Testing of alternative diesel fuel from tallow and soybean oil in cummins N14-410 diesel engine

ELSEVIER

Bioresource Technology 53 (1995) 243-254 0 1995 Elsevier Science Limited

Printed in Great Britain. All rights reserved 0960-85241951Ff.9.50 0960-8524(95)00092-5

TESTING OF ALTERNATIVE DIESEL FUEL FROM TALLOW AND SOYBEAN OIL IN CUMMINS N14-410 DIESEL ENGINE*

Yusuf Ali,” Kent M. Eskridge,” Milford A. Hanna”

“Department of Biological Systems Engineering, Univerity of Nebraska-Lincoln, Lincoln, NE 6853-0726, USA ‘Department of Biometry, University of Nebraska-Lincoln, Lincoln, NE 68583-0712, USA

‘Department of Biological Systems Engineering and Directol; Industrial Agticultural Products Center; University of Nebraska- Lincoln, Lincoln, NE 68583-0726, USA

(Received 1 February 1995; revised version received 9 June 1995; accepted 10 June 1995)

Abstract Performance and emissions characteristics were evaluated in a Cummins N14-410 diesel engine operating on 12 different blends of methyl tallowate, methyl soyate, ethanol andlor high sulfur No. 2 diesel fuel. Engine performance on each fuel blend, exhaust emissions and smoke were monitored and compared with diesel fuel. Engine per$ormance was found satisfactory without significant drops in power and torque. There was a slight increase in brake specific fuel consumption. Most engine exhaust emissions were not affected by an increase in the amount of alternative fuel in the blend. There was a signi’cant quadratic trend in HC emissions. Brake specific HC emissions were reduced with increases in alternative fuel in blends up to 80:20 ratio of diesel:altemative fuel; beyond that HC emissions increased.

Key words: Methyl tallowate, methyl soyate, ethanol, corrected power, corrected torque, brake specific fuel consumption, engine emissions.

INTRODUCTION

Since the 1973 OPEC oil crisis, the rise of imported crude oil prices, and the questionable availability of petroleum supplies, the western world has been investigating liquid-fuel alternatives. Alcohol fuels, including methanol, ethanol, and esters of vegetable oils and animal fats, appear to offer the most real- istic near-term potential as diesel fuel extenders or substitutes. Renewable fuels derived from vegetable oils are capable of providing good engine performance in the short term (Goering & Fry, 1984). In more extended operations, the same fuels caused degradation of engine performance, excessive carbon and lacquer deposits and actual damage to the engine because of the high viscosity of vegetable oils and fats. Esterification removes glycerol from the

*Journal series No. 11022 of the University of Nebraska Agricultural Research Division.

oils and fats and lower-viscosity esters are obtained. The esters of oils and fats have fuel properties that compare much better with diesel fuel than do neat oils and fats (Wagner et al., 1984).

Alcohol fuels have low cetane numbers. There- fore, little research has been done on their use in diesel engines. Ethanol, for example, has a cetane rating of 6, and methanol a rating of 35 (Houghton- Alice, 1982). The cetane number for diesel fuels ranges from 45 to 55. Straight alcohol fuels cannot be used in unmodified diesel engines. However, there are possible uses for alcohol, ester and diesel fuel blends.

Goering and Fry (1984) performed a 200 h Engine Manufacturer Association (EMA) test using diesel fuel and microemulsified vegetable oil fuel (diesel oil/soy oil/l90-proof ethanol/l-butanol microemulsion, 50:25:5:20% (v/v)) without difficulty. They observed engine wear comparable to normal, and in some cases, less wear than with No. 2 diesel fuel. Clark et al. (1984) used soybean oil methyl and ethyl esters in a John Deere 4239TF direct-injection, turbocharged diesel engine. They found that engine performance during the 200 h test with the soybean esters did not differ greatly from that of diesel fuel. A slight power loss, combined with an increase in fuel consumption was attributed to the lower calo- rific value of the esters. Emissions for both methyl and ethyl esters, as well as No. 2 diesel fuel were essentially the same. They concluded that the methyl and ethyl esters of vegetable oils could be used as alternative fuels on a short-term basis, provided cer- tain fuel quality standards were met.

Sims (1985) used a Ford 5000-6Y tractor powered by a four cylinder, Ford FD5NN6 0095, 3.8 1 direct injection engine for evaluating the performance of tallow ester as diesel fuel. He concluded that fuel properties of methyl tallowate were remarkably similar to diesel fuel. The major drawback with its use was when the temperature was below 5°C. He also concluded that a blend of diesel fuel and tallow ester gave improved combustion characteristics. Spe- cific fuel consumption was increased because of the

243

244 Y Ali, K. M. Eskridge, M. A. Hanna

lower energy content of the esters. Schumacher et al. (1993) noted few differences

when tractors were fueled with No. 2 diesel fuel as compared to soydiesel, a blend of soybean oil methyl ester (methyl soyate) and No. 2 diesel fuel. They observed an average power difference of less than 0.4% when the tractors were fueled with a 20% methyl soyate and 80% No. 2 diesel fuel as compared to No. 2 diesel fuel only. The greatest reduction (75%) in power occurred when the tractor engines were fueled with 100% methyl soyate.

