BRAKE DUST MEASUREMENTS-SELECTION OF THE MOST SUITABLE SAMPLING METHOD

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Melvyn Wilkins
5 years ago
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2 Agenda 1 Motivation 2 Comparison of exiting sampling concepts 3 Horiba-AUDI concept 4 Selection of functional parameters 5 Findings 6 Outlook

3 Motivation

4 Motivation Two main drivers Health Effect Dirty Rims Rim of my car ETC/ACC Technical Paper 2009/1 June 2009 Source:

5 Motivation: Concern about Nano-particle Fine particles (diameter < 2.5 μm) may reach deep into the lung. Alveolar Deposition Fraction Nasal Large particles Oral Trachea Bronchial Alveolar Ultra-fine particles Alveolar Duct Nano-PM Dangerous For Health? Source: Ishihara

6 Activities in Europe

7 Activities in Europe Which activities are ongoing at HORIBA Europe? HORIBA Europe R&D for Brake Emissions First measurements done with MEXA 1000 SPCS in HORIBA Darmstadt in Joint project with University of Ilmenau Since than, exchange with University of Ilmenau. They are using MEXA 2100 SPCS. In 2014 HE hired two R&D Engineers for a Brake Dust Project. In 2015 joint measurements with University of Ilmenau and HORIBA have been done -> Correlation between two test stands In December HORIBA started the joint work with OEM for measuring particles from the Brake Test Stand Exhaust System using 10nm SPCS vs. PMP SPCS. In 2016 joint work with TU Ilmenau and OEMs will be / is being progressed. Since 2 nd half of 2015 huge interest from OEMs and Tier 1 / Tier 2.

8 Activities in Europe Deliverables 2015 Eurobrake: Inertia Brake Dynamometer Dust Particle Measurement, Michael Wirth, Prof. Klaus Augsburg & Hannes Sachse (TU Ilmenau), Dmytro Lugovyy & Peter Lienerth (HORIBA Europe) Europe) SAE Brake Colloquium: INERTIA BRAKE DYNAMOMETER DUST PARTICLE MEASUREMENT, Michael Wirtz, Dmytro Lugovyy & Peter Lienerth (HORIBA Europe),Prof. Klaus Augsburg & Hannes Sachse (TU Ilmenau) 2016 Eurobrake: Sampling of Brake Dust Particles, Hannes Sachse, Prof. Klaus Augsburg, David Hesse, Felix Wenzel (Technische Universität Ilmenau, Germany), Dmytro Lugovyy, Matthias Schröder (HORIBA Europe GmbH) Brake Colloquium: BRAKE PARTICLE EMISSION MEASUREMENTS A NEW DYNAMOMETER APPROACH, Dr.-Ing. S. Gramstat, J. Münchhoff, AUDI AG, Dr.rer.nat. D. Lugovyy, M. Schröder, HORIBA Europe GmbH Patent Application: Device for detecting and measuring brake dust

9 Motivation: PMP Protocol for car engine Cold diluter (PND2) with room temperature air, to minimize particle formation by re-nucleation and particle loss by thermo-pherotic CVS tunnel, with carbon and HEPA filter Evaporation tube (ET) 300 to 400 ºC, to evaporate volatile particle Pre-classifier cut-off: > 2.5 mm VPR Condensation particle counter (CPC),cut-off: < 23 Unstable Heated diluter (PND1) with 191 ºC air, to suppress the formation of volatile particle GRPE Informal Document: GRPE Rev.1

10 Motivation: Brake dust, first approximation -PMP Protocol Cold diluter (PND2) with room temperature air, to minimize particle formation by re-nucleation and particle loss by thermo-pherotic GRPE Informal Document: GRPE Rev.1 Evaporation tube (ET) 300 to 400 ºC, to evaporate volatile particle Pre-classifier cut-off: > 2.5 mm SPCS VPR Condensation particle counter (CPC),cut-off: < Heated diluter (PND1) with 191 ºC air, to suppress the formation of volatile particle Stable Unstable

11 To be solved Measurements equipment Test procedure Sampling procedure

12 Aim of the project Developing new particle measuring principle for analysis of Brake Dust pollutions

13 To be solved by Brake Dust Project Building up new measurements set-up Investigation of chemical and physical properties of brake dust particles Definition of test procedure Role of test parameters and modification of sampling system Measurements equipment Test procedure Sampling procedure

