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Pressure drop characteristics of soot generated by a DPG and a Euro IV, 2 litre
diesel engine
Greg Inman, Andrew Todd, Kingsley Reavell, Tim Hands
2
Introduction
� The DPG is part of the Cambustion DPF Testing System which tests Diesel Particulate Filters for
– Backpressure vs soot load
– Regeneration characteristics
– Filtration efficiency (with a soot monitoring system)
� This is done by loading filters with soot generated in a Diesel burner, at flows and temperatures similar to engine conditions.
� This work compares the backpressure produced by the soot from the DPG burner with that from and engine.
� Effects causing variability in the backpressure associated with
– Engine cold starts
– High flow conditions
were measured in these tests and are discussed.
3
The Cambustion DPG
� More repeatable and rapid testing of DPGs than engine tests� Burner conditions unaffected by DPF backpressure� Automated, unattended testing except for loading & weighing the filter.
4
DPG Schematic
5
DPG Flow – Temperature CapabilityStandard LD version
DPG - LD Operating Temperature : Flow Rate Capabi li ty
0
100
200
300
400
500
600
700
800
0 100 200 300 400 500 600 700 800 900
DPF flow kg / hr
DPF
in
let
tem
pe
ratu
re º
C
regenerat ion mode
max imum system loading capabil it y
standard loadingcondi t ions
burner o ff condit ions
6
DPG Flow – Temperature CapabilityNew MD Version
DPG - Medium Duty Operating Temperature : Flow Rate Capability
0
100
200
300
400
500
600
700
800
0 100 200 300 400 500 600 700 800 900
DPF flow kg/ hr
DP
F in
let
tem
per
atu
re º
C
typical loading setpoint
burner off condit ions
regen / warm up
max possible loading limits
Increased fuel flow: approximately doubled loading & regeneration flows
7
DPG Application for Dp vs Soot Mass Testing
Instrument : instrument repeatability
0
10
20
30
40
50
60
70
80
90
0 2 4 6 8 10 12 14 16
Corrected soot mass (g)
Bac
kpre
ssur
e m
bar
part 1
part 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
8
DPG Flow Sweep Testing
� DPG measures backpressure vs flow up to ~ 600 m3/h� For comparison with engine results, Reynolds number should be the same
– Cold flow test at a lower flow rate than the engine!
– This keeps the balance of viscous & inertial pressure drops the same.
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
9
Previous Engine Correlation WorkT Hands et al, DEER 2007:Pressure drop vs soot load for Engine soots compare d with DPG soot
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 Cycle
High Load Steady State
DPG
� Difference between cycle & steady state engine soot� Engine soot backpressure measured on engine: less accurate� Other private data also shows significant variation between engines
10
New Test Programme� DPF canned for easy connection to engine� Load on engine or DPG.� Cold flow test at 0g, 5g, 15g, 20g & 30g on DPG
– Improved accuracy compared with engine backpressure measurement due to accurate & stable temperature and flow
� Original plan:
load
load
load
load
regen
weigh
weigh
weigh
weigh
weigh
flow test
flow test
flow test
flow test
flow test
warmup0g
5g
15g
20g
30g
Engine / DPG DPG
11
Engine Details
� 2l Common rail Diesel engine� Stage 4 emissions compliant� Mounted on dynamic dyno
– Comparisons made with cycle soot
� Fitted with Diesel Oxidation Catalyst upstream of DPF
– In this test programme, the DPG testing was not fitted with the DOC. This is to simulate best the application of the DPG for testing filters which are then used with an upstream DOC, currently the majority application.
– For single brick systems, the engine soot would differ mainly via higher levels of volatile components.
� All tests performed on the same DPF:
– 5.66” dia x 10” 4.1 l
– Uncatalysed SiC.