Fosseen et al. (1993) while studying the use of methyl soyate and diesel fuel blends in a DDC 6V- 92 TA engine, found that the addition of up to 40% methyl soyate did not affect peak torque, but observed a small reduction in power at the 40% level. They also observed a steady reduction in exhaust gas temperature at both the rated and peak torque conditions, which resulted in a shift in the peak pressure point towards top dead center, caus- ing an increasingly shorter ignition delay. Fuel consumption on a mass basis was very similar for all blends tested.

Ali et al. (1995a) used blends of methyl soyate and diesel in the range from 0 to 100% in a DDC 6V-92 TA engine and found that there was no significant reduction in the power output of the engine up to a range of 70% diesel and 30% methyl soyate. All exhaust emissions, except NO,, were reduced with increasing concentration of methyl soyate. Ali et al. (1995a) conducted emissions and power characteristics of a Cummins NTA-855-C engine using blends of methyl soyate and diesel in the range of 70:30 to 100:0 diesel:methyl soyate. They observed that engine performance did not differ to a great extent from that of diesel-fueled engine performance. A slight power loss (1.38%) combined with an increase in fuel consumption was observed with increasing methyl soyate content of the blend. Hydrocarbons, CO and smoke emissions decreased with an increase in the methyl soyate content of the blend but there was an increase (13%) in NO, emissions.

The purpose of this investigation was to deter- mine the effects of fueling a diesel engine with different blends of methyl tallowate, methyl soyate, ethanol and No. 2 diesel fuel on performance and emissions of a Cummins N14-410 truck/bus engine.

METHODS

Engine and instrumentation A Cummins N14-410 diesel engine was used in this study. Specifications of the engine are presented in Table 1.

The engine was coupled to an Eaton 522 kW (700 hp) dynamatic eddy current dry gap dynamometer (EATON Power Transmission Systems, Eaton Corp., Kenosha, WI) with a DANA 1810 coupler. Engine torque was measured with a load cell and Daytronic system 10 integrator (Daytronic Corp.,

Miamisburg, OH), and speed was measured using a 60-tooth wheel and magnetic pick-up attached to the dynamometer. Fuel consumption was measured with an EM Corp. (Lincoln, NE), custom-built, mass measurement system in which fuel weight was measured over an operator-selected time period. Air flow into the engine was measured with a Badger BVT- IF venturi flow meter (Badger Meter, Inc., Tulsa, OK). The air flow meter was positioned in a 0.15 m diameter, 5.2 m long pipe with a surge tank between the meter and the engine. A throttle valve was used at the inlet of the surge tank to control engine inlet pressure. The exhaust system consisted of 2.1 m of 0.13 m diameter exhaust tubing leading into a 0.25 m diameter duct with an evacuation fan to the out- side air. A centrifugal fan provided exhaust ventilation. A throttle valve was positioned in the exhaust tubing to control exhaust back pressure.

Temperatures were measured using type K, E and T thermocouples and a Daytronic System 10 coupled with an AutoNet data-acquisition system. Pressures were measured with analog gages and manometers (Hz0 and Hg), calibrated with a dead-weight tester.

Oxides of nitrogen (NO/NO,) were measured with a Beckman model 955 chemiluminescent analyzer (Beckman Industrial Corp., La Habra, CA). Hydro- carbons (HC) were determined by a total HC analyzer model JUM VE7 flame ionization detector (FID) (J.U.M. Engineering, Karlsfeld, Germany). This analyzer was designed to continuously measure the concentration of total organic HC in gaseous samples. Carbon monoxide (CO) and carbon dioxide (CO,) were measured with a Beckman non-disper-

Table 1. Engine specifications

Specifications Cummins N14-410 engine

Engine data Type of engine

Bore x stroke, mm Displacement, 1 Compression ratio Valves per cylinder

Intake Exhaust

Fuel system

Aspiration Turbocharger type

Aftercooling type

Perfomance data Rated power,

kW (BHP) at RPM Peak torque,

Nm (ft lb) at RPM Idle speed, RPM Maximum no load

governed speed, rpm

Six-cylinder, four-stroke, direct injection

140 x 152 mm 14 16.3:1

2 2 PT step timing

control Turbocharged Holsett type

BHT 3B Charge air

cooled

306 (410) at 1800

1966 (1450) at 1200

700 2060

Alternative diesel fuel testing 245

sive infrared analyzer model 880-A (Rosemount Analytical, Inc., La Habra, CA). Smoke units were measured with a Bosch EFAW 65-A smoke probe (Robert Bosch GMBH, Stuttgart, Germany).

Fuels Several blends of high sulfur (0.24%) No. 2 diesel fuel, methyl tallowate, methyl soyate and ethanol were prepared and tested. Specific blend composi- tions are given in Table 2. The methyl tallowate and methyl soyate were produced by Proctor and Gam- ble and purchased from Interchem, Inc. of Kansas City, MO. Physical properties of methyl tallowate and its blends with diesel fuel and ethanol were determined (Ah & Hanna, 1994).

Test run and performance map Engine testing on the above fuels was performed at speeds ranging from 1100 to 1900 rpm and loads ranging from 100 to 10%. The testing was divided into two sets: (1) engine performance tests at speeds ranging from 1100 to 1900 rpm at full load using standard engine power test code SAE 51349 (SAE 51349, 1994) and (2) exhaust emissions testing at four speeds with variable loads using the standard, eight-mode, steady-state engine test code SAE 51003 (SAE 51003, 1994). The engine smoke measure- ments were taken with a Bosch spot smoke meter and Bosch smoke units were converted into soot concentration using standard diesel engine smoke measurement code SAE J255a (SAE J255a, 1994). Table 3 presents the speeds and loads used in this study. The testing was done in the Nebraska Power Laboratory at the University of Nebraska-Lincoln. The sequence of fuels used was randomized and within each fuel blend the engine speed sequence was randomized. Standard performance and exhaust emission data were recorded. The entire set of fuels and speeds were then re-randomized and data recorded giving replication in two complete blocks.

