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AD 633 632

PERFORMANCE OF ANHYDROUS AMMONIA ASA SPARK IGNITION ENGINE FUEL

D. S. Smith, et al

California UniversityBerkeley, California

February 1966

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DEFENSE DOCUMENTATION CENTERDEFENSE SUPPLY AGENCY

FOR FEDERAL SCIENTIFIC AND TECHNICAL INFORMATION

U. S. DEPARTMENT OF COMMERCE / NATIONAL BUREAU OF STANDARDS ' 1NSTT UYL FOR AflPLIt" TCHOLCG

UNCLASSIFIED

PERFORMANCE OF ANHYDROUS AMMONIA AS

A SPARK IGNITION ENGINE FUEL

by

D. S. SmithE. S. Starkman

Report No. TS-66-2

Contract DA-04-200-AMC-791 (XFebruary 1966 D C

IrMAY 2 519

COLLEGE OF ENGINEER WG

UNIVERSITY OF CALIFORNIA, Berkeley

4

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UNIVERSITY OF CALIFORNIADepartment of Mechanical Engineering

Thermal Systern Division

PERFORMANCE OF ANHYDROUS AMMONIA AS A SPARK IGNITION ENGINE FUEL

by

D. S. Smith

E. S. Starkman

J Technical Report No. 6

Under ContractDA-O4-200-AMC-791(X) Ammonia Fuel

Army Material Command.

R & D DirectorateChemistry and Materials Branch

Project DirectorE, S. ar1an

4, February, 1966

F

SUMMARY

The operating characteristics of anhydrous ammonia as a fuel for a

spark ignition engine were determined and compared, experimentally and

theoretically, to those of iso-octane, the reference hydrocarbon fuel.

Experimental data obtained over a wide range of parameters--compression

ratio, engine speed, manifold pressure--displayed no grossly divergent

fuel characteristics for ammonia compared to iso-octane.

Anhydrous ammonia was demonstrated to operate successfully as a fuel

for spark ignition engit. . Principal requirements are that it be intro-

duced into the engine in the vapor phase and be partly dissociated to

hydrogen and nitrogen (NH3 -a PH + H + Dissociation wascatalyst ' 3 2 2

accomplished in a temperature controlled catalvtic dissociator using pel-

letized activated iron catalyst. The optimal weight concentration of

hydrogen to insure against power ioss 4s approximately 5 per cent.

The maximum theoretically possible indicated output using ammonia vapor

when adjusted for 5 per cent hydrogen dissociation is about 75 per cent of

that with ydrocarbi.n. The presently obtained maximum experimental level

is 7" per cent at a compression ratio of 10.

Specific fuel consumption, both by theory and experiment, is twofold

at maximum power and 2-1/2 fold at maximum economy when using ammonia as a

replacemlent for hydrocarbon.

Spark timing for maximum performance must be advanced slightly for

emonia but eensitlvity to spark timing is very little greater than with

hydrocarbons.

i

TABLE OF CONTENTS

eage

I. INTPr,;DUCTION . . . . . . . . . . . . . . . . . . . . . . . . . 1

II. EXPERIMENTAL FACILITIES AND EQUIPMENT..... . . . . . . . . 2

III. EXPERIMENTAL RESULTS ... .................. 10

1. Power Output. . . . . . . . . . . . . . . . . .. . .

2. Specific Fuel Consumption . . ............... .*.

3 Influence of Hydrogen ConcentrationResulting from Ammonia Dissociation . . . . . . . . . 17

4. Spark Timing. . . . . . . . . . . . .. . .. .

5. Engine Oil Analysis ... . . . . . .. . . . . . . .

IV. CONCLUSIONS. . . . . . . . . . . . . . . . . . . . . . 20

V. REFERENCES . . . . . . . . . . . . . . . . . . ..... . . 48

VI. ACKNOnW Em..ENT . . . . . . . . . . . . . . . . . . . . 49

VII. APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . 50

g

IA' -

ii

LIST OF ILLUSTRATIONS

Fige Title Page

1 CFR Engine Test Facility 5

2 System Schematic Diagram 6

3 Schematic Diagram of Air Supply System T

4 Schematic Diagram of Ammonia Fuel Supply System 8

5 Liquid Fuel Flow Meter 9

6-11 Influence of Fuel-Air Ratio on Power Output 21-26

12 Comparative Performance of Ammonia and Iso- 27Octane

13 Effect of Engine Speed on Power Output 28

14 Effect of Manifold Pressure on Power Output 29

15 Variation of Maximum Power uutput with Compression 30Ratio

16 Relative Maximum Output for Ammonia as compared to 31Iso-Octane

17-22 Influence c' Fuel-Air Ratio upon Fuel Consumption 32-37

23 Comparat:i'e Fuel Consumption of Ammonia and Iso- 38Octane, Varlable Compression Ratio

24 Comparative Fuel Consumption of Ammonia and Iso- 39Octane, Variable Manifold Pressure

25 Comparative Fuel Consumption of Ammonia and Iso- 4oOctane, Variable Engine Speed

26 Fuel Consumption of Ammonia Compared To Iso-Octane 41

27 Influence of Compression Ratio on Fuel Consumption 42

28 Influence of Compression Ratio on Relative Fuel 43Consumption

IA

Fig Title iag

29 Effect of~ Predissociation of Ammonia on Power 44

Output

30-31 Influence of Spark Advance on Power Output As 45-46a Function of Mixture Strength

32 Influence of Spark Timing on Power Output at 47Fuel-Air Equivalence Ratio for Maximum Power

iv

LIST OF EXHIBITS

Exhibit Title Page

I Engine Oil Analysis 51

II Tabulation of Data, Engine Oil Analysis 52

LIST OF TABLES

Table List of Tables _

I Experimental Data, Iso-Octane 53

II Experimental Data, Ammonia 55

55F

1

I. INTRODUCTION

Investigation of the operating characteristics of anhydrous ammcrnia

as a fuel for spark ignition engines and comparison with a reference hydro-

carbon, iso-octane, was conducted under Contract DA-04-200-AMC-791(X)

AMMONIA FUEL, Army Material Command, R & D Directorate, Chemistry and

Materials Branch. The general objective was to extend the area of applied

information relative to successful substitution of gaseous, predissociated

ammonia for hydrocarbons as a fuel for spark ignition engines. The reasons

for renewed interest in ammonia as a fuel and a review of early success in

its application are presented in the SAE literature. (* The experimental

investigation reported here was initiated in August of 1964 and completed

in August of 1965.

