So how will it work in practice? “Cooling is a good example,” says Marko. To make engines more efficient, we need thermal efficiency, which in simple terms, is how much heat an engine needs to do its work. Higher operating temperatures are generally a good thing thermodynamically speaking, but can often exceed the melting point of the materials used inside a jet engine, and so certain parts of the engine require cooling. To create and pump cooler air where it is needed, we need to burn more fuel. But it doesn’t have to be this way.
“Not all parts of the engine require an equal amount of cooling during all parts of the flight,” he says. “We need cooling during take-off and climb, when the engine is at maximum power. But we don’t need as much of it during cruise, which makes up the bulk of the flight time. During cruise, if we’re cooling the engine more than we need to, we’re not being as efficient as we can be. If we can adapt the cooling flows for each stage of the flight then we can minimise fuel burn.”