Test 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 sufficient load was applied to raise the coolant temperature to 71°C. After completion of the warm-up procedure, the intake and exhaust restrictions were fixed at rated engine speed (1800 rpm) and full power and from then on were not adjusted for different speed or load changes after initial settings were completed.

The engine was run at the specified speeds and loads for a minimum of 6 min and data were recorded during the last 2 min of operation. The response variables included torque, fuel consumption, CO, CO*, 02, NO,, HC and smoke. These data were recorded at 5 s intervals for 2 min and averaged over that period. After completion of one set of experiments with 12 fuels, the whole set was repli- cated.

Experimental design and data analysis

Engine performance The experimental design used in evaluating engine performance was a randomized, complete block, split-plot design with the 12 fuel blends as the main plot treatments, the six engine speeds as the split- plot treatments and two blocks. There were two types of experimental unit: (1) main-plot units asso-

Table 3. Engine speeds and loads used for each fuel blend

Engine performance

Engine Load, % speed, rpm

1100 100 1200 100 1400 100 1600 100 1800 100 1900 100

Exhaust emission analysis

Engine Load, % speed, rpm

1800 100 1800 75 1800 50 1800 10 1200 100 1200 75 1200 50 Idle 0

Table 2. Fuel blends tested

Blend number No. 2 Diesel fuel, %

Methyl tallowate, %

Methyl soyate, %

Ethanol, % Fuel group

Energy content, kJ/kg

8 9

10 11 12

100 80 70 60

;: 60 80

;: 0 0

0 13 19.5 26

:::5 13

:: 40 65 32.5

0 0 6-5

9.75 13 0 0

: 32.5

0 7

10.5 14

l70.5 14 0

: 35 35

45509 42288 40997 39148 42803 41522 38350 43616 43147 42807 36158 35560


ciated with each fuel blend in each block and (2) split-plot units associated with engine speed within one fuel blend in each block. The means of each response variable for each split-plot unit were used for statistical analyses.

Statistical analyses were conducted in three steps using analysis of variance (ANOVA) and regression. First, an ANOVA model was fit on the split plot with 12 fuel blends as the main-plot treatment and six engine speeds as sub-plot treatments, to estimate main-plot and split-plot mean square errors. In the second step, all the fuel blends were divided into five groups of identical fuel blends, keeping 100% diesel fuel as the control in each group (Table 2). A new ANOVA model was fit on a full factorial with two-way interactions. The main effects (fuel blend and engine speeds) and interactions were broken into one degree of freedom polynomial contrasts. The mean square for each polynomial contrast was compared with the respective mean square errors determined in step one, to find the significant terms. In the third step, significant contrasts from the second step were used to identify polynomial terms that were fit in a regression model (Milliken & Johnson, 1984). The estimated regression model was then used to generate predicted points on a response sur- face which was plotted against engine speed and fuel blends.

Emissions analyses The experimental design used in performing emissions analyses was a randomized complete block design with two blocks and the 12 fuel blends as treatments. Experimental units were test runs for each fuel type in each block. Emission gas values from the eight-mode emission analyses method were obtained for each experimental unit and used for statistical analyses.

Statistical analyses were conducted in three steps using analysis of variance (ANOVA) and regression as with engine performance. All procedures were the same except that in the first step an ANOVA model was fit for the randomized complete block with the 12 fuel blends as treatments. Also, in the second step, all fuel blends were divided into five groups of identical blends, as was done in engine performance analysis and for each group an ANOVA model was fit with the fuel blend as a single treatment factor. Significance was evaluated at the 5% level for all statistical analyses.

RESULTS AND DISCUSSION

Engine performance Engine performance on different fuel blends in terms of corrected power output, corrected torque and corrected brake specific fuel consumption (BSFC) are shown in Figs (l)-(4). For analyses, the fuel blends were divided into the following four cat- agories: (1) diesel fuel blended with methyl

tallowate (group 3); (2) diesel fuel blended with methyl tallowate and ethanol (group 1); (3) diesel fuel blended with methyl tallowate, methyl soyate and ethanol (group 2); and (4) methyl tallowate blended with methyl soyate and ethanol with no diesel fuel (groups 4 and 5).

Diesel and methyl tallowate blends Statistical analysis conducted on effects of blending diesel with methyl tallowate at different levels and engine speeds on power output showed that there was no significant interaction between engine speed and fuel blend. The regression analysis had a significant quartic effect of engine speed on the power output of the engine while there was no significant fuel blend effect [Fig. l(a)]. The corrected power output was the same for all fuel blends at a given engine speed. The power output increased with engine speed and maximum power output was observed at about 1700 ‘pm. Differences in power output for different fuel blends were not expected as the energy content of No. 2 diesel fuel was 45509 kJ/ kg, and the energy content of the 60:40 diesel:methyl tallowate blend was 42807 kJ/kg. This difference in the energy contents was not sufficient to show any significant trend in power output with fuel blend.

