Optimization of the mixture formation in DI hydrogen combustion engines by modified injector nozzle design

Authors

M. Brauer, J. Maass, L. von Römer, M. Sens - IAV, A. Fink, O. Nett - TU Berlin

Summary

Hydrogen combustion engines are once more subject of research and development work. They are seen as a technology for the short and midterm decarbonization of the transport sector. To achieve competitive power densities and to reduce the risk of backfire in the intake system, work is being carried out on injection systems and combustion processes with direct hydrogen injection. Outward-opening A-nozzles are ideal for direct gas-in-gas mixture formation, as they enable high gas flow rates compared to multi-hole nozzles and immanently bring along good sealing properties. However, the relatively slow homogenization of the mixture is particularly challenging for direct injection (DI) engines. This effect is further aggravated by short homogenization periods since the required injection time for hydrogen is relatively long.

In this article, both the advantages and disadvantages of low-pressure direct injection (LP DI) in relation to port fuel injection (PFI) are discussed. Based on this the challenges of direct injection and mixture formation with hydrogen are demonstrated and analyzed by means of optical tests in a high-pressure chamber. The last part of this article focuses on the optimization of the LP DI mixture formation in a commercial vehicle engine. The key objective of the investigation is the design of suitable jet forming devices ("spray caps") to support the primary combustion chamber penetration and thus a successful mixture homogenization.

This work was supported by the joint research project of the Commercial Vehicle Cluster (CVC) WaVe “Entwicklung und prototypische Erprobung eines Medium-Duty Wasserstoffverbrennungsmotors” funded by the German Federal Ministry for Eco-nomic Affairs and Climate Action (BMWK).