The goal of the experimental work, carried out in a single cylinder CFR

engine, was to point the way to successful operational application and at

the same time to do this with the minimum of engine modification. Thus, the

investigation was pursued using nominal and existing engine compression ratios,

normal ignition systems, atmospheric or throttled manifold pressures and

ammonia dissociation methods well within practical capabilities of a military

application.

The purpose of this report is twofold; to present the comparative experi-

mental results and to compare the experimental results with the previously

published theoretical predictions (2 ) which were based on thermodyrnamic cal-

culationb of the relative performance to be expected when operating a spark

Ignition engine on gaseous ammonia and iso-octane.

* Numbers in parenthesis designate references.

II. EXPERIMENTAL FACILITIES AND EOUIPMENT

The CFR engine test facilit- and a schematic diagram of the test

system for gaseous ammonia are shown in Figures 1 and 2. They provide

a general orientation to the physical arrangement of the test facilities

and show the significant flow processes.

1. Kanen -and _!ynamometer

A CFR single cylinder engine of 3-1/4" x 4-1/2" dimensions, the

primary research apparatus, was used for obtaining all of the experimental

data. The engine was well suited for this combustion research because of

its small fuel requirement and the ease with which the test variables could

be changed, controlled, and observed. Cooling jacket temperatures were

fixed by evaporation and recycle of coolants--a J&cket terperature of

152*F was maintained for iso-octane by the use of methanol, ethylene

glycol was used to maintain a jacket temperature of 3540F for ammonia.

The usual "supercharge method" instrumentation was provided in order to

facilitate close control and accurate measurement of air pressure and flow

rate as shown in Figure 3. Engine speed was monitored by an electronic

counter actuated by a magnetic pick up.

The engine was connected to a Sprague electric dynamometer capable

of a wide speed range for motoring or power absorbtion. The d.c. output

from the dyna-ometer was dumped into a resistance bank with fine adjust-

ment controls for accurate speed control and power output measurements.

2. Ammonia Suvvlv and M etering

A schematic diagram of the ,mmonia fuel supply system is shown in

3

Figure 4. Ammonia vapor was drpwn from a refillable high pressure bottle

maintained in a tempering tank of water. Constant temperature of the bath

and replacement of the ammonia latent heat were affected by supplying sub-

merged steam to the water bath. Primary measurement and calibration of

ammonia flow were accomplished with volume calibrated sight glass on the

ammonia bottle. Continuous flow rate determinations of ammonia were made D"

with turbine flow meter with data read-out from an electronic counter.

Suitable regulators and needle 'alve were installed to reduce the pressure

and meter the ammonia flow. The pressure and temperature of the ammonia

were monitored at several points in the fuel supply line. Introduction to

the engine ras by simple standpipe in the intake manifold.

3. Ammonia Dissociator

Partial decomposition of the ammonia vapor was carried out in a 266

cubic inch capacity stainless steel catalyst chamber. This was loosely

filled with a pelletized activated iron catalyst. Two kilowatts of

electrical resistance element heaters of the globar type were submerged

in the catalyst bed.

A limitation of the catalytic dissociator was its very large thermal

lag. It was difficult to quickly adjust the temperature or electrical

energy supply to a predetermined level of decomposition. Future considera-

tions of similar dissociators should incorporate a more flexible and rapid

means of control of the ammonia decomposition. In addition, there was

inadequate dissociation capacity to supDly the engine with sufficient

hydrogen at an engine speed of 1800 rpm for rich vixtures (this condition

is discussed extensively in a later section).

4. Iso-Octane Supply and Metejrin

Iso-octane was supplied to the erigine by the standard CFR pump and

injector system.

Metering was accomplished by means r-f an electrically co-.trolled U-

tube type meter shown in Figure 5. This type of meter has the advantage

of not requiring buoyancy effect corrections as does the ASTM bean balance

method. Water in the left leg is balanced at an immiscible inner face by

the iso-octane in the right leg. A calibrated weight of fuel is withdrawn

from the meter as the water level drops from electrode B to electrode C.

The water serves as a conductor between the electrodes and the breaking

of the miniscus on the various electrodes actuates the clock and solenoid

values thus affecting the operations of timing, draining, and filling.

5. Gas Chromatograph

A Beckman GC-2 gas chromatograph was used tr, determine the hydrogen

dissociation at engine inlet. The sample was withdrawn by hypodermic

syringe from the fuel line sample septum shown in Figure 2 and injected

into the chromatograph.

For hydrogen detection a stainless steel molecular sieve (Beckman

Column 70015) w~s used. Nitrogen was used as the carrier gas to make

the chromatograph sensitive to hydrogen and quite insensitive to ammonia.

The chromatograph was calibrated on the peak height basis using

laboratory prepared samples consisting of ammonia, nitrogen and hydrogen

in proportions comparable to the range of dissociation products from the

catalytic dissociator.

'4L

FIGURE 1. CFR ENGINE TEST FACILITY

w

M00>42 J

o 01m w 4

ca 0

0 04 w w~ CO

)-0 C0

W WO a -X WW 2

4zw4

> MO42.4

xwo w

-Jg I 0M0iz -.

ilo0 LL

04

AIR SUPPLY HEATERCONTROL

PRESSUREAFILTER REGULATOR

ORI FICE

AAIR

AIR INLET FLOWPRESSURE AIR SUPPLY RATE

(MERIAM TANKS (MERIAMMODEL MODEL

30 F 10)30EB25)

CFRNH 3 VARIABLE

SUPPLY SPEEDENGINE

FIGURE 3

SCHEMATIC DIAGRAM OF AIR SUPPLY SYSTEMTO CFR ENGINE

ELECTR ICALSOLENOID 60 MICRONSAFETY FITEVALVE

-------- PRESSUREREGULATOR

FILL LINE POTENTIOMETER.. 'STEAM

NH 3 NHCALIBRATED

SIGHT LIQGLASS NH ELECTRONIC

-'--'-COUNTER

WATER BATH Cox GL.-TURBINE

FLOW METER

TPOWERSTATS

01 CHAMBER

:- 0- 2000- WATTS

! GCo lH r'---l_._FLOW CONTROL

0 OLINGLJ- VALVEi COIL ----

POTENT IOMETERL

CATALYSTCHAMBER

CFRVARIABLESPEED

ENGINEENGINE LMNFLINTAKE |SNAE POTENTIOMETERSAMPLE

SEPTUM

FIGURE 4

SCHEMATIC DIAGRAM OF AMMONIAFUEL SUPPLY SYSTEM

" '. fPr- m x . .. .