The torque produced by the engine with the same fuel blends also showed no interaction between engine speed and fuel blend. Regression analyses once again showed that engine speed had a quartic effect on torque, while there was no significant fuel blend effect [Fig. l(b)]. It was observed that the corrected torque produced was the same for all fuel blends. Maximum torque was produced at 1200 rpm. This observation was in agreement with the engine performance data provided by the Cummins Engine Co., Inc. (Anon, 1991).

For brake specific fuel consumptions (BSFC) at full load, there was no significant interaction between fuel blend and engine speed. The regression analysis had a significant linear effect on fuel blend, whereas speed had a significant quadratic effect on BSFC [Fig. l(c)]. Fuel consumption with 100% diesel fuel was minimum at all speeds and increased linearly by 2.07% for each 10% decrease in diesel fuel content of the blend. For each fuel blend, the BSFC was minimum at an engine speed of 1400 rpm. Since the densities of methyl tallowate fuels were more than the density of diesel fuel, and since the injection pump metered fuel on a volu- metric basis, the mass fuel consumption increased with higher methyl tallowate content blends. A similar trend was observed by Ali et al. (1995a) for diesel fuel and methyl soyate blends in a Cummins NTA-855-C engine.

Diesel, methyl tallowate and ethanol blends Ethanol was blended with methyl tallowate to obtain a blend viscosity similar to No. 2 diesel fuel. Statis-

(a)

Alternative diesel fuel testing

L i

, ~ m ,@ "

247

(b)

Fig. 1.

(c) ..... -. :.:.-:: :: :: .:.: .:: :.. . . " . . . . - . . . . . ~ - - ' - - " - ~ 1 9 o

90:10 ~^ ~ / J . . . . . . . . . . . . . . . . . . . . . . , ~ ' t - 2 / gO:' °\°

'~J'ne Speed, rprn ~ ~ ~=~d~ 6o:40

Effects of diesel fuel:methyl tallowate blends and engine speeds on corrected power output, corrected torque and brake specific fuel consumption.

tical analyses of power output showed that there was no interaction between fuel blend and engine speed. The regression analysis had a significant linear effect of fuel blend, whereas engine speed had a significant quartic effect on the power output of the engine [Fig. 2(a)]. Corrected power output was reduced as methyl tallowate and ethanol contents of the fuel blend increased. Maximum power output was observed at 1700 rpm. At this speed the power pro-

duced by No. 2 diesel fuel was 320-6 kW. Power output was reduced to 307-3 kW for a 60:26:14% (v/ v) blend of diesel:methyl tallowate:ethanol. The drop of 1"1% power output for each 10% decrease in diesel fuel content was expected as the total energy content of the blend was reduced by 3-5% for each 10% decrease in diesel fuel in the blend. The reduction in the total energy content of the blend was a result of the addition of ethanol which had

248 Y. Ali, K. M. Eskridge, M. A. Hanna

(a)

, , ~ + 9.21x10"6S ' - 1.62x10"~'S 4 ,~:'13:7 b"

(b)

. ~ ~ R 2 = 0.995 ~ 220o

,,?

Fig. 2.

(c) i,o =

100:0:0

80:13:7 ~ "

Effects of diesel fuel:methyl tallowate:ethanol blends and engine speeds on corrected power output, corrected torque and brake specific fuel consumption.

about 38% less energy content than No. 2 diesel fuel.

The torque produced by the engine for the same fuel blends showed a significant interaction between blend (quadratic) and speed (linear); fuel blend had a significant linear main effect, whereas engine speed had a significant quartic effect [Fig. 2(b)]. It was observed that the corrected torque reduced at any one speed as the methyl tallowate and ethanol

content was increased. Maximum torque was produced at an engine speed of 1200 rpm. At this speed the torque produced by No. 2 diesel fuel was 2097 N-m and was reduced to 1972 N-m for a 60:26:14% (v/v) blend of diesel:methyl tallowate:ethanol. The values of torque produced by the engine were in agreement with the engine performance data provided by the Cummins Engine Co., Inc. (Anon, 1991).


The BSFC at full load for different blends of diesel, methyl tallowate and ethanol and six engine speeds are shown in Fig. 2(c). Statistical analysis showed that there was no significant interaction between fuel blend and engine speed and that fuel blend had a significant linear effect, whereas engine speed had a significant quartic effect on the BSFC. BSFC was minimum at all speeds with No. 2 diesel fuel and increased linearly with increasing methyl tallowate and ethanol contents. For each fuel blend, the BSFC was minimum at 1200 rpm. Cummins Engine Co., Inc. reported minimum fuel consumption between 1300 and 1400 rpm. At 1200 rpm, the BSFC for No. 2 diesel fuel was 195 g/kW-h and increased to 215 gJkW-h with a 60:26:14% (v/v) blend of diesel fuel:methyl tallowate:ethanol. The 2.3% increase in fuel consumption for each 10% decrease in diesel content was expected because of the reduced energy content of the blend.

Diesel fuel, methyl tallowate, methyl soyate and ethanol blends This fuel blend was considered for its potential improvement in the physical properties, especially pour point and melting point, and for reducing the crystallization problem of methyl tallowate by replacing 50% methyl tallowate with methyl soyate. Statistical analysis showed that there was no significant difference between the blends of diesel, methyl tallowate and ethanol, and the blends of diesel, methyl tallowate, methyl soyate and ethanol as far as engine performance was concerned. The power, torque and BSFC regression models for diesel, methyl tallowate and ethanol blends can be used for the diesel, methyl tallowate, methyl soyate and ethanol blends.

