High spatio-temporal resolution pollutant measurements of on-board vehicle emissions using ultra-fast response gas analyzers

Abstract

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.

Dynamic shape factor and mixing state of refractory black carbon particles in winter in Beijing using an AAC-DMA-SP2 tandem system

“…Effective density of the PSL particles was determined by the AAC-DMA system at 1.08-1.12 g/cm 3 , approximately 3-6% higher than material density (1.05 g/cm 3 ), as shown in Figure 2. Our result was consistent with the experiment using DOS (Bis-2-ethylhexyl sebacate) aerosol by (Irwin et al, 2018). For Aquadag particles, To avoid fragmentation of Aquadag particle clusters at dramatic motion in the high-speed rotating cylinder of the AAC, a DMA-AAC tandem experiment was tested.…”

Identifying NOx Hotspots in Transient Urban Driving of Two Diesel Buses and a Diesel Car

“…Previous work measuring emissions from both a Euro 4 gasoline and a Euro 5 diesel car have shown that speed bumps can cause substantial emissions of NOx [12]. Similar trends were seen from the Euro V bus in this work.…”

“…Recently, ultra-fast response gas analysers have been used to provide high spatio-temporal resolution RDE data from vehicles [11,12]. Such analysers, which have a response time of a few milliseconds, have been used for a long time in engine development, for example in cyclically resolved engine measurements [13,14], cold start [15,16], and emission reduction [17,18].…”

A large eddy simulation of the dispersion of traffic emissions by moving vehicles at an intersection

“…The highly variable nature of pollution concentrations within the urban environment is due to many factors including weather conditions, traffic flow rates, proximity to passing vehicles, vehicle type, isolated high pollution sources including highly polluting vehicles. The use of onboard measurement systems (Irwin et al 2018) and portable emission measurement systems (PEMS) (O'Driscoll et al 2016) have shown that vehicle emissions are dominated by high emission peaks during vehicle acceleration or gear changes, further contributing to the heterogeneity of concentrations within urban streets. In order to accurately evaluate the health impact of pollutants inhaled within urban areas beyond measurement field studies, the occurrence of these acute concentration events must be modelled.…”

“…In order to realistically model traffic induced dispersion, it is important to use a realistic emissions model for the vehicles. It is well known that the emissions of petrol and diesel vehicles within an urban environment are highly variable, with high emission peaks occurring during high engine loads (O'Driscoll et al 2016, Irwin et al 2018, for example when a vehicle accelerates from standstill. The emissions model COPERT (Computer Program to Calculate Emissions from Road Transport), which is widely used across Europe, estimates the average emission factors as functions of a vehicle speed only, with the average speed along a road often used.…”