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Water in diesel emulsions: Improved efficiency with reduced emissions

Diesel internal combustion engines are widely used in powering automobiles, mechanical engines, and power generators. However, there are issues that diesel engines are a major source of air pollution that can be damaging to human health. One method of reducing these harmful emissions is the introduction of water into the fuel by using a water in oil emulsion. This has the advantage of reducing the emissions of particulates, CO2 and NOx whilst increasing the efficiency of combustion resulting in improved economy.


The introduction of water in the form of a water in oil emulsion, where the oil is the external phase, produces a fuel with similar properties to the base oil. Typical emulsions contain up to 20% water however, higher levels of water can be used but this can have adverse effects on power output without modification to the fuel injection systems. The emulsion technology can be used with both traditional fossil fuels and biobased fuel or mixtures.


The introduction of water beneficially effects the combustion process by burst evaporation. As the temperature of the fuel droplet containing the water increases during the compression stage, the water rapidly evaporates inside the fuel droplet. This rapid evaporation breaks down the fuel into a smaller droplet size which increases the combustion efficiency and significantly reduces the mass of particulate matter with a resulting reduction in visible emissions and smoke. The loss of energy during the evaporation of the water decreases the combustion temperature slowing down the reaction between oxygen and nitrogen, providing an overall reduction in NOx formation.


Lankem have developed an emulsifier that can produce a stable water in oil emulsions in a range of diesel and biobased fuel. Lansurf LKD1484 was independently tested at Manchester University using a light duty diesel engine. These tests showed that at higher engine loads significant benefits were observed, with the particle mass having reductions of >50%, with an overall reduction in particle size, lower emissions of NOx were also observed with >40% reduction. Benefits were also seen in fuel consumption with an overall reduction being observed.


Test Formulation

​Diesel

82

​Lansurf LKD1484

3

Water

15

Key Findings

Compared to standard diesel, the Lankem fuel emits:

• Less NOx and CO2 at the higher engine load

• Comparable NOx and more CO2 at the lower engine load

• Less NO at higher engine load and more NO2 at lower engine load

• Substantially less particulate matter mass at all tested engine load conditions

• Substantially more particulate number at all tested engine conditions

• Substantially more small particles with a modal size of 10nm


Importantly, these findings appear to be generally true when normalising the data for engine

power or for CO2 emissions as a proxy for fuel consumption.


Total NOx levels (ppm) at high engine load

​RPM

1500

2000

2500

3000

Average

Std Diesel

118

142

125

140

131

Emulsified Diesel

91

70

62

89

78

% Reduction

23

51

50

36

41

Total CO2 (ppm) levels at high engine load

​RPM

1500

2000

2500

3000

Average

Std Diesel

21

23

29

25

24.5

Emulsified Diesel

15

12

16

22

16.3

% Reduction

29

48

45

12

34

Particulate Mass per metre cube at high engine load

​RPM

1500

2000

2500

3000

Average

Std Diesel

21

23

29

25

24.5

Emulsified Diesel

15

12

16

22

16.3

% Reduction

29

48

45

12

34



For more details of the study please see:

Lankem_Fuel_Evaluation
.
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