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Bioresource Techno/ogy $2 (1995) 237-243 Elsevier Science Limited Printed in Great Britain

0960-8524/95/$9.50

OPTIMIZATION OF DIESEL, METHYL TAILOWATE AND ETHANOL BLEND FOR REDUCING EMISSIONS FROM

DIESEL ENGINE*

Y u s u f Ali, a Mi l fo rd A. H a n n a a'b & J o s e p h E. Borg"

aDepattment of Biological Systems Engineering University of Nebraska-Lincoln, Lincoln, NE 68583-0726, USA ~lndustrial Agricultural Products Center, University of Nebraska-Lincoln, Lincoln, NE 68583-0726, USA

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

Abstract A Cummins N14-410 engine was operated on different fuels produced by blending methyl tallowate and etha- nol with No. 2 diesel fuel. Four fuel blends, namely: neat No. 2 diesel fuel; and 80:13:7, 70:19.5:10.5 and 60:26:14 (% v/v) blends of diesel:methyl tallo- wate:ethanol, were prepared and tested for engine performance and emission analyses. Engine perform- ance and emission data were used to optimize the blend of diesel fuel:methyl tallowate:ethanol for reducing engine emissions. The emissions were found to be minimum with a 80:13: 7 blend of diesel:methyl tallowate : ethanol, without a significant drop in engine power output.

Key words: Methyl tallowate, biodiesel, ethanol, Cummins engine, power, torque, fuel consumption, exhaust emissions.

INTRODUCTION

The use of vegetable oils and animal fats as alter- nate fuel sources or fuel extenders has been studied extensively. Much research has been done in the past two decades on the use of oils and fats from plant and animal sources as alternative diesel fuel. The major problem associated with the direct use of oils is their high viscosity, which interferes with fuel injection and atomization, which contribute to incomplete combustion, nozzle coking, engine deposits, lubricating oil dilution and ring sticking (Knothe, 1992). The problems caused by high oil- and fat-viscosity can be reduced to a certain degree by transesterification. In the process of transester- ification, triglycerides are reacted with an alcohol for 1 h at 75-80"C in the presence of NaOH or NaHCO3 catalyst, which removes the glycerol from

*Journal Series Number 10947 of the University of Nebraska Agricultural Research Division.

237

the triglycerides. This process leaves alcohol fatty- acid esters, which have a viscosity far less than that of oils and fats.

The esters of oils and fats can be directly blended with diesel fuel. The advantage of blending esters with diesel fuel is reduced emissions. As the EPA imposes limits on exhaust emissions, these esters should become increasingly attractive as a cleaner- burning fuel. Research on blending alcohol esters of different types of oils and fats in different ratios with diesel fuel have been reported. Schumacher et al. (1993) reported a reduction in carbon monoxide (CO), hydrocarbons (HC) and smoke with an increase in soydiesel (methyl esters of soybean oil) concentration in the blend, whereas oxides of nitro- gen (NOx) increased. Schlautman et al. (1986) conducted a 200 h screening test using a 3:1 (v/v) blend of unrefined, mechanically expelled, soybean oil and No. 2 diesel fuel in a direct injection engine. They had to terminate the screening test after 159 h because the engine could not hold a constant load and there was a 670% increase in the viscosity of the lubricating oil. They further observed abnormal car- bon deposits on all combustion chamber parts, including the injectors. Schlick et al. (1988) evalu- ated the performance of a direct injection engine with 1:3 (v/v) blends of soybean oil and sunflower oil with No. 2 diesel fuel. They reported satisfactory engine performance as far as power output, thermal efficiency and lubricating oil data from the Engine Manufacturer Association (EMA, 1982) screening test was concerned, but when the general condition of the combustion chamber and the fuel injectors was investigated, heavy carbon deposits were dis- covered. Foseen et al. (1993) used methyl soyate (from 0-40%) and diesel fuel blends in a transient mode test of a DDC 6V-92 TA engine and found that the addition of up to 40% methyl soyate did not affect peak torque, but there was a small drop in power at the 40% level of substitution. They repor- ted a reduction in CO, HC and particulate matter

238 Y Ali, M. A. Hanna, J. E. Borg

and an increase in NOx emissions. They recommen- ded use of 20% methyl soyate blend with diesel fuel.

The purpose of this investigation was to optimize the blend of No. 2 diesel fuel, methyl tallowate and ethanol to reduce emissions without significantly affecting engine performance.

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 a Daytronic system 10 integrator (Daytronic Corp., Miamisburg, OH) and speed was measured using a 60-tooth sprocket 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 a 2-1 m length of 0.13 m diameter exhaust tubing leading into a 0.25 m diameter duct to the outside air. A centrifugal fan provided exhaust ventilation. A throttle valve was positioned in the exhaust tubing to control exhaust back pressure.

Temperatures of the exhaust of each cylinder, fuel and coolant going into and out of the engine, and crank-case oil, were measured using thermocouples and a Daytronic System 10 coupled with an AutoNet data-acquisition system. Pressures were measured with analog gauges and manometers (H20 and Hg) calibrated with a dead-weight tester.

