment. As the shape memory alloy is heated up, it changes shape, which activates the opening mechanism and allows the cooler air to enter the compartment.
Test, adjust, repeat
On paper, the solution is groundbreaking. The question is, does it work? To find out, the PALOMA project, which received support from the Clean Sky 2 Joint Undertaking, put it to the test. Using a test bench, researchers ran a thorough investigation on a prototype adaptive ventilation system – a process that allowed them to identify and solve issues. In addition to some mechanical issues, one unexpected challenge was how to exploit the data from the device. This required that the test bench be modified, the numerical model adapted, and the algorithmic methods properly calibrated. “Our team was very reactive and able to quickly solve this issue, allowing us to perform significant tests on the efficiency of the device in operational conditions,” remarks Baillot d’Etivaux.
Adaptive ventilation nearly ready for take-off
Despite these initial challenges, the path forward towards achieving a totally passive system for reactor ventilation is clearer than ever. For example, thanks to the project’s state-of-the-art test bench, researchers now have a better understanding of the physical complexity involved when dealing with the coupling of shape memory alloy and heat pipes. According to Baillot d’Etivaux, by knowing the limits of such a system, researchers can use the numerical model to improve the design, by diminishing frictions, and update the prototype for further testing. “While there’s certainly more work to do, thanks to the PALOMA project, our adaptive ventilation system is about ready for take-off,” he concludes.
Keywords
PALOMA, aircraft engines, ventilation systems, aviation, shape memory alloy, Clean Sky 2
