14th Annual Conference on Ammonia, Oct 15 – 16, 2007

Demonstrate Ammonia Combustion in

Diesel Engines

Aaron Reiter

Song-Charng kong

Department of Mechanical Engineering

Iowa State University

Acknowledgements:Iowa Energy Center (Norman Olson, Floyd Barwig)

2Department of Mechanical Engineering, Iowa State University

Background

• Motivation

• Ammonia (NH3) combustion does not generate CO2

• Biorenewable; Hydrogen carrier, key to hydrogen economy, etc.

• Challenges

• Ammonia is very difficult to ignite

• Octane number ~ 130

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

• Erosive to some materials

• Fuel induction system modification

• Less energy content – maximize energy substitution using NH3

• Others …..

3Department of Mechanical Engineering, Iowa State University

Approach

• Introduce ammonia to the intake manifold

• Create premixed ammonia/air mixture in the cylinder

• Inject diesel (or biodiesel) to initiate combustion

• Without modifying the existing injection system

Diesel ignition

Induce NH3

combustion

Burn out

premixed NH3

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Presentation Outline

• Ammonia combustion properties and implications

• Chemical kinetics study

• Experimental setup

• Baseline engine performance with diesel fuels

• Engine test using dual fuel – diesel/NH3

• Emissions results

• Summary

5Department of Mechanical Engineering, Iowa State University

Thermodynamics/Chemistry

• Stoichiometric chemical reaction

3 2 2 2 20.75 ( 3.76 ) 1.5 1.91NH O N H O N+ ⋅ + ⋅ → ⋅ + ⋅

2.641418.610313716.0456-33.5NH3Ammonia

2.766042.3823014.3217---C14.4H24.9Diesel

2.57814431015.291---C7H17Gasoline

2.702726.98508.95378.4C2H5OHEthanol

2.69002012036.43564.7CH3OHMethanol

Energy Content(MJ/kg-

stoichiometric mixture)

Energy Content

(MJ/kg-fuel)

Latent Heat

(kJ/kg)(Air/Fuel)s

Boiling Point (°C)

MoleculeFuel

6Department of Mechanical Engineering, Iowa State University

Thermo-Chemistry

• Adiabatic flame temperature of NH3/diesel mixture

• NH3 energy fraction with different equivalence ratios

0 0.2 0.4 0.6 0.8 11400

1600

1800

2000

2200

2400

fracenergy,NH3

Tad

iab

ati

c

[K]

PHI=0.5

PHI=1.0

Phi=0.9

PHI=0.8

PHI=0.7

PHI=0.6

Adiabatic T is the final equilibrium T.

In engines, we need to know how fast the reaction goes!

7Department of Mechanical Engineering, Iowa State University

Chemical Kinetics – Methane/Ammonia

• Ignition delay – important parameter in CI engines

• Replacing HC fuel with NH3 will delay ignition

500

1000

1500

2000

2500

3000

1 10 100 1000

Autoignition of CH4-NH3-Air System

Syste

m T

em

pera

ture

(K

)

Time (ms)

9.5%-CH4/0%-NH3

4.5%-CH4/5.0%-NH3

1.5%-CH4/8.0%-NH3

autoignition

Need to rely on HC fuel

to initiate combustion!

8Department of Mechanical Engineering, Iowa State University

Chemical Kinetics – Diesel/Ammonia

• Ignition delay in a constant-volume chamber

• Diesel/NH3 system

800

1000

1200

1400

1600

1800

2000

2200

2400

0 0.5 1 1.5 2 2.5

T History

10-9020-8040-6090-10

Syst

em

Te

mp

era

ture

(K

)

T ime (ms)

Diesel-NH3 (%):

IncreasingNH3

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Test Engine

• John Deere 4045 Engine

• Turbocharged, 4-cylinder, 4.5 liter displacement

• Popular Deere engine – various tracker & Genset applications

• Peak torque range – 280 ft-lb at 1400 rpm

• Test conditions

• Various engine speeds (1000 ~ 1800 rpm)

