DUAL FUEL ENGINE FUELLED WITH ETHANOL AND DIESEL …ilot.edu.pl/KONES/2003/1-2/16.pdf · Journal of...

Journal of KONES Internal Combustion Engines 2003, vol. 10, No 1-2

DUAL FUEL ENGINE FUELLED WITH ETHANOL AND DIESEL FUEL

Andrzej Kowalewicz Technical University of Radom

Al. Chrobrego 45, 26-600 Radom tel. (+48 48) 3617643, fax (+48 48) 3617644

e-mail: [email protected]

Zbigniew Pajączek Scania Polska S.A.

Stara Wieś k/Nadarzyna Al. Katowicka 316, 05-830 Nadarzyn

tel. (+48 22) 3560174, fax (+48 22) 3560171 e-mail: [email protected]

Abstract Keywords: ethanol, diesel fuel, thermal efficiency, emissions Investigation of the possibility of dual fuelling of compression ignition (CI) engine with diesel fuel and additionally with ethanol, which is injected into inlet manifold, was carried out. Due to physico-chemicals properties of ethanol, such as: poor lubrication properties, poor miscibility with diesel fuel in presence of water, corrosion and chemical degradation of engine materials neat ethanol and diesel fuel – ethanol mixture cannot be used in CI engines. Investigation was carried out on one-cylinder, direct injection CI engine with modified inlet duct for injection of ethanol. Investigations showed that: – energy ratio of ethanol to diesel fuel up to over 50% may be applied, – engine thermal efficiency increased, with the increasing load, – soot emission was decreased dramatically already for small amount of injected ethanol, – emission of greenhouse gas (CO2) was decreased with increasing amount of ethanol, – NOx emission was decreased for small load but for high load is kept at the same level as when the engine is

fuelled only on diesel fuel. Optimization of the energy ratio of both fuels and injection timing of diesel fuel is being carried out.

1. Introduction

In the last years the worldwide interest in application of alternative fuels, especially these

fabricated from biomass, may be observed. Such a fuel is ethyl alcohol (ethanol), which may be made from corn, sugarcane and biomass. Neither neat ethanol nor ethanol-diesel fuel mixtures cannot be applied to CI engines due to its physico-chemical properties (table 1) as low cetane number, low lubricity, weak mixing with diesel fuel in the presence of water and degradation of lubricating oil. It also causes corrosion. Scania CV AB company experimentally fuelled its city buses with mixture of diesel fuel and ethanol, but only 5% of ethanol by volume [4].

In this paper the possibility of application of ethyl alcohol to CI engines was undertaken. Experiments were carried out in Politechnika Radomska. Ten years ago the project on diesel engine fuelled with evaporated methyl alcohol as a main fuel and diesel fuel as a pilot ignition fuel was developed [5]. Methanol entered to the cylinder as a gas, where was burnt, do not

giving occasion to corrosion of cylinder liner [6]. In the present work ethanol was injected to inlet port, where it evaporated (beginning of its injection had no influence on engine operation) and entered to the cylinder as a vapour.

Table 1. Physico-chemical properties of diesel fuel and ethanol used in experiment [1 .. 3] Property Diesel fuel Ethanol

Chemical formula (n=12,32) CnH1.8n C2H5OH Molecular weight ~170 46 Density @20oC, kg/m3 840 - 880 789 Calorific value, MJ/kg ~42,5 26,8 Calorific value of stechiometric mixture with air, MJ/m3

3,66 – 3,83 3,85

Heat of evaporation, kJ/kg 270 840 Temperature of selfignition, K ~500 665 Stechiometric air/fuel ratio, kg air/kg fuel 14,5 9,06 Lower flammability limit λl 0,98 2,06 Higher flammability limit λh 0,19 0,30 Kinematic viscosity, mm2/s 2,97 1,4 Octane number - motored - research

-

~3

94

111 Cetane number 45 - 55 8 Flame temperature, K - 2235

The idea of such fuelling system is as follows: diesel fuel droplets after self ignition will

ignite ethanol vapour which together with them burns much more quickly than droplets in air. This will result in higher rate of heat release and – due to that – higher thermal efficiency and some emissions, especially soot. The main objectives of the present work were as follows: • to investigate, whether the ethanol may be used as an alternative fuel for CI engines • to examine the system of dual fuelling and the benefits of its application from the point of

view of efficiency and emission. Preliminary investigations were very promising and proved that these objectives may be

fulfilled. 2. Engine test stand

For experiment a test stand shown in Figure 1 was prepared. Main part of it is one-cylinder 1 HC 102 diesel engine.

