The burn factor

New combustor technologies keep engine temperatures down to reduce emissions.

Designing aircraft engines is a game of trade-offs. For example, operators desire hotter-burning engines because they run more efficiently. But increasing the temperature that air and fuel are burned in the combustor results in greater emissions of nitrogen oxides (NOx).

On the face of it, reducing fuel consumption while at the same time cutting emissions is mutually exclusive. For propulsion engineers it is like trying to bring together the opposite poles of a magnet.