A-

in4

MMI"MM

N'IGtURP

1,TQUI) Vr

W'

10

III. EXPERIMENTAL RESULTS

As indicated previously, all experimental results were obtained from

a CFR spark ignition engine with gaseous premixed anhydrous ammonia and

manifold injected iso-octaie as the fuels. The test parameters were com-

pression ratio, engine speed, manifold pressure and for certain tests hydrogen

dissociation and spark advance. Iso-octane, C8H1 8 , was selected as a repre-

sentative hydrocarbon for the experimental reference fuel. Iso-octane

was also used as the model for theoretical calculations (2) comparing ammonia

and hydrocarbon fuels. The comparison in this report of experimental and

theoretical results are thus compatible.

Throughout this report, fuel-air ratio will be presented in terms

of the fuel-air equivalence ratio, 0, defined as the actual fuel-air ratio

divided by the stoichiometrically correct fuel-air ratio. Therefore, 0 = 1

corresponds to a stoichiometrically correct fuel-air ratio. Use of equivalence

ratio rather than fuel-air ratio displays the data in better perspective,

particularly since ammonia has a chemically correct mixture with 6:1 parts

of air by weight and iso-octane has a chemically correct mixture with 15:1

parts of air by weight.

The experimental results were obtained for a cooling jacket temperature

of 1520F for iso-octane and 3540F for ammonia. The ase of a relatively high

jacket temperature when burning ammonia was for the purpose of enhancing

ammonia decomposition during the compression stroke. A relatively low

jacket temperature was used with iso-octane in order to suppress a tendency

to knock at a compression ratio of 10.

Ammonia dissociation and thus hydrogen supply rates were held only

as high as was felt necessary to obtain optimum performance at any given

operating point. The amourt of dissociated ammonia was thus a variable.

It is now recognized that the quantity of ammonia which was dissociated was

in a few instances marginally low or even below a critical amount. Thisen

factor will be considered in a later section at length. Nevertheless, the

results shown in Figures 6 through 32 are completely satisfactory for com-

prehensive and reliable illustration of the important functional relation-

ships.

1. Power Output

Indicated mean effective pressure, the universal expression for the

power output to be obtained from an engine of given volumetric capacity, is

shown as a function of the fuel-air equivalence ratio in Figures 6-11. The

parameters are compression ratio, engine speed and manifold pressure. Thece

data for each curve was collected at a fixed spark setting; the spark advance

was adjusted for optimum at maximum power output. The range of optimum spark

advance for iso-octane was 220 - 430, and 350 - 550 BTDC for ammonia.

At an engine speed of 1800 rpm the predissociation of hydrogen, due

to the limited capacity of the catalytic dissoclator, was insufficient for

ammonia to produce full power above a fuel-air equivalence ratio of approxi-

mately 0.90. The range of hydrogen deficiency is represented by the dashed

portion of the curves.

Figures 12-14 present comparative power output data for ammonia and

iso-octane as a function of fuel-air equivalence ratio over the range of

12

parameters. Power output for iso-octane is greater than for ammonia at

the same test conditions over the c(cnplete range of interest of variables

and parameters. However, it is also evident from these figures that ammonia

V, has ao grossly divergent power performance characteristics from iso-octane

and that the ammonia data are consistent and orderly within the limitations

of hydrogen deficiency (for an engine speed of 1800 rpm at an equivalence

ratio greater than 0 = 0.90). Peak power output for iso-octane occurs near

0 a 1.15; in contrast, peak power for ammonia is obtained at a mixture ratio

which is about 10 per cent lean.

Power output for ammonia, as indicated by Figure 12, is affected to

a much greater extent by low compression ratios than is iso-octane. The

increase in maximum output for a compression ratio increase from 6 tc 8

is 22 per cent for ammonia and 8 per cent for Iso-octane. However, an increase

in compression ratio from 8 to 10 produced modest increases in power output

of nearly the same magnitude - 10 per cent for ammonia and 7 per cent for

iso-octane.

Figure 13 shows power cutput as influenced by engine speed. The dashed

portion of the 1800 rpm ammonia curve reflects a subcritical hydrogen supply

rate, as previously mentioned. This decline in performance is dramatic as

the mixture is richened. Reflected here is the self-generating character

of the ammonia decomposition and flame phenomena, or the failure thereof when

insufficient precombustion decomposition has been effected. Observation of

this same sudden drop off was noted by Cornelius. HulLantel and 4t-CU-h1 (i)

The trend of mean effective pressure with speed is a slightly increasing

13

one, except of course for that portion of the 1800 rpm cu've where the

ammonia dissociator, because of its size, was unable to provide sufficient

dissociation. For ammonia an increasing trend w&s not expected. Power out-

put for ammonia is highly dependent upon hydrogen dissociation. Some dis-

sociation occurs during the compression p.-ocess and is dependent upon the

time for reaction. Since at higher engine speeds there is less dwell time,

less dissociation would be expected to occur in the cylinder. Therefore,

the increasing trend for ammonia seems to indicate that the dissociation

in the cylinder at these low compression rates is not significant compared

to the amount of prediesociation or other effects, perhaps related to

turbulence and mixing factors.

The curves at the lower engine speeds, without hydrogen deficiency,

indicate that the sensitivity of power output to fuel-air equivalence ratio

is approximately the same for the two fuels.

Figure 14 shows the effect of manifold pressure on power output for

a compression ratio of 8 and an engine speed of 1800 rpm. The increase in

maximum power output for ammonia is in direct proportion to the absolute

manifold pressure.

