Hydrogen internal combustion engines (H2 ICE) are showing impressive
potential to replace fossil fuel–based ICE platforms with zero-carbon engine-out
emissions. However, adopting 100% hydrogen has its challenges due to its unique
properties, such as the rapid flame velocity, the minimum igniting energy, and
the lowest density.
These unique properties of hydrogen impose an increased risk of ignition and
combustion of hydrogen in the engine system due to leakage or inadequate
ventilation. One of such scenarios is the hydrogen gas in the crankcase as a
result of hydrogen slip through the piston rings. In this study, an experimental
investigation was conducted on a single-cylinder hydrogen direct injection spark
ignition engine, which was originally designed for boosted DI gasoline engine
operation. A crankcase-forced ventilation system was designed and adopted with a
hydrogen sensor in the closed feedback loop. The hydrogen concentrations in the
exhaust gases and crankcase were measured simultaneously by two V&F hydrogen
analyzers to assess the total hydrogen slip phenomenon. In particular, the
impact of the intake boost and forced ventilation system on hydrogen slip and
engine performance was investigated by varying the relative air-to-fuel ratio
(lambda) and forced crankcase flow rate, respectively. The study reveals that
the hydrogen slip was significantly increased by adopting lean-burn combustion
at high-load operations. The results show that the hydrogen slip in the
crankcase can be as high as 100,000 ppm with only the natural crankcase
ventilation. Forced crankcase ventilation has been shown to be an effective
method to avoid hydrogen accumulation in the crankcase and to drop the hydrogen
slip in the crankcase by more than 86%. Additionally, the indicated thermal
efficiency can be increased by 1.24% by fully recovering the hydrogen into the
intake system through the forced ventilation system.
