Demonstrate Ammonia Combustion in Diesel Engines• Baseline engine performance with diesel fuels...
Transcript of Demonstrate Ammonia Combustion in Diesel Engines• Baseline engine performance with diesel fuels...
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)
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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 …..
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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
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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
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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!
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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!
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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
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Ammonia Fueling System
• Fuel system
• Vapor ammonia introduced into the intake duct – after turbo,
before manifold
Liquid NH3 tank
Fuel lineInduction
point
Fuel line
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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
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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
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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
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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
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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
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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
?
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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
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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)?
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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
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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