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Biofuel Combustion Improvement with
Ignition Control Innovations
Clean Combustion Engine Laboratory
University of Windsor, Canada
By Ming Zheng
Professor, Director of Clean Combustion Engine Laboratory
Department of Mechanical, Automotive & Materials Engineering
University of Windsor
2016 Advanced Biofuels SymposiumVancouver, BC Canada
Outline:
1. Introduction
2. Clean Combustion Engine Principals
3. Impact of Biofuels on Clean Combustion
4. Progresses in Multi-pole and Corona Ignition
Clean Diesel Engines
Low-load
HCCI
1000 1500 2000 2500 3000
Soot
Local Flame Temperature (K)
Lo
ca
l A
ir E
xce
ss R
atio
(λ=
1/Φ
)
Ric
hL
ea
nLow Temperature
Combustion
High Temperature
Combustion
NOx
Loca
l Φ ≠
Glo
bal Φ
10
0.1
1
Fuel
Reforming
Rich burn
with EGR
High-load
HCCI + EGR
Loca
l Φ =
G
lobal Φ
Low NOx &
Soot
Pathway
Internal Combustion
2. Clean Combustion Engine Principals:
• Air Management
• Fuel Management
• Internal Combustion
• Exhaust Emission Control
Air ManagementEngine downsizing with dual-stage
turbocharging & dual-loop EGR
Clean Diesel EnginesIntake
Exhaust
EGR cooler
Air filter
EGR valve
After-treatment
Exhaust brake
Inter-cooler
EGR cooler
Bypass valve
EGR valve
NOx sensor
Gas path
CAN bus
CAN data
ECU signal
O2 sensor
Tint / pintsensor
Swirl valves
CrankΔp
sensor
EGR valves
Inte
r-co
ole
r
Variable Geometry Turbocharger (VGT)
Controller Area Network (CAN)
Low-pressureExhaust Gas Recirculation (EGR)
EG
R
hig
h-p
ress
ure
Two-stage VGT
Bypass valve
Engine Control Unit
(ECU)
CAN Controllers
Variable Valve Actuation (VVA)
Cam & VVA
Advanced diesel engine air management
𝑇𝑜𝑟𝑞𝑢𝑒
𝑉𝑑 = 7.958 × 𝐵𝑀𝐸𝑃
80[N-m/L] 10[bar]
160 20
240 30
Port Fuelling
TDCIntake CompressionBDCTDC Expansion
Port Fuelling
TDCIntake CompressionBDCTDC Expansion
Gasoline-Diesel Dual Fuel Combustion
RCCI: Reactivity Controlled Compression Ignition
DIDC: Diesel Initiated Dual-fuel Combustion
Diesel HCCI: Homogeneous Charge Compression Ignition
Gasoline/Ethanol PPC: Partially Premixed Combustion
Diesel Single Shot LTC: Low Temperature Combustion
Conventional Diesel Combustion DI
SOC HTC, close to TDC single shot1
LTC, high EGR + late SS diesel
Multiple early shots, diesel
DI split shots, high octane fuels
PFI + DI, reactivity stratification
Diesel Initiated Dual-fuel Combustion
Fuel Injection & Combustion Control
Challenges for Low Temperature
Combustion (LTC)
• Difficult to ignite
• Long ignition delay
• High ignition timing discrepancy
• Incomplete combustion
• High combustion noise
• Less tolerate to fuel property departures
Solutions for Adapting Biofuels
• Ignition volume and event control (e.g. pilot
fuel, multiple pole and corona ignition)
• Charge and fuel chemical reactivity control
(e.g. pilot fuel scheduling)
• EGR rate and temperature modulation
• Boost and intake temperature modulation
• Corona ignition and flame acceleration
• Combustion chamber innovation
3. Fuel Type & Fueling Strategy
• Fuel premixing enhancement
• Ethanol and n-butanol as surrogates for