Exhaust emission analyses were performed using different analyzers for each of the exhaust gases.

Table 1. Engine specifications

Specifications Cummins N14-410 engine

Type of engine Horsepower (Rated) Bore x stroke Displacement Compression ratio Valves per cylinder Aspiration Turbocharger

6 cylinder, 4-stroke, direct injection 410 140 mm x 152 mm 14 liters 16.3:1 4 Turbocharged & charge air cooler Holsett type BHT 3B

Oxides of nitrogen (NO/NO2) were measured with a Beckman model 955 chemiluminescent analyzer (Beckman Industrial Corp., La Habra, CA). Hydro- carbons were measured with a total HC analyzer, model JUM VE7 flame-ionization detector (J.U.M. Engineering, Karlsfeld, Germany), designed to con- tinuously measure the concentration of total organic HC in gaseous samples. Carbon monoxide and CO2 were measured with two Beckman non-dispersive infrared analyzers, model 880-A (Rosemount Ana- lytical, Inc., La Habra, CA). Oxygen was measured with a paramagnetic oxygen analyzer, model 755R (Rosemount Analytical, Inc., La Habra, CA). The determination of O2 was based on the measurement of the magnetic susceptibility of the sample gas. Oxygen is strongly paramagnetic, while most other common gases are weakly diamagnetic. Smoke units were measured with a Bosch EFAW 65-A smoke probe (Robert Bosch GMBH, Stuttgart, Germany).

Fuels The following test fuels were used in this study:

1. 100% No. 2 diesel fuel (baseline). 2. 80% No. 2 diesel fuel, 13% methyl tallowate

and 7% ethanol. 3. 70% No. 2 diesel fuel, 19.5% methyl tallowate

and 10-5% ethanol. 4. 60% No. 2 diesel fuel, 26% methyl tallowate

and 14% ethanol.

The above blends were selected on the basis that Ali et al. (1995) reported that engine performance was not significantly affected by diesel:methyl soyate blends up to a ratio of 70:30. Therefore, blends 10% above and 10% below that level were used in this study. A high sulfur (0.24%) No. 2 diesel fuel was used. Methyl tallowate was procured from Inter- chem Environmental, Inc. of Overland Park, KS. Methyl tallowate was blended with ethanol in a 65:35 (v/v) ratio to reduce its viscosity, as suggested by Ali and Hanna (1994a). The mixture of methyl tallowate and ethanol was blended with No. 2 diesel fuel in ratios as presented above. Physical properties of methyl tallowate, ethanol and diesel fuel were determined and reported (Ali & Hanna, 1994b).

Test runs and performance maps Engine testing on the above fuels was performed at speeds ranging from 1100 to 1900 rpm; at full load using standard method SAE J1349 (SALE, 1993a); and emissions characteristics were determined using SAE J1312 standard, eight-mode, steady-state, engine testing code (SAE, 1993b). Table 2 presents the speeds and loads used for different tests. The testing was done in the Nebraska Power Laboratory at the University of Nebraska-Lincoln. The sequence of fuels used was completely randomized. Standard performance and exhaust emission data were recor- ded and each test run replicated twice.

Fuel blend to reduce diesel engine emissions 239

Table 2. Engine speeds and loads used for each fuel blend

Engine performance Exhaust emission analysis

Engine speed, Load, % Engine speed, Load, % 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

Testing 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.

Optimization of fuel blends 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 tallowate: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.

Engine performance 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, P r > F = 0.0001), whereas engine speed had a significant fourth order polynomial effect (F = 15.21, Pr>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=power 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 reduction in power was 1-1% with every 10%

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

increase in methyl tallowate:ethanol blend. The engine power output with No. 2 diesel fuel was 305.4 kW, which reduced to 298-7 kW with the 80:13:7 blend of diesel:methyl tallowate:ethanol and to 295.3 kW with the 70:19.5:10.5 blend. The reduc- tion in power output with an increase in methyl tallowate:ethanol was expected as this blend had 20% less energy content than diesel fuel.

The response surface for torque produced by the engine at full load for four fuel blends and six engine speeds is shown in Fig. 2. once again statis- tical analyses performed to find effects of fuel blends and engine speeds on torque showed that there was a significant linear effect (F = 19-32, P r > F = 0.0001) of fuel blends and a significant fourth order polyno- mial effect (F = 9"29, P r > F = 0-0041) of engine speed. There was no interaction between engine speed and fuel blend. This trend was expected as the engine power output is dependent upon torque pro- duced by the engine at a particular speed. The regression model for torque was

T --- -33875 + 100.19S- 0.104457S 2

+4"8151 x 1 0 - 5 S 3 -8"3282 x 1 0 - 9 S 4 + 2"1414D

(R 2 = 0"9702)

where T = torque (Nm); S = engine speed (rpm); and D = diesel content in fuel blend (%).

