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Performance Evaluation of Diesel Particulate Filters during Loading

from Clean

K. StJ Reavell & T. HandsCambustion Ltd, J6 The Paddocks, Cambridge CB1 8DH UK.

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ContentsNeed for rig based DPF testing Equipment Used

– Cambustion DPG – DPF Test System– AVL 415 Smoke meter– VPR + CPC system– Filter test housing

System capability & validation dataMeasurements of DPF Behaviour

– Δp vs soot load– Repeatability & reproducibility– DPF Filtration efficiency measurements– Mass based and PMP number based efficiency– Backpressure vs flow and temperature

Regeneration comparison with engine behaviour

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Motivation

Issues with engine testingcost of engine, dynamometer + infrastructurerepeatability of engine based testingcompounding of warm up and soot load formation

Solution : rig based testing: DPG developed from Johnson Matthey’s ISG technology.

durability fuel economy impact

backpressure based regen strategies

move to catalysed DPFsdp vs soot mass testing

Stage 5 particle number limits

optimised substrate porosity

filtration efficiency measurement

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System Configuration

DPG

AVL 415Smokemeter

VPRCPC

TSI 3022

Monitoring Instruments

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Housing

Adaptor

Filter under test

Filter Test Housing for Uncanned Substrates

Housing

Adaptor

Filter under test

Filter

Clamping nut (4)

AdaptorClamping plate

Seal

Flow

Close up of sealing:seal is aluminiumized glass fibre fabric with stainless steel mesh or ceramic rope filling

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Operating Capability

DPG Operating Temperature : Flow Rate Capability

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600 700

DPF flow kg/hr

DPF i

nle

t te

mp

era

ture

ºC

regeneration mode

maximum system loading capability

standard loadingconditions

burner off conditions

2 – 20 g/h loading rate

150 / 300 mbar backpressure(1 / 2 blowers)

Loading, regeneration and cold flow testing modes

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Transmission Electron Microscopy Images of Diesel Soot

Light Duty Diesel engine soot

Dr Peter Harris, Centre for Advanced Microscopy, University of Reading

200nm

Cambustion DPG soot

200nm

Heavy Duty Diesel engine soot

200nm

Khalid Al Qurashi, EMS Energy Inst, Penn State Uni

Primary particle size close to 20nm for DPG and engine soot Morphology appears similar

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Backpressure vs Soot Load

Except for initial transient due to warm up differences, rig backpressure is close to soot produced from transient cycle operation of engine.

Backpressure vs Soot Load : Different Engine Conditions

0

20

40

60

80

100

0 5 10 15 20 25 30 35

Total Soot (g)

Nor

mal

ised

Pre

ssur

e dr

op

Transient CycleHigh Load Steady State

Backpressure vs Soot Load : Engine vs DPG

0

20

40

60

80

100

0 5 10 15 20 25 30 35

Total Soot (g)

Nor

mal

ised

Pre

ssur

e dr

op

Transient CycleHigh Load Steady StateDPG

variation in soot backpressure with engine condition

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Empty filter, cold flow repeatability3 parts, nominally identical, no soot load repeated 5/6 times45ºC, 400 kg/haverage standard deviation 0.14 mbar / 0.37%production variation clearly detected

35.5

36

36.5

37

37.5

38

38.5

39

39.5

back

pre

ssu

re a

t 400 k

g/h

45 C

part #1mean 37.9 σ 0.114 mbar

part #2mean 37.0 σ 0.153 mbar

part #3mean 39.0 σ 0.151 mbar

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Reproducibility of Dp vs Soot LoadAccurate Measurement of Dp vs Soot Load Characteristic:

–‘no soot’ warm-up phase followed by soot load–discriminates warm-up from pore filling effects in initial pressure rise

Two nominally identical partsLoaded to approximately 15gLoaded on 4 DPG systems – on site and at CambustionRepeated loads on one instrument Soot load established by weighing at > 200ºCBackpressure measurements referred to common conditions: 240ºC, 250

kg/hr and corrected for differences in barometric pressure

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Delta P vs Soot Load Repeatability 4 Instruments, 2 parts

Instrument : instrument repeatability

0

10

20

30

40

50

60

70

80

90

0 2 4 6 8 10 12 14 16Corrected soot mass (g)

Bac

kpre

ssur

e m

bar

part 1part 2

2 parts, nominally identical are clearly distinguished on all instruments.Uncoated 2.8 l SiC filters

pore filling and cake formation behaviour clearly quantified

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Repeatability Test Results

In these tests, measurements for backpressure of a given part at given load were all within ± 2% across all systems, 95% confidence interval < ± 3%

Test Part System Number

2 g backpressurembar

deviation from mean 12 g backpressurembar

deviation from mean

1 1 38.0 +0.9% 69.4 +0.5%

1 2 38.1 +1.1% 68.2 -1.4%

1 3 37.2 -1.2% 68.7 -0.6%

1 1 37.4 -0.8% 69.3 +0.2%

1 4 37.7 0% 70.0 +1.3%

mean = 37.3 mbarσ

= 0.39 mbarmean = 69.1 mbarσ

= 0.70 mbar

2 1 35.3 +0.8% 67.0 +0.4%

2 3 34.6 -1.2% 66.8 0%

2 2 35.1 +0.4% 66.5 -0.4%

mean = 35.0 mbarσ

= 0.24 mbarmean = 66.8 mbarσ

= 0.24 mbar

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DPF Filtration Efficiency Measurement

Controlled rig conditions allows the relatively slow AVL smokemeter (paper blackening type, sample time 10 – 120s) to resolve particulate concentration downstream of DPF.Correlated with soot mass measurement.

Stage 5 like CPC + VPR system produces number based filtration efficiency.CPC does not have 23nm cut, but DPG does not produce solid particles in this size range.

