Stuttgart researchers develop AM fuel injector for gas turbines
The nozzle design tolerated the surface roughness of printed metal parts, and the university research team reported clean combustion in laboratory tests
Researchers at the University of Stuttgart have developed an additively manufactured injection system for compact gas turbines, designed to burn hydrogen, e-fuels and conventional fuels with low emissions.
“It is no longer unusual to use additive manufacturing to construct gas turbines. However, this has generally not been the case for one of the most important components—the injection systems that spray fuel into the combustion chamber,” said Dr. Fabian Hampp, Junior Research Group Leader at the Institute of Combustion Technology for Aerospace Engineering at the University of Stuttgart.
Hampp worked with Professor Dr. Hans-Christian Möhring, Director of the Institute for Machine Tools at the University of Stuttgart, and Dr. Oliver Lammel, Senior Researcher at the Institute of Combustion Technology at the German Aerospace Center (DLR).
Injectors must produce a fine fuel mist and homogeneous mixture to limit soot and nitrogen oxides, a requirement that to date had prevented injectors for smaller turbines from being made by powder bed fusion of metals.
“The problem is that the surfaces of these printed structures are never completely smooth. This causes problems when a specific amount of fuel needs to be injected into a combustion chamber as a fine mist through very small openings,” Möhring said.
The researchers designed an injector that worked despite the roughness, miniaturizing a principle used in aircraft turbines for the first time, the university reported. “This allowed us to realise very clean combustion processes in the lab,” Möhring said.
Injection systems are typically designed for one fuel, because hydrogen, natural gas and kerosene differ widely in properties. “However, the special design of our nozzles makes it possible to cleanly burn a wide range of fuels,” Hampp said. The university stated retrofitting older turbines could help reduce geopolitical dependence on certain energy sources.
Prototype testing planned
The injector has so far only been tested in the laboratory. The teams plan to refine the manufacturing process and nozzle geometry, then build a prototype and test it with various fuels under real-world conditions with DLR Stuttgart.
The Federal Ministry of Research, Technology, and Space is providing €1.5 million ($1.7m) through the end of 2029 for the AMFlexInj project.
