EMISSIONS AND TIER 4
magazine continues its series on emission standards with this summary of emerging technologies. This is a comprehensive list of the available technologies to reach interim T4/Tier 4 compliance.
Engine manufacturers identifi ed the fuel injection system as a major focus point to help meet the EPA non-road diesel engine emission levels for iT4/Tier 4. Fuel injection systems affect the diesel engine’s fuel consumption, torque, noise and emission levels.
High-Pressure Common-
Rail Fuel System (HPCR) The fuel injection system is a major area of focus for advancement toward clean-operating diesel engines. HPCR is an advanced fuel-injection design that regulates fuel pressure and injection timing.
Fuel Pressure
• The pump applies high pressure to fuel (22,000 to 34,000 psi).
• The common rail stores pressurized fuel. • The injectors deliver fuel to the engine.
Injection Timing
The electronic control unit (ECU) precisely controls each injector to allow multiple fuel injections during each combustion cycle.
HPCR Benefits
High pressure transforms fuel into an extremely fi ne mist as it leaves the injectors. Fuel mist combusts (burns) more thoroughly.
Cleaner exhaust: When fuel combusts more thoroughly, less of it is left over in the exhaust after combustion. The result is cleaner exhaust.
When fuel is injected multiple times during each combustion cycle, the combustion lasts longer to create more energy and lower peak engine cylinder pressure.
Better performance: Creating more energy during combustion results in more torque output from the engine.
More operator comfort: Lower peak engine cylinder pressure reduces engine noise levels.
After-Treatment Systems
The good news for non-road engine manufacturers is this: Car and light-duty truck manufacturers complied with EPA
10 WorkSaver | SPRING 2011
INTERIM TIER 4 AND TIER 4 TECHNOLOGIES WorkSaver®
DIESEL OXIDATION CATALYSTS AND DIESEL PARTICULATE FILTERS
ILLUSTRATED
regulations years earlier and developed technologies that are now being used on non-road engines. These after-treatment systems take the diesel engine exhaust that has already been created by the engine and clean it further by using one or a combination of the following:
• Catalytic oxidation • Heat
• Filtering
• Diesel exhaust fl uid (DEF) Treatment Systems
These after-treatment devices use fi ltering, heat and catalytic oxidation to lower emissions in diesel engine exhaust. They’re commonly combined with one another in a single canister. Together they lower many emissions but, most importantly, they reduce particulate matter.
DOC/DPF Systems
The diesel oxidation catalysts (DOC) Engine exhaust is transformed by the DOC to reduce particulate matter. The DOC is a special catalyst that reacts with engine exhaust upon contact. The reaction transforms particulate matter emissions in the exhaust into harmless substances such as water and carbon dioxide. See Fig. 1.
The diesel particulate fi lter (DPF) Engine exhaust is fi ltered by the DPF to reduce particulate matter. The DPF is a special ceramic wall fl ow fi ltration system that further separates particulate matter from the engine exhaust. See Fig. 2.
DPF regeneration To keep the DPF clean and working effi ciently, the high temperature of the exhaust itself is used to remove accumulated particulate matter from the DPF. This DPF cleaning process is called regeneration. See Fig. 3.
Selective catalyst reduction (SCR) Engine exhaust is transformed by SCR to reduce nitrogen oxides (NOx
ammonia- and water-based liquid called diesel exhaust fl uid (DEF). Combining exhaust with DEF causes it to react with a SCR catalyst. This reaction turns harmful NOx
into harmless nitrogen and water vapor. See Fig. 4. ). SCR uses an EXHAUST
Diesel Exhaust Fluid (DEF)
DEF & NOx react with the catalyst forming non-harmful nitrogen and water vapors
Fig. 4 EXHAUST
Containing Diesel Particulate Matter
Heavier particulate matter concentration goes IN
DOC/DPF — Diesel Oxidation Catalyst/ Diesel Particulate Filters
DOC/DPF — Diesel Oxidation Catalyst/Diesel Particulate Filters Fig. 1
Diesel exhaust from engine combustion flows out of engine
Cleaner diesel exhaust with lower particulate matter concentration comes OUT
Fig. 2
Lower particulate matter concentration comes OUT
Heavier particulate matter concentration goes IN
Barriers exist to ensure exhaust passes through fi lter walls.
Particulate matter is captured in the Diesel Particulate Filter (pictured above).
Wall fl ow fi lter (pictured right) Dirty exhaust (brown arrows) passes through fi lter walls. Particulate matter is left behind and cleaner exhaust (blue arrows) exits.
DPF Regeneration
Diesel exhaust lo particulate matt concentration O
Fig. 3
Diesel exhaust particulate ma concentration
To keep the DPF clean and working effi ciently, the high temperature of the exhaust itself is used to burn accumulated PM off of the DPF. This DPF cleaning process is called regeneration.
SCR — Selective Catalyst Reduction System SCR — Selective Catalyst Reduction System
Diesel exhaust from engine combustion flows out of engine
Cleaner diesel exhaust with lower NOx
comes OUT
DEF mixes with exhaust and flows into catalyst
Tier 4 questions? Visit
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DPF DOC
DPF DOC
DEF T
ank
SRCTLS
C AAYT
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