future biofuel studies
• Fuel delivery impact & suitability of dual
fuel combustion
Diesel combustion:
o Up to 3 injections per cycle, pilot, main,
and post injections for noise control and
optimal emissions
o Postponed CA50 at higher load to control
NOx and smoke
o Moderate EGR to avoid high smoke
o Engine efficiency reduces at higher load
primarily due to postponed CA50
Gasoline-diesel DFC:
o Near-TDC injected diesel to ignite premixed
gasoline-air mixture
o Advantages in NOx and smoke emissions
across engine load map
o High load is limited by premature auto-
ignition
o Higher EGR required, can afford earlier
CA50
o Improvements in engine efficiency
Diesel Combustion (NOx~0.5 g/kW-hr, smoke<2 FSN)
versus
Gasoline-diesel Dual-fuel Combustion
(NOx~0.2 g/kW-hr, smoke<2 FSN)0
1
2
3
4
0 2 4 6 8 10 12 14 16 18 20
Sm
oke [
FS
N]
IMEP [bar]
Diesel Only
DFC
DFC offers significant
smoke reduction up to
medium engine loads
0.0
0.5
1.0
1.5
2.0
0 2 4 6 8 10 12 14 16 18 20
NO
x [
g/k
W-h
r]
IMEP [bar]
Diesel Only
DFC
DFC:
NOx ~ 0.2 g/kW-hr
Diesel Only:
NOx > 0.5 g/kW-hr
0
20
40
60
80
100
0 2 4 6 8 10 12 14 16 18 20
EG
R R
ate
[%
]
IMEP [bar]
Diesel Only
DFC
In DFC operation, EGR
rate increases from 12 to
16 bar IMEP to withhold
premature auto-ignition
For diesel, EGR rate reduces to avoid
high smoke emissions at higher loads
360
365
370
375
380
385
390
0 2 4 6 8 10 12 14 16 18 20
CA
50 [ C
A]
IMEP [bar]
Diesel Only
DFC
DFC can afford
earlier combustion
phasing than diesel
Delayed diesel
combustion for
NOx reduction
30
35
40
45
50
0 2 4 6 8 10 12 14 16 18 20
ηin
d[%
]
IMEP [bar]
Diesel Only
DFC
Higher engine efficiency
is achieved in DFC
Speed: 1600 rpm
Compression ratio: 15.3:1
Pre-ignition
dp/dθ ↑↑
-40
0
40
80
120
350 360 370 380
HR
R [
J/
CA
]
Crank Angle [ CA]
Ethanol ratio 0.8
Diesel only
Inj. Command
Ethanol:
EL 4.2ms@10 CA &
DL 330μs@353 CA
Diesel Only:
610μs@355 CA
0.4
0.8
1.2
1.6
12 13 14 15 16 17 18 19 20
Ign
itio
n D
ela
y [
ms]
Intake O2 [%]
0 0.2 0.4
0.6 0.8
30
35
40
45
50
55
60
12 13 14 15 16 17 18 19 20
ηin
d[%
]
Intake O2 [%]
0 0.2 0.4
0.6 0.8
Prolonged ignition
delay for diesel
Slightly reduced efficiency
o Increasing use of ethanol significantly
enhances the cylinder charge homogeneity
o Substantial improvements in smoke
o Combustion phasing is maintained via
diesel injection timing adjustment across
EGR sweep
Diesel-Ignited Ethanol Combustion
0
2
4
6
8
12 13 14 15 16 17 18 19 20
NO
x [
g/k
W-h
r]
Intake O2 [%]
0 0.2 0.4
0.6 0.8
0
1
2
3
4
5
12 13 14 15 16 17 18 19 20
Sm
oke [
FS
N]
Intake O2 [%]
00.20.40.60.8
Ethanol ratio
Speed: 1500 rpm
Ethanol Diesel DF
IMEP: 10 bar
CA50: 369 CA
pint: 2 bar abs
Diesel pinj: 1200 bar
0
0.2
0.4
0.6
0.8
12 13 14 15 16 17 18 19 20
CO
[%
]
Intake O2 [%]
0 0.2 0.4
0.6 0.8
0
500
1000
1500
2000
2500
12 13 14 15 16 17 18 19 20
HC
[p
pm
]
Intake O2 [%]
0 0.2 0.4
0.6 0.8
EGR for NOx
reduction
HC increase
CO increase
Substantial
smoke
reduction
Clean Combustion of Ethanol with Diesel-pilot ignition
at high and full loads
-50
0
50
100
150
200
250
300
0
50
100
150
