Ethanol
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earlier. Also it is necessary to overcome the immiscibility of ethanol in diesel fuel using suitable additives. E-diesel fuel refers to blends of ethanol
with diesel fuel, which typically contain an additive to ensure diesel-like
combustion and lubricity, as well as providing a stable blend. Commercial
additives have been developed that allow anhydrous ethanol to be splashblended with diesel fuel (Hansen, Zhang, and Lyne 2005). The amount of
additive required varies in proportion to the percentage of ethanol in the
blend.
The physical properties of diesel fuel are changed when ethanol is added
into the solution (blend). The addition of ethanol causes the viscosity of diesel fuel to decrease. Also, the addition of ethanol in solutions with diesel fuel
causes the cetane rating to drop and the heating values to be lower.
Blend stability is a key aspect in the formulation of ethanol–diesel fuel
blends. This stability is affected primarily by two factors; namely, fuel temperature and water content. Ethanol and diesel fuel will separate when any
water is added to the blend, or when the blend is cooled below about 10°C in
the case of dry ethanol blends (Hansen, Zhang, and Lyne 2005). Prevention
of this separation can be accomplished through the use of either emulsifiers
or cosolvents. Figures 5.15 and 5.16 illustrate phase separation as functions of
temperature and water addition (Letcher 1980, 1983).
Wrage and Goering (1980) investigated diesohol, a blend of 10% anhydrous ethanol and 90% No. 2 petroleum diesel fuel. Their concern as to
whether the blend would have sufficient viscosity to lubricate the injection
system led them to develop Figure 5.17. The blend of 10% anhydrous ethanol and 90% No. 2 diesel had viscosity well above the minimum for No. 2
diesel. In addition to measuring fuel properties, Wrage and Goering tested
the fuel in a John Deere 37 kW, 3-cyinder, DI, CI engine equipped with a
distributor type injection pump. The ethanol in the diesohol lowered the
viscosity and cetane rating but both properties were above the lower limit
for No. 2 diesel fuel. When used in the engine, the ethanol vaporized in
the injection pump, causing the engine to lose power and stall. That problem was solved by pressurizing the diesohol before it reached the injector pump. Chilling the diesohol also solved the vapor lock problem but
was considered less practical than pressurizing the fuel. The engine produced approximately the same power output on both fuels, but consumed
the diesohol at a higher rate. Finally, the engine produced 30% less smoke
when running on diesohol.
Boruff et al. (1982) used microemulsions to solve the phase separation
problem. Microemulsions are transparent, thermodynamically stable colloidal dispersions in which the diameter of the dispersed-phase particles is less
than one-fourth the wave length of visible light. A surface-active agent (i.e., a
surfactant) is added to the ethanol–diesel blend to form the microemulsion.
Boruff et al. evaluated a fuel blend containing 66.7% of No. 2 diesel fuel, 16.7%
of 190-proof ethanol, 12.5% of Emersol 315, a commercial surfactant containing a blend of soy oil fatty acids, and 4.1% of N,N-dimethylethanolamine.
153
earlier. Also it is necessary to overcome the immiscibility of ethanol in diesel fuel using suitable additives. E-diesel fuel refers to blends of ethanol
with diesel fuel, which typically contain an additive to ensure diesel-like
combustion and lubricity, as well as providing a stable blend. Commercial
additives have been developed that allow anhydrous ethanol to be splashblended with diesel fuel (Hansen, Zhang, and Lyne 2005). The amount of
additive required varies in proportion to the percentage of ethanol in the
blend.
The physical properties of diesel fuel are changed when ethanol is added
into the solution (blend). The addition of ethanol causes the viscosity of diesel fuel to decrease. Also, the addition of ethanol in solutions with diesel fuel
causes the cetane rating to drop and the heating values to be lower.
Blend stability is a key aspect in the formulation of ethanol–diesel fuel
blends. This stability is affected primarily by two factors; namely, fuel temperature and water content. Ethanol and diesel fuel will separate when any
water is added to the blend, or when the blend is cooled below about 10°C in
the case of dry ethanol blends (Hansen, Zhang, and Lyne 2005). Prevention
of this separation can be accomplished through the use of either emulsifiers
or cosolvents. Figures 5.15 and 5.16 illustrate phase separation as functions of
temperature and water addition (Letcher 1980, 1983).
Wrage and Goering (1980) investigated diesohol, a blend of 10% anhydrous ethanol and 90% No. 2 petroleum diesel fuel. Their concern as to
whether the blend would have sufficient viscosity to lubricate the injection
system led them to develop Figure 5.17. The blend of 10% anhydrous ethanol and 90% No. 2 diesel had viscosity well above the minimum for No. 2
diesel. In addition to measuring fuel properties, Wrage and Goering tested
the fuel in a John Deere 37 kW, 3-cyinder, DI, CI engine equipped with a
distributor type injection pump. The ethanol in the diesohol lowered the
viscosity and cetane rating but both properties were above the lower limit
for No. 2 diesel fuel. When used in the engine, the ethanol vaporized in
the injection pump, causing the engine to lose power and stall. That problem was solved by pressurizing the diesohol before it reached the injector pump. Chilling the diesohol also solved the vapor lock problem but
was considered less practical than pressurizing the fuel. The engine produced approximately the same power output on both fuels, but consumed
the diesohol at a higher rate. Finally, the engine produced 30% less smoke
when running on diesohol.
Boruff et al. (1982) used microemulsions to solve the phase separation
problem. Microemulsions are transparent, thermodynamically stable colloidal dispersions in which the diameter of the dispersed-phase particles is less
than one-fourth the wave length of visible light. A surface-active agent (i.e., a
surfactant) is added to the ethanol–diesel blend to form the microemulsion.
Boruff et al. evaluated a fuel blend containing 66.7% of No. 2 diesel fuel, 16.7%
of 190-proof ethanol, 12.5% of Emersol 315, a commercial surfactant containing a blend of soy oil fatty acids, and 4.1% of N,N-dimethylethanolamine.