Figures 15 and 16 display the variation of maximum power output,

relative maximum power output and theoretical power output with compression

ratio. Figure 16 shows directly the relative indicated mean effective

pressure obtained when using ammonia as a substitute for iso-octane. Also

shown, as dashed lines, are the theoretical prediction of relative power

ountput of approximately .80 and the theoretical prediction adjusted for

4

5 per cent hydrogen dissociation. The predicted output was obtained by

comparing the theoretical output for ammonia at 0 = 0.90 with that for iso-

octane at 0 = 1.15 (the respective fuel-air equivalence ratios for maximum

output).

The experimentally determined relative output falls about 8 per cent

short of the 80 per cent predicted at a compression ratio of 10 and about

17 per cent less for a compression ratio of 6. There are at least two

reasons for this disDarity between experiment and theory.

Z* The first and most straight forward is related to prior dissociation

of ammonia into H2 and N2 before introduction into the cylinder. Theoretical

calculations did not account for the accompanying increase in volume of fuel

and resulting decrease in volumetric efficiency. For example, decomposition

of 25 per cent of the ammonia (for 4 to 5 per cent level of H2 by weight)

will increase the total volume of fuel by the same 25 per cent. At a

stoichiometric fuel-air ratio this reducei. the amount of air inducted by

about 5 per cent. The power output will drop off accordingly. This then

accounts fo: a significant portion of the difference between theory and

experiment at a compression ratio of 10.

The other factor involved in tbe disparity between theory and experi-

ment and particularly the improvement with increasing compression ratio is

concerned with the reluctance with which ammonia burns. It has already been

indicated that hydrogen in the fuel feed improves the combustion process

and so does an increase in compression ratio. It is almost certain that

decomposition of ammonia takes place during the compression process. The

15

decomposition produces more hydrogen, but also intermediate species. Thus,

as compression ratio and temperature of compression are increased, so are

hydrogen and intermediate species concentrations.

This later phenomenon is different from that of dissociating the

ammonia in a catalytic dissociator prior to induction. With prior decom-

position the engine will receive substantially only hydrogen, nitrogen

and ammonia. Because of the time factor involved the engine cannot r.-ceive

intermediate dissociation species which may have an important role in com-

bustion.

Note also that overly decomposing the ammonia prior to introduction

into the engine will result in a mixture which is too rich in hydrogen and

attendant difficulties with rapid burn and engine roughness. There is

undoubtedly an optimum amount of predissociation corresponding to maximum

obtainable output and smooth operation. This latter type of optimization

has not been carried out to completion under this program. This optimizing

procedure will be a function o' engine combustion chamber shape in addition

to such other factors as speed, compression ratio, engine ttmperatures, load

and other items.

2. Specific Fuel Consumption

The most significant measure of engine economy is specific fuel con-

sumption. Figures 17 - 22 are the basic comparative fuel consumption curves

for ammonia and iso-octane. Indicated specific fuel consumption is shown

as a function of the fuel-air equivalence ratio. The parameters are comprepsion

ratio, engine speed, and manifold pressure. Cooling jacket temperatures,

16

spark advance and regions of hydrogen deficiency are identical to those for

the power output curves. The range of hydrogen deficiency is again repre-

sented as the dashed portion of the curves.

Figures 23 - 25 present comparative indicated specific fuel consumption

4ata for ammonia and iso-octane as a function of fuel-air equivalence ratio

C over the range of the parameters. Over the complete range of interest of

parameters and variables, for the same test conditions, the indicated specific

fuel consumption for ammonia is greater than that for iso-octane. It is also

evident from these curves that, as for 1ower output, ammonia has no grossly

divergent characteristics from iso-octane and that the ammonia data are

consistent and orderly within the limitations of hydrogen deficiency (at an

engine speed of 1800 rpm for a fuel-air equivalence ratio greater than 0 -

0.90). These figures illustrate directly that specific fuel consumption for

ammonia is over twice that of iso-octane on comparable operations. They

also illustrate that minimum specific fuel consumption with ammonia occurs

at fuel-air equivalence ratios wlich are 20 to 25 per ce-t lean in contrast

to iso-octane for which minimum values occur at mixtures which are approxi-

mately 10 per cent lean.

Figure 23 indicates that specific fuel consumption for ammonia is

affected to a much greater extent than for iso-octane by low compression

ratios. The decrease in minimum specific fuel consumption for a compression

ratio increase from 6 to 8 is 22 per cent for ammonia and 8 per cent for

iso-octane. However, an increase in compression ratio from 8 to 10 produced

modest decreases in indicated specific fuel consumption of nearly the same

17

magnitudes--3 per cent for ammoria and 2 Der cent for iso-octane.

Figure 24 shows the effect of manifold pressur- on indicated specific

fuel consumption. For both fuelE, the change in manifold pressure produced

only a very modest effect of approximately 2 - 3 per cent on fuel consump-

tion. However, for ammonia the decrease in manifold pressure prCduced a

reduction in fuel consumption whilE the opposite effect was produced for

c iso-octane.

The effect of engine speed on indicated specific fuel consumption is

shown in Figure 25. The curves for bo"h fuels display, as would be expected,

little or no effect of engine speed cn fuel consumption. The effect of

hydrogen deficiency is again quite noticeable from the ammonia curve for

an engine speed of 1800 rpm. The curves at the lower engine speeds, without

hydrogen deficiency, indicate that the sensitivity of fuel consumption to

fuel-air equivalence ratio is similar for the two fuels.

The variation of actual, relative, and theoretical indicated specific

fuel consumption with compression ratio is displayed, in Figures 26 - 28.

Figure 26 shows a comparison of actual and theoretical fuel consumption for

the condition of minimum fuel consumption and maximum power output. At

minimum consumption, ammonia must be supplied at two and one-half tim s

the weight flow rate of iso-octane. For maximum power ammonia flow is

double that of iso-octane. The experimental results fall remarkably close

to the theoretical.

3. Influence of Hydrogen Concentration Resulting From Ammonia

Dissociation

Figure 29 contains the results of an investization into the jnfluences

. . .

18

of hydrogen concentration on power output. Hydrogen content of the

partially dissociated ammonia stream was determined directly by gas chroma-

tography as previously described in Section II. The figure shows that 4

to 5 per cent hydrogen is necessary to obtain maximum power at any given

mixture ratio when running at 1800 rpm, a compression ratio of eight, and

manifold pressure of 30" Hg. This 3et of relationships would be expected

to apply generally to other operating conditions.

