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14th Annual Conference on Ammonia, Oct 15 – 16, 2007
Combustion Efficiency and Exhaust Emissions of Ammonia Combustion in
Diesel Engines
Song-Charng kong
Department of Mechanical Engineering
Iowa State University
Acknowledgements:Iowa Energy Center (Norman Olson, Tom Barton)
2Department of Mechanical Engineering, Iowa State University
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
• Erosive to some materials
• Ammonia emissions can be harmful
• Potential high NOx emissions due to fuel-bound nitrogen
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 diesel injection system
Diesel ignition
Induce NH3
combustion
Burn out
premixed NH3
4Department 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
5Department of Mechanical Engineering, Iowa State University
Review – Previous Results
• Demonstrated ammonia combustion with D2 and B100
2. Varied diesel and ammonia flow rates to maintain constant torque
0
50
100
150
200
250
300
0 20 40 60 80 100
1000 rpm
To
rqu
e (
ft-lb
)
Load (%)
Diesel+NH3
Diesel
1. Constant ammonia flow rate � constant torque increase
3. Used 5% diesel, varied ammonia flow rate for variable 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
Diesel
6Department of Mechanical Engineering, Iowa State University
Present Results
• Ammonia flow rate control
• Gaseous and particulate emissions
measurements
• Exhaust ammonia measurements
• Ammonia combustion efficiency
• Engine thermal efficiency analysis
7Department of Mechanical Engineering, Iowa State University
Ammonia Flow Rate Control
• Issues:
• Materials – require stainless steel, carbon steel
• High pressure, high flow rate (as compared to other lab uses)
• 0.5 lb/min for 1000 rpm, full load, 95% energy replacement
• Ag industrial application – regulating liquid ammonia at
higher flow rates
• Developed control mechanismFine tune
Coarse
adjustment
Safety
NH3
8Department of Mechanical Engineering, Iowa State University
Engine Test Results
• Obtained stable engine power output
Constant Peak Torque
Power vs. Load
0
5
10
15
20
25
30
35
40
45
0 20 40 60 80 100
Diesel Load %
Po
wer
(kW
)
Diesel Only
NH3 + Diesel
5% Diesel + NH3 Power vs. Load
0
5
10
15
20
25
30
35
40
45
0 20 40 60 80 100
Load %
Po
wer
(kW
)Diesel Only Full Curve
NH3 + Diesel
9Department of Mechanical Engineering, Iowa State University
CO2 Emissions
• Always much lower than diesel values
5% Diesel + NH3
CO2 (%Vol)
0
2
4
6
8
10
12
14
0 20 40 60 80 100
Load %
CO
2 (
%V
ol)
Diesel
Diesel + NH3
Constant Peak Torque
CO2 (%Vol)
0
2
4
6
8
10
12
14
0 20 40 60 80 100
Diesel Load %
CO
2 (
%V
ol)
Diesel 100% Load
NH3 + Diesel
Reduced CO2
10Department of Mechanical Engineering, Iowa State University
NO Emissions
• Ammonia can poison NO converter • Replace material from COM-03 to COM-GC3
• This “glassy carbon” is resistant to such poisoning
• Thermal NO & fuel-bound NO
5% Diesel + NH3
NO (ppm)
0
200
400
600
800
1000
1200
1400
1600
1800
0 20 40 60 80 100
Load %
NO
(p
pm
)
Diesel
Diesel + NH3
Constan Peak Torque
NO (ppm)
0
200
400
600
800
1000
1200
1400
1600
0 20 40 60 80 100
Diesel Load %
NO
(p
pm
)
Diesel 100% Load
NH3 + Diesel
11Department of Mechanical Engineering, Iowa State University
Hydrocarbon Emissions
• Hydrocarbons are higher
• Due possibly to incomplete combustion of diesel fuel caused
by lower flame temperature of ammonia
5% Diesel + NH3
HC (ppm)
0
50
100
150
200
250
300
0 20 40 60 80 100
Load %
HC
(pp
m)
Diesel
Diesel + NH3
Constan Peak Torque
HC (ppm)
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
0 20 40 60 80 100
Diesel Load %
HC
(pp
m)
Diesel 100% Load
NH3 + Diesel
12Department of Mechanical Engineering, Iowa State University
Soot Emissions
• Soot emissions vary depending on fueling rates
Constant Peak Torque
Soot
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0 20 40 60 80 100
Diesel Load %
Filte
r S
mo
ke
Nu
mb
er
Diesel 100% Load
NH3 + Diesel
5% Diesel + NH3 Soot
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0 20 40 60 80 100
Load %
Filte
r S
mo
ke
Nu
mb
er
Diesel 100% Load
NH3 + Diesel
13Department of Mechanical Engineering, Iowa State University
NH3 Exhaust Concentrations
• Concentrations vary depending on NH3 fueling rate
• Further study is required to reduce NH3 emissions.
Constan Peak Torque
NH3 in Exhaust (ppmV)
0
500
1000
1500
2000
2500
3000
3500
0.00 20.00 40.00 60.00 80.00 100.00
Diesel Load %
NH
3 (
pp
mV
)
5% Diesel + NH3
NH3 in Exhaust (ppmV)
0
2000
4000
6000
8000
10000
12000
14000
0 20 40 60 80 100
Load %
NH
3 p
pm
V
This strategy might not be feasible – not sufficient diesel energy to initiate combustion.
High
NH3
fueling Low NH3
fueling
14Department of Mechanical Engineering, Iowa State University
NH3 Intake/Exhaust Concentration
• Constant torque conditions
0
2
4
6
8
10
0 20 40 60 80 100
Constant Torque Conditions
NH
3 C
on
cen
tratio
n (
%)
Diesel Load (%)
Intake
Exhaust
15Department of Mechanical Engineering, Iowa State University
NH3 Combustion Efficiency
• Constant engine torque conditions
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
Constant Engine Torque
Vo
lum
etr
ic C
on
ve
rsio
n E
ffic
ien
cy (
%)
Diesel Load (%) 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 (%)
Volume conversion efficiencyMass conversion efficiency
16Department of Mechanical Engineering, Iowa State University
Summary
• Reasonable fuel economy between 40~60% diesel fueling
• Ammonia combustion efficiency ~ 95%
• Ammonia emissions: 1000 ~ 3000 ppm under the specific conditions tested
• Future work –
• Improve combustion efficiency of ammonia
• Ammonia flow rate control depending on engine loads
• Optimize diesel/ammonia dual-fuel system
• Ammonia removal in exhaust