Comparison of No. 2 diesel fuel with blends containing no diesel The effect of methyl tallowate and ethanol blends, and methyl tallowate, methyl soyate and ethanol blends were compared separately with No. 2 diesel fuel. Statistical analysis performed for comparing diesel fuel with methyl tallowate and ethanol showed that there was a significant interaction between diesel fuel and methyl tallowate with engine speed and that engine speed had a significant quartic effect on the power output of the engine [Fig. 3(a)]. In the case when 50% of the methyl tallowate was replaced with methyl soyate, statistical analysis showed a significant interaction between fuel blend and engine speed, while engine speed had a significant quartic effect on the power output of the engine [Fig. 3(a)]. It was observed that there was no difference in power output for the methyl tallowate and ethanol blend and methyl tallowate, methyl soyate and ethanol, but the power outputs of both fuel blends were significantly less than No. 2 diesel fuel. The trend of power output was the same as that observed for all other fuels used. The reduction in power output was

of the order of 12-14%, which was expected as the energy contents of the methyl tallowate and ethanol blend, and the methyl tallowate, methyl soyate and ethanol blend were 20.5 and 21.9% less than No. 2 diesel fuel, respectively.

The torques produced by the engine at all engine speeds for the three fuel blends are shown in Fig. 3(b). Statistical analysis conducted showed that there was no significant interaction between fuels used and engine speeds. There was also no difference in torque produced with the methyl tallowate and ethanol blend and the methyl tallowate, methyl soyate and ethanol blend, but the torques produced were significantly less than No. 2 diesel fuel. The regression analysis showed that engine speed had a significant quartic effect on torques for the methyl tallowate and ethanol blend and for the methyl tallowate, methyl soyate and ethanol blend.

For BSFC at full load, statistical analysis showed that there was a significant interaction between fuel blend and engine speed for the diesel, methyl tallowate and ethanol blend, and for the diesel, methyl tallowate, methyl soyate and ethanol blend. The regression analyses performed for both fuel blends showed that engine speed had a significant quadratic trend for the diesel, methyl tallowate and ethanol blend, and for the diesel fuel, methyl tallowate, methyl soyate and ethanol blend on BSFC [Fig. 3(c)]. It can be observed from Fig. 3(c) that there was no difference in BSFC for the ester fuel blend, but the BSFC for both blends was significantly higher than that for No. 2 diesel fuel. In all cases BSFC was minimum at 1400 rpm. These results were in agreement with the engine performance data provided by the Cummins Engine Co., Inc. (Anon, 1991).

Emissions analyses

EPA off-highway emission standards The U.S. Environmental Protection Agency (EPA) published its final emissions standards for heavy- duty off-highway diesels (Brezonick, 1994). The new regulations apply to all new off-road compression ignition engines at or above 37 kW (50 hp). The new EPA off-highway emissions standards are presented in Table 4. The Cummins N14-410 engine was rated at 306 kW (410 hp) and according to this regulation the maximum allowable emissions were 1.3 g/kW-h for HC, 11.4 g/kW-h for CO, 9.2 gJkW-h for NO, and 0.54 g/kW-h for particulate matter.

Diesel and methyl tallowate blends Statistical analyses performed on the effects of blending methyl tallowate with diesel fuel on exhaust emissions showed that there were no significant fuel effects for CO, COZ, 02, and NO, emissions with increasing amounts of methyl tallowate in the fuel blends (Fig. 4). Therefore, the mean values over all blends of the dependent variables


320

(a) 300

220

200 - 6005 + 0.1 B + 17.16 S - 0.02 .S’+ 6.34xld’s’ - 1.46x1dgS4+ 0.2xlO’kl S

n M

1,800 -

$

2 1,600 - CT f5 c

1,400 -

1200 - 0,. T= - 34737 + 2.46 B + 101.6 S - 0.1 S=+ 46.2xld‘s’ - 8.27xld’S

O,A T=- 36065+2.35B+111.24S-0.12S1+52.66x1d’~ -9.03dS’ 1,000 I I I I

1,000 1,200 1,600 &a00 2,000

I w 0, l BSFC = 423.4 - 0.16 B - 0.26 S + l.ld s’ - 2.2xld’B S I+= 0.990

280 - aA BSFC=416.6-0.134B-0.26S+1.1x1d’$-2.27x16’8S

180 -

No.*sel 65z35JdJ:E 32.532.5~3$tT:MS:E

160 I I , I 1,000 1$200 1,400 1,~ 1,800 2,000

Engine Speed, rpm

Fig. 3. Comparison of No. 2 diesel fuel and methyl tallowate:methyl soyate:ethanol blends for corrected power output, torque and brake specific fuel consumption (in regression equations, B = diesel content in blend, %, and S = engine speed,

rpm) .

were used to interpret the results. The mean CO, CO*, 0, and NO, values were 0.788, 7.01, 12.02 and

smoke, there was a significant quadratic effect of

6.39 g/kW-h, respectively. There was a significant methyl tallowate content of the blend (Fig. 4).

quadratic effect of methyl tallowate content of the Hydrocarbon emissions decreased with increasing

blend on HC emissions (Fig. 4). Similarly, for methyl tallowate content of the blend. Minimum HC emissions were observed for a blend of 70:30 die-


Table 4. EPA off-highway emissions standards (Brezonick, 1994)

Net power, kW (HP) gikW-hT&Hp-h) g/kW-hT&Hp-h) g&W-r$Hp-h) g/kW-hqMpi&Hp-h)

Smoke AIL/P”, %

2 130 (2 175) 1.3 (1.0) 11.4 (85) 175-<130 (loo-<175) - ;‘; . 2 37- < 75 (50- < 100)

$9,’ . 054 (0.4) 20/15/50

- 20/15/50 - - 9.2 (6.9) - 20/15/50

nSmoke opacity standards are reported in terms of percent opacity during an acceleration mode, lug mode and the peak opacity on either the acceleration or lug modes.