200
330 345 360 375 390 405 420
Heat
Rele
ase R
ate
[J/
CA
]
Cyli
nd
er
Pre
ssu
re [
bar]
Crank Angle [ CA]
Speed: 1500 rpm
Ethanol Diesel DF
CA50: 372 CA
pint: 2.25 bar abs
pinj: 1200 bar
dp/dθ: 9.9 bar/ CA
[O2]int: 13%
ηind: 44%
IMEP: 16.4 bar
NOx: 24 ppm, 0.14 g/kW-hr
Smoke: 0.27 FSN
-50
0
50
100
150
200
250
300
0
50
100
150
200
330 345 360 375 390 405 420
Heat
Rele
ase R
ate
[J/
CA
]
Cyli
nd
er
Pre
ssu
re [
bar]
Crank Angle [ CA]
Speed: 1500 rpm
Ethanol Diesel DF
CA50: 376 CA
pint: 2.5 bar abs
pinj: 900 bar
dp/dθ: 13.8 bar/ CA
[O2]int: 15.4%
ηind: 46.9%
IMEP: 18.5 bar
NOx: 42 ppm, 0.23 g/kW-hr
Smoke: 0.81 FSN
-50
0
50
100
150
200
250
300
0
50
100
150
200
330 345 360 375 390 405 420
Heat
Rele
ase R
ate
[J/
CA
]
Cyli
nd
er
Pre
ssu
re [
bar]
Crank Angle [ CA]
Speed: 1500 rpm
Ethanol Diesel DF
CA50: 374 CA
pint: 2.5 bar abs
pinj: 1500 bar
dp/dθ: 7.3 bar/ CA
[O2]int: 14.5%
ηind: 45.7%
IMEP: 19.2 bar
NOx: 70 ppm, 0.35 g/kW-hr
Smoke: 0.52 FSN
-50
0
50
100
150
200
250
300
0
50
100
150
200
330 345 360 375 390 405 420
Heat
Rele
ase R
ate
[J/
CA
]
Cyli
nd
er
Pre
ssu
re [
bar]
Crank Angle [ CA]
Speed: 1500 rpm
Ethanol Diesel DF
CA50: 374 CA
pint: 2.5 bar abs
pinj: 1500 bar
dp/dθ: 11 bar/ CA
[O2]int: 15%
ηind: 46.8%
IMEP: 19.5 bar
NOx: 130 ppm, 0.7 g/kW-hr
Smoke: 0.54 FSN
o Ultralow NOx and smoke emissions from
n-butanol HCCI
o Medium engine load of 7.2 bar IMEP
o Comparable efficiency (44%) to diesel HTC,
substantial improvements over HCCI on SI
engines (30~35%)
o High compression ratio of 18.2:1
o At zero EGR
o Without additional preheating or negative
valve overlap
Clean Combustion with n-Butanol HCCI (PFI)Compared with diesel LTC enabling
30
35
40
45
50
0 10 20 30 40 50 60 70 80
ηin
d[%
]
EGR Ratio [%]
DL, 1.5, 900, 367DL, 2.0, 1500, 367DL, 2.0, 1500, 375DL, 2.0, 1500, 380BL, 2.0, 7, 360
0
0.3
0.6
0.9
1.2
0 10 20 30 40 50 60 70 80
So
ot
[g.k
W-h
r]
EGR Ratio [%]
DL, 1.5, 900, 367
DL, 2.0, 1500, 367
DL, 2.0, 1500, 375
DL, 2.0, 1500, 380
BL, 2.0, 7, 360
0.01
0.1
1
10
100
0 10 20 30 40 50 60 70 80
NO
x [
g.k
W-h
r]
EGR Ratio [%]
DL, 1.5, 900, 367DL, 2.0, 1500, 367DL, 2.0, 1500, 375DL, 2.0, 1500, 380BL, 2.0, 7, 360
Speed: 1500 rpm
IMEP: ~7.2 bar
DL: DI, SS
BL: PFI
Fuel, pint, pinj, CA50
0.07
0.005
Zero
EGRModerate Heavy Ultra-high
Diesel
LTC
Diesel
LTC
EGR usage on LTC enabling
Diesel
LTC
44%
Diesel
n-Butanol
HCCI
n-Butanol
HCCI
Diesel
Diesel
BL,
-50
0
50
100
150
200
250
300
350
0
30
60
90
120
150
180
340 350 360 370 380 390
Heat
Rele
ase R
ate
[J/
CA
]
Cyli
nd
er
Pre
ssu
re [
bar]
Crank Angle [ CA]
Speed: 1500 rpm
IMEP: ~7.2 bar
pint: 2 bar abs
pinj: 1500 bar (DL)
BL, PFI,
HCCI,
Zero EGRDL, HTC,
Zero EGR
DL, LTC,
70% EGR
0
40
80
120
160
345 360 375 390
Hea
t R
elea
se R
ate
[J/
CA
]
Crank angle [ CA]
6.7
5.4
4.0
2.1
IMEP
[bar]
Engine Speed: 1500 rpm
Intake Boost: 2 bar abs
Intake O2: 20.7%
NOx: < 5 ppm
Smoke:~ 0.02 FSN
n-Butanol HCCI:Near-zero smoke emissions
Near-zero NOx emissions
Desirable low load performance
-50
0
50
100
150
200
250
300
350
400
450
500
0
30
60
90
120
150
180
340 350 360 370 380 390
