Automated Repeatable DPF Testing with the Cambustion DPG

�� CAMBUSTION ��

Automated Repeatable DPF Testing with the Cambustion DPG

Kingsley ReavellCambustion


Contents

� DPG concept and production instrument

� Soot mass vs ∆p

– Soot generation repeatability

– test to test & stability within test

– instrument to instrument

� DPF flow testing –

– effect of vacuum vs pressure testing

� Regeneration

– measurement of effect of varying soot load

� DPF efficiency testing

– smoke meter and number count based


Challenges posed by DPF testing

� Repeatability

– Engine soot rate (g/hr) variability – affected by DPF backpressure

– Behaviour of soot depends on engine operating mode

– Weighing of soot variable with conditions

� Cost

– Representative testing requires DPF loading with engines on transient cycles

– Expensive transient dynamometer facilities

– High manpower requirements

� Control of conditions

– Flow rate, temperature, soot rate, passive regeneration all compounded

– Makes discrimination of effects of different factors very difficult


Cambustion DPG

� System for DPF testing:

– ∆p vs soot load characteristics

– Filtration efficiency

– Regeneration behaviour

� Diesel burner for soot generation 2 – 20 g/hr

� Testing at engine – like conditions

– load over 250ºC, 300 kg/hr

– flow test up to 600 m3hr-1

� Automated execution of test protocols

– unattended operation


DPG Configuration

Airflow is sucked through DPF

– soot generator unaffected by DPF backpressure

– system at sub-ambient pressure for inherent safety

Primary & Secondary airflows & fuel flow control soot generation

– tertiary airflow & temperature allows independent control of DPF conditions


Demonstration of Soot Rate Repeatability

Test ProtocolPart loaded 5 times over the course of 1 weekEach time loaded for 2 hours @ 10 g/hr nominal, in 5 phasesSoot mass recorded at the end of each phase.

To minimise variability in weighing:

– measurements performed on uncanned brick

– weighing performed ~200 C

– DPG can hold part in elevated temperature state until operator is ready to weigh.


Soot Generation Rate Repeatability

Repeatability of Soot Load Between and During Tests.

0

2

4

6

8

10

12

14

16

18

20

0 24 48 72 96 120

Time (mins)

So

ot

load

(g

) Test E

Test D

Test C

Test B

Test A


Mass Repeatability – Numerical Data

3.53.73.63.63.696 - 120

3.53.83.84.03.772 – 96

3.53.73.53.53.748 – 72

3.63.73.93.83.524 – 48

3.73.83.73.63.60 – 24

Test ETest DTest CTest BTest A

g load / phase

-4.5%+1.0%-1.7%-1.7%-1.7%96 - 120

-4.5%+3.7%+3.7%+9.2%+1.0%72 – 96

-4.5%+1.0%-4.5%-4.5%+1.0%48 – 72

-1.7%+1.0%+6.4%+3.7%-4.5%24 – 48

+1.0%+3.7%+1.0%-1.7%-1.7%0 – 24

Test ETest DTest CTest BTest A

Mean load 3.66 g / phase

deviation from mean

standard deviation 3.7% of mean, max 9.2 %


Repeatability of Dp vs Soot Load

� Accurate 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

� Same part loaded to 25g nominal� Loaded on 2 DPG instruments� 3 tests on one instrument � Soot load established by weighing at 200ºC� Backpressure measurements corrected to common conditions: 240ºC,

250 kg/hr


Soot Load Test Schedule

1. Stabilise airflows2. Light burner and warm DPF under test without soot3. Hold DPF at temperature until operator is ready for zero weight4. Weigh DPF5. Relight burner and warm DPF back up6. Switch to soot loading condition and load for prescribed period7. Switch to no soot condition and hold DPF at temperature for weighing8. Weigh DPF


Features of Loading Test

Loading test : Dp vs time

0

20

40

60

80

100

120

140

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

time (s)

DP

F b

ackp

ress

ure

war

m u

p

wei

gh

war

m u

p

load

wei

gh

hold

at

tem

p


Dp Test : Test Repeatability

Instrument : Instrument and Test : Test Repeatability

0

20

40

60

80

100

120

140

0 5 10 15 20 25

corrected soot load (g)

eq

uiv

ale

nt d

elta

P (

no

rma

lise

d to

24

0C

, 25

0 k

g/h

r)

D1 Test 1

D1 Test 2

D1 Test 3

P Test


DPF Flow Testing

DPG testing based on inlet p at atmosphere, exhaust sub atmosphericcompare with engine or blown bench test with exhaust at atmosphere.

∴ overall pressure in DPF is lower in DPG than application⇒ lower density⇒ higher volumetric flow⇒ higher measured backpressure

For comparability, consider pressure drop in element dl of DPF:

02

2

=++ dlPA

fuudu

dp

ρ

momentum term: small in walls of DPF

viscous pressure drop


Corrections between DPG and Blown Tests

Pressure drop from whole DPF

– f = friction factor

– [A/P3] – length scale (hard to define for comparison between different DPFs)

Allows conversion of ‘sucked’ DPF measurements to blown conditions.

