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Phenomena contributing to environmental
concerns
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Development of Komatsu Environmentally Friendly
Engines
Komatsu has incorporated a heavy-duty High-Pressure Common Rail (HPCR) fuel injection
system in its current diesel engines to achieve both nitrogen oxide (NOx) and
particulate matter (PM) reductions and improved fuel efficiency.
Specific features of the heavy-duty HPCR fuel system include its ability to inject
high-pressure fuel accumulated in the common rail into the combustion chamber,
thus atomizing fuel spray and optimizing combustion for better fuel efficiency,
lower emissions and higher performance. Another feature is its flexibility to
maintain the optimal fuel injection volume, pressure and timing through precision
electronic control. This results in near complete combustion, contributing to
PM emissions reduction and dramatically improved fuel efficiency (diagram 1).
Komatsu is one of the front runners in the construction and mining equipment
industry to use the heavy-duty cooled Exhaust Gas Recirculation (EGR) system
in medium and large engines, which is effective in lowering NOx without sacrificing
fuel economy.
Cooled EGR is a proven technology and one of the best solutions for reducing
NOx in diesel engines, and many engine manufacturers have employed cooled EGR
with resounding success in engines that meet stringent on-road engine regulations
since 2002.
The air-to-air charge air-cooling system is effective for lowering the charge
air temperature to inhibit NOx emissions without sacrificing fuel economy.
Importance of Fuel Management
As the fuel injection pressure of the HPCR fuel system is extremely high (1,600
kgf/cm2 [22,752 psi]), clearance at the supply pump and injector has been designed
at the micron level of accuracy. As a result, it is much more difficult for water
and dirt to get mixed into the fuel circuit because the pre fuel filter (with
a water separator) and main fuel filter remove the majority of dirt, up to a
diameter of 10 µm and 2 µm, respectively (diagram 2). It is thought
that over 85% of all fuel system failures are caused by water and dirt. For effective
and economic operation, it is therefore imperative to ensure that neither of
these elements mix with the fuel.
Komatsu Genuine Fuel Filters
The injection-type components of the common rail engine have a complex
structure to enable fuel to be injected at high pressure. The purity level of
the fuel that the common rail system can accept needs to be higher versus conventional
systems. However, it is not possible to prevent all dirt and water from entering
the fuel, so it is critical to remove as much contaminants as possible with the
fuel filter to guarantee the durability of the fuel system.
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