In-flight and ground-based measurements of nitrogen oxide emissions from latest generation jet engines and 100% sustainable aviation fuel

Nitrogen oxides, emitted from air traffic, are of concern due to their impact on climate by changing atmospheric ozone and methane levels. Using the DLR research aircraft Falcon, total reactive nitrogen (NOy) measurements were carried out at high altitudes to characterize emissions in the fresh aircraft exhaust from the latest generation Rolls-Royce Trent XWB-84 engine aboard the long-range Airbus A350-941 aircraft. The impact of different engine thrust settings, monitored in terms of combustor inlet temperature, pressure, and engine fuel flow, was tested for three different fuel types under similar atmospheric conditions: Jet A-1, for the first time a 100% sustainable aviation fuel (SAF), and a blend of both fuels. In addition, a range of combustor temperatures were tested during ground emission measurements. We confirm that the NOx emission index increases with increasing combustion temperature, pressure and fuel flow. We find that as expected, the fuel type has no measurable effect on the NOx emission index. These measurements are used to evaluate cruise NOx emission index estimates from three engine emission models. Our measurements thus help to evaluate the ground to cruise correlation of current engine models, serve as input for climate modelling, and extend the extremely sparse data set on in-flight aircraft NOx emissions to newer engine generations.