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L S V I R

0 9 6 0 - 8 5 2 4 9 5 ) 0 0 0 3 3 - X

ioresourceTechno/ogy 2 (1995) 237-24 3

Elsevier Sc ience L imi ted

Pr i n t e d i n Gre a t B r i t a in

0960-8524/95/ 9.50

O P T I M I Z A T I O N O F D I E S E L , M E T H Y L T A I L O W A T E A N D

E T H A N O L B L E N D F O R R E D U C I N G E M I S S I O N S F R O M

D I E S E L E N G I N E

Y u s u f A l i , a M i l f o r d A . H a n n a a 'b & J o s e p h E . B o r g

aDepattment o f B iological Systems Engineering Universityo f Nebraska-Lincoln, Lincoln, N E 68583-0726, USA

~lndustrial Agricultural Prod ucts C enter, Universityo f Nebraska-Lincoln, Lincoln , NE 68583-0726, USA

(Received 19 October 1994; revised version received 27 February 1995; accepted 2 March 1995)

bs t ra c t

A Cu mm ins N14 -410 engine was operated on di fferent

fuels produced by blending methyl tal lowate and etha-

nol with No. 2 diesel fuel . Fou r fue l blend s, namely:

neat No. 2 diese l fue l ; and 8 0:13 :7, 70 :19 .5:1 0.5

and 60: 26 :14 ( v /v ) blends of diese l :methy l tallo-

wate:ethanol, were prepared a nd tested fo r engine

performance and emission analyses. Engine perform-

ance and emission data were used to optimiz the

blend of diese l fue l :methy l tal lowate:e thanol for

reducing engine emissions. The emissions were fou nd

to be minim um wi th a 8 0:13 : 7 blend of diese l:methy l

tallowate : ethanol, with ou t a significant dro p in engine

po wer output .

K e y w ords : M e thy l t a l l owa te , b iod i e se l , e t ha no l ,

C u m m i n s e n g i n e , p o w e r , t o r q u e , f u e l c o n s u m p t i o n ,

e xha us t e m i s s ions .

I N T R O D U C T I O N

T h e use o f ve ge t a b l e o i ls a nd a n im a l fa t s a s a l t e r -

n a t e f u e l s o u r c e s o r f u e l e x t e n d e r s h a s b e e n s t u d i e d

e x t e n s i v e l y . M u c h r e s e a r c h h a s b e e n d o n e i n t h e

pa s t two de c a de s on t he use o f o i l s a nd f a t s f r om

pla n t a nd a n im a l sour c e s a s a l t e r na t i ve d i e se l f ue l .

T h e m a j o r p r o b l e m a s s o c ia t e d w i t h t h e d i r e c t u s e o f

oi l s i s the i r high viscosi ty , which inte r fe res wi th fue l

i n j e c t i on a nd a tom iz a t i on , whic h c on t r i bu t e t o

i n c o m p l e t e c o m b u s t i o n , n o z z l e c o k i n g , e n g i n e

de pos i t s , l ubr i c a t i ng o i l d i l u t i on a nd r i ng s t i c k ing

( Knothe , 1992) . T he p r ob l e m s c a use d by h igh o i l -

a nd f a t - v i sc os i t y c a n be r e duc e d t o a c e r t a in de gr e e

by t r a nse s t e r i f i c a t i on . I n t he p r oc e ss o f t r a nse s t e r -

i f ic a t ion , t r ig lyc e r ide s a r e r e a c t e d w i th a n a l c oho l f o r

1 h a t 7 5 - 8 0 C i n th e p r e s e n c e o f N a O H o r

Na H CO 3 c a t a lyst , wh ic h r e m ove s t he g lyc e r o l f r om

*Journal Series Num ber 1094 7 of the University of

Nebraska Agricultural Research Division.

237

the t r iglycer ides . This process leaves a lcohol fa t ty-

ac id es te r s , which hav e a viscosity fa r less than tha t

of oi l s and fa ts.

T h e e s t e r s o f o il s a nd f a ts c a n b e d i r e c t l y b l e n de d

wi th d i e se l f ue l . T he a dva n ta ge o f b l e nd ing e s t e r s

w i th d i e se l f ue l i s r e duc e d e m iss ions . As t he E PA

im pose s l im i t s on e xha us t e m i s s ions , t he se e s t e r s

shou ld be c o m e inc r e a s ing ly a t t ra c t i ve a s a c l e a n e r -

b u r n i n g f u e l. R e s e a r c h o n b l e n d i n g a l c o h o l es t e rs o f

d i f f e r e n t t ype s o f o i l s a nd f a ts i n d i f f e r e n t r a t i os w i th

d i e s e l f u e l h a v e b e e n r e p o r t e d . S c h u m a c h e r

et al.

( 1993) r e por t e d a r e duc t ion i n c a r bon m onoxide

( C O ) , h y d r o c a r b o n s ( H C ) a n d s m o k e w i t h a n

inc r e a se i n soyd ie se l ( m e thy l e s t e r s o f soybe a n o i l )

c onc e n t r a t i on i n t he b l e nd , whe r e a s ox ide s o f n i t r o -

ge n ( NOx) i nc r e a se d . Sc h l a u tm a n e t

al.