Ol IO 50:50 60:40 70:30 60:20 00:10 1w:o

(W

- 0.6 16 -

f

2 4 10 - e 2 0 ‘Ii m 0” 6_ HC = 2% - 0.052 q : 0.000969 8’ - 0.2

o’. 50:50 60:40 70:30 8o:m w:10 100:0

10 ) #1

R';O.nO

6 - - 0.8

f f

L 0 0 0 NOx (’ 0 0.6 2 01 n‘ 0 7 e 5

(a e .s

. - 0.4 - Smoke

. 2 - S = - 0.6996 + 0.0276 B - 0.000163 B*

I Z3:60 I 60:40 70:r) 8o:zo 90:10 ,oo:“o

Diesel fuel : methyl tallowate blend

Fig. 4. Effects of diesekmethyl tallowate blends on brake specific emissions (in regression equations, B = die-

sel content of blend, %).

sel:methyl tallowate. HC emissions were maximum with No. 2 diesel fuel and increased when methyl tallowate content was increased above 30%. The reduction in the HC emissions with methyl tallowate indicates complete combustion (a cleaner burn) of the fuel. Ali et al. (1995a) also observed a decrease

in the HC emissions with an increase in methyl soyate content in fuel blends with a Cummins NTA- 855-C engine. They reported an increase in HC emissions produced by methyl soyate blends of 20% or more because of the leaning effect coupled with the under-mixing of air and fuel.

Smoke emissions had a reverse trend when compared to HC [Fig. 4(c)]. Smoke emissions increased with decreasing diesel content of the blend up to a blend of 80:20 and then they started decreasing. A maximum smoke emission of 0.346 g/kW-h was produced with a 80:20% (v/v) diesel:methyl tallowate blend. From the reduction in HC emissions and no change in CO and NO, emissions, the smoke also should have been reduced. The reverse trend of smoke emission as calculated from Bosch smoke units suggests that a better method for smoke analysis is needed.

Comparing the emissions values observed with the diesel and methyl tallowate blends with EPA’s regulations shows maximum HC emissions of 0.577 g/kW-h with diesel fuel as compared to the upper limit of l-3 g/kW-h, maximum CO emissions of 0.788 g/kW-h (average) as compared to an upper limit of 11.4 g./kW-h, NO, emissions of 6.39 g/kW-h as compared to an upper limit of 9.2 g/kW-h and maximum smoke produced of 0.346 g/kW-h as compared to an upper limit of 0.54 g/kW-h. Thus, it was concluded that all blends were acceptable within EPA’s emissions standards.

Diesel, methyl tallowate and ethanol blends Statistical analyses performed to find the effects of blending ethanol with diesel and methyl tallowate blends once again showed that there was no significant trend of CO, COz, O2 and NO, emissions with an increasing amount of methyl tallowate and ethanol in diesel fuel. The CO, C02, O2 and NO, emissions averaged over all blends were once again used to interpret the results and were found to be O-8, 7.25, 12.26 and 6.52 gJkW-h, respectively. There was no significant change in the amount of average exhaust emissions as compared to the diesel and methyl tallowate blend. Regression analyses performed for HC and smoke emissions showed that there was a significant quadratic effect of fuel blend on HC emissions and a significant linear trend of fuel blend on smoke emissions (Fig. 5). Similarly,


the regression model for variation in smoke emissions (S) with diesel content of the blend (B) was found to be linear (Fig. 5). Hydrocarbon emissions decreased with an increasing amount of methyl tallowate and ethanol content of the blend (Fig. 5). The HC emissions decreased for blends up to 80:13:7% (v/v) diesel:methyl tallowate:ethanol content. Fur- ther increases in methyl tallowate and ethanol contents increased HC emissions. Minimum HC emissions of 0.243 g/kW-h were observed with the 80:13:7% (v/v) blend. Maximum HC emissions of 0577 g/kW-h were found with No. 2 diesel fuel.

The smoke emissions had a linear increasing trend with increasing methyl tallowate and ethanol content of the blend. Minimum exhaust smoke of 0.232 g/ kW-h was observed with No. 2 diesel fuel which increased to 0.38 g/kW-h with 60:26:14% (v/v) blend of diesel:methyl tallowate:ethanol. Fosseen et al. (1993) concluded that there was an increase in NO, and a decrease in particulate matter with increases in the level of methyl soyate in the blend. In this research, there was no change in NO, emissions but smoke increased with increasing methyl tallowate and ethanol content of the blend.

All exhaust emissions were well below the EPA’s standards for off-highway diesel engines.