• Various engine loads (5% ~ 100%) for each speed

• Each speed/load point – with and without NH3 induction

• Test data – torque, BSFC, emissions

• Only selected data are shown

10Department of Mechanical Engineering, Iowa State University

Ammonia Fueling System

• Fuel system

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

before manifold

Liquid NH3 tank

Fuel lineInduction

point

Fuel line

11Department of Mechanical Engineering, Iowa State University

Test Results – Constant NH3 Flow Rate

• Using one ammonia tank and single fuel line

0

100

200

300

400

500

-80

-60

-40

-20

0

20

40

0 20 40 60 80 100 120

1800rpm Engine Torque

En

gin

e T

orq

ue

(ft

-lb

)

En

erg

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

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Test Results – Constant Torque

• Induce more NH3

• Fixed at different diesel fueling, adjusted NH3 flow

rate to maintain constant torque

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

0

50

100

150

200

250

300

0 20 40 60 80 100

1000 rpm

To

rqu

e (

ft-lb

)

Load (%)

Diesel+NH3

Diesel

0

1

2

3

4

5

0 20 40 60 80 100

1000 rpm

Flo

w R

ate

(g

/s)

Load (%)

NH3

Diesel

0

200

400

600

800

1000

0 20 40 60 80 100

1000 rpm

BS

FC

(g

/kW

-hr)

Load (%)

NH3

DieselBSFC_diesel & BSFC_NH3 calculated separately

based on individual flow rate and torque contribution

Poor diesel BSFC

Poor NH3 BSFC

13Department of Mechanical Engineering, Iowa State University

Test Results – Variable Torque

• Goal – to achieve maximum energy substitution

• Diesel fueling was maintained at approximately 5%

• Adjusted NH3 rate for desirable engine torque

0

50

100

150

200

250

0 20 40 60 80 100

1400 rpm, 5% Diesel Energy

To

rqu

e (

ft-lb

)

Load (%)

Diesel+NH3

Diesel0

1

2

3

4

5

6

0 20 40 60 80 100

1400 rpm, 5% Diesel Energy

Flo

w R

ate

(g

/s)

Load (%)

NH3

Diesel

0

200

400

600

800

1000

1200

0 20 40 60 80 100

1400 rpm, 5% Diesel Energy

BS

FC

(g

/kW

-hr)

Load (%)

NH3

Diesel

Can achieve high NH3 ratio

but poor fuel economy

14Department of Mechanical Engineering, Iowa State University

Test Results – Using Biodiesel

• B100 was used

• Can achieve similar results as regular diesel fuel

0

50

100

150

200

250

300

0 20 40 60 80 100

1000 rpm, Biodiesel

To

rqu

e (

ft-lb

)

Load (%)

Diesel+NH3

Diesel

0

50

100

150

200

250

300

10 20 30 40 50 60 70 80

1400 rpm, 5% Biodiesel Energy

To

rqu

e (

ft-lb

)

Load (%)

Diesel+NH3

Diesel

Constant engine torque Variable engine torque

15Department of Mechanical Engineering, Iowa State University

Emissions Measurement

• Gaseous emissions – HC, CO, CO2, NOx, O2

• Emission analyzer modification for this study

• Certain materials were replaced by stainless steel

• Baseline diesel conditions

2

4

6

8

10

12

0 20 40 60 80 100

Pure Diesel Fuel

CO

2 (

%)

Diesel Load (%)

0

400

800

1200

1600

20

30

40

50

60

70

20 40 60 80 100 120

Pure Diesel Fuel

NO

x (

pp

m) H

C (p

pm

)

Diesel Load (%)

NOx

HC

These data will be used for comparisons

16Department of Mechanical Engineering, Iowa State University

CO2 Results

• Maintained constant torque by varying diesel & NH3

2

4

6

8

10

12

0 20 40 60 80 100

Pure Diesel Fuel

CO

2 (

%)

