Transcript Northeast States CLEAN AIR ACADEMY

Advanced Mobile Source Training Course
MS 201 - Diesel
III. Emission Testing and Diagnostics of Diesel
Engines
© 2005 Northeast States for Coordinated Air Use Management (NESCAUM)
Overview
• This section of the course will discuss:
– The purposes for and the characteristics of a good
emission test
– The development of emission testing for diesel
engines
– Recent developments in Not-To-Exceed standards
and portable emission testing equipment
– On-board diagnostics for heavy-duty diesels
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Why Emission Tests?
• Accurate estimates of emissions are needed to:
– Certify that vehicles and engines are designed and
built to meet emission standards
– Assess the durability of these designs over time
– Develop emission factors from in-use vehicles
– Support enforcement action against manufacturers
– Identify individual high emitters that can be
repaired
– Evaluate the effectiveness of retrofit programs
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A Good Emission Test
• A good emission test:
– Accurately represents the duty cycle of a vehicle or
engine in-use
– Accurately measures the pollutants of concern
– Is repeatable
– Is affordable
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Barriers to Testing Diesels
• Light duty diesels can use the same chassis procedures
as gasoline vehicles but require additional filter
procedures to measure particulate
• High PM levels require more frequent calibration and
maintenance of test equipment
• Engines for heavy-duty and non-road applications
operate over vastly different duty cycles
• Engine bench testing and emission measurement is
more complicated and expensive than chassis testing
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Certification Testing
• Before 1990:
– Heavy duty engines were certified with a 13-mode
steady-state test
– The concentration of each pollutant, the fuel flow,
and the power output in each mode were
measured
– A smoke test was also conducted
– Essentially no in-use testing was performed
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Certification Testing
• After 1990:
– The 13-mode test was replaced with a “transient”
dynamometer driving cycle
– Particulate was collected on filters and weighed
– Each engine’s driving cycle was based on a “map”
of its capability, that is, its ability to produce a
certain amount of power at engine speeds from
idle to full open throttle
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The Need for Better Testing
• In the 1990’s electronically controlled engines
defeated emission controls while cruising on the
highway
• In-use smoke testing couldn’t control for the
particulates of concern
• Need to control non-road engines
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Real World vs. Certification Testing
Real World vs Lab
US06
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FTP
FTP
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Real World Emissions
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The “Ultimate” Diesel Emission Test
• Refer back to the basic requirements:
– Accurately reflect actual use
– Accurately measure pollutants
– Repeatable
– Affordable
• Prevent defeat devices
• Enable in-use testing
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Recent Developments
• Standards established for non-road engines
• Both transient and steady-state tests required
• An off-cycle test added – NTE (not-to-exceed standard
applied to most operating modes)
• Development of portable emission measurements for
in-use testing
• Complete revision and standardization of heavy-duty
certification tests proposed by EPA
• Development of a world-wide certification test
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NTE Standards and Testing
• Historically, EPA relied on a defeat device prohibition
to help ensure that vehicles and engines would meet
standards in use
• A defeat device is any auxiliary emissions control
device (AECD) (electronic, mechanical or otherwise)
which reduces the effectiveness of the emission control
system that is in effect under the specific test
conditions but not in effect under normal operating
conditions, except:
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NTE Standards and Testing
• Except:
– If substantially included in the certification test
– If needed for protection from accident or damage
– If needed for engine starting
• Implementation of the defeat device regulation often
requires case-by-case determinations
• Electronically controlled engines have many AECDs
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NTE Standards and Testing
• The NTE standard is applied in addition to the existing
certification test cycle and standards and the existing
defeat device prohibition
• NTE expands coverage beyond the driving cycles and
ambient temperatures in the certification test
• It provides certainty to the manufacturers about the
acceptability of AECDs
• NTE can be tested in-use
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NTE Standards and Testing
• NTE contains several key concepts:
– A defined engine operating region (engine speeds
and loads)
– Defined ambient operating conditions
(temperature and altitude)
– Defined in-use operating conditions (minimum of
30 seconds duration)
– Specified numerical emission limits (1.25 x the
primary emission standard)
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NTE Standards and Testing
(US EPA)
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NTE Standards and Testing
(US EPA)
NTE Altitude & Temperature Regions
110
Ambient Temperature (degrees F)
100
90
80
70
NTE
Maximum temp. - 100 deg. F at sea-level
down to 86 deg. F at 5,500 feet
60
50
40
Minimum temp. - no lower bound
Altitude - all altitudes less than or equal to
5,500 feet
30
20
-
1,000
2,000
3,000
4,000
Altitude (Feet relative to sea-level)
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5,000
6,000
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NTE Standards and Testing
(US EPA)
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Manufacturer In-Use Testing
• Pilot program in calendar years 2005 and 2006
• Minimum of 5 to a maximum of 10 vehicles per
engine family
• All engine families over 1500 sales are tested over a
four year period
• Portable emission measurements of gaseous and
particulate emissions
• Test vehicles from at least two owner sources
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Portable Emission Measurement
• Design requirements:
– Simple installation on a wide variety of vehicles
– Unattended operation
• Weather and tamper proof
• Low power consumption
• Remote communication
– Multiple measurement capabilities
• Flow measurement
• Ambient conditions
• Engine speed, temperature, etc.