12
Soot Loading Conditions
� Engine – 3 conditions used
– NEDC – approx 3g/h for this engine
– ‘Rural’ drive cycle – 6g/h
– Steady state accelerated soot loading (modified engine operating points) – 10g/h
� DPG
– All tests at approx 10 g/h setpoint
13
Effect 1: Backpressure ‘Relaxation’ in flow test27g load
0
10
20
30
40
50
60
70
80
90
0 50 100 150 200 250 300 350 400
Equivalent flow (m3/hr)
first flow test
0
10
20
30
40
50
60
70
80
90
0 50 100 150 200 250 300 350 400
Equivalent flow (m3/hr)
first flow test
repeat test
Flow test sweeps flow up and then down.First flow test shows reduced pressure on downsweep
Further repeats then stable up and down same trajectoryShape closer to expected quadratic
14
High Flow Relaxation Conclusions
� Deposited soot is disturbed by high flow conditions� Once relaxation has occurred, soot is then stable.� Flow tests all repeated twice in this work, and data quoted from repeat.
15
Backpressure reduction in multistage loading (1)
0
20
40
60
80
100
120
0 5 10 15 20 25
Soot load (g)
Equ
ival
ent d
elta
p @
300
m3/
hour
(m
bar)
Accelerated soot load
Loaded to 14.3g and then on to 19.7g
Backpressure lower at 19.7g than 14.3!
16
Backpressure Reduction In multistage loading (2)
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30 35
Sootload (g)
Pre
ssur
e dr
op a
t 300
m³/
hr (
mba
r)
Loaded and flow tested same day
Part loaded and topped up from cold, then flow tested
SS Engine sootloads
17
DPG soot subjected to cold start on engine
Load on DPG
Flow test
Engine cold start
Flow test
Load on DPG
Flow test
Engine cold start
Flow test
Flow test
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30 35
Sootload (g)
Pre
ssur
e dr
op a
t 300
m³/
hr (
mba
r) DPG sootloads
18
Cold Restart Backpressure Reduction
0
20
40
60
80
100
120
140
160
30 35 40 45 50 55 60 65 70
Time (s)
MA
F (
kg/h
r), T
empe
ratu
re (°
C)
0
2
4
6
8
10
12
14
16
dP (
mba
r)
maf_kgh_mes
DPF In
delta p
Engine Started
Speed increasedto 2000rpm
Dry gas enetering DPF
Pressure drop decreasing
MAF constant
'Wet' gas entering DPF (Condensate heating)
19
Recovery of Reduced Backpressure
0
20
40
60
80
100
120
140
160
0 5 10 15 20 25 30
DPF dP corr DPF dP corr DPF dP corr
Part loaded to 17g on DPG
Cold start on EngineLoading continued to 29.5g
Compared with continuous load to 29g
20
Effect of Cold Start - summary
� Regardless of soot type, engine cold start appears to cause reduction in backpressure
� Does not occur with restart in loading on DPG� Reduction in backpressure is visible in real time during engine start� Possibly connected with condensation & re-evaporation of water from soot
cake, damaging the structure.� Reduction in backpressure not fully recovered with further loading.� All engine loaded data in the comparison is therefore loaded directly from
zero to the final weight.
– Significant increase in the amount of testing required.
21
Backpressure vs Soot Load Engine & DPG
0
20
40
60
80
100
120
0 5 10 15 20 25 30 35
Sootload (g)
Pre
ssur
e dr
op a
t 300
m³/
hr (
mba
r)
NEDC Soot (3g/hr)
Accelerated Steady State Soot (10g/hr)
Rural Drivecycle Soot (6g/hr)
DPG Soot (10g/hr)
Empty
Coated DPF DPG Soot (10g/hr)
All cycles produce effectively identical backpressureDPG also the same, except for possible slight increase at very high loads
22
Conclusions
� Significant effects on backpressure measurement noted in this work:
– Relaxation of soot at high flow rates
– Permanent reduction in backpressure by engine cold start
� With these effects avoided, all engine cycles produced very similar backpressure vs soot load.
� DPG soot also behaves the same as engine soot.� Inconsistent with earlier experience
– Previous tests did not carefully avoid effects above
– Increased variability in engine rather than DPG tests
– Different behaviour of different engines.
23
Further Work
� There is scope for further work:
– Variation in soot behaviour between different engines.
– Effect of different filter types (catalysed, materials)
– Investigation of effects at very high loads
– Comparison of regeneration behaviour of engine & DPG soot – ongoing.
24
Acknowledgements
Thanks to all the coauthors who did more of this work than me, and also Ray Brand and Jason Sumner who did most of the testing.
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