Diesel Load (%)

(repeated plot from previous)

2

4

6

8

10

12

0

40

80

120

160

200

240

280

0 20 40 60 80 100

Diesel-NH3, 100% Torque

CO

2 (

%)

To

tal T

orq

ue

(ft-lb)

Diesel Load (%)

CO2

Torque

CO2 for 100% diesel

decreasing CO2 due to increased NH3 fueling

All the CO2 comes from

diesel combustion

CO2 reduction

17Department of Mechanical Engineering, Iowa State University

NH3 Results

• Speculation – burning NH3 will …..

• Increase NOx – due to fuel-bound nitrogen

• Reduce NOx – due to lower combustion temperature

• Constant torque conditions

0

400

800

1200

1600

0

40

80

120

160

200

240

280

0 20 40 60 80 100

Diesel-NH3, 100% Torque

NO

x (

ppm

)

Tota

l To

rque (ft-lb

)

Diesel Load (%)

NOx

Torque

NOx for 100% diesel

Low NOx due

to low comb T

High NOx due

to N in NH3

?

18Department of Mechanical Engineering, Iowa State University

More on NOx Emissions

• Repeated testing

Another effect – NH3 can

reduce NOx in diesel SCR

(selective catalytic reduction)

Urea � NH3

(NH2)2CO + H2O � 2NH3 + CO2

SCR Catalyst

4NH3 + 4NO + O2 → 4N2 + 6H2O

2NH3 + NO + NO2 → 2N2 + 3H2O

8NH3 + 6NO2 → 7N2 + 12H2O

0

200

400

600

800

1000

1200

1400

1600

0 20 40 60 80 100

Diesel-NH3, 100% Torque

NO

x (

ppm

)

Diesel Load (%)

Sudden

NOx

decrease

NOx for 100% diesel

19Department of Mechanical Engineering, Iowa State University

20

30

40

50

60

70

80

0

40

80

120

160

200

240

280

0 20 40 60 80 100

Diesel-NH3, 100% Torque

HC

(ppm

)

Tota

l Torq

ue (ft-lb

)

Diesel Load (%)

HC

Torque

HC for 100% diesel

decreasing HC due to lower diesel fueling

Increasing HC due to lower comb T

HC Results

• Maintained constant torque conditions

Additional reasons for

HC increase?

Re-combination between

C (from diesel) and H

(from NH3)?

20Department of Mechanical Engineering, Iowa State University

Biodiesel/NH3 Emissions

• Same trend as in the diesel case

• B100 produced lower HC than regular diesel at baseline

0

400

800

1200

1600

0

50

100

150

200

250

300

0 20 40 60 80 100

B100-NH3, 100% Torque

NO

x (

ppm

)

Tota

l Torq

ue (ft-lb

)

B100 Load (%)

NOx

Torque

NOx for 100% B100

Low NOx due to lower comb T of NH3

Increasing NOx due to nitrogen molecule in NH3

20

30

40

50

60

70

80

0

50

100

150

200

250

300

0 20 40 60 80 100

B100-NH3, 100% Torque

HC

(p

pm

)

To

tal T

orq

ue

(ft-lb)

B100 Load (%)

HC

Torque

HC for 100% B100

decreasing HC due to lower diesel fueling

Increasing HC due to lower comb T

21Department of Mechanical Engineering, Iowa State University

Summary

• Demonstrated ammonia combustion in diesel engines

• Premixed NH3/air with direct-injection diesel for ignition

• Effective in CO2 reduction while maintaining the same engine

torque output

• Reasonable fuel economy between 20~60% diesel fueling

• NOx emissions are not a concern as originally expected

• Lower NOx for certain diesel fueling range

• HC has an opposite trend to NOx

• Further investigations are required for –

• Emissions formation mechanisms

• Precise control of NH3/diesel flow rates for optimal fuel economy

and exhaust emissions