(1986)

c on duc t e d a 200 h sc r e e n ing te s t us ing a 3 :1 ( v/v)

b l e nd o f unr e f ine d , m e c h a n ic a l l y e xpe l l e d , soybe a n

o i l a nd N o . 2 d i e se l f ue l i n a d i r e c t i n j e c t ion e ng ine .

T he y ha d t o t e r m ina t e t he sc r e e n ing t e s t a f te r 159 h

b e c a u s e t h e e n g i n e c o u l d n o t h o l d a c o n s t a n t l o a d

a nd the r e w a s a 670% inc r e a se i n t he v i sc os i ty o f t he

lubr i c a t i ng o i l . T he y f u r the r obse r ve d a bnor m a l c a r -

bon de pos i t s on a l l c om bus t ion c ha m be r pa r t s ,

inc luding the injec tors . Schl ick et al. (1988) evalu-

a t e d t h e p e r f o r m a n c e o f a d i r e c t i n je c t io n e n g i n e

wi th 1 :3 ( v /v ) b l e nds o f soybe a n o i l a nd sunf lowe r

o i l w i th N o . 2 d i e se l fue l . T he y r e por t e d sa t is f a c to r y

e n g i n e p e r f o r m a n c e a s fa r a s p o w e r o u t p u t , t h e r m a l

e f f ic i e nc y a nd l ubr i c a t ing o i l da t a f r om the E ng in e

M a n u f a c t u r e r A s s o c i a t i o n ( E M A , 1 9 8 2 ) s c r e e n i n g

t e s t w a s c o n c e r n e d , b u t w h e n t h e g e n e r a l c o n d i t i o n

o f t h e c o m b u s t i o n c h a m b e r a n d t h e f u e l i n j e c t o r s

wa s i nve s t i ga t e d , he a vy c a r bon de pos i t s we r e d i s -

c o v e r e d . F o s e e n e t al. ( 1993) use d m e thy l soya t e

( f ro m 0 - 4 0 % ) a n d d i e s e l f u e l b l e n d s i n a t r a n s ie n t

m o d e t e s t o f a D D C 6 V - 9 2 T A e n g i n e a n d f o u n d

t h a t t h e a d d i t io n o f u p t o 4 0 % m e t h y l so y a t e d id n o t

a f f e c t pe a k t o r que , bu t t he r e wa s a sm a l l d r op i n

powe r a t t he 40% l e ve l o f subs t i t u t i on . T he y r e por -

t e d a r e d u c t i o n i n C O , H C a n d p a r t i c u l a t e m a t t e r



238 Y Al i M. A. H anna J . E . Borg

a n d a n i n c r e a s e i n N O x e m i ss i on s . T h e y r e c o m m e n -

d e d u s e o f 2 0 % m e t h y l s o y a t e b l e n d w i t h d ie s e l f ue l .

T h e p u r p o s e o f t h is i n v e s ti g a ti o n w a s t o o p t i m i z e

t he b l end o f No . 2 d i e s e l fue l , m e t hy l t a l l owa t e and

e t han o l t o r e duce em i s s i ons w i t ho u t s i gn if i can t ly

a f f e c ti n g e n g i n e p e r f o r m a n c e .

M E T H O D S

E n g i n e a n d i n s t r u m e n t a t i o n

A C u m m i ns N14-410 d i es e l eng i ne was u s ed i n t h is

s t udy . S pec i f i ca ti ons o f t he en g i ne a re p re s en t ed i n

Table 1 .

T h e e n g i n e w a s c o u p l e d t o a n E a t o n 5 2 2 k W ( 7 00

h p ) d y n a m a t i c , e d d y - c u r r e n t , d r y g a p d y n a m o m e t e r

( E A T O N P o w e r T r a n s m i s s i o n S y s t e m s , E a t o n

C o r p . , K e n o s h a , W I ) w i t h a D A N A 1 8 1 0 c o u p l e r .

E n g i n e t o r q u e w a s m e a s u r e d w i t h a l o a d c e l l a n d a

Day t ron i c s y s t em 10 i n t eg ra t o r (Day t ron i c C orp . ,

M i a m i s b u r g , O H ) a n d s p e e d w a s m e a s u r e d u s i n g a

6 0 - t o o th s p r o c k e t a n d m a g n e t i c p i c k - u p a t t a c h e d t o

t h e d y n a m o m e t e r . F u e l c o n s u m p t i o n w a s m e a s u r e d

w i t h a n E M C o r p . ( L i n c o l n , N E ) c u s t o m - b u i l t m a s s -

m e a s u r e m e n t s y s t e m , i n w h i c h f u e l w e i g h t w a s

m e a s u r e d o v e r a n o p e r a t o r - s e l e c t e d ti m e p e r i o d . A i r

f l o w i n t o t h e e n g i n e w a s m e a s u r e d w i t h a B a d g e r

B V T - I F v e n t u r i fl ow m e t e r ( B a d g e r M e t e r , I n c .,

Tu l s a , OK) . The a i r f l ow m et e r was pos i t i oned i n a

0 15 m d i am et e r , 5 . 2 m l ong p i pe wi t h a s u rge t ank

b e t w e e n t h e m e t e r a n d t h e e n g i n e . A t h r o t t l e v a l v e

