The experimental measurements were carried out on a four-stroke, air-cooled engine. This is a one-cylinder engine with 123cm3 displacement that is connected with a phase single alter­native generator (230V/50Hz) with maximum electrical load approximately 1KW(picture 1). The engine according to the manufacturer uses as fuel gasoline. The engine functioned with­out load and under full load conditions (1KW) using different fuel mixtures: gasoline, gaso — line-10%ethanol, gasoline-20%ethanol, gasoline-30%ethanol, gasoline-40%ethanol, gasoline-50%ethanol, gasoline-60%ethanol, gasoline-70%ethanol gasoline-80%ethanol gaso- line-90%ethanol and 100% ethanol, gasoline-10% methanol, gasoline-20%methanol, gaso — line-30%methanol, gasoline-40%methanol, gasoline-50%methanol, gasoline-60%methanol, gasoline-70%methanol. During the tests, exhaust gases measurements, were also monitored for every fuel mixture and for every load conditions. Also, during the function of the engine the consumption was recorded for every fuel. There was lack of engine regulation concern-

ing the stable air/fuel ratio. For this purpose, data Acquisition cart was used with the termi­nal wiring board with on-board Cold Junction The data acquisition card was installed at a PC. This particular measuring system and software completed a scanning cycle per channel every 0.1 second approximately. This measuring speed was considered adequate for the purpose of the experiment and the sampling capabilities of the chemical sensors. For the ex­haust gas (CO and HC) measurements a analyzer was used.

The figures of CO and HC emissions, for every fuel and for every load conditions, are represented below [4—7]:

gasoline

10

9

8

7

6

5

4

time(s)

time(s)

i. The CO variation when mixture of gasoline-30%methanol is used as fuel

40%methanol

10 9 8 7 6 5 4 3 2 1 0

0 50 100 150 200 250 300 350 400 450 500

time(s)

The CO variation when mixture of gasoline-50%methanol is used as fuel.

60%methanol

70%methanol

Figure2 represents CO emissions when the fuel that is used is gasoline. The engine functions without load at first and then (after 250s) functions under full load conditions (1KW). The average value of CO emissions during the function of the engine without load is 6,41%, while at full load conditions the average value of CO emissions is 8,7%. Following, a mixture of gasoline with 10% methanol is used (fig. 3) and the same test is conducted with this mixture. From figure 3 it is being observed that the average value of CO emissions without load conditions of the engine is 4,87%, while at full load conditions the percentage of CO emissions is 6,9%. The same tests are conducted while increasing the percentage of the methanol in the fuel, using the mixtures: gasoline-20%methanol(fig. 4), gasoline-30%methanol(fig. 5), gaso- line-40%methanol(fig. 6), gasoline-50%methanol(fig. 7), gasoline-60%methanol(fig. 8), and gasoline-70%methanol(fig. 9).

The HC emissions when the fuel that is used is gasoline are represented at figure 10. As it was mentioned above, the engine functioned without load at first and then (after 250s approxi­mately) functioned under full load conditions (1KW). During the function of the engine without load the average value of HC emissions is 1091ppm, while at full load conditions the average value of HC emissions is 730ppm. The mixture of gasoline with 10% methanol is illustrated at figure 11. At this figure is being observed that the average value of HC emissions without load conditions of the engine is 496ppm, while at full load conditions the HC emissions is 613ppm. When the percentage of the methanol in the fuel increases: gasoline-20%metha — nol(fig. 11), gasoline-30%methanol(fig. 13), gasoline-40%methanol(fig. 14), gasoline-50%meth — anol(fig. 15), gasoline-60%methanol(fig. 16), and gasoline-70%methanol(fig. 17).

gasoline

time(s)

Figure 10. The HC variation when gasoline is used as fuel.

