Spray Targeting to Minimize Soot & CO Formation in Premixed
Compression Ignition (PCI) Combustion with a HSDI Diesel Engine
SANGSUK LEE & Rolf D. REITZ
Single Injection _ Soot & CO
Motivation
Why Targeting?
Spray Targeting
SOI Sweep (Nozzle Comparison : IMEP=4.8bar)
 PCI (Premixed Compression Ignition) is a practical
way to achieve near zero levels of soot and NOx
trade-off even under fairly rich conditions.
151 kPa
EGR
about 55%
Intake Air Temp.
90oC
Injection Pressure
1500 bar
-30
-25
-20
-15
-10
-5
-35'
-6
-8
-30'
-20'
-25'
-25'
-20'
Piston
120' Nozzle
85' Nozzle
50' Nozzle
0
-14
 Soot was minimized
when the spray was
targeted at the
bottom of the piston
bowl.
SOI Sweep (Nozzle Comparison : IMEP=4.8bar)
CO
2000rpm, Rail P = 1500bar, Pin = 151kPa, ~55% EGR, Const IMEP Test
300
CO (140')
CO (120')
250
CO (85')
CO (50')
200
150
100
SOI=-40'
-35'
-20'
-25'
-30'
-16
0
2
4
6
8
10
12
14
16
18
20
22
24
CO
CO & Spray Targetting
0
SOI=-43
-2
-40'
-4
-35'
-6
Y (mm)
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
SOI (deg ATDC)
NOx
SOI Sweep (Nozzle Comparison : IMEP=4.8bar)
2000rpm, Rail P = 1500bar, Pin = 151kPa, ~55% EGR, Const IMEP Test
2.0
NOx (154')
NOx (140')
NOx (120')
1.6
NOx (85')
NOx (50')
 Targeting at the inner
surface of the piston
gave optimized CO
emissions.
26
X (mm)
50
; No simple rule to
describe the emission
trends in PCI
combustion.
 No significant NOx
emission difference
observed under high
levels of EGR.
-4
SOI (deg ATDC)
NOx (g/kW-hr)
Boost Pressure
-35
120° Nozzle
-40'
-12
-40
120° Nozzle
SOI=-43
-2
0.0
-45
Worst Targeting (SOI = - 30o )
0
-30'
0
2000 rpm
Optimum Targeting (SOI = - 43o )
SOI=-35'
 PCI (SOI < -20°)
Operation Conditions
Soot
Soot & Spray Targetting
-10
CO (g/kW-hr)
; Soot & CO increase
as SOI retarded. No big
difference in levels
except 50 °nozzle.
 To understand how the spray targeting affects on
emission formation.
4.8bar IMEP
0.8
CO (154')
 To find the best way to realize low emissions.
Load
1.2
0.4
 Conventional diesel
combustion
 To investigate key factors which determine the
characteristics of PCI and Conventional Diesel
Combustion .
 Spray Targeting at a
piston bowl edge
gave the minimum
emissions both soot
and CO.
Soot (154')
Soot (140')
Soot (130')
Soot (120')
Soot (85')
Soot (50')
1.6
 MK (SOI > -5°)
Objectives
Engine Speed
Soot
2.0
Y (mm)
 Three combustion
regimes (MK,
Conventional, PCI)
were identified with
respect to SOI.
Soot (g/kW-hr)
 Stringent future emission regulations require low
emission strategies.
2000rpm, Rail P = 1500bar, Pin = 151kPa, ~55% EGR, Const IMEP Test
-10'-15'
-20'
-25'
-8
-30'
-30'
 Fuel can be dispersed more effectively when the
spray is targeted at a spot where the interaction
between the spray and the squish flow is
enhanced.
-25'
-10
-20'
SOI=-35'
-12
Piston
120' Nozzle
85' Nozzle
50' Nozzle
-14
SOI=-40'
-35'
-20'
-25'
-30'
-16
0
2
4
6
8
10
12
14
16
18
20
22
24
26
X (mm)
1.2
0.8
0.4
0.0
-40
-35
-30
-25
-20
-15
-10
-5
0
SOI (deg ATDC)
Split Injections
Start of Burn & Burn Duration
Burn Duration
Burn Duration (10% to 90% Burn)
10-90% Burn Duration
2000rpm, Pin = 151kPa, Pinj = 1500bar, ~55% EGR
20
15
Probably partially PCI
probably controlled by
Swirl & Squish Flow
10
Mixing Controlled Regime
(Diffusion Burn)
advantage of split
injections compared to
single injection
optimum in PCI.
