Lowering emissions through better design
The innovation at the heart of the Centreline project is the way the air which is already dragged along by the plane close to the fuselage is accelerated by the rear fan, to create thrust.
Centreline Project Coordinator Arne Seitz explains: “It takes the air that is flowing along around the fuselage, takes it up, re-energises it, and thereby produces the required thrust at a lower power input, and this improves efficiency. It will allow us to reduce greenhouse gas emissions. So that’s predominantly CO2 emissions, but also NOx, and so forth.
That same effect is already used in boats and submarines, but the experiments in the wind tunnel reveal how adding a large fan at the rear of the plane has a big impact on a modern passenger aircraft fuselage, as Biagio Della Corte, PhD Student at TU Delft, explains.
“A thing to keep in mind when making this kind of design compared to conventional designs is there is a strong interaction between the propulsive system and the aerodynamic surface, this interaction is really important, and you can’t forget it during the design process,” he says.
Significant fuel savings on long-haul flights
The engineers talk of fuel savings from 3 to 6 percent, even up to 11 percent, meaning important emissions reductions on long-haul flights.
“So if I install the additional weight on the aft of the fuselage, I certainly want to utilize the additional efficiency gain on a long cruise flight. So, for example, flying from London to Tokyo.”
The first aircraft with the third, electrical fan at the rear could be seen flying in the skies in the mid 2030s.
Turbines in turbulent air
“The air that’s coming into the inlet of the engine is very distorted, that’s to say it’s not uniform, it’s not all travelling at the same speed,” says Research Associate Alejandro Castillo Pardo. “What happens with the engine in these cases means it tends to stall. So we have to improve the design of our fan blades to prevent any the failure. And apart from never failing, the design needs to be more efficient to reduce the fuel used in the flight.”