Maximum torque was produced at an engine speed of 1200 rpm. At this speed there was a linear drop in torque with an increase in the methyl tallo- ware:ethanol content in the fuel blend. As in the case of power output, the torque produced by the engine also reduced by 1.03% each time, with a 10% increase in the methyl tallowate:ethanol blend in the fuel. The maximum torque of 2085 Nm was pro- duced at 1200 rpm with No. 2 diesel fuel, which dropped by 21.4 Nm each time another 10% of die- sel was replaced with the methyl taUowate and ethanol blend.

The BSFCs at full load for all fuel blends and speeds are shown in Fig. 3. Statistical analyses

showed that there was no interaction between engine speeds and fuel blends but there was a sig- nificant linear effect (F= 34.45, P r > F = 0-0001) of fuel blends and significant quadratic effect (F-'27.21, Pr>F=0.0001) of engine speed on BSFC. The engine performance curves for power output, torque and BSFC were the same as recom- mended by the Cummins Engine Co., Inc. for the N14-410 diesel engine (Anon, 1991). The regression model for BSFC was

BSFC = 442.57-0.2941S + 1.09 × 10-4S2-0.508D

(R 2 = 0"72)

where BSFC = brake specific fuel consumption (g/ kW-h); S = engine speed (rpm); and D = diesel content in fuel blend (%).

The BSFC at any speed was minimum with No. 2 diesel fuel and it increased linearly with an increase in the methyl tallowate:ethanol content in the blend. The rate of increase in fuel consumption was 2-37% for each 10% increase in methyl tallowate: ethanol content. At rated speed the BSFC with 100% diesel fuel was 215.4 g/kW-h, which increased to 225.5 g/kW-h with the 80:13:7 blend of diesel: methyl tallowate:ethanol. When the fuel consump- tion of the engine was considered on the basis of energy supplied per kW-h, it was observed that a total of 9805 kJ/kW-h energy were supplied with No. 2 diesel, whereas only 9536 kJ/kW-h were supplied with a blend of 80:13: 7 diesel: methyl tallowate: ethanol. That once again showed that there was a drop of about 1.3% energy available for each 10% increase in methyl tallowate:ethanol blend per kW- h and thus a drop of power by 1-1% for the respective blend was justified.

Emission analysis The brake specific emissions for all test fuels are shown in Figs 4-6. The BSCO, BSCO2, BSO2, BSHC, BSNOx and smoke emissions were measured using the standard, eight-mode, steady-state, engine testing code SAE J1312.

Fig. 2. Effects of engine speed and fuel blends on cor- rected torque.

Fig. 3. Effects of engine speed and fuel blends on brake specific fuel consumption.

Fuel blend to reduce diesel engine emissions 241

0 o 5

O.g

0.75

0.7 50:32.5:1"L5 (10:28:14 70:19.5:100 80:15:7 00:60:3.5 100:0:0

DlelOI Fuel : Methyl Tallowato : Ethanol Blend

Fig. 4. Effects of diesel fuel: methyl taUowate: ethanol blends on brake specific CO and C02 emissions.

10 10

)8 8 • _ C O a

CO 4 # 4

o I I I I 0

S0:320:17.5

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Fig. 6.

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"i 00".,28:14 79:10.5:10.5 80:13:7 110:8.11:3.5 1000.'0

D l u e l Fuel : Methyl T I I I ow I l~ : Ethanol Blend

Effects of diesel fuel: methyl tallowate: ethanol blend on NOx and smoke emissions.

0.8 14

0.7

OO

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S0:323:170 (10:26:14 "/0:19.S:10.5 80:13:7 90:6.5:3.5 100:0:0

D le le l Fuel : Methyl Ta l lowaN : Ethanol Blend

Fig. 5. Effects of diesel fuel:methyl tallowate: ethanol blend on brake specific O2 and HC emissions.

Variations in BSCO and BSCO2 emissions 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 there was a significant quadratic trend (F -- 9.86, Pr>F=0.0184). 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 = 6.288- 0.154D + 9.74 x 10-4D 2

(R E = 0.9881)

where BSHC = brake specific HC emissions (g/kW- h) and D = diesel content 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. Hanna, 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/m 3) 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, P r > F = 0.0001) of fuel blend. The regression model describing the trend of smoke with fuel blend was

BSS = 0.605- 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).

Optimization of fuel blend The fuel blend was optimized on the basis of 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 further 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 of 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.

CONCLUSIONS

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. There 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 of 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,

Fuel blend to reduce diesel engine emissions 243

Nebraska Power Laboratory, University of Nebraska-Lincoln, for engine operation and data collection and analysis; and Dr Louis Leviticus, Pro- fessor of Biological Systems Engineering and engineer in charge of Test and Development, Nebraska Power Laboratory, University of Nebraska-Lincoln, for making the power-testing lab- oratory available.

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Schlautman, N. J., Schinstock, J. L. & Hanna, M. A. (1986). Unrefined expelled soybean oil performance in a diesel engine. Trans. ASAE, 29, 70-3.

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