Heat
Rele
ase R
ate
[J/
CA
]
Cyli
nd
er
Pre
ssu
re [
bar]
Crank Angle [ CA]
IMEP: 10.1 bar
EGR: 56%
λ: 1.25
9.6 bar
54%
1.34
6.6 bar
0%
4.54
7.5 bar
40%
2.24
8.5 bar
50%
1.61
o Ultralow NOx and smoke emissions across
low to medium engine loads
o Intake boost is necessary to attain
successful ignition at low loads
o EGR is applied at higher engine loads to
avoid premature combustion
o Clean and efficient combustion is achieved
up to 10 bar IMEP
Clean Combustion with n-Butanol HCCI (PFI)Engine load performance
0
0.01
0.02
0.03
0.04
-0.4
-0.2
0
0.2
0.4
0 1 2 3 4 5 6 7 8
Sm
oke
[g
/kW
-hr]
NO
x [
g/k
W-h
r]
IMEP [bar]
2.0 1.8 1.5
0369121518212427
-9-7-5-3-113579
0 1 2 3 4 5 6 7 8
CO
VIM
EP
[%]
λ[-
]
IMEP [bar]
Speed: 1500 rpm
BL, PFI, HCCI, Zero EGR
Unstable
combustion
Intake pressure [bar abs]
Fuel & Fueling Research Summary
• Fuel property needs to comply with
delivery, dispersion, mixing & combustion
• Fuel injection strategy is sensitive to LTC
• The LTC enabling with neat n-butanol is
narrow and rough
• Ethanol is suitable for LTC
4. Our Progresses in Multi-pole
and Corona Ignition
• LTC ignition control: a major challenge
• Multi-event & high energy sparking helpful
• Multi-pole sparking unique & effective
• Corona igntion potentially helps cold start
and transience
• Corona igntion complements CI LTC
Improvement on Ignition Source
Based on the conventional system
• Enhance energy and transient power
• Prolong duration
• Multiple events
New architectures
• Multiple ignition sites
• Volume spark
• Variable spark number and size
Temporally
control
Spatially
control
Patented by Zheng’s teams
3-pole (3P) spark plug prototypes
Iridium spark plug In-house made
3P-spark plug
Manufacturing level
prototype
M14 3P-spark:
3 spark gaps at Φ4mm perimeter
M18 3P-spark:
3 spark gaps at Φ8mm perimeter
Direct-Capacitor Discharge Enhance
the Spark Power/Energy
-200
-100
0
100
200
300
-2
0
2
4
6
8
10
36.1 36.5 36.9
Po
wer
(kW
) &
Cu
rren
t(A
)
Vo
ltag
e (k
V)
time (μs)
voltagecurrentpower
Breakdown
start Peak
power
300kW
-50
50
150
250
350
450
-0.5
0
0.5
10 15 20 25 30 35
Po
wer(
kW
)&C
urr
en
t(A
)
Vo
ltag
e (
kV
)
time (μs)
voltagecurrentpower
Breakdown
power
30kW
High power discharge
~ 70 mJ, 300kW
High energy discharge
~ 1 J
3pole igniter discharging video
• Conventional
Low energy
low power
• 3-pole spark
• Low energy
• low power
• Low energy
• high power
• >3 MW
• High energy
volume plasma
• ~3J
• Self-resonant
multiple restrikes
• Low energy
0 ms 3.3 ms 6.6 ms
0 ms 3.3 ms 6.6 ms
0 ms 3.3 ms 6.6 ms
0 ms 3.3 ms 6.6 ms
15mm
40mJ/1pole
120mJ/3pole
120mJ/3pole
high power
3J/3pole
high energy
3-pole can deliver more energy and produce a bigger flame kernel
3pole Ignition Flame Kernel4 barλ=1.6
3pole benefit to combustion
phasing control (preliminary engine results)
355
360
365
370
375
380
385
390
345 350 355 360 365 370C
A50 (
CA
D)
CA5 (CAD)
SOI 326
SOI 341
3 pole
1 pole
3 pole
1 pole
Stability Scattter Plot
Single cylinder engine tests• 3pole advances CA50
• 3pole provides more stable
combustion phasing