w a s u s e d a t t h e i n l e t o f t h e s u r g e t a n k t o c o n t r o l

eng i ne i n l e t p res s u re . The exhaus t s y s t em cons i s t ed

o f a 2 -1 m l eng t h o f 0 . 13 m d i am et e r exhaus t t ub i ng

l ead i ng i n t o a 0 . 25 m d i am et e r duc t t o t he ou t s i de

a i r. A cen t r i fuga l f an p rov i d ed exhaus t ven t i l a t i on . A

t h ro t t l e va l ve was pos i t i oned i n t he ex haus t t ub i ng t o

con t ro l exhaus t back p res s u re .

T e m p e r a t u r e s o f t h e e x h a u s t o f e a c h c y l i n d er , f u e l

a n d c o o l a n t g o i n g i n t o a n d o u t o f t h e e n g i n e , a n d

c r a n k - c a s e o i l , w e r e m e a s u r e d u s i n g t h e r m o c o u p l e s

a n d a D a y t r o n i c S y s t e m 10 c o u p l e d w i t h a n A u t o N e t

d a t a - a c q u i s i t i o n s y s t e m . P r e s s u r e s w e r e m e a s u r e d

w i th a n a lo g g a u g es a n d m a n o m e t e r s ( H 2 0 a n d H g )

ca l i b ra t ed wi t h a dead -we i gh t t e s t e r .

E x h a u s t e m i s s i o n a n a l y s e s w e r e p e r f o r m e d u s i n g

d i f f e ren t ana l yze r s fo r each o f t he exhaus t gas es .

Table 1 Eng ine speci f icat ions

Specifications Cumm ins N14-410 engine

Type o f engine

Horsepower (Rated)

Bore x stroke

Displacement

Compression ratio

Valves per cy linder

Aspiration

Turbocharger

6 cylinder, 4-stroke, direct injection

410

140 mm x 152 m m

14 liters

16.3:1

4

Turbo charged & charge air cooler

Holset t type BHT 3B

O x i d e s o f n i t r o g e n N O / N O 2 ) w e r e m e a s u r e d w i t h a

B e c k m a n m o d e l 9 55 c h e m i l u m i n e s c e n t a n a l y ze r

( B e c k m a n I n d u s t r i a l C o r p . , L a H a b r a , C A ) . H y d r o -

c a r b o n s w e r e m e a s u r e d w i t h a t o t a l H C a n a l y z e r ,

m o d e l J U M V E 7 f l a m e - i o n i z a ti o n d e t e c t o r ( J . U .M .

E n g i n e e r i n g , K a r l sf e ld , G e r m a n y ) , d e s i g n e d t o c o n -

t i n u o u s ly m e a s u r e t h e c o n c e n t r a t i o n o f t o t a l o r g a n ic

H C i n g a s e o u s s a m p l e s . C a r b o n m o n o x i d e a n d C O 2

w e r e m e a s u r e d w i t h t w o B e c k m a n n o n - d i s p e r s i v e

i n f r a r e d a n a ly z e rs , m o d e l 8 8 0 - A ( R o s e m o u n t A n a -

l y ti cal , Inc . , La H ab ra , C A ) . Oxygen was m ea s u re d

w i t h a p a r a m a g n e t i c o x y g e n a n a l y z e r , m o d e l 7 5 5 R

( R o s e m o u n t A n a l y ti c a l, I nc . , L a H a b r a , C A ) . T h e

d e t e r m i n a t i o n o f O 2 w as b a s e d o n t h e m e a s u r e m e n t

o f t he m a gne t i c s u s cep t i b i li t y o f t he s am p l e gas .

O x y g e n i s s t r o n g l y p a r a m a g n e t i c , w h i l e m o s t o t h e r

c o m m o n g a se s a r e w e a k l y d i a m a g n e t ic . S m o k e u n i t s

w e r e m e a s u r e d w i t h a B o s c h E F A W 6 5 - A s m o k e

p r o b e ( R o b e r t B o s c h G M B H , S t u t t g a r t , G e r m a n y ) .

F u e l s

Th e fo l l owi ng t e s t fue l s we re u s ed i n t h is s t udy :

1 . 100% N o. 2 d iesel fuel (basel ine) .

2 . 80% No . 2 d i e s e l fue l, 13% m et h y l ta l l owa t e

a n d 7 % e t h a n o l .

3 . 70% No . 2 d i e s e l fue l, 19 .5% m e t hy l ta l l owa t e

and 10 -5% e t hano l .

4 . 60% N o . 2 d i e s e l fue l , 26% m et h y l t a l lowa t e

a n d 1 4 % e t h a n o l .