Diesel, methyl tallowate, methyl soyate and ethanol blends Regression analyses on the effects of replacing 50% of the methyl tallowate with methyl soyate on exhaust emissions showed that there were no significant trends of CO, C02, 0, and NO, emissions with increasing amounts of methyl tallowate, methyl soyate and ethanol in the blend. These results were the same as those obtained for the two blends dis- cussed previously and the mean values of CO, COz, O2 and NO, emissions were used to interpret the results. The mean values of CO, C02, 0, and NO, were found to be O-832, 7.08, 12.03 and 6.24 g/kW-h, respectively. These values were very close to the values obtained for the other two blends. The regression analyses performed for HC and smoke emissions showed that there were significant quadratic effects of fuel blends on both HC emissions and smoke (Fig. 6).

Hydrocarbon emissions again decreased with increasing methyl tallowate, methyl soyate and ethanol contents up to 70-80% diesel and then increased again (Fig. 6). Minimum HC emissions were found to be 0.34 g/kW-h for somewhere between 70 and 80% (v/v) diesel fuel content, whereas maximum HC emissions were found to be 0.579 g/kW-h with No. 2 diesel fuel.

The smoke emissions had a quadratic trend. Max- imum smoke of 0.326 g/kW-h was observed with 80% diesel fuel content and was reduced with increased or decreased diesel fuel content. Mini- mum smoke of 0.227 g/kW-h was observed with No. 2 diesel fuel.

A comparison of No. 2 diesel fuel and blends of methyl tallowate and ethanol blend and methyl tallowate, methyl soyate and ethanol with no diesel fuel were made to find their effects on exhaust emissions. The diesel fuel and alternate fuels had no significant effects on CO, C02, 02, NO, and smoke emissions. However, there were significant differences in HC emissions for the diesel, methyl tallowate and ethanol blend and the diesel, methyl tallowate, methyl soyate and ethanol blend.

Comparison of engine performance using different fuel blends The performance of the Cummins N14-410 engine was evaluated with different fuel blends in terms of power output, torque produced, BSFC and emissions analyses. Maximum power was produced at an

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Diesel : methyl tallowate : ethanol blend

Fig. 5. Effects of diesel:methyl tallowate:ethanol blends on brake specific emissions (in regression equation,

B = diesel content of blend, %).

Alternative diesel jkel testing 253

engine speed of 1700 rpm and maximum torque was produced at 1200 rpm for all blends. These were in agreement with the data provided by the Cummins Engine Co., Inc. (Anon, 1991).

A different set of statistical analyses were conducted for comparing performance of No. 2 diesel fuel with blends of 80, 70 and 60% diesel fuel and combinations of methyl tallowate, methyl soyate and ethanol, as given in Table 2. It was observed that there was no significant difference between No. 2 diesel fuel and 80% diesel and 20% alternative fuel for power, torque and BSFC. A comparison between No. 2 diesel fuel and 70% diesel fuel and 30% alternative fuel showed that there was no significant difference as far as power and torque output were concerned. However, BSFC was significantly affected. This showed that, since the 70:30% (v/v) blend of diesel and alternate fuel had a low energy con-

OL I I IO 50:16.25:‘6.25:17.5 50:,3:,3:14 70:9.75:0.,5:,0.5 80:6.6:6.6:, 903.28:3.25:3.5 imoaa ‘O 1

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Diesel fuel : methyl tallowate : methyl soyate : elhanol blend

Fig. 6. Effects of diesel:methyl tallowate:methyl soyate:ethanol blends on brake specific emissions (in

regression equations, B = diesel content of blend, %).

tent, BSFC of engine was increased significantly. In the third case, a comparison of No. 2 diesel fuel with 60% diesel and 40% alternative fuel showed that there was a significant difference in power output, torque and BSFC. This time the difference in power output between No. 2 diesel fuel and the 60:40% (v/v) blend of diesel and alternative fuel was so much that even maximum fuel consumption by the engine could not compensate for the reduction in the energy content of the blend.

When ethanol was added with the above blend there was a reduction in power output by 1.1% for each 10% increase in methyl tallowate and ethanol content, which was due mainly to the reduction in energy content of the blend. Similar results were obtained when 50% of the methyl tallowate was replaced with methyl soyate. The advantage of blending ethanol was the reduction in the viscosity of the resulting blend. Ali and Hanna (1994) studied the effects of adding ethanol with methyl tallowate on viscosity and reported that adding 35% (v/v) ethanol with methyl tallowate reduced its viscosity to that of No. 2 diesel fuel at 40°C. A further advantage of adding ethanol with methyl tallowate was a reduction in the crystallization problem. Adding methyl soyate with methyl tallowate had an additional advantage of reducing the pour point and melting point of the blends as reported by Ali et al. (1995b).

A similar response was obtained for torque produced by the engine for different fuel blends. However, the BSFC increased by 2.07% for each 10% increase in methyl tallowate and 2.3% for each 10% increase in methyl tallowate and ethanol content of the blend and a similar increase in fuel consumption was observed when 50% of the methyl tallowate was replaced with methyl soyate.

As far as exhaust emissions were concerned, the responses for all fuel blends were the same. In all cases, there were no effects on CO, COz, O2 and NO, emissions. The HC emissions followed a quadratic trend with all fuel blends and it was observed that HC emissions were minimum with about 70-80% diesel fuel content and 20-30% alternate fuels. Smoke showed a slight increasing trend with decreasing diesel content of all blends but all smoke emissions were less than the EPA’s standards.

