Abstract. Existing ultra-fast response engine exhaust emissions analyzers have been
adapted for on-board vehicle use combined with GPS data. We present, for the
first time, how high spatio-temporal resolution data products allow transient
features associated with internal combustion engines to be examined in detail
during on-road driving. Such data are both useful to examine the circumstances
leading to high emissions, and reveals the accurate position of urban air
quality “hot spots” as deposited by the candidate vehicle, useful for
source attribution and dispersion modelling. The fast response time of the
analyzers, which results in 100 Hz data, makes accurate
time-alignment with the vehicle's engine control unit (ECU) signals possible.
This enables correlation with transient air fuel ratio, engine speed, load,
and other engine parameters, which helps to explain the causes of the
emissions “spikes” that portable emissions measurement systems (PEMS) and
conventional slow response analyzers would miss or smooth out due to mixing
within their sampling systems. The data presented is from NO and
NOx analyzers, but other fast analyzers (e.g. total hydrocarbons
(THC), CO and CO2) can be used similarly. The high levels of
NOx pollution associated with accelerating on entry ramps to
motorways, driving over speed bumps, accelerating away from traffic lights,
are explored in detail. The time-aligned ultra-fast analyzers offer unique
insight allowing more accurate quantification and better interpretation of
engine and driver activity and the associated emissions impact on local air
quality.
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