Brake emission measurement-what we can mesure?
Dekati LtdIntroduction• “Road transport is one of the most important sources of urban pollutantemissions”• “Given the more stringent legislation foreseen for exhaust emissions,brake and tyre emissions have been estimated to become the main
contributor to PM road transport sector emissions”– Brakes = 10x tailpipe emissions• “At present, airborne PM generated from different brake systems iscurrently not regulated mainly owing to the lack of a standardized
sampling procedure and measurement techniques.”

Towards the ranking of airborne particle emissions from car brakes – a system approach.
Perricone et al. Proc IMechE Part D: J Automobile Engineering 1–17, 2016
© Dekati Ltd.

PMP – Particle Measurement Program
UNECE Informal Group Non-exhaust particle emissions• PMP group is working on the development of a suggested common test
procedure for sampling and assessing brake wear particles:– The selection/development of a braking test cycle appropriate for the investigation of particle
emissions from brake wear
– selection of an appropriate methodology for particles generation and sampling– selection of the appropriate instrumentation for the measurement and characterization of
brake wear particles• JRC has established a Task Force focusing on the particle measurement
related aspects comprising the experts in this specific field© Dekati Ltd.

What can we measure?
What we would like to measure?
What we should measure?
Why we are measuring?

Why? Oh Why?
Curiosity

Aerosol science
Modeling

Particle formation

ScienceFriction

Health effects

Chemistry
Enviromental effects
Elemental analysis

Material science

Test development
Durability
Tribology
Braking process

R&DEmissions© Dekati Ltd.

Emission factorsRoutine tests

Product development
Product testing

Future Regulation

Future complianceWhy?
• There are multiple good reasons/needs• We need harmonisation• We cannot accommodate all needs• We should think as extensively as possible(but only as much as is needed)© Dekati Ltd.

What can we measure?

What we can?
• Estimate, measure and model the losses and representativeness ofsampling• Minimize losses from 10 nm to 10 um• Measure total number (PN) in real time
• Measure total cumulative mass (PM10/PM2.5/PM1)• Measure number size distribution 10 nm to 10 um in real time
• Measure mass size distribution from 10 nm to 10 um• Collect particles for analysis (size fractionated)• Measure density of particles as function of particle size
• Measure volatile particles (within limits)© Dekati Ltd.

What we cannot (or is too impractical)
••
•
•
•
•

Measure above 10-15 um
Measure/handle all volatiles accurately
Measure all particles below 10 nm -> nucleation mode
Measure mass size distribution in real time
Avoid losses completely
Simulate the real world emission conditions© Dekati Ltd.

What should we measure?

Aerosol Physics: particle formation
Gas to particle formation

Mechanical processes

High temperature/
Temperature drop

Primaryparticles

Break-up, fragmentation

Condensation growth
FAST!
Coagulation/
agglomeration

Gravitation
Sedimentation,
washout

Diffusion

FAST!

FAST!
Nucleation mode

© Dekati Ltd.

Accumulation mode

Coarse mode© Dekati Ltd.

What should we?
Questions

Notes

Size range of interest
Above 10 um

Difficulties sampling (losses), environmental effects

Below 23 nm?

Difficulties sampling (losses), volatiles/nucleation

Size Distribution

Distribution vs. total

Measurand
Particle Number (PN)

Dominated by ultrafines

Particle Mass (PM)Dominated by coarse fraction

Surface area (LDSA)

Health effect related

Size definition

Aerodynamic or electrical mobility diameter?

Volatile fraction

Need to characterize? Sample conditioning

Time resolution

1 Hz? Actual time response of system?

© Dekati Ltd.

What should we?
Questions

Notes

Size range of interest
Diffusion

Flow rate vs. sampling line diameter

Inertial losses

Isokinetic sampling, length of sampling line

Thermophoretic/electric

Conductive measurement lines

Sample collectionFull flow/partial

Flow control, sample extraction

Sample analysis

What analysis methods are used? Requirements

Dilution

Concentration range

Conditioning

Removal of the volatiles, thermodenuder?

Flow and enclosures

Physical construction, representativeness

Volume of sampling system

Time constant, memory effect© Dekati Ltd.

Beware: here be Dragons:•Brake emission is not tailpipe emission––••
•
•
•
•
•
•
•

© Dekati Ltd.

There are lot of coarse particles (by mass)
Nucleation mode has solid particles

Underestimation of importance of isokinetics or diffusional losses
PM10/PM2.5 = Aerodynamical diameter
Electrical mobility to aerodynamical to optical particle size calculations or transformations (orbetween any different size definitions)
Number size distribution to mass size distribution calculation
Instrument calibrations which are dependent on particle properties or size distribution”Black box” calculations
Concept of volatiles is tricky
Mass above 10 um is tricky too
Nucleation mode PN is very tricky below 23 nm (accuracy and sharpness of cut-off ordetection of instruments)

Existing setup for brake measurement• ELPI+– High Resolution or High Temperature
options• DLPI– Gravimetric & analysis• Dilution or conditioning– Optional dilution/thermodenuder• eFilter– Total cumulative mass concentration,
mass correlation together with ELPI+– Routine measurements (future)© Dekati Ltd.

Measurement solutions• ELPI+ (HT/HR)– Real-time PN/LDSA/PM– Distribution• eFilter– Real-time LDSA
– Total mass

© Dekati Ltd.

Less complex– Gravimetric mass
– Distribution– Analysis

More information• DLPI+Real-time signal

Wide size distribution© Dekati Ltd.

Gravimetric massand analysis

DLPI+ for gravimetric and analysis
••
•
•
•
•
•
•
•

© Dekati Ltd.

Cascade low-pressure impactor
14 size fractions
16 nm – 10 µm
Ø25 mmNo filter stage
10 lpm flow rate
40 mbar low pressure
Max 50 °C
Can be upgraded into an ELPI+™

eFilter™ mass comparison, diesel exhaust
Standard gravimetric filter measurement
Real-time signal throughout the filter sampling
Real-time PM accumulation during different stages of themeasurement
eFilter™ and gravimetric PM
180

1200

160

eFilter

140PM Mass800

120100600

8060400

4020020001020Test #Niemelä et al. 26th CRC Real World Emissions Workshop
Data courtesy by Ford Motor Company300PM Mass [µg/m3]

1000

eFilter™ current [fA]•••

Brake Emission Measurements: Dekati® ELPI®+

Large particles >1µm
from brake wear

High Resolution ELPI®+
Particle number concentration

Braking pattern
Small particles < 300nm
from brake wear

© Dekati Ltd.

Large particles >1µm
from brake wear

High Resolution ELPI®+
Particle mass concentration

Braking pattern© Dekati Ltd.

Dekati measurement solutions
ELPI+, real-time, distribution, PN, PM, LDSA
eFilter, PM, LDSA real-time
DLPI+, PM, distribution
PM10/2.5/1 Impactor, distribution, PM

Sampling and dilution of sample up to 450C

© Dekati Ltd.

Cyclone, PMThank you for your attention!
www.dekati.com