CONCLUSIONS

(1) Engine performance with diesel fuel and methyl tallowate blends was no different than with No. 2 diesel fuel. When ethanol was added with methyl tallowate there was 1.1% power reduction for each 10% replacement of diesel fuel with methyl tallowate and ethanol blend. Engine performance with diesel, methyl tallowate, methyl soyate and ethanol blend was similar to that with a diesel, methyl tallowate and ethanol blend. There was about


(4

(3)

(4)

(5)

(6)

(7)

a 12-14% loss of power output when the engine was operated on a methyl tallowate: ethanol blend of 65:35% (v/v) or on a methyl tallowate:methyl soyate:ethanol blend of 32*5:32.5:35% (v/v) as compared to No. 2 diesel fuel. The torque produced by the engine with different fuel blends followed the same trend as power output with respect to the dependent variables used. Brake specific fuel consumption was increased by 2.07% for each 10% increase in methyl tallowate, 2.3% for each 10% increase in methyl tallowate and ethanol blend and 2.3% for each 10% increase in methyl tallowate, methyl soyate and ethanol blend in the fuel. There was no change in CO, COZ, O2 and NO, emissions with any of the fuel blends. The CO, C02, O2 and NO, emissions were less than the limits set by EPA. Hydrocarbon emissions had a significant quadratic trend with fuel blend. Minimum HC emissions were observed with 80% diesel and 20% methyl tallowate or methyl tallowate and ethanol or methyl tallowate, methyl soyate and ethanol blends. Smoke emissions showed an increasing trend with decreasing diesel content of the blend but the maximum smoke produced was less than the limit set by EPA. Engine performance was best with the 80:20% (v/v) blend of diesel:methyl tallowate. Blend- ing ethanol with methyl tallowate had the advantage of reducing the viscosity as well as reducing crystallization of methyl tallowate. Replacing 50% of the methyl tallowate with methyl soyate had an additional advantage of reducing the pour point and the melting point of the blends.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the contribu- tions of Joseph E. Borg and Kevin G. Johnson, Lab Technicians, Nebraska Power Laboratory, University of Nebraska-Lincoln for engine operation and data collection and analyses.

REFERENCES

Ali, Y. & Hanna, M. A. (1994). Physical properties of tallow ester and diesel fuel blends. Biores. Technol., 47, 131-4.

Ali, Y., Hanna, M. A. & Leviticus, L. I. (199%). Emis- sions and power characteristics of diesel engines on methyl soyate and diesel fuel blends. Biores. Technol., 52, 185-95.

Ali, Y., Hanna, M. A. & Cuppett, S. L. (199%). Fuel properties of tallow and soybean oil esters. JAOCS (accepted).

Anon. (1991). Automotive Performance Curve. Cummins Engine Co., Columbus, IN.

Brezonick, M. (1994). Harmony! EPA unveils off-road rules. Diesel progress; Engine and Drives, July 1994, 10-4.

Clark, S. J., Wagner, L. W., Schrock, M. D. & Piennaar, P. G. (1984). Methyl and ethyl soybean esters as renewable fuels for diesel engines. JAOCS, 61, 1632-8.

Fosseen, D., Malcom, B., Green, C. & Goetz, W. (1993). Methyl soyate evaluation of various diesel blends in a DDC 6V-92 TA engine. Fosseen Manufacturing and Development. Radcliff, IA. Report prepared for National Soydiesel Development Board, Jefferson City, MO.

Goering, C. E. & Fry, B. (1984). Engine durability screen- ing test of a diesel oil/soy oil/alcohol microemulsion fuel. JAOCS, 61, 1627-32.

Houghton-Alice, D. (1982). Uses of alcohol fuels. In Alco- hol Fuels: Policies, Production, and Potential. Westview Press, Boulder, CO 80301, pp. 118-25.

Milliken, G. A. & Johnson, D. E. (1984). Analysis ofMes.yy Data, Vol. 1. Van Northand, New York, NY.

SAE J255a (1994). Diesel engine smoke measurement. In SAE Handbook of Engines, Fuels, Lubricants, Emissions, and Noise, Vol. 2(13), pp. 56-64. Society of Automotive Engineers, Warrendale, PA.

SAE 51003 (1994). Diesel engine emission measurement procedure. In SAE Handbook of Engines, Fuels, Lubri- cants, Emissions, and Noise, Vol. 2(13), pp. 33-7. Society of Automotive Engineers, Warrendale, PA.

SAE 51349 (1994). Engine power test code - spark ignition and compression ignition engines - net power rating. In SAE Handbook of Engines, Fuels, Lubricants, Emissions, and Noise, Vol. 2(24), pp. 16-21. Society of Automotive Engineers, Warrendale, PA.

Schumacher, L. G., Borgelt, S. C. & Hires, W. G. (1993). Soydieselipetroleum blend research. Paper No. 936523, presented at 1993 Winter Meeting of American Society of Agricultural Engineers, St Joseph, MI 49085.

Sims, R. E. H. (1985). Tallow esters as an alternative diesel fuel. Trans. ASAE, 28, 716-21.

Wagner, L. E., Clark, S. J. & Schrock, M. D. (1984). Effect of soybean oil esters on the performance, lubri- cating oil, and water of diesel engines. SAE technical paper No. 841385. Society of Automotive Engineers, Warrendale, PA.

Testing of alternative diesel fuel from tallow and soybean oil in cummins N14-410 diesel engine

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