Performance of a Compression-Ignition Engine Using Direct-Injection of Liquid Ammonia … · 2021....

Department of Mechanical Engineering, Iowa State University

1

Performance of a Compression-Ignition

Engine Using Direct-Injection of Liquid

Ammonia/DME Mixture

Song-Charng Kong

Matthias Veltman, Christopher Gross

Department of Mechanical Engineering

Iowa State University

Acknowledgements:

Iowa Energy Center;

Norm Olson, Kevin Nordmeyer

Department of Mechanical Engineering, Iowa State University 2

Background

• Motivation

• Ammonia (NH3) combustion does not generate CO2

• Hydrogen carrier, renewable, etc.

• Challenges

• Ammonia is very difficult to ignite

• Octane number ~ 130

• Autoignition T ~ 651 ºC (gasoline: 440 ºC; diesel: 225 ºC)

• Ammonia flame temperature is lower than diesel flame T

• Ammonia emissions can be harmful

• Potential high NOx emissions due to fuel-bound nitrogen

• Gas phase at atmospheric pressure; Erosive to some materials

• Low energy content (~40% of that of diesel fuel per unit mass)


Thermodynamics/Chemistry

• Stoichiometric chemical reaction

3 2 2 2 20.75 ( 3.76 ) 1.5 3.32NH O N H O N

Fuel Molecule Boiling

Point (°C) (Air/Fuel)s

Latent

Heat

(kJ/kg)

Energy

Content

(MJ/kg-fuel)

Energy Content

(MJ/kg-

stoichiometric

mixture)

Methanol CH3OH 64.7 6.435 1203 20 2.6900

Ethanol C2H5OH 78.4 8.953 850 26.9 2.7027

Gasoline C7H17 --- 15.291 310 44 2.5781

Diesel C14.4H24.9 --- 14.3217 230 42.38 2.7660

Ammonia NH3 –33.5 6.0456 1371 18.6103 2.6414


Approach #1

• Introduce ammonia to the intake manifold

• Create premixed ammonia/air mixture in the cylinder

• Inject diesel fuel to initiate combustion

• Without modifying the existing injection system

Diesel ignition

Induce NH3

combustion

Burn out

premixed NH3


Engine Setup

• John Deere (4 cylinder, 4.5 liter)

• Operated at various load and speed conditions

• Vapor ammonia introduced into the intake duct – after turbo,

before manifold

Induction

point

Liquid NH3 tank

Fuel line

Fuel line


Test Results – Constant NH3 Flow Rate

• Engine torque increases suddenly once ammonia is

inducted

0

100

200

300

400

500

-80

-60

-40

-20

0

20

40

0 20 40 60 80 100 120

1800rpm Engine Torque

Engin

e T

orq

ue

(ft-lb)

Energ

y b

y N

H3 (%

)

Engine Load (%)

Diesel baseline

Diesel+ NH3

Energy replacement

by NH3

0

100

200

300

400

500

-50

0

50

0 20 40 60 80 100 120

1400rpm Engine Torque

Engin

e T

orq

ue

(ft-lb)

Energ

y b

y N

H3 (%

)

Engine Load (%)

Diesel baseline

Diesel+ NH3

Energy replacement

by NH3


• Fixed at specific diesel fueling, adjusted NH3 flow

rate to maintain constant torque

• Can achieve 5% diesel / 95% NH3 energy ratio

0

5

10

15

20

25

30

35

40

45

0 20 40 60 80 100

Power Contribution from Diesel Fuel (%)

Po

we

r (k

W)

Diesel Only

NH3 + Diesel

Contribution

from NH3

0

5

10

15

20

25

30

35

40

45

0 20 40 60 80 100


Po

we

r (k

W)

Diesel Only

NH3 + Diesel

Contribution

from NH3

7

Test Results – Constant Torque

from

NH3

diesel


0

500

1000

1500

2000

2500

3000

3500

0 20 40 60 80 100


NH

3 (

pp

mV

)

8

NH3 Exhaust Concentrations

• Concentrations vary depending on NH3 fueling rate

• Further study is required to reduce NH3 emissions.

High NH3

fueling

Low NH3

fueling 20

30

40

50

60

70

80

90

100

0 20 40 60 80 100

Constant Engine Torque

Ma

ss C

on

ve

rsio

n E

ffic

ien

cy (

%)

Diesel Load (%)

Ammonia combustion

efficiency


Approach #2

• Use direct liquid fuel injection

• Confine combustion mixture near the center

• To reduce exhaust ammonia emissions

• Ignition source – dimethyl ether (CH3-O-CH3)

• Mixture of DME and NH3

• Fuel mixing and storage at high pressure

• New fuel injection system – without fuel return

• Injection pump, injector, electronic control

9

Fuel injector


Engine Setup

• Yanmar diesel engine (L70V, 320 c.c.)