Hydrogen was supplied to the test engine in the most likely piactical

manner, by partially decomposing the ammonia supply. This procedure results

in a fuel-air mixture which is exactly corresponding in ammonia, hydrogen,

oxygen and nitrogen concentrations to that in any proposed practical apli-

cation which would use ammonia dissociation for hydrogen.

4. Spark Advance

The effect of spark timing on power output for ammonia and iso-octane

is shown in Figures 30 - 32.

Figures 30 sad 31 show how optimizing spark timing can influence power

output over a range of fuel-air equivalence ratios at a compression ratio

of 8 and an engine speed of 1800 rpm. For ammonia the spark should be

slightly retarded and for iso-octane slightly advanced frcm peak power

optimum for maximum performance at richer mixtures. For lean mixtures,

ammonia required :,o sark adjustment; iso-octane requiree slightly greater

advancement than for rich mixtures. For both fuels the increase in power

output with spark adjustment was quite small over a normal operating range

+of - 10 per cent from 0 at maximum power. Ammonia appears to be slightly

19

more sensitive than iso-octane to spark setting at rich mixtures. For the

same engine speed and compression ratio, reduced manifold pressure produced

the same power output trends due to spark adjustments.

Illustrated in Figure 32 is the effect of spark timing on power output

at the fuel-air equivalence ratio for maximum power output. This data ic for

a compression ratio of 8, an engine speed of 1800 rpm, and a manifold pressure

of 30" of Hg. The optimum timing for ammonia is about 55 degrees before

dead center and for iso-octane about 30 degrees at these operating conditions.

Both fuels show only a modest sensitivity of the same magnitude to spark

+setting over a range of optimum - 10 degrees. Ammonia experiences about a

5 per cent loss in power over this range compared to a 4 per cent loss for

iso-octane over the same range.

5. Engine Oil Analysis

A sample of crankcase oil was analyzed through the courtesy of Chevron

Research Company to determine the effect of using ammonia as a fuel on engine

oil under normal engine operating conditions. Detailed results of the

chemical and spectrochemical analysis are included in the Appendix, Exhibits

I and II. There was no indication that the oil was deteriorating from

operation with ammonia fuel. However, an abnormally high amount of copper

and lead in the oil sample might indicate possible corrosion of a copper-

lead bearing.

....

20

IV. CONCLUSIONS

1. Ammonia can be used successfully as a spark ignition engine fuel and

at presently existing compression ratios, if introduced as a vapor and if

first partly dissociated to hydrogen and nitrogen. Under such circumstances

little engine modification is necessary other than a means for flow control

of the ammonia and adjustment of the spark timing.

2. Maximum experimental power output for ammonia was 72 per cent of that

for iso-octane. This result compares favorably with a theoretically pre-

dicted output, when adjusted for 5 per cent hydrogen dissociation, of 75

per cent.

3. Specific fuel consumption using ammonia is increased by a factor of 2

over that of hydrocarbon when compared at peak power and 2-1/2 times when

compared at maximum economy.

4. Hydrogen concentration in the fuel feed is a critical factor for

auccessful operation on ammonia as fuel. Minimum concentrations appear

to be 4 to 5 per cent by weight at intermediate engine speeds of 1800 rpm.

5. Engine performance rapidly falls if less than minimum concentrations

of hydrogen are used. This seems to relate to the self-generating character

of the ammonia decomposition during the compression and combustion processes.

6. Performance factors such as are influenced by engine speed, spalk timing

and manifold pressure are not far different with ammonia than with hydro-

carbons as long as minimum amounts of hydrogen are inducted as a part of

the fuel flow.

FIGURE 6

21 :

INFLUENCE OF FUEL-AIR RATIOUPON POWER OUTPUT I

L aCOMPRESSION RATIO- 6R.P.M. - 1800MANIFOLD PRESSURE - 30" Hg.

a.1 160

w

(nO OCTANE

cJ 140-w c

a-

0

wu. 100-LLJw

z ON 14

0w

<60 ---- H2 DEFICIENCY

Z 0,6 0.8 ! 1.2 1.4 1,6

FUEL-AIR EQUIVALENCE RATIO

FIGURE 7

22

INFLUENCE OF FUEL-AIR PATIOUPON POWER OUTPUT

COMPRESSION RATIO - 8R.P.M. - 1800MANIFOLD PRESSURE -301 Hg.

wo 160

% OCTANE

c. 140

w

Q120wU.

w Iz 100" c,

4 XNw

I-- ---- H DEFICIENCY4- 4

0.6 O,8 1.0 1.2 1.4 1.6


FIGURE 8

23

INFLUENCE OF FUEL-AIR RATIOUPON POWER OUTPUT

COMPRESSION RATIO - 10R. P.M. - 1800MANIFOLD PRESSURE - 30" Hg.

cnC':)a. 60- ISO OC TAN~EI

w

cn140C')W0o

120

lI. bUL.

W

z /1< 80

w 60 Ha DEFICIENCY

a 0.6 0.8 1.0 1.2 1.4 1.6


FIGURE 9 24


COMPRESSION RATIO - 8R.P.M. - 1300MANIFOLD PRESSURE - 30" Hg.

* 160-

:o - OC TAN1 eCo 140-ILa

C.

a.

> 120.-

U. 100

z4

80

60I-

ZAz0.6 0.8 1.0 1.2 1.4 1.6


FIGURE 1025~


COMPRESSION RATIO -8

R. P.M. - 1000MANIFOLD PRESSURE -3081 Hg.

a- 160-

w

(n 140- 0wa-

w120-

wU. 100-LLwz

480-w

w 60

00.6 0.8 1.0 1.2 1.4 1.6


F IG IU 40%E

INFLUENCE OF FUEL-AIR RATIO 2

UPON POWER OUTPUT

COMPRESSION RATIO - 8R. P.M. - 1800MANIFOLD PRESSURE - 21 Hg.

a-120

U) ~ISO -OCTANf

0.

>80-

U

w 60-z4La

40-

H2 DEFI-CIENCY

O0.6 0.8 1.0 1.2 1.4 .