λ=1.35
IMEP=3.3 bar
0
10
20
30
40
330 360 390 420 450
Pre
ssu
re (
bar)
CAD
SOI 326 SOI 341
3 pole
1 pole
3 pole
1 pole
0.00
0.25
0.50
0.75
1.00
330 360 390 420 450
Ma
ss
Fra
cti
on
Bu
rnt
CAD
SOI 326
SOI 3413 pole
1 pole3 pole
1 pole
3pole high power/energy results
01020304050607080
0 3 6 9 12 15 18 21 24 27 30 33 36
t_5
0%
(m
s)
t_5% (ms)
1.0 - 1J/1pole1.0 - 3J/3pole1.6 - 1J/1pole1.6 - 3J/3pole1.8 - 1J/1pole1.8 - 3J/3pole
3pole1pole
01020304050607080
0 3 6 9 12 15 18 21 24 27 30 33 36
t_5
0%
(m
s)
t_5% (ms)
1.0 - 1pole1.0 - 3pole1.6 - 1pole1.6 - 3pole1.8 - 1pole1.8 - 3pole
3pole
1pole
01020304050607080
0 3 6 9 12 15 18 21 24 27 30 33 36
t_5
0%
(m
s)
t_5% (ms)
1.0 - 200pF/1pole1.0 - 600pF/3pole1.6 - 200pF/1pole1.6 - 600pF/3pole1.8 - 200pF/1pole1.8 - 600pF/3pole
3pole
1pole
Combustion chamber
tests• Three-pole ignition
shows significantly
acceleration on early
ignition period
• In combination with
direct-capacitor
discharge, the ignition
robustness can be
significantly improved
3pole ignition success rate
0
20
40
60
80
100
1.6 1.8 2 2.2
Ign
itio
n S
ucc
ess
Rat
e (%
)
Lambda [-]
1 pole 70mJ
3 pole 200 mJ
1 pole 200 pF
3 pole 600 pF
1 pole 1 J
3 pole 3 J
0
20
40
60
80
100
10 11 12 13 14 15 16 17 18 19
Ign
itio
n S
ucc
ess
Rat
e (%
)
CO2 concentration [%]
1 pole 70 mJ3 pole 200 mJ1 pole 200 pF3 pole 600 pF1 pole 1 J3 pole 3 J
Combustion chamber
tests• Ignition success rate
was obtained from 20
time repeated tests fro
each test condition.
• Both lambda sweep and
CO2 dilution tests were
conducted
• Improvement of ignition
success rate is more
obvious with direct-
capacitor discharge
• The combination of
three-pole and direct-
capacitor discharge
provides the best result
Open spark gap
RF corona discharge in ambient
11mm
Iridium spark
14mm
Corona-based volume spark igniter
Corona discharge can
offer a much bigger
ignition volume
Volume sparking video
Comparison of ignition by spark and corona
-- high speed Schlieren imaging~1ms spark discharge into Ф 1.0 propane-air
~40 mJ
353 μs 1579 μs 1933 μs518 μs27 μs
~800 mJ
353 μs 1579 μs 1933 μs518 μs27 μs
353 μs 1579 μs 1933 μs518 μs27 μs
1ms, <~500mJ corona discharge into Ф 1.0 propane-air
t = 472 µst = 32 µs t = 232 µs
Direct imaging in green
Shadowgraph image in red
Test conducted with propane-air
mixture in 1” diameter chamber at 1
barg
Non-thermal Plasma Ignition
Combustion modulation via. electrification (λ=1.0)
54 μs 600 μs 1690 μs327 μs 1145 μs
54 μs 600 μs 1690 μs327 μs 1145 μs
54 μs 600 μs 1690 μs327 μs 1145 μs
Case 1: Corona duration 200μs + 1500 μs mild electrification
Case 2: Corona duration 200μs + 1500 μs moderate electrification
Case 3: Corona duration 200μs + 1500 μs strong electrification
Thank you!Acknowledgements:
NCE BioFuelNet
Ford Motor Company Canada
NSERC CRD, Discovery, CREATE
CFI-ORF New Initiative Program
University of Windsor
Fast Cambustion FID1 2
43
Lab Facilities
H2 analyzer
FTIR
PM Counter
PM Analyzer
Fast Cambustion CLD
HVA system Single-cylinder engine research platforms
Fuel Injection ROI Bench Combustion Vessel