Validation of Novel Light Scattering Sensors for Soot Opacity … · 2016-04-13 · Validation of Novel Light Scattering Sensors for Soot Opacity and Soot Mass ... use, traceable)

Division 3 / DP 3.2 / WG 3.2117th ETH, CCGN, Andreas Nowak

Validation of Novel Light Scattering Sensors

for Soot Opacity and Soot Mass

A.Nowak

M. Hildebrandt, G. Lindner, A. Jordan-Gerkens, A. Kuntze, S. Pratzler, N. Böse,

V. Ebert


Outline of presentation

Legal bases and framework for soot opacity

• In Europe and Germany

Research project

• Challenges and objectives

• New method for measurement of soot opacity and soot mass concentration

• Experimental setup for validation and special dilution system

Results of research project

• Correlation for high soot concentration

• Correlation for low soot concentration

Conclusion

217.07.2013

Division 3 / DP 3.2 / WG 3.2117th ETH, CCGN, Andreas Nowak 3

Periodical emission control of vehicles European Commission Directive 2010/48/EU Vehicles with type approval since 2006: On-Board-Diagnostic Older vehicles: regular - particle emission controlled via opacimeter

Measuring the opacity N (in %) or the light absorption coefficient k (m-1)

Maximum limit for exhaust of modern engines: k = 1,5 (error limit ± 0,3)

Legal Bases in Europe for Opacity

Wellenlänge562 - 572 nm

light source

exhaust inlet exhaust outlet

Detectorsoot

effective optical path length

01

IIN

Light intensity without smoke

Light intensity with smoke

0ln1

II

Lk

A

17.07.2013


Framework for vehicle inspection in Germany

Type approval of opacimeters required verification ordinance 18.9 at PTB Traceability of reference opacimeter to the SI via optical filters that are calibrated

at PTB Verification in the field via calibrated optical filters

Points of criticism since years: Insufficient resolution of type approved opacimeter k = 0,5 (± 0,3) as lower limit is too high in contrast to the regular motor type

approval (k < 0,3) No signal when measuring exhaust of modern diesel engines with particle filters

17.07.2013


Research project with ASA¹-association

Project duration: 3 years (finished in Nov.2013)

Goal: Development of a metrological background for future type approvals of new soot sensors based on light scattering

Challenges: German verification act requires devices to measure the opacity and the light

absorption coefficient Indication on the screen of devices must be k in m-1 or N in % Verification method in the field should be similar to transmission filters (easy to

use, traceable)

¹ Bundesverband der Hersteller und Importeure von Automobil-Service Ausrüstungen e.V.

17.07.2013


PTB – ASA Research cooperation

Objectives

Traceable and improved correlation between soot opacity and soot mass concentration are needed for the novel devices experimental validation!

Investigate if a general correlation between the soot opacity and the soot mass concentration

– for different particle sizes / particle number size distributions– for different light scattering sensor types– for improved uncertainty

opacimeter

soot

opa

city

soot mass concentration

light scattering soot sensor

x xx x x x

x xx x

17.07.2013


PTB-ASA research cooperationNew method for particle measurement: light scatteringBasic physical concept : The Mie Theory for light scattering

Light is scattered by small particles Scattered light intensity and angle distribution depends on the sensor angle between

laser beam and detector Detected signal of sensors depends on particle size, shape and number concentration

Typically, higher sensitivity than opacimeter at low particle concentrations17.07.2013


HiMassCAST

HEPA-filter

exhausair

propaneair

electr. magnetvalve

filter for grav. mass

opaci-meter DUT

air RVD1:1000 PASS

heated CVS

SMPSnitrogen

flow rateventuri pressure

°tpressure-, temperature

additionalports (x4)

gillibrator °tU

filter

filter

MFC

filter

heater

°t°t

compressor

°t

controlbydifferentialperssure

room temperatureair pressure

CFM

dilutioncounter flow m

ixer

°t

°t

(AVL 486)compressor

air

(AVL 439)

