DLR and Rolls-Royce reduce soot emissions in latest engine generation

New combustion chamber technology used in the current Pearl engine family, and the resulting reduction in pollutant emissions, are the result of more than 30 years of collaboration between the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and Rolls-Royce Deutschland.

As part of several projects funded by the German Federal Ministry for Economic Affairs and Climate Action (BMWK) under the national aviation research programme (LuFo), a wide range of combustion tests and endoscopic measurements have been conducted by the DLR Institute of Propulsion Technology. In cooperation with industrial collaborators, DLR researchers improved the injection of fuel into the combustion chamber, reducing the formation of soot. The institute validated the engine manufacturer’s computer-based modelling at one of its combustion test benches by using laser measurement techniques developed in-house to investigate combustion processes – and soot formation in particular – directly in the flow. Alongside this, the combustion chamber experts conducted exhaust gas analysis downstream of the combustion chamber to investigate pollutant emissions (both gaseous and particulate).

Jörg Au, Director of Engineering Technology and Safety at Rolls-Royce, said: "Rolls-Royce and DLR have enjoyed an extremely fruitful partnership for three decades. Thanks in part to this collaboration, our engines are among the best in the world today. But to remain competitive, we must continue to innovate and invest in technology. Our cooperative projects with DLR researchers play a key role in that."

By analysing extensive data, Rolls-Royce Deutschland gained a deep insight into the complex processes taking place in the combustion chamber early in the development process. Soot formation in particular is one of the most complex aspects of combustion, as even the slightest changes in boundary conditions can lead to dramatic changes in soot emissions. Establishing a direct link between combustion processes and the corresponding emissions provides a sound footing for understanding and targeting the development of low-emission technologies.

The DLR Institute of Combustion Technology also made valuable contributions towards the numerical simulation of sooty combustion. In generic turbulent high-pressure flames, researchers used various laser-based measurement techniques to generate highly accurate validation data under well-defined conditions. The engine manufacturer then used these data to further develop and validate its PRECISE-UNS code. This data also helped the Institute of Combustion Technology develop and validate its own code, ThetaCOM.

Successful research continues apace

In upcoming projects, the DLR Institutes of Propulsion Technology and Combustion Technology will work together to investigate the soot propensity of various sustainable aviation fuels (SAFs), contributing to the advancement of spray atomisation for next-generation fuel injectors.

"Through our long-standing collaboration with Rolls-Royce Deutschland, DLR is making a crucial contribution towards the engine manufacturer's product portfolio while continuing to develop its own expertise and methods," says Florian Herbst, Director of the DLR Institute of Propulsion Technology. "This approach allows innovation to be driven forward at an early stage of development, mitigating the risks associated with extremely expensive high-TRL (Technology Readiness Level) testing."