Engine torque was measured by means of an eddy-current dynamometer Vibrometer 3WB15. Diesel fuel consumption was measured with the use of automatic dose meter PG-80. Ethanol dose per cycle was measured indirectly with the use of measured time of opening of injection nozzle. Air flow was measured with the use of a flow meter installed on the air tank which reduced pressure pulsations. Pressure transducer AVL8QP505 ca. was inserted in the cylinder head for measuring the pressure-time history in the cylinder with the use of high speed measurement system worked out Department of Internal Combustion Engine and Automobile [8]. For exhaust gas analysis, especially CO, CO2, HC, AVL DiGas 465 analyser was used. NOx emission was measured by Beckman analyser Model 951.

Figure 1. Test stand

3. Course of investigation

Investigation was carried out for constant speed n=1800 rpm and two loads 20Nm and 40Nm for three injection timings of diesel fuel: 25, 30 and 35 deg CA BTDC and different energy ratio pf ethanol to both fuels. Measurements points were chosen in such a way, that the comparison of engine parameters and emission could be obtained for the same load but for different proportion of diesel fuel to ethanol. For comparison of both fuelling system (i.e. standard and dual fuelling), investigation was carried out in the case when the engine was fuelled with diesel fuel only. Dual-fuel engine as an object of experiments is shown in Figure 2.

Load Diesel fuel inj. timing

Changeable parameters

Air

Fuels

Atmospheric parameters n=const

Emission

Engine Fuel energy consumption

Pressure in engine cylinder

Ethanol energy ratio of both fuels

Figure 2. Engine as an object of investigations

4. Results and discussion 4.1 Introduction Results of investigation have been shown mainly for the middle range of engine speed i.e. for n=1800rpm.

4.2 Performance Engine thermal efficiency depends on engine load:

- for low load is almost constant and independent of injection angle of diesel fuel (Figure 3).

- for high load increases with increasing energy ratio of ethanol to both fuels (Figure 4). Optimal injection timing of diesel fuel was 35 deg CA BTDC.

Engine thermal efficiencyload M=20 Nm, n=1800 rpm

0,240,260,280,300,320,34

0 0,1 0,2 0,3 0,4 0,5

energy ratio of ethanol to both fuels

effic

ienc

y

alfa DF 30 deg. alfa DF 25 deg. alfa DF 35 deg.

Figure 3 Engine thermal efficiency for load M=20Nm

Engine thermal efficiencyload M=40 Nm, n=1800 rpm.

0,25

0,30

0,35

0,40

0 0,1 0,2 0,3 0,4


effic

ienc

y

alfa DF 30 deg. alfa DF 25 deg alfa DF 35 deg.

Figure 4. Engine thermal efficiency for load M=40Nm 4.3 Emissions As far as emissions are concerned, the following results were obtained:

• Smoke level decreases with increase the energy ratio of ethanol to both fuel for all injection timings of diesel fuel and for both low and high load, Figure 5 and Figure 6.

Smoke levelM=20Nm, n=1800 rpm

05

1015

0 0,1 0,2 0,3 0,4 0,5


smok

e le

vel [

% ]


Figure 5. Smoke level for small load

Smoke level M=40Nm, n=1800rpm

6264666

0 0,1 0,2 0,3 0,4


smok

e le

vel [

%]


Figure 6. Smoke level for high load

• Greenhouse gas emission decreases with increasing of the energy ratio of ethanol to both fuels for all injection timings of diesel fuel and for both low and high load, Figure 7 and Figure 8.

Greenhouse gas emissionM=20Nm, n=1800rpm

4

5

6

0 0,1 0,2 0,3 0,4 0,5


CO

2 em

issi

on [%

vo

l]


Figure 7. Greenhouse gas emission for low load

Greenhouse gas emission M=40Nm, n=1800rpm

7

8

9

10

0 0,1 0,2 0,3 0,4


CO

2 em

issi

on [%

vol]


Figure 8. Greenhouse gas emission for high load

• NOx emission with increase of the energy ratio of ethanol to both fuels : o decreases for low load (Figure 9). o is approximately constant for high load and depends strongly on injection

timing of diesel fuel (Figure 10). Optimal injection timing of diesel fuel was 25 deg CA BTDC.

NOx emissionload M=20Nm, n=1800 rpm

300500

700900

11001300

0 0,1 0,2 0,3 0,4 0,5energy ratio of ethanol to both fuels

NO

x em

issi

on [p

pm]


Figure 9. NOx emission for low load

NOx emission load M=40Nm, n=1800 rpm.

600

1100

1600

0 0,1 0,2 0,3 0,4


NO

x em

issi

on

[ppm

]


Figure 10. NOx emission for high load As far as carbon monoxides and hydrocarbons emissions are concerned, they are not so advantageous as smoke level, greenhouse gas and nitric oxide. For example CO emission (shown in Figure 11 and Figure 12) in general increases with energy ratio of ethanol to both fuels.