14 Selection of functional parameters: Measurement equipment

15 Measurement equipment Definition of measurement range Measurement of particle size distribution. Modification exiting and/ or developing of new equipment Probe treatment Role of volatile content Dilution of the probe and sampling velocity Physical and chemical properties of Brake Dust particles. Investigation of morphology and chemical properties of Brake Dust particles Modification of measurement equipment

16 Measurement equipment Definition of measurement range Measurement of particle size distribution. Modification exiting and/ or developing of new equipment Probe treatment Role of volatile content Dilution of the probe and sampling velocity Point of our research Physical and chemical properties of Brake Dust particles. Investigation of morphology and chemical properties of Brake Dust particles Modification of measurement equipment

Measuremetns of Particle Number Aerodynamic Particle Sizer Optical system with two partially overlapping laser beams to detect coincidence.

Instrument does effectively limit the effect of coincidence on particle-size distributions.

17 Measuremetns of Particle Number Aerodynamic Particle Sizer Optical system with two partially overlapping laser beams to detect coincidence. One signal is generated with two crests Time between the crests provides aerodynamic particle-size information. Instrument does effectively limit the effect of coincidence on particle-size distributions. Lower detection limit 370nm CPC The saturator provides saturated butanol vapor that mixes with particles in the condenser. Particle growth occurs in the condenser. The detector counts the electrical pulses generated from the light scattered by the particles. Lower detection limit 5-23nm Particle is illuminated by a sheet of laser light. DustTruck Gold coated spherical mirror captures a significant fraction of the light scattered by the particles and focuses it on to a photo detector. The voltage across the photo detector is proportional to the mass concentration of the aerosol over a wide range of concentrations. Lower detection limit 100nm

Measurements of particle size distribution Electrometer-based spectrometer Features Unipolar corona discharge to place a prescribed charge on each particle proportional to its surface area.

18 Measurements of particle size distribution Electrometer-based spectrometer Features Unipolar corona discharge to place a prescribed charge on each particle proportional to its surface area. The charged aerosol is introduced into a strong radial electrical field inside a classifier column. Particles are drifted through a sheath flow to the electrometer detectors. Particles are detected at different distances down the column, depending upon their electrical mobility. Concentration Low detection limit: from #/cm 3 Upper detection limit: 1x10 7 #/cm 3 Size Low detection limit: 5 nm Upper detection limit : 1µm

to: 0 #/cm 3 Upper detection limit : 3x10 8 #/cm 3 Size

19 Measuremetns of Particle Number-Horiba Solution for Exhaust Legislation Concentration Low detection limit up to: 0 #/cm 3 Upper detection limit : 3x10 8 #/cm 3 Size Low detection limit : Upper detection limit : nm 2,5µm

20 Measuremetns of Particle Mass-Horiba Solution for Exhaust Legislation DLS-7000 PMP-conform

21 dn/dlog(dp) Definition of measurement range: Influence of sub-23 nm particle 2,5E+06 2,0E+06 1,5E+06 1,0E+06 5,0E+05 Section km/h 10 bar 20 bar 30 bar 40 bar 50 bar 60 bar 70 bar 80 bar 4,0E+07 3,0E+07 2,0E+07 1,0E+07 Section km/h SAE BC bar 20 bar 30 bar 40 bar 50 bar 60 bar 70 bar 80 bar 5,0E+07 4,0E+07 3,0E+07 2,0E+07 1,0E+07 Section km/h 10 bar 20 bar 30 bar 40 bar 50 bar 60 bar 70 bar 80 bar 0,0E Particle size, nm 0,0E Particle size, nm 0,0E Particle size, nm Eurobrake2015 EFP-008 Appearance of ultra-fine particle depends on wheel speed rather than on brake pressure or temperature Ultra-fine particles demonstrate first peak around 13 nm Disagreement between DMS and SPCS was observed

22 Definition of measurement range: Influence of sub-23 nm particle Aerosol sample-splitter after the exhaust duct standard SPCS (23 nm) versus prototype SPCS (10 nm) Comparison of measured particle concentration using a standard SPCS 2000(red line ) and a sub-23 nm SPCS (black line). AK-Master Zoomed time history of PN using a standard SPCS 2000 (red line) and a sub-23 nm SPCS (black line). AK-Master No significant variations of qualitative time history Difference: same order of magnitude but factor varies between 2 and 6 Ratio PN sub23 /PN standard between single brake events is almost stable (around 1,5) Prototype with cut-off D 50 at 10 nm is used in our research