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Mass based filter efficiency with AVL 415

65

70

75

80

85

90

95

100

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Soot load (g)

Fil

trati

on

Eff

icie

ncy

%

type 2 #1 2.5l

type 2 #2 2.5l

type 3 #1 2.5l

type 3 #2 2.5l

type 1 4l

Filtration Efficiency with AVL415

Three different filter types, all uncoated: 2 examples of 2Different filtration behaviour during pore filling phaseAll terminate at >99.8% efficiency

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DPF Filtration Efficiency - DPG

65

70

75

80

85

90

95

100

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

soot load g

Num

ber

bas

ed f

iltr

atio

n e

ffic

iency

%

CPC+VPR filtration efficiency

CPC+VPR system gives faster resolution of change in filtration Penetration straight after regen provides a significant fraction of the

overall cumulative vehicle emissions.

first 0.5g load gives ~43% emissions of full

32g regen

interval

terminal efficiency ~99.8% for this filter – relatively low

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Effect of flow rate & temperature on DPF Backpressure

Compare measured dp vs flow and backpressure with Darcy and turbulent assumptions

Backpressure vs Temperature - Loaded 5 g/l

86.0

88.0

90.0

92.0

94.0

96.0

98.0

100.0

102.0

190.0 200.0 210.0 220.0 230.0 240.0 250.0

Temperature C

bac

kp

ress

ure

mb

ar

loaded

Darcy

turbulent

compressible viscous

Backpressure vs Temperature - Empty

27.5

28.0

28.5

29.0

29.5

30.0

30.5

31.0

31.5

32.0

32.5

190.0 200.0 210.0 220.0 230.0 240.0 250.0

Temperature C

bac

kp

ress

ure

mb

ar

empty

Darcy

turbulent

compressible viscous

Backpressure vs Flow - Loaded 5 g/l

70.0

75.0

80.0

85.0

90.0

95.0

100.0

105.0

110.0

115.0

240.0 250.0 260.0 270.0 280.0 290.0 300.0 310.0

flow rate kg/h

bac

kp

ress

ure

mb

ar

loaded

Darcy

turbulent

compressible viscous

Backpressure vs Flow - Empty

20.0

22.0

24.0

26.0

28.0

30.0

32.0

34.0

36.0

38.0

240.0 250.0 260.0 270.0 280.0 290.0 300.0 310.0

flow rate kg/h

bac

kp

ress

ure

mb

arempty

Darcy

turbulent

compressible viscous

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Comparison to Engine – regeneration

DPG MSL regen 330C for engine soot (thin line) and DPG soot (thick line)

250

350

450

550

650

750

1150 1200 1250 1300 1350 1400 1450 1500 1550 1600 1650

Real time (Secs)

Tem

pera

ture

(C)

0

20

40

60

80

100

120

DP

(mba

r)

Engine DPF in (degC)

DPG DPF in (degC)

Engine 115mm (degC)

DPG 115mm (degC)

Engine 200mm (degC)

DPG DPF out (degC)

Engine DPF out (degC)

DPG 200mm (degC)

Engine DPF dP (mBar)

DPG DPF dP (mBar)

Max temperatures similar

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Repeatability of Regen on DPG at 7.5 g/l soot; 2 tests; temperatures at inlet, exit + 3 locations in brick

DPG MSL regen from 330C and repeat

250

350

450

550

650

750

1150 1200 1250 1300 1350 1400 1450 1500 1550 1600 1650

Real time (Secs)

Tem

pera

ture

(C)

0

20

40

60

80

100

120

DP

(mba

r)load #1 DPF in (degC)

load #2 DPF in (deg C)

load #1 DPF 115mm (degC)

load #2 DPF 115mm (degC)

load #1 DPF 200mm (degC)

load #2 DPF 200mm (degC)

load #1 DPF out (degC)

load #2 DPF out (degC)

load #1 DPF DP (mBar)

load #2 DPF DP (mBar)

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ConclusionsThe Cambustion DPG allows testing of Diesel Particulate Filters at conditions

representative of engine operation.The backpressure vs soot load characteristic is shown to be repeatable for a

given filter to within less than 3%, but sample : sample variation is seen.Filtration efficiency can be measured either with an AVL415 smokemeter or

CPC + VPR system. Due to size sensitivity, efficiency measurements are different for the two techniques.

The penetration during initial loading for this filter would almost double the number emissions if averaged over all cycles

– and if such complete regeneration is obtained in normal use.Variation of backpressure of a DPF with flow and temperature lies

somewhere between laminar (Darcy) and turbulent assumptions: – cannot ignore inertial effects at entry / exit face when considering whole filter behaviour. – variation with soot load surprising

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Acknowledgements

Collaborators at Cambustion:Tim Hands Ray Brand Mark Rushton Nick Collings Bruce Campbell

Johnson Matthey and other DPG customers

And the organisers of the ETH conference

Thank you.

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Testing Uncanned Parts: Cambustion FTH Filter Test Housing

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Maximum DPF Flow Rate vs Backpressure(ambient temperature)

0

50

100

150

200

250

300

350

0 100 200 300 400 500 600 700 800 900

DPF flow rate kg/h

Max

DPF

Bac

kpre

ssure

mBar

pressure : flow capability with turbo blower option

basic system

Backpressure Capability

Backpressure of over 300 mbar is possible at typical soot loading conditions

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Effect of Soot Load on Exothermic temperature rise at DPF exit: 4, 6 and 8 g/l

Regen Exotherm vs Soot Load g/l

0

100

200

300

400

500

600

700

800

-140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100

time (s) post cut to idle

tem

p C

elsi

us

Inlet 8gInlet 6gInlet 4gPost 8gPost 6gPost 4g

exotherm increases with soot load on DPF