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