T h e a b o v e b l e n d s w e r e s e l e c t e d o n t h e b a s i s t h a t

Al i e t a l . ( 1 9 9 5 ) r e p o r t e d t h a t e n g i n e p e r f o r m a n c e

was n o t s i gn i f ican t ly a f f ec t ed by d i e s e l : m e t hy l s oya t e

b l e n d s u p t o a r a t i o o f 7 0 : 3 0 . T h e r e f o r e , b l e n d s

1 0 % a b o v e a n d 1 0 % b e l o w t h a t l e v el w e r e u s e d i n

th i s s tudy. A h igh su l fur (0 .24%) No. 2 d iesel fuel

w a s u s e d . M e t h y l ta l lo w a t e w a s p r o c u r e d f r o m I n t e r -

c h e m E n v i r o n m e n t a l , I n c . o f O v e r l a n d P a r k , K S .

M e t h y l t a l l o w a t e w a s b l e n d e d w i t h e t h a n o l i n a

65:35 (v /v) ra t io to reduce i t s v i scos i ty , as sugges ted

b y A l i a n d H a n n a ( 1 9 9 4 a ) . T h e m i x t u r e o f m e t h y l

t a l l owa t e and e t hano l was b l ended wi t h No . 2 d i e s e l

fue l i n r a t i o s a s p res en t ed above . P hys i ca l p rope r t i e s

o f m e t hy l t a l l owa t e , e t hano l and d i e s e l fue l were

d e t e r m i n e d a n d r e p o r t e d ( A l i & H a n n a , 1 99 4b ).

T e s t r u n s a n d p e r f o r m a n c e m a p s

E n g i n e t e s t i n g o n t h e a b o v e f u e l s w a s p e r f o r m e d a t

s peeds r ang i ng f rom 1100 t o 1900 rpm ; a t fu l l l oad

us i ng s t andard m e t h od S A E J 1349 (S ALE, 1993a);

a n d e m i s s i o n s c h a r a c te r is t ic s w e r e d e t e r m i n e d u s i n g

S A E J 1312 s t andard , e i gh t -m ode , s t eady - s t a te ,

eng i ne t e s t i ng cod e (S AE , 1993b ). Tab l e 2 p res e n t s

t he s peeds and l oads u s ed fo r d i f f e ren t t e s t s . The

t e s ti n g w a s d o n e i n t h e N e b r a s k a P o w e r L a b o r a t o r y

a t t h e U n i v e r s it y o f N e b r a s k a - L i n c o l n . T h e s e q u e n c e

o f f u e ls u s e d w a s c o m p l e t e l y r a n d o m i z e d . S t a n d a r d

p e r f o r m a n c e a n d e x h a u s t e m i s s i o n d a t a w e r e r e c o r -

ded and each t e s t run r ep l i ca t ed t w i ce .



Fuel b lend to reduce d iesel engine emiss ions 239

Table 2 En gin e speeds and loads used for each fuel

blend

Engine performance

Exhaust emission analysis

Engine speed, Lo ad ,% Engine speed, Lo ad ,%

rpm rpm

1100 100 1800 100

1200 100 1800 75

1400 100 1800 50

1600 100 1800 10

1800 100 1200 100

1900 100 1200 75

1200 50

Idle 0

Test ing procedure

The engine was warmed-up at low idle long enough

to establish correct oil pressure and was checked for

any fuel, oil, water and air leaks. The speed was

then increased to 1600 rpm and a sufficient load was

applied to raise the coolant temperature to 71°C.

After completion of a standard warm-up procedure,

the intake and exhaust restrictions were set at rated

engine speed (1800 rpm) and fall power and from

then on were not adjusted for different speeds or

loads after initial settings were completed.

The engine was run at the specific speeds and

loads for a minimum of 6 min and data were recor-

ded during the last 2 min of operation. The response

variables included power, torque, brake specific fuel

consumption (BSFC), BSHC, BSCO, BSCO2,

BSNOx, BSO2 and brake specific smoke. These data

were recorded at 5 s intervals for 2 min and aver-

aged over that period. After completion of one set

of experiments with four fuels the whole set was

replicated.

O p t im iz a t ion o f f u e l b l e n d s

Engine performance, corrected to SAE conditions,

and emissions analyses were conducted for each fuel

blend as described above. Statistical analyses for the

response of the engine with different fuel blends

were performed to determine the trends of the

response variables. The response variables consid-

ered were engine power output, torque, BSFC,

BSCO, BSCO2, BSHC, BSNOx, BSO2 and smoke.

The optimization was based on maximizing power

output and minimizing engine emissions. Response

surfaces for power, torque and BSFC and response

curves for emission characteristics using standard,

eight-mode, steady-state tests were plotted.

RESULTS AND DISCUSSION

A blend of ethanol and methyl tallowate was opti-

mized to reduce the viscosity of methyl tallowate by

Ali and Hanna (1994a). They recommended a blend

of 65:35 methyl tallowate and ethanol, respectively,

to have a viscosity similar to No. 2 diesel fuel at

Fig 1 Effects of engine speed and fuel blends on cor-

rected power output.

