In Europe, standards are
about to get tougher, though, forcing diesel makers into a race
against time. One option is to use catalytic converters to
remove pollutants, but they degrade over time and more importantly
damage performance. However, meeting the new Euro 6 caps
standard without a catalytic converter is a steep
Researchers at Technische Universitaet Muenchen
(TUM), located in Munich, Germany, have developed
a new engine that just may be able to meet the tough new
standards without necessitating a catalytic converter. The
engine, which may usher in a new era of green performance weighs in
at two tons, has hardly any odor of exhaust fumes even when running
at full blast.
To design the engine, researchers had to go
back to the drawing board. Modern diesels meet Europe's Euro 5
Norm for emissions by recirculating the polluting nitrogen oxides
produced from the combustion of diesel fuel back into the engine.
Mixed with fresh air and re-reacted at a lower temperature, the
result is less nitrogen pollution, but more polluting soot. The
new standard calls for a reduction in soot, as well, making this
Instead, the new engine, dubbed NEMo
(Niedrigst-Emissions-LKW-Dieselmotor, the German acronym for "lowest
emission truck diesel engine), uses a combination of turbocharging
and direct injection to burn the fuel more completely.
recirculation the exhaust gases are compressed to ten times the
pressure of the Earth's atmosphere (10 bar), giving enough oxygen for
the diesel fuel to burn cleanly. While the pressure is over
twice what current engines can handle, NEMo can handle it with
Improved direct injection also plays a pivotal role.
Traditionally injectors spray large droplets. Fuel is burned
from these droplets, stripping away a layer of fuel akin to "peeling
a layer off an onion". As you peel off more layers, the
fuel becomes more dense and compressed, and it becomes difficult for
the oxygen to react with the fuel. The result is soot. By
using higher pressure direct injection, the engine sprays finer
droplets, leading to more complete combustion and less soot.
NEMo ups the DI pressure from 1,800 bar to 3,000 bar, allowing this
Led by Georg Wachtmeister from the Chair of
Internal Combustion Engines at the university, the engine team has
tune NEMo to almost meet the upcoming standard. The emissions
from the engine are so low they had to invent a new in-engine probe
to measure them more accurately.
The team wants to improve
their design even more. They're currently trying to better
understand how soot particles form. To do this they've created
the aforementioned probe -- a speedy sample collector that sucks up a
tiny sample of combustion chamber gas in one millisecond. Using
the gas sampling valve, 13 samples can be taken during a single
ignition, giving the researchers a wealth of new data to better
understand and combat soot growth.