FIGURE 1227

COMPARATIVE PERFORMANCE OFAMMONIA AND ISO-OCTANE

NJ

R. P.M. - 1800MANIFOLD PRESSURE - 30" Hg.

CL. 160 - .R. "/0

w ISO-OCTANE 8

140(.n 6,_

w 120

w

wZ AMMONIA

44

0

w<- 60- Ht DEFICIENCY,

z0.6 0.8 1.0 1.2 1.4 1.6


FIGURE 1328

EFFECT OF ENGINE SPEEDON POWER OUTPUT


MANIFOLD PRESSURE -30" H g.

a.160-

uiISO--OCTANE I .~p

S140-

U.) 1000W MMNI

10-L4i 1

U.4

FUEHAI EQIA EC RATI

0.6 0. .-. . .

FIGURE 14

29

EFFECT OF MANIFOLD PRESSUREON POWER OUTPUT

COMPRESSION RATIO - 8R.P.M. - 1800

a-160

SPRESSURE30iw

S140-(I)co

w120 ISO - OCTANE

w

w 100 Aa.

z<80- AMMONIA0

w

w 60- H DEFICIENCY

eb. A

0j V. 90L*o .6 0.8 1.0 12 i.4 1.6z

FUEL -AI R EQUIVALENCE RATIO

FIGURE 15

30

VARIATION OF MAXIMUM POWEROUTPUT WITH COMPRESSION RATIO

R. P.M. - 1800oMANIFOLD PRESSURE - 30" Hg.

co~1801

w

CO 1601 -w

w 140m

w.

zw

00

w

go3mo 6 8 10

COMPRESSION RATIO

FIGURE 16 31

RELATIVE MAXIMUM OUTPUT FOR AMMONIAAS COMPARED TO ISO - OCTANE

R. P.M. - 1800MANIFOLD PRESSURE - 30" Hg.

I--

-0.9

0

w THEORETICAL? 0.800- THEORETICAL WITH 5%

=E H2 DISSOCIATION

0O.7- X

w 0.6 -

I-

w 0.5

6 8 10

COMPRESSION RATIO

FIGURE 1732

INFLUENCE OF FUEL-AIR RATIOUPON FUEL CONSUMPTION

COMPRESSION RATIO 6R.P.M. - 1800MANIFOLD PRESSURE - 30 Hg.a.:

3! 1.4',

A 1.2N

1.0z0

J 0.8w

.62 0.6- 00Uw0.cl) 0.4-

w9 "--- H, DEFICIENCY

z 0.6 0.8 1.0 1.2 1.4 1.6


FIGURE 1833 ,5



ce~R. P. M. - 18003: MANIFOLD PRESSURE -30 Hg.

a 1.43!

1.2 /

0

1.0-

0-J 0.8

-0 "6w

owC')

0.4aw

'I "2DEFICIENCY

Z 0.6 0.8 1.0 1.2 1.4 1.6


FIGURE 1934



1.4 "co_J

z .20

co 1.2 3fa.

Z/1.0-0

-J 0.8a

IAL

0.6

w

.

0.4-

w

H2 DEFICIENCY

Z 0.6 0.8 1.0 1.2 1.4 1.6


FIGURE 2035


COMPRESSION RATIO - 8R.P.M. - 1300

Iz1 MANIFOLD PRESSURE - 30" Hg.

c'5 1.4..J

0 1.2 0

i-

cn 1.0-zo

S0.80

wIL.

U-S0.6-

"'.4

0-S0.4-

I.L

Z 0.6 0.8 Io 1.2 1.4 1.6FFUEL-AIR EQUIVALEwNCE RATIO

Iiiiiiiim r' o ', - , - ._

FIGURE 2136

INFLUENCE OF FUEL-AIR RATIOUPON FUEL CONSUMPThON

COMPRESSION RATIO - 8R. P.M. - 1000MANIFOLD PRESSURE - 30"Hg.

a:

. 1.4

0J

z 1.2-

[0z0

w

_o 0.6 0

wa.

n 0.4-

w

a

0.6 0.8 1.0 12 1.4 1.6


FIGURE 22 37


COMPRESSION RATIO - 8R.P.M.- 1800

3: MANIFOLD PRESSURE- 21" Hg.a:-I 1.4

..J

1.2 1z0a.

2 1.0-C,,z0(o 0.8-iw

o 0.6

a0.4

W Ha DEFICIENCY

0.6 0.8 1.0 1.2 1.4 1.6

FUEL-AIR EPUIVALENCE RATIO

FIGURE 2338

COMPARATIVE FUEL CONSUMPTIONAMMONIA AND ISO-OCTANE

R.P.M. - 1800MANIFOLD PRESSURE 350i Hg.VARIABLE COMPRESSION RATIO

:i1.4 -

z / 1

0C. 6. /

o CR6" ,oI'IAMMONIA

0.8ow

1.0/00

0.8- 10LL

w0.0-1

H2 DEFICIENCY

O06 0.8 1.0 1.2 1.4 1.6zFUEL-AIR EQUIVALENCE RATIO

FIGURE 24 39 )COMPARATIVE FUEL CONSUMPTION

A MONIA AND ISO-OCTANE -VARIABLE MANIFOLD PRESSURE

X COMPRESSION RATIO - 8a: R.P.M. - 1800: 1.4

IMANIFOLD-J PRESSURE

1.2 30"Hg/z0

a-.01

''AMMONIA

z0

0.8w

0O.63d

0

CL ISO-OCTANEc)O.40

Hp DEFICIENCY

O0.6 0.8 1.0 1.2 1.4 1.6aFUEL- AIR EQUIVALENCE RATIO

c -----

FIGURE 2540

COMPARATIVE FUEL CONSUMPTIONAMMONIA AND ISO-OCTANE

VARIABLE ENGINE SPEEDCOMPRESSION RATIO - 8MANIFOLD PRESSURE- 30" Hg.

3:a:

a

_ 1.4 2z

00

1.2

a-

Ur)z00

0. 0.8 -w

U--

0O.6-

w0-U)O0.4-0

w ~-~-H 2 DEFIENCY

O0.6 0.8 1.0 1.2 1.4 1,6


FIGURE 26 41

FUEL CONSUMPTION OF AMMONIACOMPARED TO ISO-OCTANE

(ISFC AMMONIA/ISFC ISO-OCTANE)

R.P.M. - 1800MANIFOLD PRESSURE 30" Hg.

z 3 .00a-0_ THEORY AT MIN. ISFC2.5 -__wo__ _--- ---

,) 0on 0z0

S 2.0 _-. C-

w THEORY AT MAX. I MEP

wL> 1.5

EXPERIMENTo AT MIN. ISFO

-o AT MAX. WEP

4 6 8 10 12

COMPRESSION RATIO

FIGURE 27 42

INFLUENCE OF COMPRESSION RATIO

ON FUEL CONSUMPTION

R.P.M. - 1800Oi

MANIFOLD PRESSURE -30" Hg.

