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