Mercedes-Benz has been resolutely committed to an electric future, but a new patent filed with the German patent and trademark office, the DPMA, suggests it may be reconsidering going all in on EVs by pursuing hydrogen combustion as an alternative propulsion system for a green future.
The patent describes a “Method for operating a gas engine, in particular a hydrogen engine.“
While it doesn’t go into detail about the size or configuration of the motor, it does specify the fuel source as hydrogen in gaseous form. That in itself is nothing new, but the patent proposes variable timing on the injection of the gaseous fuel into the combustion chamber in a bid to improve efficiency.
Variable Fuel Injection Improves Hydrogen Efficiency
Specifically, Mercedes proposes injecting hydrogen into the combustion chamber in a range or a plurality of ranges between 320 degrees and 190 degrees of crank angle before top dead center of ignition. By metering out the feed of the hydrogen through this range, and controlling intake air accordingly, Mercedes believes it can reduce the risk of premature ignition and increase the efficiency of the combustion stroke itself.
By increasing its efficiency and reducing its volatility, more power can be generated from each combustion stroke, reducing the amount of fuel required. This is one of the great flaws of hydrogen combustion, as hydrogen as a fuel has approximately 25% the energy density of gasoline. This means you need to carry more hydrogen, under immense pressure, to achieve the same power and range as a comparable car powered by traditional internal combustion.
Turbocharged Tumbling Of Intake Air
The ability to increase the efficiency of each combustion stroke partially comes down to a tumbling effect created by the rate at which the hydrogen is fed into the combustion chamber. But the airflow also plays a critical role, which is why Mercedes proposes an alternate situation where a turbocharger can be used to increase intake pressures. The increased pressure improves the tumbling effect of the air-fuel mixture, resulting in a cleaner and more even burn.
A Variety Of Applications
Mercedes proposes such an engine could be used in a variety of applications, notably trucks, vans, buses, or passenger cars, but it could even be used in isolation as a generator. The latter could prove useful as a range extender in a battery electric vehicle, or simply be used to improve electricity generation without using gasoline/petrol.
It should be noted that while Mercedes’ road cars have not used hydrogen combustion at all in the past, the automaker has dabbled with the fuel source powering prototype semi-trucks and even a Unimog.
New patent filed with the German patent and trademark office, the DPMA