40°C. The same blend of methyl tallowate and etha-

nol was used in this study. The viscosities of

80:13: 7, 70:19.5:10.5 and 60: 26:14 diesel: methyl

tallowa te:ethanol blends were found to be 1 98, 1.97

and 2.01 mPa-s, respectively, at 40°C as compared to

2.07 mPa-s for No. 2 diesel fuel at the same tem-

perature. The calculated cetane index of methyl

tallowate was found to be 57 78, which reduced to

around 50 when blended with ethanol and diesel

fuel in different ratios. The calculated cetane index

of No. 2 diesel fuel was also found to be 50. Energy

content per unit mass of the diesel fuel was 45.51 kJ/

g, whereas that of methyl tallowate: ethanol (65 : 35)

blend was 36 16 kJ/g. The energy content of the

blends of diesel: methyl taUowate: ethanol reduced

proportionately as the percentage of methyl tallo-

wate and ethanol increased in the blend.

E n gin e p e r f or m an c e

The engine power outputs corrected to the SAE

standard J1349 (1992) at full load for all four test

fuels and six speeds are shown in Fig. 1. Statistical

analyses performed to find the effects of engine

speeds and fuel blends on power output showed that

the fuel blends had a significant linear effect

(F= 20 68, Pr>F= 0.0001), whereas engine speed

had a significant fourth order polynomial effect

(F = 15.21,

P r F

= 0.0004). No interaction between

engine speed and fuel blend was observed. The

regression model for the power output, in the range

of 1100-1900, was

P = - 6505.96 + 18.66S- 0.0196S 2 + 0.91 x 10-6S3

-1 617

x 10-9S4

0 3365D (R 2 = 0 94)

where P= po wer output (kW); S = engine speed

(rpm); and D = diesel content in the fuel blend (%).

The engine power output at the rated speed of

1800 rpm was compared for each fuel blend. A lin-

ear drop in power output was observed when the

methyl tallowate :ethanol blend was increased. The

rate of reduc tion in power was 1-1% with every 10%



240 Y Ali M. A. Hanna Z E. Borg

i n c r e a s e i n m e t h y l t a l l o w a t e : e t h a n o l b l e n d . T h e

eng i ne po we r ou t p u t w i t h No . 2 d i e s e l fue l was 305 .4

k W , w h i c h r e d u c e d t o 2 9 8 - 7 k W w i t h t h e 8 0 : 1 3 : 7

b l e n d o f d i e s e l : m e t h y l t a l l o w a t e : e t h a n o l a n d t o

2 9 5 . 3 k W w i t h t h e 7 0 : 1 9 . 5 : 1 0 . 5 b l e n d . T h e r e d u c -

t i o n i n p o w e r o u t p u t w i t h a n i n c r e a s e i n m e t h y l

t a l l o w a t e : e t h a n o l w a s e x p e c t e d a s t h i s b l e n d h a d

20% l ess ene rgy con t e n t t han d i e s e l fue l .

T h e r e s p o n s e s u r f a c e f o r t o r q u e p r o d u c e d b y th e

eng i ne a t fu l l l oad fo r fou r fue l b l ends and s i x

eng i ne s peeds i s s hown i n F i g . 2 . once aga i n s t a t i s -

t ica l ana l y ses pe r fo r m e d t o f i nd e f f ec t s o f fue l b l ends

a n d e n g i n e s p e e d s o n t o r q u e s h o w e d t h a t t h e r e w a s

a s i gn i f ican t l i nea r e f f ec t (F = 19 -32 , P r > F = 0 .0001 )

o f fue l b l ends and a s i gn i f i can t fou r t h o rde r po l yno -

m i a l e f f ec t (F = 9 29 , P r > F = 0 -0041 ) o f eng i n e

s p e e d . T h e r e w a s n o i n t e r a c t i o n b e t w e e n e n g i n e

s p e e d a n d f u e l b le n d . T h i s t r e n d w a s e x p e c t e d a s t h e

e n g i ne p o w e r o u t p u t i s d e p e n d e n t u p o n t o r q u e p r o -

d u c e d b y t h e e n g i n e a t a p a r t i c u l a r s p e e d . T h e

r e g r e s si o n m o d e l f o r t o r q u e w a s

T --- -33 87 5 + 10 0 .1 9S - 0 .104457S 2

+4 8151 x 10 5S 3 - 8 3 2 8 2 x 10 9S 4 + 2 1414D

(R 2 = 0 9702)

w h e r e T = t o rq u e ( N m ) ; S = e n g i ne s p e e d ( r pm ) ;

a n d D = d i e s e l c o n t e n t i n fu e l b l e n d ( % ) .

M a x i m u m t o r q u e w a s p r o d u c e d a t a n e n g i n e

s peed o f 1200 rpm . At t h i s s peed t he re was a l i nea r

d rop i n t o rque wi t h an i nc reas e i n t he m e t hy l t a l l o -

w a r e : e t h a n o l c o n t e n t i n t h e f u e l b l e n d . A s i n t h e

c a s e o f p o w e r o u t p u t , t h e t o r q u e p r o d u c e d b y t h e

e n g i n e a l s o r e d u c e d b y 1 . 0 3% e a c h t i m e , w i th a 1 0 %

i n c r e a s e i n t h e m e t h y l t a l l o w a t e : e t h a n o l b l e n d i n

t h e f u e l. T h e m a x i m u m t o r q u e o f 2 0 85 N m w a s p r o -

duced a t 1200 rpm wi t h No . 2 d i e s e l fue l , wh i ch

d r o p p e d b y 2 1 . 4 N m e a c h t i m e a n o t h e r 1 0 % o f d i e -

s e l w a s r e p l a c e d w i t h t h e m e t h y l t a U o w a t e a n d

e t h a n o l b l e n d .

