Transient RDE gaseous emissions from a hybrid & other vehicles Mark Peckham, Harry Bradley, Matthew Duckhouse, Martin Irwin & Matthew Hammond (Hybrid vehicle courtesy of Byron Mason, Loughborough University)
Introduction Company summary Engineering services division Emissions calibration Engine and after-treatment systems evaluation Using dyno simulation of vehicle drive cycles, and vehicle chassis rolls Products division Develop, manufacture and support specialised fast response analyzers and other emissions-related equipment Gaseous pollutants (HC, NOx, COx) Particulates DPF & GPF testing system
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Real world Driving Emissions (RDE) more realistic than European Drive Cycle 4
New European Drive Cycle 5
HFR500 fast FID
Why use fast response analysers? 7
PFI gasoline cold start 20000 Transient HC measurement 0-105 seconds of FTP 75 drive-cycle 60 18000 Maximum HC occurs during Cold-Start. Fast FID accurately resolves magnitude of initial transients in real time Fast FID Engine Out 50 [HC] as ppm propane 16000 14000 12000 10000 8000 Individual cylinder exhaust events visible in engine out HC Fast FID Tailpipe Conventional bench Slow FID Engine Out analyzer Desired Speed (mph) 40 30 20 Vehicle speed (mph) 6000 10 4000 0 2000 0 0 20 40 60 80 100 Time since start (seconds) -10
Fast response Real World Driving Emissions kit 9
Basic advantages of using fast on-board analyzers T 10-90% = 10ms at 30mph corresponds to 14cm resolution whereas typical on-board (PEMS) analyzers with T 10-90% = 3 seconds yields 42 metres resolution Two channels allows both pre- and post-catalyst measurements simultaneously checks catalyst conversion efficiency Easy and accurate correlation with Engine Control Unit parameters 10
The main causes of emissions 11
3-way catalyst for most petrol engines Gasoline/petrol engine perfect running conditions are with air:fuel ratio of 14.7 : 1. This is known as lambda = 1 Lambda < 1 is rich (excess fuel) Lambda > 1 is lean (excess air) The 3-way catalyst requires lambda = 1 and needs to be hot! 12
Typical engine transients Cold start Accelerations Decelerations (decel fuel shut-off) Gear changes 13
Negotiating the humble speed bump! 4 3 2 1 1. Decelerate, combustion stops 2. Clutch in and engine starts (idle) 3. Accelerate away from speed bump DIRECTION OF TRAVEL 4. Change up gear and head for speed limit 14
Speed bump Euro 4 gasoline
Vehicle motion = distance = velocity = = 16
Euro 6 gasoline plug-in hybrid, purchased October 2017 Vehicle courtesy of Byron Mason, Loughborough Univ 17
Added instrumentation Gas sample points Thermocouples 18
Sample pipe and thermocouple path 19
TfL West London Route with PHEV vehicle [NO] tailpipe (ppm) Generally very good for NOx emissions, but Trouble at Swiss Cottage and in West London over speed bumps Bus lane convergence 20
Main emissions contributors Neasden Swiss Cottage Montpelier Park Euro 6 NEDC limit is 0.06g/km of NOx TfL route yielded 0.09g/km, 70% of which was caused by these 3 sites 21
What to watch for in videos During accelerations, engine start delayed first by electric traction Engine switch-on causes PHEV cough Lambda shows PFI lean excursion causing NOx breakthrough Engine off/on frequently (especially over consecutive speed bumps) Best viewed with audio on (poor quality but helps perception of electric vs engine split) 22
Swiss Cottage Video omitted due to size 23
Swiss Cottage [NO] tailpipe (ppm) Deceleration fuel shut-off then insufficient rich purge at acceleration leads to breakthrough Acceleration round corner Long idle at traffic lights then pull-away Slow-down to let car in then accelerate Acceleration after corners 24
West London residential speed bumps Video omitted due to size 25
Map of Montpelier Park NOx pollution hot spots 26
Kensington 27
Kensington Video omitted due to size 28
Euro 5 diesel passenger car 29
Euro 5 diesel passenger car NOx emissions 30
Piccadilly NOx
Piccadilly Video omitted due to size 32
Joining M1
Joining M1 Video omitted due to size 34
Euro 6 diesel passenger car equipped with SCR 35
Cambridge RDE route 36
General overview test 1 - Urban 37
RDE cumulative NO and NOx test 1 - Urban NO 2 was about 1/2 of total cumulative NOx High levels at start and end of urban Cumulative NOx Cumulative NO Distance Total: 4.082 g Total: 2.032 g Total: 20.466 km 0.199 g/km 0.099 g/km LIMIT: 0.08 g/km Conformity: 2.48x limit 38
Cambridge route vehicle comparisons 39
Cambridge route vehicle comparisons Variations in climate, congestion, battery state of charge etc etc will greatly affect the above treat comparisons with great care! 40
On-going and future work Repeats of the same (look for repeatable hot-spots ) Time of day and congestion effects CO and HC London cab Bus really? Stop/start engine control good or bad? 41
In conclusion Vehicles are generally getting cleaner RDE presents unpredictable transients Fast response analyzers can measure transient emissions and correlate these with other engine parameters Observed emissions issues are solvable using conventional means Mostly appear to be lambda control related 42
Contact details Dr. Mark Peckham Cambustion Ltd J6 The Paddocks 347 Cherry Hinton Road Cambridge CB1 8DH United Kingdom msp@cambustion.com 43