Carbon monoxide emissionM=20Nm, n=1800rpm

00,050,1

0,150,2

0,250,3

0 0,1 0,2 0,3 0,4 0,5


CO

em

issi

on [%

vol

]


Figure 11. CO emission for low load

Carbon monoxide emission M=40Nm, n=1800rpm

0,05

0,1

0,15

0,2

0,25

0 0,1 0,2 0,3 0,4


CO

em

issi

on [%

vol

]


Figure 12. CO emission for high load HC emission is shown in Figure 13 and 14. For energy ratio of ethanol to both fuels lower than 0,2 is almost constant but for higher increases.

Hydrocarbons emissionM=20Nm, n=1800rpm

2575

125175225275325

0 0,1 0,2 0,3 0,4 0,5


HC

em

issi

on [p

pm]


Figure 13. Hydrocarbons emission for low load

Hydrocarbons emission M=40Nm, n=1800rpm

10

30

50

70

0 0,1 0,2 0,3 0,4


HC

em

issi

on [p

pm]


Figure 14. Hydrocarbons emission for high load 4.4 Combustion characteristics

• Combustion time of dual fuelling is shorter than combustion time of neat diesel fuelling. For example, fraction fuel burnt vs CA and relative rate of heat release are shown in Figure 15 and 16, respectively.

350 360 370 380 390 400352 354 356 358 362 364 366 368 372 374 376 378 382 384 386 388 392 394 396 398

CA [deg]

0

0.2

0.4

0.6

0.8

1

0.04

0.08

0.12

0.16

0.24

0.28

0.32

0.36

0.44

0.48

0.52

0.56

0.64

0.68

0.72

0.76

0.84

0.88

0.92

0.96

Mas

s fra

ctio

n of

fuel

bur

nt

DF onlyDF + ethanol dose 0,104 kJ/cycleDF + ethanol dose 0,241 kJ/cycleDF + ethanol dose 0,552 kJ/cycle

Figure 15. Mass fraction of fuel burnt for M=40Nm, n=1800rpm, alfa DF 30 deg BTDC

350 360 370 380 390 40352 354 356 358 362 364 366 368 372 374 376 378 382 384 386 388 392 394 396 398

CA [deg]0

0

20

40

60

80

100

4

8

12

16

24

28

32

36

44

48

52

56

64

68

72

76

84

88

92

96

rela

tive

rate

of h

eat r

elea

se

DF onlyDF + ethanol dose 0,104 kJ/cycleDF + ethanol dose 0,241 kJ/cycleDF + ethanol dose 0,552 kJ/cycle

Figure 16. Relative rate of heat release for M=40Nm, r=1800rpm, alfa DF 30 deg BTDC

• Maximum combustion pressure depend on the energy ratio of ethanol to both fuels and on the load:

o for low load is the highest for diesel fuel only and decreases with increase of the energy ratio of ethanol to both fuels.

o for high load increases with increase of the energy ratio of ethanol both fuels and is the highest for maximum (ethanol to both fuels energy ratio).

5. Conclusions For all conditions of experiment, shown in table 2, obtained results lead to the following conclusions:

Ethanol may be a good additional fuel to CI engines when being injected into inlet port in a proper proportion to diesel fuel. Brake fuel conversion efficiency of the dual fuel engine is better than pure diesel

engine. Dual fuelling results also in decrease of some emissions as NOx, smoke level and

greenhouse gas. Ratio of ethanol to diesel fuel may be optimized from any point of view (efficiency or

any toxic component of exhaust gases). Injection timing of diesel fuel may also be optimized. The most promising seems to be

35 deg CA BTDC for best efficiency and 25 deg CA BTDC for NOx emission. References

[1] Heywood J.B., Internal combustion engine fundamentals, McGraw Hill Co., New York, 1988.

[2] Measurements carried out at Politechnika Radomska and at Central Laboratory of Petroleum Warsaw 2003.

[3] Kowalewicz A., Fundamentals of combustion processes (in Polish), Science and Technology Publ. House, Warsaw 2000.

[4] Boman G., Ethanol buses strengthen image, Scania World no 2, 2001. [5] Kowalewicz A., Luft S., Analysis of combustion in compression ignition engine

fuelled with methanol vapour, Archiwum Combustionis, vol 14 (1994) no 3-4 [6] Kowalewicz A., Gola M., Evaluation of durability of cylinder liner-piston of

Ciengine fuelled with methanol vapour (in Polish), 22nd International Scientific Conference on Combustion Engines KONES’96, Zakopane 1996.

[7] Kowalewicz A., Pawlak G., Pajaczek Z., Preliminary investigation of diesel engine with additional injection of ethyl alcohol, Journal of KONES, vol 9 no 3-4, 2002

[8] Różycki A., Measurement system for high-speed parameters, work of Politechnika Radomska, 1995

This project is sponsored by Polish National Commetee of Scientific Research under the grant no 5 T12D 026 24.

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