The B S F C s a t fu l l l oad fo r a l l fue l b l ends and

speeds are shown in F ig . 3 . S ta t i s t i ca l analyses

s h o w e d t h a t t h e r e w a s n o i n t e r a c t i o n b e t w e e n

eng i ne s peeds and fue l b l ends bu t t he re was a s i g -

n i f i can t l i nea r e f f ec t ( F = 34 .45 , P r > F = 0 -0001 ) o f

fue l b l ends and s i gn i f i can t quad ra t i c e f f ec t

( F - ' 2 7 .2 1 , P r > F = 0 . 0 0 0 1 ) o f e n g in e s p e ed o n

B S F C . T h e e n g i n e p e r f o r m a n c e c u r v e s f o r p o w e r

o u t p u t , t o r q u e a n d B S F C w e r e t h e s a m e a s r e c o m -

m e n d e d b y t h e C u m m i n s E n g i n e C o . , I n c . f o r t h e

N14-410 d i es e l eng i ne (Anon , 1991 ) . The r eg res s i on

m o d e l f o r B S F C w a s

B S F C = 4 4 2 . 5 7 - 0 . 2 9 4 1 S + 1 .0 9 × 1 0 - 4 S 2 - 0 . 5 0 8 D

(R 2 = 0 72)

w h e r e B S F C = b r a k e s p e ci fi c fu e l c o n s u m p t i o n ( g /

kW -h) ; S = eng i ne s pee d ( rpm ) ; and D = d i e s e l

c o n t e n t i n f u e l b l e n d ( % ) .

T h e B S F C a t a n y s p e e d w a s m i n i m u m w i t h N o . 2

d i es e l fue l and i t i nc reas ed l i nea r l y w i t h an i nc reas e

i n t h e m e t h y l t a l l o w a t e : e t h a n o l c o n t e n t i n t h e

b l e n d . T h e r a t e o f i n c r e a s e i n f u e l c o n s u m p t i o n w a s

2 -37% fo r each 10% i nc reas e i n m e t hy l t a l l owa t e :

e t h a n o l c o n t e n t . A t r a t e d s p e e d t h e B S F C w i t h

100% d i es e l fue l was 215 .4 g / kW-h , wh i ch i nc reas ed

t o 2 2 5 . 5 g / k W - h w i t h t h e 8 0 : 1 3 : 7 b l e n d o f d i e s e l :

m e t h y l t a l l o w a t e : e t h a n o l . W h e n t h e f u e l c o n s u m p -

t i o n o f t h e e n g i n e w a s c o n s i d e r e d o n t h e b a s i s o f

e n e r g y s u p p l i e d p e r k W - h , i t w a s o b s e r v e d t h a t a

t o t a l o f 9 8 0 5 k J /k W - h e n e r g y w e r e s u p p l i e d w i th N o .

2 d i e s e l , whereas on l y 9536 k J / kW-h were s upp l i ed

w i t h a b l e n d o f 8 0 : 1 3 : 7 d i e s e l: m e t h y l t a l lo w a t e :

e t h a n o l . T h a t o n c e a g a i n s h o w e d t h a t t h e r e w a s a

d r o p o f a b o u t 1 . 3 % e n e r g y a v a i l a b l e f o r e a c h 1 0 %

i n c r e a s e i n m e t h y l t a l l o w a t e : e t h a n o l b l e n d p e r k W -

h a n d t h u s a d r o p o f p o w e r b y 1- 1% f o r t h e

res pec t i ve b l en d w as j u s t if i ed .

E m i s s i o n a n a l y s i s

Th e b rake s pec if i c em i s s i ons fo r a l l t e s t fue l s a r e

s h o w n i n F i g s 4 - 6 . T h e B S C O , B S C O 2 , B S O 2 ,

B S H C , B S N O x a n d s m o k e e m i s s io n s w e r e m e a s u r e d

us i ng t he s t andard , e i gh t -m ode , s t eady - s t a t e , eng i ne

t es t i ng code S A E J 1312 .

F i g 2

Effects of engine speed and fuel blends on cor-

rected torque.

F i g 3 Effects of engine speed a nd fuel blends on brak e

specific fuel consumption.



Fue l b lend to reduce d ie se l engine emiss ions 241

0 o 5

O . g

0.75

0.7

5 0 :3 2 .5 :1 L 5 (1 0 :2 8 :1 4 7 0 : 1 9 . 5 :1 0 0 8 0 : 1 5 : 7 0 0 : 6 0 : 3 . 5 1 0 0 : 0 : 0

D l e l O I F u e l : M e th y l T a l l o w a to E th a n o l B l e n d

Fig. 4. Effects of diesel fuel: methyl taUowate:ethanol

blends on brake specific CO and C02 emissions.