23 Definition of measurement range: Influence of sub-23 nm particle Electrometer based Mean per test particle concentration #/cm 3 Comparison of measured particle concentration using Palas particle generator Comparison of particle concentration measured during brake tests Electrometer based total Electrometer based 23nm ECE 17 inch AKM Inertia 81kg/m 2 ECE Cu-free 19 inch SPCS Electrometer based NAO 19 inch AKM Inertia 110kg/m AKM Inertia 110kg/m 2 AKM Inertia 81kg/m WLTP like Inertia 81kg/m 2 AKM Inertia 81kg/m CPC-based Different factors can affect results of measurements for electrometer based instruments Only CPC based instruments fulfilled exhaust legislation requirements Electrometer-based techniques can be used for indicative measurements only

24 Comparison of exiting sampling systems

25 Sampling of Brake Dust Hose Sampling Box Environmental chamber Exhaust duct Pro Easy to install Different sampling points are possible Pro Easy to install Reproducibility of results Fast response on emissions events Reduction of background particle concentration level Possibility to use for RDE Pro Calculation PN per km Reproducibility of results Reduction of background particle concentration level Pro Calculation PN per km Reproducibility of results No modification of brake dyno is required Probe homogeneity Reduction of background particle concentration level Probe homogeneity Contra Reproducibility of results Calculation PN per km High level of background particle concentration Probe homogeneity Contra Probe homogeneity Calculation PN per km Limited number of applications Contra Complicated installation Limited number of applications Probe homogeneity Emissions response is averaged over time and volume Contra Special requirements to air ventilations system Emissions response is averaged over time and volume

26 Sampling of Brake Dust Hose Sampling Box Environmental chamber Exhaust duct Pro Easy to install Different sampling points are possible Contra Reproducibility of results Calculation PN per km High level of background particle concentration Probe homogeneity Pro Easy to install Reproducibility of results Fast response on emissions events Reduction of background particle concentration level Possibility to use for RDE Contra Probe homogeneity Calculation PN per km Limited number of applications Pro Horiba focus Calculation PN per km Reproducibility of results Reduction of background particle concentration level Contra Complicated installation Limited number of applications Probe homogeneity Emissions response is averaged over time and volume Pro Calculation PN per km Reproducibility of results No modification of brake dyno is required Probe homogeneity Reduction of background particle concentration level Probe homogeneity Contra Special requirements to air ventilations system Emissions response is averaged over time and volume

Environmental chamber much lower to measured in exhaust duct Measurements with Sampling box is

27 Prticle number per test Sampling concepts: Comparison 7x10 12 AK Master Exhaust Chamber 6x10 12 AK Master 5x x10 12 AK Master 3x10 12 WLTP 2x x10 12 WLTP 0 PN measured using Environmental chamber much lower to measured in exhaust duct Measurements with Sampling box is not representative Strong particle coagulation is expected for Environmental chamber and Sampling box

Prticle number per test dn/dlog(dp) Sampling concepts: Comparison Exhaust 7x10 12 6x10 12 5x10 12 AK Master AK Master Exhaust Chamber 10 5 10 4 10 3 10 2 10 bar 20 bar 30 bar 40 bar 50 bar 60 bar 70

28 Prticle number per test dn/dlog(dp) Sampling concepts: Comparison Exhaust 7x x x10 12 AK Master AK Master Exhaust Chamber bar 20 bar 30 bar 40 bar 50 bar 60 bar 70 bar 80 bar x10 12 AK Master 10 6 Chamber 3x x x10 12 WLTP WLTP bar 20 bar 30 bar 40 bar 50 bar 60 bar 70 bar 80 bar Particle size, nm PN measured using Environmental chamber much lower to measured in exhaust duct Measurements with Sampling box is not representative Strong particle coagulation is expected for Environmental chamber and Sampling box

