Transient RDE NOx emissions from gasoline and diesel vehicles Mark Peckham, Harry Bradley, Matthew Duckhouse, Martin Irwin Note: many videos were included in this presentation; please ask Mark Peckham (msp@cambustion.com) for these separately if required
Fast gas analyzers for alignment of emissions with engine conditions
HFR500 fast FID
PFI gasoline cold start 20000 18000 Maximum HC occurs during Cold-Start. Fast FID accurately resolves magnitude of initial transients in real time Transient HC measurement 0-105 seconds of FTP 75 drive-cycle Fast FID Engine Out 60 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 RDE configuration 12V battery Easily changeable by customer between lab and RDE configuration One or two channels (on short conduits) Integration with other vehicle/engine parameters (lambda, speed, load) so that transient emissions can be correlated. Real-time calculation of cumulative gram emissions Cope with climatic conditions Durable and vibration insensitive T 10-90% response time <10ms Minimal changes to vehicle
Sampling and data collection Fast [NO] sampling point: 40mm before silencer/muffler Engine Control Unit data recorded from vehicle s own OBD port and logged alongside fast [NO] Software was developed to combine the vehicle s exhaust mass flow rate with the fast [NO] to provide fast cumulative gram emissions, providing insight in to the causes of short-duration emissions spikes which may not be visible with slower equipment.
User-interface
RDE - Lab - RDE 1. RDE on-road cycle logging emissions and ECU data 2. Auto-identify problems and associated engine conditions 4. Adjust vehicle s emissions calibration 3. Translate problem transients on to dyno for repeatability 9
Comparison of fast RDE CLD500 with PEMS
Candidate Vehicle Information
PEMS vs fast RDE comparison Testing performed at MAHLE Powertrain s EU6 emissions test facility - VCA certified facility Simulated RDE Testing performed on MAHLE Emissions Development Centre - RDE Limit cycle for trip dynamics and cumulative positive gradient MAHLE supplementing the current RDE capability in Q2 2018 with the Real Driving Emissions Centre - Fully climatic -40 C to +50 C - Full hypobaric chamber 0-5000m - 4WD facility MAHLE 12
Decel. fuel shut-off - Engine Operation
Decel. fuel shut-off with restart of combustion
Prolonged Acceleration (Engine Operation) High engine torque Low engine speed Scavenging employed
Prolonged Acceleration (Fast NO) 0% conversion when no reductants are present. Fresh air from scavenging event skews Lambda lean Scavenged oxygen strips reductants from catalyst Oxygen storage limit reached. Breakthrough occurs.
Prolonged Acceleration (Tailpipe Emissions) Enhanced clarity of emissions transients.
Speed bump Euro 4 gasoline
Euro 5 diesel 19
TfL West London route emissions overview
Piccadilly NOx
Piccadilly
Joining M1
Joining M1 24
Euro 6 diesel 25
Sampling point post-scr 26
Cambridge RDE route 27
General overview test 1 - Urban 28
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 29
SCR system activating from cold Large spike on vehicle s NOx sensor at wake-up 30
SCR NOx sensor settling time Vehicle s NOx sensor continues to over-read for a further ~700s note aftertreatment working well despite transient urban conditions 31
NOx breakthrough begins later on urban section
Aggressively-negotiated speed bumps During these harsh transients, most of NOx is NO2! (NOx-NO = NO2)
Effect of each urea injection pulse motorway phase
2017 Euro 6 gasoline plug-in hybrid (vehicle available courtesy of Byron Mason, Loughborough University) 35
Cambridge Air quality route 36
Focus on 2 major transients sections 37
Comparison of two transients 38
Cumulative mass calculated from OBD exh mass flow 39
Comparison of two transients in detail Engine firing frequency Lean excursion causes catalyst breakthrough 40
NOx breakthrough in a single street 41
Are vehicle comparisons valid? Variations in climate, congestion, battery state of charge etc etc will greatly affect the above treat comparisons with great care! 42
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 43
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) 44
Swiss Cottage 45
West London residential speed bumps 46
In conclusion 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 47
Contact details Dr. Mark Peckham Cambustion Ltd J6 The Paddocks 347 Cherry Hinton Road Cambridge CB1 8DH United Kingdom msp@cambustion.com 48