= EQUIVALENCE RATIO

c-J

2.

a.2 N ~ AMMONIA

.2

""mo, 1.0

w .

La- 0.8

ISO-OCTANE *:.10.

0.4 *: .0

Ha DEFICIENCYw

0-a06 8 10

-COMPRESSION RATIO

FIGURE 28 4

INFLUENCE OF C;OMPREScI0N RATIO

ON RELATIVE FUEL CONSUMPTION

R.P.M. 1800 31 g

MANIFOLD PRESSURE -30Hg

0= EQUIVALENCE RATIO

Q5

0

.. .--.. AMMONIA

n ~AT #=I.O2

0 ______ ISO OCTANE 1.

W -________

*~1. 0

6 8 t0

Or COMPRESSION4 RATIO

FIGURE 29 44

EFFECT OF PREDISSOCIATION OFAMMONIA ON POWER OUTPUT

COMPRESSION RATIO- 8R. P.M. - 1800MANIFOLD PRESSURE- 30" Hg.

120

IDISSOCIATOR L/4f

100-

CL 80 -

wI6o % H2 bi' 4EIGHT

0.6 0.7 0.8 0.9 1.0 1.1


imp

FIGURE 3045

INFLUENCE OF SPARK ADVANCE ONPOWER OUTPUT AS A FUNCTIONOF MIXTURE STRENGTH


zl)a.I 160w. /CI NF-- 340

140 - iwcra-u 120

560w N

U100 -4w %480

zw 80- o SPARK ADVANCE OPTIMIZED0 o0 SPARK ADVANCE FIXED AT MAX. POWER

l..!.- --- H12 DEFICIENCYI,.

0.6 0.8 1.0 1.2 [,4 1.6

FUEL-AIR EQUWALENCE RATIO

FIGURE 31 46

INFLUENCE OF SPARK ADVANCE ONPOWER OUTPUT AS A FUNCTIONOF MIXTURE STRENGTH

COMPRESSION RATIO 8R.P.M. - 1800MANIFOLD PRESSURE - 21" Hg.

oIOF

0 20

cn

wIlJ

wr 6060~ 4005

w

80O50"

U4

z

=E40oSPARK ADVANCE OPTIMICZED

{3uJ o SPARK ADVANCE FIXED AT MAX. POWER< ---- H2 DEFICIENCY

0.6J~ i.2 1.4 1.6


SI

FIGURE 32 47

INFLUENCE OF SPARK TIMING ON POWEROUTPUT AT FUEL-AIR EQUIVALENCERATIO FOR MAXIMUM POWER

COMPRESSION RATIO - 8R.P.M. - 1800MANIFOLD PRESSURE - 30 "Hg.

1 160w

,(°)140

w

/ t * .93)L

0 -20 Tw

P.