29 concentration N(t) #/cm 3 concentration N 0 /concentration N (t), % Sampling concepts: Comparison Polydisperse coagulation N t = N tn 0 K 0 where N 0 is original particle concentration t is time, K 0 is coagulation coefficient, calculated as K 0 = 4kTC c 3η Geometric standard deviation (GSD) 2.5. Strong coagulation is calculated for Environmental chamber and Sampling box 1x10 8 1x10 8 9x10 7 8x10 7 7x10 7 6x10 7 5x10 7 7x10 6 6x10 6 5x10 6 4x10 6 3x10 6 2x10 6 1x10 6 Exhaust duct is validated as sampling point! 0 chamber duct 39 kmh box 51 kmh box 39 kmh box 13 kmh size, nm Size, nm chamber duct 39 kmh box 51 kmh box 39 kmh box 13 kmh

30 Testing and validation of Horiba-AUDI concept

31 Experimental set-up AUDI-Horiba 17 2 piston frame-design caliper, low steel (ECE) brake pads (AUDI A8) 2 sampling points Inside testing chamber Exhaust duct 31

# particle/ cm 3 Testing procedure: Air Flow effect 2x10 6 flow3300_duct flow3300_chamber 1x10 6 1.5x10 5 1.0x10 5 5.

32 # particle/ cm 3 Testing procedure: Air Flow effect 2x10 6 flow3300_duct flow3300_chamber 1x x x x10 4 2x10 6 1x flow2700_duct flow2700_chamber 1.0x x x x10 6 flow930_duct flow930_chamber 5.0x time,s Particle emission depends on air flow sequence Increasing air flow leads to reduction of residuals in brake dynamometer cabin

33 Particle concentration #/cm 3 Testing and Validation of Horiba-AUDI concept Implementation of housing : Airborne collection 1.4E E E E E E+04 Duct Reference without Housing Refernece with Housing Air flow 3500 m 3 /h Improving of sampling 2.0E E E E E E E E E time, s Without housing With housing Application of housing allow to collect 100% Brake Dust Airborne Horiba-AUDI concept is validated for PN measurements!

34 Testing and Validation of Horiba-AUDI concept Implementation of Housing: Set-up temperature Improving of sampling Without housing With housing Application of housing does not change set-up temperature Temperature of Brake Pads stay 220ºC even if rotor temperature is 500ºC

Testing and Validation of Horiba-AUDI concept Implementation of Housing: Air Flow effect Improving of sampling Without housing With housing Horiba-AUDI

35 Testing and Validation of Horiba-AUDI concept Implementation of Housing: Air Flow effect Improving of sampling Without housing With housing Horiba-AUDI concept is validated for PN measurements! Application of housing is strongly improved reproducibility of test results Particle emission depends on air flow sequence

36 Selection of functional parameters: Testing procedure

37 Testing procedure Testing conditions Air velocity and air quality. Position brake in car Vehicle load and environmental conditions Test cycle Conditioning of brake pad and brake disk Developing of new cycle based on driving conditions Modification of existing cycle Object of Investigations Particle Number per test(pn) Particle Mass(PM): gravimetrical and/or on-line.

38 Testing procedure Testing conditions Air velocity and air quality. Position brake in car Loading of the car and environmental conditions Test cycle Conditioning of brake pad and brake disk Developing of new cycle based on driving conditions Modification of exiting cycle Point of our research Object of Investigations. Particle Number per test(pn) Particle Mass: gravimetrical and/or on-line

39 Testing procedure: New Bedding cycle AK Master without sections 1-3, 5-7, 11 and Air flow: 430, 930, 2700 and 3450 m 3 /h No RDE cycle intended yet!

Background Particle Concentration #/cm 3 Testing procedure: Inlet Air quality and Stabilization of Particle Emission Air flow 2700 m 3 /h Without H13 filter With H13 Filter 8000 6000 4000 2000

40 Background Particle Concentration #/cm 3 Testing procedure: Inlet Air quality and Stabilization of Particle Emission Air flow 2700 m 3 /h Without H13 filter With H13 Filter Application of H13 filter leads to strong reduction of particle background concentration as well as stabilization of background level Particle emission was stabilizing by third repetition. For tests measured with inlet air velocity 2700 m 3 /h variation of PN is not higher as ±20%. 0 Test number

41 Testing procedure: Volatile content and role of inertia Measurements equipment demonstrate reproducibility within ±5%. Increasing of inertia strongly increases particle emission No volatile content with T 190 C was observed in emission from ECE pads

