Background and Motivation
The Engine Combustion Network’s hydrogen research topic was first identified during the ECN8 workshop as a future research direction and was formally launched at the ECN9 workshop held in Naples, Italy in September 2023. The motivation for establishing this research area stems from the clear future projected for hydrogen engines in heavy-duty, off-road, and stationary applications.
The ECN’s hydrogen research initiative builds on the network’s successful collaborative model, bringing together experimental and computational researchers from institutions worldwide to advance the state of knowledge in hydrogen combustion at engine-relevant conditions. A dataset of hydrogen mixing and combustion in a running optical engine is also available on the ECN.
Research Focus Areas
The primary aim of the hydrogen topic is to gain better understanding of injection, mixture formation, and ignition of direct injection (DI) hydrogen systems. The research encompasses both experimental characterization and computational fluid dynamics (CFD) modeling of hydrogen jets under conditions relevant to internal combustion engines.
Key areas of investigation include:
- Hydrogen jet penetration and mixing dynamics
- Shock cell formation and stability in supersonic hydrogen jets
- Ignition characteristics and flame propagation
- Internal nozzle flow effects and needle/pintle dynamics
- Near-field spray structure and far-field dispersion
- Gas temperature distribution
- Differential mass diffusivity of hydrogen
Standardized Hardware Selection
Following extensive discussion during the ECN9 breakout sessions, the community decided to adopt the Bosch HDEV4 outward-opening injector as the standard hardware for future collaborative hydrogen spray research. This decision was driven by several factors:
The HDEV4 is an off-the-shelf commercial injector that can be purchased in batches to minimize variability between different injectors, addressing a key requirement for the ECN’s collaborative research model. The injector offers injection pressures up to 200 bar.
The HDEV4 injector was selected based on its compatibility with hydrogen, comprehensive characterization in the literature, and suitability for open-access research.
It is acknowledged that injecting sufficient hydrogen mass using the small-needle-lift HDEV4 at these conditions presents challenges, requiring long injection durations even during the compression stroke.
Future Directions
The ECN hydrogen research community continues to develop and refine:
- Advanced optical diagnostic techniques for hydrogen jet visualization
- Computational models capable of accurately predicting near-field shock structures
- Understanding of the relationship between injector design and hydrogen jet behavior
- Experimental databases suitable for model validation across multiple facilities
The goal is to ensure consistency in both experimental measurements and computational predictions, with sufficiently accurate near-field modeling to enable reliable downstream predictions. The community recognizes that the models and diagnostic techniques being developed will be applicable to future hydrogen engine research beyond the specific ECN target conditions.