10 10

)8 8

• _ C O a

C O 4 # 4

o

I I I I 0

S0:320:17.5

0

I I i I

F i g 6

1

O . 8

i

00 . ,28:14 79:10.5 :10.5 80 :1 3: 7 110:8.11:3.5 1000. '0

D l u e l F u e l : M e t h y l T I I I o w I l ~ : E t h a n o l

B l e n d

Effects of diesel fuel: methyl tallowate: ethanol

blend on NOx and smoke emissions.

0.8 14

0.7

OO

9.

o

I O.4

0.3

0.2

• • O~

| . . . . . . . - e . . . . . . . . e. . . . . . . . . . . . . . . . . 1 2

10

.

0

4

2

t i t L

0

S0:3 23 :17 0 (10 :26 :14 /0 :19 .S:10 .5 80 : 13 : 7 90 :6 .5 :3 .5 100 :0 :0

D l e l e l F u e l : M e t h y l T a l l o w a N :

E th a n o l B l e n d

Fig. 5. Effects of diesel fuel:methyl tallowate: ethanol

blend on brake specific O2 and HC emissions.

Variations in BSCO and BSCO2emissions for dif-

ferent fuel blends and eight-mode tests are shown in

Fig. 4. Regression analyses performed for the effect

of fuel blends on BSCO emissions showed that t here

was a significant quadratic trend (F -- 9.86,

Pr> F=0 .01 84) . The regression model for BSCO

emissions as a function of fuel blend was

BSCO = 1.0724-0.011144D + 9.3 x 10-5D2

(R 2 = 0.7977)

where BSCO = brake specific CO emissions (g/kW-

h) and D = diesel content in the fuel blend ( ).

It was observed that BSCO emissions decreased

with an increase in methyl tallowate:ethanol blend

in the fuel. Maximum BSCO emissions of 0.8875 g/

kW-h were observed with No. 2 diesel, which was

well below the upper limit of 11.4 g/kW-h set by the

EPA (Brezonick, 1994).

The

BSCO2

emissions did not have any significant

trend with the fuel blends used in this study. Statis-

tical analyses performed for BSCO2 emissions

showed that the slope of the regression line was

almost zero. It was concluded that BSCO2 emissions

do not depend on the fuel blend. In such a case the

mean value of the dependent variable, i.e.

BSCO2

was used to interpret the results. The mean BSCO2

emission was 7-04 g/kW-h.

Variations in BSO: and BSHC emissions with dif-

ferent fuel blends and the eight-mode test are shown

in Fig. 5. Once again, BSO2 emissions with different

fuel blends did not show a statistically significant

trend. Statistical analyses, in this case, also showed

that the slope of the regression line was almost zero

and the mean value of BSO2 emissions was used to

interpret the results. The mean BSO2 emission was

12-42 g/kW-h, within the range of the fuel blends

used.

Regression analyses performed for the effect of

fuel blends on BSHC emissions showed a significant

quadratic effect (F = 207.3, P r > F = 0-0001). The

regression model for variation in BSHC emissions

with fuel blends was

BSHC = 6 .2 88 - 0.154D + 9.74 x 10-4D 2

(R E = 0.9881)

where BSHC = brake specific HC emissions (g/kW-

h) and D = diesel conten t in the fuel blend ( ).

A significant reduction in BSHC emissions was

observed when diesel was blended with methyl tallo-

wate and ethanol in the ratio of 80:13:7 percent,

respectively. The BSHC emission with this blend was

0.28 g/kW-h, as compared to 0.6 g/kW-h with No. 2

diesel fuel and 0.7 g/kW-h with a 60:26:14 blend of

diesel: methyl tallowate: ethanol. The recommended

amount of BSHC emissions by the EPA was 1.3 g/

kW-h (Brezonick, 1994) for 130 kW and larger

engines. All

et al

(1995) also observed a decrease in

the BSHC emissions with an increase in the methyl

soyate content, up to 20 , in the fuel blends with a

Cummins NTA-855-C engine. They reported an

increase in BSHC emissions produced by methyl

soyate blends of 20 or more because of the lean-

ing effect coupled with the undermixing of air and

fuel.

The effects of fuel blends on BSNOx emissions

and smoke in the eight-mode test are shown in Fig.



242 Y Ali M. A. Ha nna J. E. Borg

6. A regression analysis performed on BSNOx emis-

sions data did not show a statistically significant

trend. The mean value of the BSNOx emissions was

used to interpret the results. The mean BSNOx

emission was 6.33 g/kW-h, as compared to the allow-

able 9.2 g/kW-h set by the EPA (Brezonick, 1994)

for a diesel engine of 130 kW size or more.

Bosch smoke units are an indication of particulate

and soot formation in the exhaust of an engine.

Particulates contain primarily carbon particles and

some unburned HCs. The observed smoke readings,

in Bosch smoke units, were converted into soot con-

centrations (mg/m3) at 15°C and 760 mm Hg using

conversion chart SAE J255a (SAE, 1994) and then

converted to soot and particulates (g/kW-h) for the

eight-mode test. The trend of smoke emissions with

fuel blends is shown in Fig. 6. A regression analysis

performed on smoke emissions data showed a sig-

nificant linear effect (F = 453.06, Pr>F = 0.0001) of

fuel blend. The regression model describing the

trend of smoke with fuel blend was

BSS = 0.60 5- 0.00365D (R 2 = 0.9971)

where BSS = brake specific smoke (g/kW-h) and

D = diesel content in the fuel blend (%).

