Abstract
The production of Hydrogen from regenerative sources has the potential to be a sustainable substitute for fossil fuels. General requirements for future H2 powertrain systems are high power density, good efficiency, low emissions, a cost efficient production and life cycles comparable to current engine concepts. The hydrogen internal combustion engine (H2- ICE) fulfils all these requirements.
The new bi-fuel 12-cylinder H2-ICE, operated with external mixture formation in H2 mode and internal mixture formation in gasoline mode, is an important step towards this direction. The bi-fuelled 12-cylinder engine offers the advantages of hydrogen operation without the need of a fully developed hydrogen infrastructure. Due to the bi-fuel option the driver has the opportunity to run the car on gasoline when no hydrogen filling station can be reached.
Achieving high power densities = 1 operation for all engine speeds is a decisive factor in H2 operation. Furthermore, = 1 operation offers the possibility to reduce the only relevant raw emissions of a hydrogen engine, namely NOX emissions, using a conventional three way catalyst (TWC). At partial load an H2 engine is operated with very lean homogeneous H2-air mixtures, where no NOX raw emissions are produced. Combining these two modes offers entirely new perspectives to avoid NOX emissions by the use of an appropriate operation strategy.
A mono-fuel derivative of the bi-fuel 12-cylinder engine has further potential to optimize engine design, combustion process and exhaust after treatment with respect to power output, consumption and emission reduction. In particular the catalyst coating can be optimized to meet the special requirements of exhaust from combustion of H2-air mixture. In this way vehicles with mono-fuel H2 engines have the potential to under-run the SULEV limit values by one order of magnitude.
This is only the beginning of hydrogen combustion engine development. Turbo charging or direct injection offers power to engine volume ratios which are comparable to those expected from future gasoline or diesel engines, and at the same time with good efficiency.
Keywords:Hydrogen, Internal Combustion Engine, 12-cylinder-engine, Emission levels, Stoichiometric operation.