10%methanol

time(s)

20%methanol
50	100	150	200	250	300	350	400	450	500
0
time(s)
!. The HC variation when mixture of gasoline-20%methanol is used as fuel.
30%methanol
time(s)

0 50 100 150 200 250 300 350 400 450 500

time(s)

14. The HC variation when mixture of gasoline-40%methanol is used as fuel.

50%methanol

time(s)

0

50 100 150 200 250 300 350 400 450 500

time(s)

16. The HC variation when mixture of gasoline-60%methanol is used as fuel.

70%methanol

time(s)

In the case of HC emissions there is also a decrease of emissions when the percentage of methanol in the fuel increases at idle and under full load conditions. There is an exception at the mixture gasoline-70%methanol where the average value of HC without load is 534ppm and under full load is 367ppm. These values are higher than the values that correspond to the mixture of gasoline-60%methanol (295ppm, 298ppm). This is explained by mentioning the fact that during the use of the mixture gasoline-70%methanol there was a malfunction of the engine that was cause by the bad mixture of the air with the fuel(gasoline-70%methanol), since the engine was not regulated(ratio air/fuel) for every mixture maintaining the adjustments for gasoline. Also it must reported that the addition of methanol in the fuel led to HC decrease for the same mixture but for different load conditions. When gasoline was used HC emissions were higher at no load conditions than at full load conditions(1KW), while during the use of gasoline-methanol mixtures this was reversed. This is due to the better combustion under full load conditions because methanol has higher octane number than gasoline [4—7].

It is important to mention that when mixture gasoline-80%methanol was tested the engine could not function properly.

The CO and HC emissions are represented in the figures below, for the mixtures: gasoline, gasoline-ethanol, for every fuel and for every load conditions. For these mixtures the average values of the emissions (CO, HC) are presented at the figures below. From the average values, the variation of those emissions can be better understood.

10%ethanol

20%ethanol

time(s)

Figure19. The COvariationforthegasoline-20%ethanolmixtureisusedasfuel

30%ethanol

time(s)

time(s)

60%ethanol

time(s)

23. TheCOvariationwhengasoline-60%ethanolmixtureusedasfuel

70%ethanol

time(s)

time(s)

90%ethanol

time(s)

100%ethanol

0 50 100 150 200 250 300 350 400 450 500

time(s)

0 50 100 150 200 250 300 350 400 450 500

time(s)

29. TheHCvariationwhengasoline-20%ethanol mixtureusedasfuel

30%ethanol

0 50 100 150 200 250 300 350 400 450 500

time(s)

40%ethanol

0 50 100 150 200 250 300 350 400 450 500

time(s)

31. TheHCvariationwhen gasoline-40%ethanolmixtureusedasfuel

50%ethanol

0 50 100 150 200 250 300 350 400 450 500

time(s)

0 50 100 150 200 250 300 350 400 450 500

time(s)

Figure33. TheHCvariationwhengasoNne-60%ethanolmixtureusedasfuel

70%ethanol

0 50 100 150 200 250 300 350 400 450 500

time(s)

0 50 100 150 200 250 300 350 400 450 500

time(s)

Figure37. TheHCvariationwhen100%ethanolusedasfuel

Figures 18 — 28 present the CO variation when as fuel is used gasoline — ethanol and gasoline — methanol mixtures when the engine functioned without load and under full load condi- tions(1KW). From these figures is observed lower CO emissions when gasoline-ethanol mixtures are used compared to the mixtures gasoline-methanol, until the mixture of 70% ethanol and methanol. Over the 70% percentage of methanol the engine could not function and that is why there is no further presentation of comparative curves of CO emissions. It must also be mentioned that for the mixtures of gasoline -70% methanol, gasoline -90%ethanol and 100%ethanol the engine malfunctioned. The average values of CO emissions for the above mixtures and for both load conditions are presented in the figure 38 below [4—7]:

In the figures 28 — 37 is observed higher decrease of HC in the case were methanol is used, with exception of the use of gasoline -70%methanol mixture where the HC are higher compared to the mixture gasoline-70%ethanol. This is due to the malfunction that occurred during the use of gasoline-70%methanol mixture. There was also malfunction of the engine when the mixtures of gasoline-90%ethanol and 100%ethanol were used, which had as result the HC increase during the use of those mixtures. These observations are presented more clearly in the figure 38 below [4—7]:

% ethanol and %methanol in fuel Figure38. TheCOemission average value for every gasoline-ethanol and gasoline-methanol mixture

Figure 39 shows the average values of HC for every mixture, when the engine functions without load and under full load conditions. It is being observed grater decrease of HC during the use of methanol in the fuel contrary to the use of ethanol.