A minimum brake specific smoke emission of 0-24

g/kW-h was observed with No. 2 diesel fuel, which

increased linearly with an increase in the methyl

tallowate:ethanol content of the blend. With the

reductions in BSHC and BSCO emissions with the

80:13: 7 blend of diesel: methyl tallowate: ethanol,

the smoke units should also decrease. From the

experimental data the trend of visible smoke with

different blends increased. It was suggested that a

better method for smoke analysis is needed.

Although more smoke was produced with the

80:13 :7 blend, as compared to 100 % diesel or

70:19.5:10-5 blends, all values of smoke emissions

were less than the limit of 0.54 g/kW-h set by the

EPA (Brezonick, 1994).

O p t i m i z a t i o n o f fu e l b l e n d

The fuel blend was optimized on the basis o f engine

performance and emissions characteristics. The

engine performance analyses showed that power

output, torque and fuel consumption were affected

only slightly by the presence of the methyl tallow-

ate:ethanol blend. The engine tested was tuned to

operate on diesel fuel and not on alternative fuels

used. Therefore, for optimization of the fuel blend,

more emphasis was given to emissions character-

istics. The most important factors considered in

emissions were BSHC, BSCO, BSNOx and smoke, as

suggested by the EPA.

From a regression model it was observed that

minimum BSHC emissions were observed with an

80:13: 7 diesel: methyl tallowate: ethanol blend. As

the diesel content in the blend was increased or

decreased there was a significant increase in BSHC

emission. From the regression model for BSCO

emission, when the diesel content in the blend was

decreased from 100 to 80% there was a 12.6%

reduction in BSCO emissions. A fu rther reduction in

diesel content reduced BSCO emissions by only

3.17%. Statistically, there was no significant change

in BSNOx emissions when the diesel content in the

blend was decreased from 100 to 60%. The BSNOx

emissions were always less than the EPA's suggested

value of 9.2 g/kW-h. The trend of visible smoke was

inconclusive but smoke produced by the engine was

less than the EPA's regulation of 0.54 g/kW-h.

On the basis of engine emissions characteristics it

can be concluded that a blend of 80:13: 7 minimized

the emissions. At this blend there was a drop in

power output o f 2.2% and a drop in torque of 2.1%.

The BSFC increased by 4.74%, which was expected

as the blend of 80:13:7 diesel methyl tallowate:

ethanol had 7% less energy than No. 2 diesel fuel.

O N L U S I O N S

1. Engine performance with a methyl tallowate:

ethanol:diesel fuel blend was not affected to a

great extent from that of diesel-fueled engine

performance. There was a 1.1% power reduc-

tion and a 1.03% torque reduction for each

10% replacement of diesel fuel with methyl tal-

lowate: ethanol blend.

2. Brake specific fuel consumption was increased

by 2 37% for each 10% increase in the methyl

tallowate: ethanol blend in the fuel.

3. There was a significant reduction in BSCO

emission with an increase in the methyl

tallowate:ethanol content in the fuel blend.

The BSCO emission was always less than the

limit set by the EPA. There was no change in

BSCO2 emissions.

4. The BSHC emissions had a significant quad-

ratic trend with fuel blend. Minimum BSHC

emissions were observed with the 80:13:7 die-

sel: methyl tallowate: ethanol blend.

5. The BSO2 emissions did not change with an

increase in methyl tallowate:ethanol content in

the blend.

6. The re was no change in BSNOx emissions with

an increasing methyl tallowate:ethanol content

in the blends. The BSNOx emissions remained

statistically the same for all the fuel blends

used in this study and were always less than the

EPA's limit of 9.2 g/kW-h.

7. Smoke emissions increased linearly with an

increase in the methyl tallowate: ethanol con-

tent o f the blends.

8. A blend of 80:13 : 7 diesel: methyl tallowate:

ethanol should be used to minimize emissions.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the contri-

butions of Kevin G. Johnson, Lab Technician,



Fue l b lend to reduce d ie se l engine emiss ions 243

N e b r a s k a P o w e r L a b o r a t o ry , U n i v e r s i ty o f

N e b r a s k a - L i n c o l n , f o r e n g i n e o p e r a t i o n a n d d a t a

c o l l e c t i o n a n d a n a ly s i s ; a n d D r L o u i s L e v i t i c u s , P r o -

f e s s o r o f B i o l o g i c a l S y s t e m s E n g i n e e r i n g a n d

e n g i n e e r in c h a r g e o f T e s t a n d D e v e l o p m e n t ,

N e b r a s k a P o w e r L a b o r a t o ry , U n i v e rs i ty o f

N e b r a s k a - L i n c o l n , f o r m a k i n g t h e p o w e r - t e s t i n g l a b -

o r a to r y a v a i l a b l e .

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optimization of diesel, methyl tailowate and ethanol blend for reducing emissions from diesel...

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