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PEMS – History of Development
• EPA investigated and developed on-highway
application – ROVER
• Photograph from EPA
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ROVER
(US EPA)
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ROVER
(US EPA)
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Portable Emission Measurement
(US EPA)
• EPA continued development for non-road
applications – SPOT
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Portable Emission Measurement
• West Virginia University -MEMS measures CO2 and
NOx –additional work on particulate with a quartz
crystal microbalance
• Commissioned by the engine manufacturers as a part
of the consent decree
• WVU also operates a portable dynamometer for
trucks and buses
• Capable of simulating up to 55,000 lbs inertia weight
and equipped with full scale dilution tunnel
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WVU Transportable Laboratory
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Portable Emission Measurement
• Ride along vehicle emission measurement system
(RAVEM) developed by Engine, Fuel and Emissions
Engineering, Inc.
• Measures gaseous emissions and samples particulate
on a filter
• Recently used in the Mexico City pilot project to
retrofit city buses
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RAVEM
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Particle Number Measurement
• Many different approaches evaluated in the UNECE
Particulate Measurement Programme (PMP)
• Approaches include:
– Scanning Mobility Particle Sizer (SMPS)
– Electrical Low-Pressure Impactor (ELPI)
– Condensation Particle Counter (CPC)
– Thermodesorber (TD)
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Particle Number vs. Mass
• Portable PM mass measurement is still not available
(except for RAVEM)
• Europe has taken the approach of setting a numberbased standard – Swiss-based VERT
• U.S. is still hoping to have an on-board measurement
of mass ready for the 2007 manufacturer in-use tests
• This subject remains under discussion and evaluation
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Heavy-Duty OBD
• CARB has adopted a rule for heavy-duty OBD to take
effect in 2010
• Diesel engine monitors:
– Fuel system
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•
•
•
Fuel pressure control
Fuel injection quantity
Fuel injection timing
Closed loop system function
– Misfire
• 2010-2012 identify continuous misfire at idle
• 2013 identify any misfire causing 1.5 x standard increase
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Heavy-Duty OBD
• Diesel engine monitors
– EGR system
• Detect faults in the flow rate, response rate, and cooling
system performance before 1.5 x emissions increase
• Monitor closed loop system function
– Boost pressure control
• Detect faults before 1.5 x emissions increase
– Under and over boost malfunctions
– Slow response
– Charge air undercooling
• Monitor closed loop system function
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Heavy Duty OBD
• Diesel engine emission control technology monitors:
– Hydrocarbon catalyst
– NOx catalyst (SCR)
– NOx adsorber
– PM filter
• Additional monitors:
– Exhaust gas sensors, variable valve timing system
– Cooling system; PCV system
– Electronic components
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Diesel Emission Testing - Summary
• Testing using an engine dynamometer is the most
accurate but very expensive and cumbersome
• Using a heavy-duty chassis dyno requires a large
capital investment, and cannot accommodate most
non-road equipment
• Current and proposed regulations aim to provide
complete control across all applications and the entire
operating cycle
• PEMS are under development but appear not to
approach the accuracy and repeatability of engine test
benches
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Go to: Projects/Academy
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