42 Particles [x10 6 /cm 3 ] Coefficient of Friction µ Particles [x10 6 /cm 3 ] Testing procedure: Section 8 and Memory effect Beginning of the test 0,6 0,5 Friction coefficient 0,4 0,3 Time [s] 0,2 After Section4.5 0, Time [s] before section 4 after section 4 Time [s] Particle concentration changes drastically for same brake conditions Friction coefficient does not change Effect is reproducible and observed at 4 different air velocities

43 Testing procedure: Particles [x10 6 /cm 3 ] Particles [x10 6 /cm 3 ] Particles [x10 6 /cm 3 ] Particles [x10 6 /cm 3 ] Disk speed Coefficient of Friction µ Section km/h Pressure and disk speed effect Section km/h 0,6 0,5 Friction coefficient 0,4 0,3 0,2 Section km/h 0, Time [s] 4_2 4_3 4_4 4_5 Section km/h Time [s] Brake pressure Particle concentration increases rather with increasing disk speed than brake pressure. Friction coefficient does not change Effect is reproducible and observed at 4 different air velocities

44 Testing Procedure: Pressure and disk speed effect - Particle size distribution Zoom Transition Temperature= ºC Bi-modal particle size distribution observed for ECE brake pads Concentration of nano-particles increases drastically after brake pressure reach 40 bar, Transition temperature~140ºc Air flow can affect particle emission

Testing Procedure Friction coefficient does not differs between bedding and brake pressure section Particle emission changes drastically at

45 Testing Procedure Friction coefficient does not differs between bedding and brake pressure section Particle emission changes drastically at the same time Global parameters can not be used for characterization of BPE Effect is reproducible and observed at 4 different air velocities

46 Particle #/cm 3 Particle #/cm 3 Testing Procedure: Section 9 and Temperature effect 3x10 4 Exhaust duct 3x10 5 2x10 5 Air Flow 930 m 3 /h 2x10 4 1x ,0x10 4 1,5x Chamber 1x ,0x10 5 1,5x10 5 1,0x10 5 5,0x Air Flow 2700 m/h 3 0, ,0x10 4 5,0x10 3 1,2x10 5 8,0x10 4 4,0x10 4 Air Flow 3300 m 3 /h time, s 0, time, s Strong reduction of BPE for disk temperature T 350 C. Effect is reproducible and observed at 4 different air velocities Effect is reproducible and observed at 3 different sampling points by 2 different brake dynos

47 Testing procedure Role of disk and brake pads temperature Particles [x10 6 /cm 3 ] Temperature [ C] Particles [x10 6 /cm 3 ] Section km/h Transition Temperature= ºC Particles [x10 6 /cm 3 ] Section km/h No Transition Temperature!!! Time [s] Transition Temperature= 350ºC Disk transition temperature depends rather on applied loading then on conventional heating No transition temperature for brake pads is observed

48 Finding's Most suitable sampling point for PN was defined Horiba-AUDI set-up provide 100% sampling of Brake Dust Airborne Testing parameters( air flow, air quality, etc.) can affect results of PN measurements SPCS particle counter was modified according special requirements for Brake Dust Emission measurements and provide fast response, high accuracy and reproducibility for measurements of Brake Dust Emission The comparison of particle measurements performed on two different dynamometers is possible Particle emission from set of new brake pads and disk can be stabilized during short time. Particle emission was measured in range 1x particle/cm 3 Particle emission depends on inertia, disk temperature, wheel velocity and less on applied pressure Horiba-AUDI set-up provide good reproducibility for particle emission measurements Horiba-AUDI set-up can be used for R&D research on material of brake pads and disks as well as for brake certification Horiba-AUDI set-up can be installed nearly at every brake dynamometer without big modification

49 Outlook Continue research on definition of sampling point and Evaluation role of probe dilution and sampling velocity Evaluation role of non-brake parameters- velocity of air flow, direction of flow, humidity etc. Comparison of brake pads produced of different materials- ECE, NAO, Ceramic Investigations on composition of brake dust emissions Robin Round at 2-3 Labs Test feasibility of PM for brake airborne measurements Break Wear was reported to be reponcible for mechanical stability of brakes as well as NVH effects-material research on this topic will siginificantly extend markt capacity from certification to material R&D

New Instruments from GRIMM

New Instruments from GRIMM Markus Pesch Symposium at Stockholm, 01.11.2016 1 Outline Motivation for new Aerosol measurement devices Objectives for measurements of particle number and sizes GRIMM EDM 665