w 00

z

SPARK TIMING - BTDC

- ~~~~-17 ~ ~ ~ - -

d

48

REFERENCES

1. "Energy Depot Concept", SAE Publication SP-263. Society of Automotive

Engineers, Inc. New York, New York, November 1964.

2. H. K. Newhall, "Calculation of Engine Performance Using Ammonia Fuel,

I. Otto Cycle," University of California, College of Engineering,

Office of Research Services. Technical Report No. 2, Ammonia Fuels

Studies, 1965.

3. "ASTM Manual for Rating Aviation Fuels by Supercharge and Aviation

Methods", American Society for Testing Materials, Philadelphia, Pa.,

1958.

49

ACKNOWLEDGEMENT

The authors gratefully acknowledge contributions by their associates

to the successful compjletion of this experimental investigation.

Messrs. G. James, T. Maguire, S. Samuelson and R. Sutton were instru-

mental in the acquisition of test data. Mr. H. Stewart was responsible for

instrumentation and developed the liquid fuel flow meter. Mr. J. DeCosta

was responsible for maintenance of the mechanical integrety of the engine

and auxillary systems.

50

APPENDIX

!jj The appendix includes the test results obtained from a chemical and

_ :spectrochemical analysis of engine oil and a tabulation of the engine

performance test data. The analysis was performed by Chevron Research

Capany on a gratis basis.

I

51

CHEVRON RESEARCH COMPANYRICHMOND, CALIFORNIA

ANALYSIS OF OIL FROMCPR ENGINE RUN ON FILE 100.01AMMONIA FUFL SEPTEMBER I, 1965

Author - N. R. Parkin

Analysis of a sample of oil from a CFR engine run on ammoniafuel at the University of California is shown in the attachedtable. The total operating time on the oil was 52 hours.The engine ran for 16 hours on isooct'.nie ft-., and ammoniawas the fuel for 36 hours. Super RE. DEL0 Special Oil (SAE 50)was the crankcase lubricant, and botn used and fresh oilsamples were analyzed,

The results show a negligible change in gravity, flash point,visco lity, and neutralization numbers which indicate that theoil is not deteriorating during operation with ammonia fuel.The spectrochemical analysis shows an abnormally high amountof copper and lead in the used oil, indicating the corrosion ofa copper-lead bearing. Apparently, the use of ammonia fuel isresulting in contamination of the oil with products that arecorrosive to copper and lead.

:sIcEnc. - Table

52

OIL ANALYSESOIL FROM AMONIA-FUELED ENGINE

-- Used --- Fresh

- Oil oilGravity, OAPI 25.8 26.2Flash Point, oF 49o 485Viscosity at 1000, S18 1288 1232Viscosity at 2100F, SUS 97.1 94.4Neutralization No., ASTM D 664

pH 7.61 7.22Total Acid No. 1.6 2.Total Base No. 2.3 2.5Carbon Residue, % 1.00 1.03

Coagulated Pentane Insolubles, % < 0.01 < 0.01Coagulated Benzene Insolubles, % < 0.01 < 0.01Calcium, % 0.15.3 o.184

Zinc % I(TypicalZinc, % 0.077 0 08.4(Typical)Phosphorus, % 0.089 O.M09

Spectrochemlcal Analyslsi ppm (Typical)

Aluminum 1.7Barium 5.1Chromium o.4Copper

51Iron 12Magnesium 1.7Molybdenum 1:6Sodium 10Lead 130Silicon

1.7Tin 8.3

CHEVRON RESEARCH COMPANYRRCT)O/ r -AT.Te iA

53TABLE I

Experimental Data, Iso-0ctane

indicated Mean Spar.Manifold Fuel-Air Effective Advance

Comp. Pressure Equivalence Pressure (DegreesRatio RPM (In, of Hg.) Ratio (0) (Psi) BTDC)

10 1800 30 .80 .28 2810 1800 30 .75 1Lo6 2810 1800 30 .86 14' 2810 1800 30 .91 j47 2810 ..8oo 30 .97 152 2810 1800 30 1.10 157 2810 1800 30 1.17 158 2810 1800 30 1.29 156 2810 1800 30 1.44 151 28]0 1800 30 .95 152 28

8 1800 30 1.15 147 348 180o 30 .76 118 348 1800 30 .88 138 348 180C 30 1.46 145 34

6 1800 30 1.o8 136 436 1800 30 1.51 129 436 1800 30 .93 129 436 1800 30 1.4i 1,33 43

8 1300 30 1.09 143 258 1300 30 1,61 124 25S 8 1300 30 1.39 139 258 1300 30 .95 135 25

8 1300 30 .68 59 25

8 1000 30 1.30 137 228 1000 30 1.00 137 228 .000 30 1.13 138 228 1000 30 .70 78 228 1000 30 .75 110 22

8 1000 30 1.54 129 22

8 1800 21 1.13 99 408 1800 21 .87 90 4o8 1803 21 1.11 98 4o8 1800 21 1.28 98 408 1800 21 1.48 92 4o

3-.8 1800 30 1.52 144 4O8 !800 30 1.68 136 468 1800 30 .71 110 568 1800 30 1.82 131 52

54

Indicated Mean SparkManifold Fuel-Air Effective AdvanceComp. Pressure Equivalence Pressure (DegreesRatio RPM (In. of Hg.) Ratio (P) (psi) BTDC)

8 1800 21 1.02 99 468 1800 21 .83 91 548 1800 21 1.55 93 48 C8 1800 21 1.7o 84 53 B8 1800 30 1.14 148 34 18 1800 30 .14 149 30 3.8 1800 30 l.,4 18 25 18 1800 30 .14 143 20 18 1800 30 L14 138 15 18 3800 ?o 1.1h 130 10 18 800 30 1.14 119 5 18 18oo 30 1.14 105 08 1800 30 1.14 91 5 (ATDC)8 1800 30 1.14 148 4o8 1800 30 1.14 143 458 1800 30 1.14 141 508 1800 30 1.14 135 55

*1

?a

55

TABLE I:

Experimental Data, Ammonia

Indicated Mean SparkManifold Fuel-Air Efrective Advance % H2

Comp. Pressure Equivalence Pressure (Degrees Dissoc-Ratio RPM (fn. of Hg.) Ratio (0) (Psi) BTDC) iation

10 1800 30 .59 83 53 5+10 1800 30 .75 ]Do 53 5+10 1800 30 .88 08 53 3.610 1800 30 .89 110 53 3.810 1800 30 .95 114 53 3.310 1800 30 1.01 I"i 53 3.110 1800 30 1.11 10]. 53 2.3

8 1800 30 .65 84 55 5+8 1800 30 .72 93 55 4.88 1800 30 .83 100 55 3.58 1800 30 .93 104 55 3.78 1800 30 1.01 99 55 3.78 1800 30 1.o8 90 55 3.3

6 1800 30 -74 74 55 4.46 1800 30 .80 82 55 4.06 1800 30 .86 85 55 4.2o 1800 30 .95 82 55 3.70 1800 30 1.06 78 55 3.1

8 1300 30 .62 80 55 5+8 1300 30 .74 90 55 5+8 1300 30 .8o 95 55 4.08 1300 30 .0 103 55 4.88 1300 30 .96 104 55 4.88 1300 30 1.03 105 55 4.38 1300 30 1.04 102 55 4.48 1300 30 1.18 99 55 5+8 1300 30 131 89 55 4.6

8 1000 30 .67 82 35 5+8 1000 30 .77 89 35 5+8 1000 30 .89 97 35 5+8 00 30 .98 100 35 5+8 2000 30 1.07 99 35 5+8 1000 30 1.22 93 35 5+

8 1800 21 .70 59 50 5+8 1800 21 .80 65 50 5+8 1800 21 .87 69 50 5+8 1800 21 .93 72 50 5.08 1800 21 .99 70 50 5+8 1800 21 1.01 69 50 5+8 1800 21 LO6 50 4.8

Indicated Mean Spark 5

Manifold Fuei-.Air Effective Advance % H2V Comp. Pressure Equivalence Pressure (Degrees Dissoc-

Ratio RPM (In. of Hg.) Ratio (0) (psi) BTDC) iation8 1800 30 .93 105 55 3.8i8 1800 30 .93 103 50 3.88 1800 30 .93 103 65 3.8

8 1800 30 .93 103 50 3.88 2800 30 .93 100 45 3.88 1800 30 .93 97 40 3.88 1800 30 .93 92 35 3.88 1800 30 .93 84 - 3.88 1800 30 .93 80 25 3.88 1800 30 .93 77 20 3.8

8 1800 30 1.05 101 48 3.78 1800 30 1.o8 94 48 3.5

8 1800 21 1.o6 62 45 4.8

8 1800 30 .79 103 55 5.08 1800 30 .62 79 55 5.08 1800 30 .94 1o6 55 4.o8 ]800 30 .79 100 55 4.08 1800 30 .62 70 55 4.08 L8oo 30 .94 97 55 3.08 18o0 30 1.o4 98 55 3.08 1800 30 .79 89 55 3.08 1800 30 .66 58 55 3.0

8 1800 30 .94 78 55 2.08 1800 30 .79 78 55 2.08 1800 30 .74 54 55 2.08 1800 30 .84 80 55 2.08 1800 30 1.04 75 55 2.0

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