10.30 Mark Peckham.pdf

1. How “gross emitting” vehicles
can spoil local air quality
Mark Peckham & Jamie Parnell

2. Why worry about gross emitters?
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• 3.9% of trucks emit 50% of all NOx *
• Significant contribution to urban pollution hot spots
• Modern diesel vehicles can be very clean
• Even “good” vehicles can emit high levels of NOx under certain conditions
• Some gross emitters may be “legitimate” (older models), some may have been tampered with
• Nominally clean Euro 6 vehicles may gain access to CAZ on the basis of their number plate but then
produce large amounts of pollution
* CARB 2020 PEAQS project

3. Cambustion’s background (founded 1987)
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• Fast response analyzers to measure transient emissions (cold start, gear changes etc)
• Development work with engine companies to develop catalytic converter systems
• Recent adaptation of products to measure transient ambient air quality

4. Roadside measurements of passing gross emitter
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5. Portable ambient NO&NO2 detection system
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6. Typical roadside NOx data set
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7. Interest in identifying “gross emitters”
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• Law enforcement and government to catch
SCR system “defeat devices”
• Local government to check which vehicles
are polluting the most (in Clean Air Zones)

8. SCR (Selective Catalytic Reduction) for lowering diesel NOx
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Converts NO to NO2
NH3 + NO2 reacts to
nitrogen and water
Ammonia “slip catalyst”
NOx sensor
Must be hot (>~180C) to work efficiently

9. NOx tailpipe ppm comparisons, TfL West London route
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Instantaneous [NOx] (ppm)

10. Cumulative NOx comparisons TfL route
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Euro 5 diesel, 937mg/km:
no NOx catalyst
Euro 6b PHEV petrol, 95mg/km
– two 3-way catalysts
Euro 6d-TEMP diesel,
60mg/km – SCR

11. Modern SCR additional measures
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Converts NO to NO2
NH3 + NO2 reacts to
nitrogen and water
NH3 “slip catalyst”
NOx sensor
Must be hot (>~180C) to work efficiently
“Post-injection”
of fuel
“NOx adsorber”
temporarily traps NOx
until system warms up

12. Portable fast response NO&NO2 analyzer for pursuit
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13. “Pursuit” measurements
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14. Chase study of bus stop manoeuvre
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15. When & where legit SCR systems can emit…
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Cold start and first few minutes of driving
• Leaving home
• Leaving place of work
• Leaving car parks
• Leaving bus depot (e.g. 60% of NOx from a 2 hour journey emitted within first 5 mins)
After long periods of deceleration or idle
• Accelerating away from the foot of a hill
• Bus stops (!)
• Pulling away from traffic lights
• Sudden acceleration in congested traffic

16. The effect of speed bumps on NOx
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17. Defeat devices (emulators)
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18. Why tamper with an SCR system?
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• No more SCR maintenance costs
• Pass MOT (warning lights suppressed)
• No need to buy any more AdBlue
• Claims of better fuel economy (save fuel) through disabling of catalyst heating etc
…but can still enter CAZs if number plate allows

19. Tampered-with SCR system
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Converts NO to NO2
NH3 + NO2 reacts to
nitrogen and water
NH3 “slip catalyst”
NOx sensor
A tampered-with SCR system may end up emitting a large proportion of primary NO2

20. Cyclist NOx exposure
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21. Child exposure to NOx
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22. msp@cambustion.com
jparnell@cambustion.com
Thank you
https://www.cambustion.com/industries/air-quality