Am Enabled Injection Systems for Enhanced Fuel Flexibility

¹ Institute of Combustion Technology for Aerospace Engineering, University of Stuttgart, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany
² Institute for Machine Tools, University of Stuttgart, Holzgartenstraße 17, 70174 Stuttgart, Germany

^* Corresponding author: fabian.hampp@ivlr.uni-stuttgart.de

Abstract

The demand for fuel-flexible combustion systems is rising with the transition to renewable energy vectors like hydrogen, ammonia, methanol, sustainable aviation fuel (SAF), and hydrogenated vegetable oils (HVO). High-momentum jet-stabilised combustion systems have shown significant benefits for hydrogen-based operation. However, achieving clean, fuel-flexible combustion imposes strict requirements on injection and mixture formation, especially as partially cracked ammonia can cause large variations in the Wobbe index, affecting fuel momentum and penetration depth. Decoupling mixture formation from fuel properties is key to ensuring homogeneous mixing before flame interaction. Additive manufacturing (AM) offers innovative solutions by enabling intricate fuel injection designs. This study explores AM-enabled space-filling injectors to enhance fuel flexibility, focusing on Powder Bed Fusion Laser Beam (PBF-LB/M) processes in In718 to create space-filling micro-structures with sub-100 μm feature sizes. The objectives are optimised fuel placement and mixture homogenisation while realising fuel jet injection momentum independence. Using schlieren imaging, the improved mixture formation with reduced Wobbe index sensitivity is demonstrated, enabling excellent multi-fuel adaptability. This research highlights AM’s potential in developing cost-effective, multi-fuel injection systems for gas turbines, particularly in applications requiring co-firing and adaptability to regional or temporal availability fluctuations of sustainable carbon-free energy vectors.