Also is shown HC emissions decrease compared to gasoline, while the percentage of methanol and ethanol in the fuel increases without load and under full electrical load conditions (1KW). At higher percentage of ethanol in the fuel 90%ethanol and 100%ethanol it is observed HC emissions increase, which is due to incomplete combustion. Indeed, during the tests of the mixtures: gasoline-70%methanol, gasoline — 90%ethanol and 100%ethanol, there was an engine malfunction mostly at without electrical load, as it was mentioned above. This malfunction is showed from the rounds per minute recording in the figures below:

Figure 39. The HC emission average value for every gasoline-ethanol and gasoline-methanol mixtures

Engine rpm

time(s)

Engine rpm

time(s)

Engine rpm

Figure 43. The rpm variation when used fuel 100%ethanol

During the tests the rounds per minute of the engine were recorded as it was mentioned above. The normal variation of the engine rpm appears in figure 40. The same variation that is illustrated in this figure corresponds to the mixtures gasoline until the mixtures gasoline-90% ethanol and gasoline-60%methanol, without any change. As it is presented in figure 39, the average value of the engine rpm without load (0-200s and 420-500s) is approximately 2990rpm while at full load conditions (200-420s) the average value of the engine rpm is 2880rpm. It must be noted that the engine has a round stabilizer. In figures 41, 42 and 43 the mixtures gaso- line-70%methanol, gasoline-90%ethanol and 100%ethanol are illustrated and irregular variation of the engine rpm is presented, which is caused from the engine malfunction. Higher irregular variation is observed at without load condition, and lower at full load conditions in the case of use ethanol. This malfunction is due to the smaller calorific value of methanol and ethanol than the gasoline, and to the fact that there is no adjustment of the air/fuel ratio during the use of gasoline-methanol and gasoline-ethanol mixtures. The initial adjustment that corresponds to gasoline as fuel is maintained [6,7].

Furthermore, during the tests the consumption of the fuel was recorded for every mixture separately and for every load conditions. The results of the consumption recording are illustrated in the figure below:

Figure 44. The fuel consumption

Figure 44 shows an increase of fuel consumption when the percentage of methanol and ethanol in the fuel increases than gasoline. Also, between the use of the mixtures of methanol and ethanol is observed small increase during the use of methanol because of the smaller calorific value that methanol has compared to ethanol. The smaller calorific value of methanol and ethanol compared to gasoline and also the lack of regulation (ratio air/fuel) of the engine, results to the consumption increase contrary to the use gasoline. This increase of consumption happens automatically for the rounds regulator that the engine has, for the maintaining of the rounds constant.

3. Conclusion

From the observations above is appeared that methanol and ethanol as mixture with gasoline results in an emissions (CO and HC) decrease when the engine functions without load and under full load conditions. There is an exception in the use of the mixtures: gasoline-70%meth — anol, gasoline -90% ethanol and 100%ethanol where there is observed an HC emissions increase because of the incomplete combustion and consequently due to engine malfunction. Also, it must be mentioned that the adjustment of the engine (air/fuel ratio) was that which referred to the use of gasoline as fuel. From the aspect of consumption, there was a consump-

tion compared to gasoline increase when the percentage of the methanol and ethanol in the fuel was increased in both load conditions. Between the use of methanol and ethanol mixtures is observed higher increase of consumption when the mixtures of methanol are used due to the fact that methanol has lower calorific value compared to ethanol. From the aspect of emissions, when the mixtures of gasoline with methanol and ethanol are compared, there is grater reduction of emissions in the case where methanol is used. It can be said that this is caused because of the smaller carbon chain of the methanol molecule, which results to the better combustion of methanol. It is also observed that the engine functions with the mixtures of methanol until the use of 70%methanol mixture with gasoline, while with ethanol mixtures until 100% ethanol as fuel (with the initial adjustment of the air/fuel ratio that is made for gasoline). This is due to the fact that ethanol has higher octane number compared to methanol. Finally, it is important the fact that methanol and ethanol are a renewable fuels, which present emissions decrease compared to gasoline, when they are used, in a time period where petroleum reservations are depleted and the environmental pollution is one of the most important problems that humanity faces [4—7].

Author details

Charalampos Arapatsakos*

Department of Production and Management Engineering, Democritus University of Thrace, Xanthi, Greece