– small effect at low ∆p

To relate DPG measurements to significantly different conditions, consider that f is a function only of Reynolds Number:

So if we want to relate DPG measurements to engine tests at different temperatures (hence viscosities), the mass flow is scaled.

Note that ambient temperature temperature flow tests are therefore equivalent to engine tests at a higher flow rate.

( ) [ ]PAT

lmTfppp

ss

soutin 3

222

ρ&

=−

µπm

d

&4Re=


Correction of Flow Sweep Data

Raw measurements: blown bench & DPG

0

5

10

15

20

25

30

35

40

45

50

0 100 200 300 400 500 600 700

Flow rate m3n/hr

Bac

kpre

ssur

e m

bar

Blown bench measurements

DPG measurements at 50 C

DPG measurements ambient temp


Compressible correction to blown bench conditions

0

5

10

15

20

25

30

35

40

45

50

0 100 200 300 400 500 600 700

Flow rate m3n/hr

Bac

kpre

ssur

e m

bar

Blown Bench Measurements

DPG measurements at 50 C

DPG measurements ambient temp

Correction of Flow Sweep Data


DPF Regeneration

DPG can easily generate temperatures in 600ºC to 800ºC range.Achieved by:

– Increased fuel flow

– Reduced total air flow

Primary airflow increased to prevent soot production.Operation is still overall lean.

Operation in the region around 600 ºC produces a relatively gentle, safe regeneration

Higher temperature regeneration followed by switch to colder flow conditions mimics DPF durability (maximum soot load) type testing.


Typical Regen : Cut to Idle Test

Regen : Cut to Idle Test

100

200

300

400

500

600

700

800

900

385 435 485 535 585 635

Time (s)

Tem

p (

C)

-5

0

5

10

15

20

25

30

35

DPF inlet temp

DPF outlet temp

DPF Dp (mbar)


Effect of Soot Load on Exotherm

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


DPF Filtration Efficiency Measurement

� Variation of DPF filtration efficiency as function of soot load measured with DPG

� Typical DPG installations use AVL415S smoke meter (paper blackening type) for soot rate monitoring and filtration measurement

– good soot mass correlation

– sensitivity just acceptable for efficiency monitoring to ~99.9%

– smoke meter control & logging fully integrated into DPG software

� DPG operation can be tailored to optimise resolution of fast-changing filtration efficiency in pore-filling phase

– soot rate reduced (2g/hr) to extend duration of pore filling phase

– soot rate then increased to 10g/hr to accelerate measurement of loaded filtration efficiency, and improve sensitivity

– smoke meter measurements scheduled to maximise downstream measurements (as DPG upstream concentration is very stable)

– smoke meter sample volume automatically adapted to optimise sensitivity

– DPF flow reduced to maximise soot concentration


Typical Filtration Efficiency Test

0

50

100

150

200

250

300

0 500 1000 1500 2000 2500 3000 3500 4000

time (s)

DP

F e

ntry

tem

p (C

), D

PF

flow

(kg

/s),

bac

kpre

ssur

e m

bar

0

5

cum

ulat

ive

soot

load

(g)

DPF flow mmt (Kg/hr) DPF temp mmt (C) DPF dP (mBar)

primary airf low (relative) cum soot load

startup w arm up 2 g/hr load 10 g/hr load


Filtration Efficiency vs Soot Load

Filtration efficiency & Dp - green part

0

10

20

30

40

50

60

70

0 1 2 3 4 5 6

soot load (g)

back

pres

sure

(m

bar)

86

88

90

92

94

96

98

100

DP

F e

ffici

ency

(%

)

dP f iltration eff iciency


Penetration Measurement Repeatability

DPF Penetration Pore Filling - part : part repeatability (green)

0

2

4

6

8

10

12

14

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

soot load (g)

pene

trea

tion

%

part 1 penetration part 2 penetration


Effect of DPF Aging

DPF Penetration and dP - Effect of degreening

0

10

20

30

40

50

60

70

80

0 1 2 3 4 5 6 7 8

soot load (g)

dP (

mba

r)

0.01

0.1

1

10

100

DP

F p

enet

ratio

n (%

)

dp - green dp - 2nd cycle penetration - green penetration - 2nd cycle

penetration mmt noise floor

2nd cycle shows improved filtration efficiency.

Effect on dp is smaller


Filtration Measurement with CPC + VPR

� Improved sensitivity compared with smoke meter� Faster time response of measurements

D1 DPF Number Efficiency

60

65

70

75

80

85

90

95

100

105

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Time / s

Eff

icie

ncy

%

2 g / hr 10 g / hr


Conclusions

Demonstrated measurements of

– Dp vs soot load characteristics

– Flow sweeps

– Regeneration behaviour

– Filtration Efficiency testing

with the DPG

Further work is continuing on extending these applications and optimising similarity of DPG measurements to engine tests.

I’d like to acknowledge the assistance of Ray Brand, Jon Symonds, Mark Rushton and Tim Hands in the experimental work reported here.

Automated Repeatable DPF Testing with the Cambustion DPG

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