Modified HighMass-CAST:approx. 460 l/min105-108 part./cm3

1 mg/m³ to 500 mg/m³70 to 220 nm, monomodal

Experimental Setup for Research Cooperation

Closed loop-SMPS: flow rate: 1 to 5size range: 8 to 880 nm

PALLFLEX FILTER EMFAB TX40HI20WW 47MM :5 l/min, 2.5 to 30 min

MSS: 1mg/m³ to 300 mg/m³

Opacimeter:0.05 to 3.0 m-1

817.07.2013

Tasks: stable soot aerosol source about longer time scale accurate and precise characterization between reference systems stable and controlled aerosol size distribution to DUT


Simulation of particle trajectories

Special Dilution System – CFD Simulation PTB internal Cooperation

A boundary layer and a developing of string jet could only be avoided by the sphere

Best results for aerosol mixture by a counter flow mixer, especially for the geometry of the sphere

17.07.2013

High flow regime: Re > 30000


Overview of parameter for intercomparisonworkshop Gravimetric soot mass (m1) via filter loading

Online optical soot mass (m2) via MSS AVL 483

Light absorption coefficient (k) via reference opacimeter AVL 439 (k in m-1)

Particle number size distribution via non-commercial SMPS ( Mean Dp, nm)

CVS tunnel parameter (T, flow)

Average means values of all parameters are predefined by gravimetrical filter loading time

Only measurements for stationary conditions (no dynamical response check)

Number of participants and DUTs

Number of measured

points

Analyzed dataof intercomparison

workshop6 (14) 117 k, m1, m2, Dp, CVS

1017.07.2013


Results of intercomparison workshopPTB internal traceable systems

Very good correlation for reference systems could be observed about 3 orders of magnitude for k and m1

1117.07.2013

y = 110.07xR² = 0.9768

0

50

100

150

200

250

300

350

0 0.5 1 1.5 2 2.5 3

m1, gravim

etric

al m

ass [m

g/m³]

k, reference opacimeter AVL 439 [m‐1]

117 data points

0

25

50

75

100

125

150

0 0.25 0.5 0.75 1 1.25 1.5

gravim

etric

al m

ass [m

g/m³]


About stability of setup: see Poster Session 5: Instrumentation, no. 40: Margit Hildebrandt


Results of intercomparison workshopPTB internal systems

Also very good correlation could be observed for gravimetric soot mass vs. optical soot mass (MSS 483)

For correlation between optical soot mass and reference opacimeter are some discrepancy for the slope of the linear correlation

1217.07.2013

y = 0.9869xR² = 0.9641

0

50

100

150

200

250

300

350

0 50 100 150 200 250 300 350

MSS 483

[mg/m³]

gravimetrical mass [mg/m³]

y = 107.65xR² = 0.9564

0

50

100

150

200

250

300

350

0 0.5 1 1.5 2 2.5 3

MSS 483

[mg/m³]

k, reference opacimeter AVL 439 [m‐1]83 data points

Less data density for MSS, because of leakage in measuring cell for two days


Results of intercomparison workshopreference systems vs. new sensors for high soot loading

Quite different deviation for DUTs could observed, one device with very good correlation (master device?)

1317.07.2013

Higher variance of data points for m > 150 µg/m³ and k > 1.6 m-1 stronger variance as well as very rare data points

0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5 m, DUT1 linear fit, DUT1 m, DUT2 linear fit, DUT2 m, DUT3 linear fit, DUT3

k, D

UT

[m-1]

k, reference opacimeter AVL 439 [m-1]

y=0.94335*x, R²=0.9901, N=22(35)

y=1.37078*x, R²=0.8973, N=25(35)y=1.55313*x, R²=0.9283, N=25(35)

0 50 100 150 200 250 300 3500

100

200

300

400

500

600

700

800

900

m, DUT1 linear fit, DUT1 m, DUT2 linear fit, DUT2 m, DUT3 linear fit, DUT3

m, D

UT

[mg/

m³]


y=0.95249*x, R²=0.9825, N=22(35)

y=1.36358*x, R²=0.8776, N=25(35)y=2.25202*x, R²=0.9096, N=25(35)

soot opacity soot mass


Results of intercomparison workshopreference systems vs. new sensors for low soot loading

For data points for m < 150 µg/m³ and k < 1.6 m-1 could observed very good correlation, especially for k

1417.07.2013

For m were observed different slopes for the linear correlation in different directions