• Rated power at 6.26 hp at 3480 rpm

• Develop new fuel injection and engine control systems

• Bosch GDI type injector (up to 200 bar injection pressure)


Setup

• Mixing and storage of ammonia/DME at high pressure

• Exhaust emissions measurements

• Horiba MEXA-7100DEGR (CO2, CO, O2, HC)

• Horiba 1170NX (NOx, NH3)

• AVL Smoke Meter (PM)

Fuel mixing system

Emissions analyzers


Operating Conditions

12

Operating map using original diesel injection system


Test Results

• Baseline operation using 100% DME

• Explore operating range before using NH3/DME mixture

• For each operating point, various start-of-injection timings

were tested

• Provide flexibility for future optimization

13

SOI= –25 ~ 5 BTDC SOI= –30 ~ 0 ATDC

SOI= –35 ~ 20

BTDC

SOI= –30 ~ 20 BTDC

SOI= –30 ~ 20 BTDC


100% DME

• Mode 7 (2548 rpm) emissions

14

0

0.002

0.004

0.006

0.008

0.01

0

100

200

300

400

500

-30 -25 -20 -15 -10 -5 0

100% DME

Soo

t (F

SN

)

NO

x (p

pm

)

SOI (ATDC)

Soot - Smoke number

NOx

0

500

1000

1500

2000

-30 -25 -20 -15 -10 -5 0

100% DME

CO

& H

C (

pp

m)

SOI (ATDC)

CO

HC


Effects of Ammonia Combustion (Mode 7)

• 100%DME vs. 20%NH3/80%DME

• Soot remains at low level

• NOx increases due to fuel-bound nitrogen

15

0

0.002

0.004

0.006

0.008

0.01

-30 -25 -20 -15 -10 -5 0

Mode 7 (2548 rpm)

Soo

t (F

SN

)

SOI (ATDC)

100%DME

20%NH3/80%DME

0

100

200

300

400

500

600

700

800

-30 -25 -20 -15 -10 -5 0

Mode 7 (2548 rpm)

NO

x (

pp

m)

SOI (ATDC)

100%DME

20%NH3/80%DME



• 100%DME vs. 20%NH3/80%DME

• Lower combustion temperature of ammonia causes more CO

and HC emissions

• Implication to fuel efficiency

16

0

500

1000

1500

2000

2500

3000

3500

4000

-30 -25 -20 -15 -10 -5 0

Mode 7 (2548 rpm)

CO

(p

pm

)

SOI (ATDC)

100%DME

20%NH3/80%DME

0

100

200

300

400

500

600

-30 -25 -20 -15 -10 -5 0

Mode 7 (2548 rpm)

HC

(pp

m)

SOI (ATDC)

100%DME

20%NH3/80%DME



• Comparable combustion and fuel efficiency at this

lower speed

17

0

0.005

0.01

0.015

0.02

-35 -30 -25 -20 -15 -10 -5 0 5

Mode 21 (2200 rpm)

So

ot

(FS

N)

SOI (ATDC)

100%DME

20%NH3/80%DME

0

100

200

300

400

500

600

-35 -30 -25 -20 -15 -10 -5 0 5

Model 21 (2200 rpm)

NO

x (

ppm

)

SOI (ATDC)

100%DME

20%NH3/80%DME0

500

1000

1500

2000

2500

0

500

1000

1500

2000

2500

-35 -30 -25 -20 -15 -10 -5 0 5

Model 21 (2200 rpm)

100%DME

20%NH3

DME-HC

20%NH3

CO

& H

C (

pp

m)

SOI (ATDC)

CO

HC


Effects of Ammonia Combustion

• Exhaust ammonia emissions much lower than Approach#1

• Direct injection strategy benefits exhaust ammonia

emissions

18

0

50

100

150

200

250

300

350

400

-40 -35 -30 -25 -20 -15 -10 -5 0

NH3 Emissions (20%NH3/80%DME)

NH

3 (

pp

m)

SOI (ATDC)

Mode 7 (2548 rpm, low)

Mode 20

(2200 rpm, medium)

Mode 21 (2200 rpm, low)


Alternate Injection Strategy

• To extend the operating range

• Proposed strategies

• Double fuel injections

• Offer flexibilities in fuel delivery

• Used in industry for emissions and noise

reduction

• New fuel injector

• Original: single hole

• Alternate: eight holes – help with air

utilization

19

x % (100–x) %

pilot main


Double Injection, 100% DME

• Current system modified for using double injections

• Engine operations possible using double injections

• Comparable fuel efficiency and emissions

• Results based on Mode 7 (2548 rpm)

• Pilot SOI= –45 ~ –35 ATDC

• Pilot quantity=30% of total fuel

• Main SOI= –10 ATDC

• Exploring other conditions

• Varying the three injection variables

• Other operating points

20

0

0.002

0.004

0.006

0.008

0.01

300

350

400

450

500

550

600

-50 -45 -40 -35 -30

Double Injections (Mode 7)

So

ot

(FS

N)

NO

x (p

pm

)

Pilot SOI (ATDC)

Soot - Smoke number

NOx


Multi-Hole Injector

• Change from single hole to 8 holes

• Higher exhaust NOx – may imply higher combustion

temperature to sustain higher load operation

• Exploring combination of using 8-hole injector in

combination with double injections

21

0

0.005

0.01

0.015

0.02

0.025

-30 -25 -20 -15 -10 -5 0

Mode 7 (2548 rpm)

Soo

t (F

SN

)

SOI (ATDC)

Single hole

8 holes

0

100

200

300

400

500

600

-30 -25 -20 -15 -10 -5 0

Mode 7 (2548 rpm)

NO

x (

pp

m)

SOI (ATDC)

Single hole

8 holes


Summary

• Demonstrated ammonia combustion in diesel engines

• Port induction of ammonia coupled with direct-injection

diesel fuel

• Exhaust ammonia level at “thousands of ppm” under the

conditions studied

• Direct injection of ammonia/DME

• Exhaust ammonia level at “hundreds of ppm” under the

conditions studied

• Exploring optimal injection strategies for ammonia combustion

• Perspectives – effects of engine size

• Challenges for small engine: more heat loss, higher engine speed

required, lower fuel injection pressure

• Large engine will favor ammonia combustion

Performance of a Compression-Ignition Engine Using Direct-Injection of Liquid Ammonia … · 2021....

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