Experimental Study on Hydrogen-Methane Co-Combustion in Small Gas Engines

Hydrogen fuel has garnered significant attention as a key method for adapting internal combustion engines to a carbon-neutral society. Hydrogen is a carbon-free fuel that does not produce CO2 emissions during combustion. However, its wide flammability range and extremely low ignition energy present technical challenges when applied to internal combustion engines, such as the frequent occurrence of abnormal combustion phenomena like pre-ignition and knocking. Furthermore, the low energy density of hydrogen makes it difficult to achieve high power output. Additionally, hydrogen’s high adiabatic flame temperature and short quenching distance result in increased NOx emissions and cooling loss, which are further obstacles to its use. To address these issues, this study focuses on methane blending as a remedial approach. Experiments were conducted using a naturally aspirated engine with a premixed intake method to investigate the effects of methane-hydrogen blending. The following key findings were obtained:

1. 1
   The heat release rate can be controlled by adjusting the blending ratio.
2. 2
   Pre-ignition and knocking can be suppressed.
3. 3
   Power output can be improved.
4. 4
   NOx emissions can be reduced.
5. 5
   Thermal efficiency can be enhanced by optimizing the blending ratio based on engine load conditions.

The insights gained through this study demonstrate the potential of internal combustion engines in achieving a low-carbon and decarbonized society.