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.80.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8 k, DUT1 linear fit, DUT1 k, DUT2 linear fit, DUT2 k, DUT3 linear fit, DUT3

k, D

UT

[m-1]

k, reference opacimeter AVL 439 [m-1]

y=1.02409*x, R²=0.9949, N=20(35)

y=0.81791*x, R²=0.9963, N=22(35)y=1.00105*x, R²=0.9970, N=22(35)

0 25 50 75 100 125 1500

25

50

75

100

125

150

m, DUT1 linear fit, DUT1 m, DUT2 linear fit, DUT2 m, DUT3 linear fit, DUT3

m, D

UT

[mg/

m³]


y=1.06341*x, R²=0.9941, N=19(35)

y=0.79584*x, R²=0.9849, N=22(35)y=1.32155*x, R²=0.9812, N=20(35)

soot opacity soot mass


Conclusion

A new stable soot reference source was installed at PTB for a large range of soot mass concentration

The new light scattering sensors are a 100xmore sensitive than commercial opacimeter on the market for vehicle inspection

In general, the correlations with respect to light absorption coefficient showed for low soot concentration (k < 1.6 m-1) significantly better results than for high soot concentration (k > 1.6 m-1)

For k < 1.6 mostly very good correlation coefficient were determined between 0.98 to 0.99 for all devices

Just few sensors with good correlation for soot mass during these campaign, especially below 150 mg/m³

1517.07.2013

So far, no universal calibration method according to verification ordinance 18.9 is available to validate the sensors during field measurements no type approval


17.07.2013

Thanks for your attention


Counter flow mixer

Scale with filters

Entire setup

Gravimetrical unit

17.07.2013


Outlook: Link to real soot data (MIRA report1)Fitted linear correlation vs. measured data

The linear fit of the MIRA report was used to calculate the MIRA soot mass based of the k-values of the intercomparison workshop Implementation of conversion factor is needed

1817.07.2013

1 A. E. Dodd und Z. Holubecki im MIRA – Report No. 1965/10, Nuneaton (1965).

y = 110.07xR² = 0.9768

y = 162.55x

0

100

200

300

400

500

0 0.5 1 1.5 2 2.5 3

gravim

etric

al m

ass [mg/m³]

k, reference opacimeter AVL 439 [m‐1]0

20

40

60

80

100

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

gravim

etric

al m

ass [m

g/m³]



Outlook: Link to real soot data Difference between diesel and propane soot

TEM analyze showed more clustered structure for diesel soot than propane soot (longer aggregates) Differences in density

Effect on optical parameter like refraction index, primary particle sizes, fractional dimension

Influence of relative humidity in the exhaust

Further research project is needed

1917.07.2013

Diesel soot after DPF

Propane soot of HIMASS-CAST at 66,81 nm


Special Dilution System – CFD Simulation PTB internal Cooperation

20

Quantification of mixing process behind the mixing unit about ∆M= Mmax – Mmin

Best results for gas mixture by a counter flow mixer including a sphere

Side view of different geometries for the mixing ratio of two gases (white for dilution air at 0.0 for 450 l/min and black for CAST exhaust at 1.0 for 450 l/min )

High flow regime: Re > 30000

17.07.2013


Non – commercial SMPS system

2117.07.2013

100 150 200 250 3000

100

200

300

400

N=103

raw

con

cent

ratio

n [#

/cm

³]

Dp [nm]

MEAN PNSD10 100 1000

0

500

1000

1500

2000

2500

10:30 11:40 12:50 14:00 15:10 16:20 17:30 18:40200.0

200.5

201.0

201.5

202.0

202.5

203.0

203.5

204.0

204.5

205.0

205.5

206.0

mean=203.783±0.481

single values floating average (x6) mean average

STD

Dp

[nm

]time [hh:mm]


k vs. m vs. Dp,mode diameter

2217.07.2013

Comparison between k‐ value of reference opacimeter (AVL 439) and mass concentration from gravimetrical mass and Gaussian fit parameter of PNSD for mode diameter

Documents

Validation of Novel Light Scattering Sensors for Soot Opacity … · 2016-04-13 · Validation of Novel Light Scattering Sensors for Soot Opacity and Soot Mass ... use, traceable)