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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
4Department of Mechanical Engineering, Iowa State University
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
9Department of Mechanical Engineering, Iowa State University
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
12Department of Mechanical Engineering, Iowa State University
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