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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
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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 .
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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%
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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.
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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.
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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,
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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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