2.0
-40
-35
-30
-25
-20
-15
-10
-5
Soot (Single)
Soot (Split : SOI_1 = -52')
Soot (Split : SOI_1 = -43')
Soot (Split : SOI_1 = -35')
Soot (Split : SOI_1 = -31')
Soot (Split : SOI_1 = -27')
1.6
0
-45
 Optimum spray
targeting near the
edge of the piston
bowl was observed
regardless of spray
angles.
2000rpm, IMEP=4.8bar, Rail P = 1500bar, Pin = 151kPa, ~55% EGR
1.2
0.8
0.4
0
SOI (deg ATDC)
0
-40
2000rpm, Pin = 151kPa, Pinj = 1500bar, ~55% EGR
10-50%
50-75%
75-90%
10-90%
Burn Duration (deg)
12.0
9.0
6.0
3.0
0.0
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
SOI (deg ATDC)
Start of Combustion (CA of 10% Burn)
Start of 10% Burn
2000rpm, Pin = 151kPa, Pinj = 1500bar, ~55% EGR
20
10
-30
-25
-20
-15
-4
-6
-10
-5
 Spray Targeting at the edge of the piston bowl is a
key factor to minimize emissions in PCI combustion.
-8
-10
-12
-14
0
SOI (deg ATDC)
-16
15
17
19
 Optimum spray
targeting moved
up piston bowl as
spray angle
became narrower.
2000rpm, IMEP=4.8bar, Rail P = 1500bar, SOI_1=-31', SOI_2=-19', 50% EGR
0.3
0.2
1st = 75%
0.1
1st = 55%
1st = 30%
1st = 0% (Single)
0.4
25
 Soot could be optimized when spray was targeted
at the bottom of piston which provided the longest
spray travel distance. However, CO emission
increased.
CO
0
Piston
120' Nozzle
130' Nozzle
140' Nozzle
154' Nozzle
-2
-4
-6
0.0
0.2
23
CO & Spray Targetting (wider Nozzles)
1st = 10%
0.0
21
X (mm)
Effect of Fueling Distribution in Split Injections
0.6
NOx (g/kw-hr)
0.8
 CO was significantly reduced when spray was
targeted at the inner surface of the bowl, with a
corresponding increase in soot emission.
-8
1.0
-10
-12
120' Nozzle
140' Nozzle
154' Nozzle
50' Nozzle
85' Nozzle
15
 Results of Pickett
(SAE2005-01-0921)
explained that soot
emission increased
when the spray
interacted with the
burnt gas due to a
shortened lift-off length.
Soot (g/kW-hr)
Details for 120o Nozzle
15.0
-35
Piston
120' Nozzle
130' Nozzle
140' Nozzle
154' Nozzle
-2
0.0
Burn Duration (120' Nozzle)
 Burn durations are good indicator to classify the
PCI combustion in diesel engines.
Soot
Soot & Spray Targetting (wider Nozzles)
Y (mm)
around -11o ATDC in PCI.
; Similar Combustion
Characteristics with different
soot formation
 What makes the difference
in soot & CO emissions?
; Pre-ignition mixing with
squish and swirl flow.
Spray Targeting
IMEP
=5.5bar
5
Start of Burn _ 10% ('ATDC)
 The Combustion starts
25
Comparison between Single and Split (85' Nozzle)
 Hard to find an
Y (mm)
30
 In Conventional regime,
duration increased as SOI
was retarded since fuel
burnt within the mixing
controlled varies with SOI.
Start of Burn
120' Nozzle
140' Nozzle
154' Nozzle
50' Nozzle
85' Nozzle
Soot (g/kW-hr)
35
Burn Duration _ 10 to 90% (deg)
 10–90 % burn durations
about 5 degree regardless of
SOI and nozzle within the
PCI regime.
Conclusions
Spray Targeting _ Squish Flow
-14
-16
15
5
17
19
21
23
25
X (mm)
0
-5
-10
-15
-20
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
SOI (deg ATDC)
University of Wisconsin Engine Research Center