99
Methanol
studied the influence of this fuel on the engine performance and exhaust
emissions. At this point, it is important to emphasize that some test results
obtained by the researchers can be contradictory to each other since different engine test conditions and engine technologies have been applied in the
experiments.
The simplest method of using methanol in a CI engine is to blend it
with diesel fuel using an additive to prevent phase separation (Bayraktar
2008; Huang et al. 2004b; Murayama et al. 1982). This application requires
no modification on the engine and fuel system. However, other methods
such as dual-fueling (Kumar et al. 2005; Song et al. 2008; Wang et al. 2008)
and fumigation (Abu-Qudais, Haddad, and Qudaisat 2000; Cheng et al.
2008a; Popa, Negurescu, and Pana 2001; Udayakumar, Sundaram, and
Sivakumar 2004; Yao et al. 2007) require additional equipments such as
another fuel-injection system and storage tank, which means additional
cost. In the fumigation mode, diesel fuel is injected through the original
high-pressure fuel injectors into the engine cylinder while the methanol
is injected in the air intake for each cylinder through low-pressure fuel
injectors.
4.7.1 engine Performance Tests
Bayraktar (2008) studied the effect of methanol-blended diesel fuel between
2.5 and 15 vol% on the engine performance and found that the methanol could reduce the effective power and brake thermal efficiency (BTE)
to some degree and moderately increase brake specific fuel consumption
(BSFC).
Sayin et al. (2009) studied the effect of methanol-blended diesel fuel on the
BSFC and brake thermal efficiency (BTE) of a single cylinder direct injection (DI) diesel engine. The reference diesel fuel was blended with methanol
from 0 to 15% with an increment of 5%. The engine was run at constant
speed (2200 rpm) and four different loads (5 Nm, 10 Nm, 15 Nm, and 20 Nm)
for three different injection timings (15°, 20° and 25° CA BTDC). The original
injection timing of the test engine is 20° CA BTDC.
The BSFC is defined as the ratio of the fuel consumption to the brake
power. The effects of methanol–diesel fuel blends and injection timings on
the BSFC are shown in Figures 4.7 and 4.8 for different engine load and injection timing, respectively. The results showed that increasing methanol ratio
in the fuel blend caused it to increase in the BSFC. This behavior is attributed to lower heating value (LHV) per unit mass of the methanol, which is
noticeably lower than that of the diesel fuel as seen in Table 4.2. Therefore,
the amount of fuel introduced into the engine cylinder for a desired fuel
energy input has to be greater with the methanol. BSFC decreased about
two times as the engine load increased from 5 to 20 Nm constant load. This
decrease in BSFC could be explained by the fact that, as the engine load
increases, the rate of increasing brake power is much more than that of
Methanol
studied the influence of this fuel on the engine performance and exhaust
emissions. At this point, it is important to emphasize that some test results
obtained by the researchers can be contradictory to each other since different engine test conditions and engine technologies have been applied in the
experiments.
The simplest method of using methanol in a CI engine is to blend it
with diesel fuel using an additive to prevent phase separation (Bayraktar
2008; Huang et al. 2004b; Murayama et al. 1982). This application requires
no modification on the engine and fuel system. However, other methods
such as dual-fueling (Kumar et al. 2005; Song et al. 2008; Wang et al. 2008)
and fumigation (Abu-Qudais, Haddad, and Qudaisat 2000; Cheng et al.
2008a; Popa, Negurescu, and Pana 2001; Udayakumar, Sundaram, and
Sivakumar 2004; Yao et al. 2007) require additional equipments such as
another fuel-injection system and storage tank, which means additional
cost. In the fumigation mode, diesel fuel is injected through the original
high-pressure fuel injectors into the engine cylinder while the methanol
is injected in the air intake for each cylinder through low-pressure fuel
injectors.
4.7.1 engine Performance Tests
Bayraktar (2008) studied the effect of methanol-blended diesel fuel between
2.5 and 15 vol% on the engine performance and found that the methanol could reduce the effective power and brake thermal efficiency (BTE)
to some degree and moderately increase brake specific fuel consumption
(BSFC).
Sayin et al. (2009) studied the effect of methanol-blended diesel fuel on the
BSFC and brake thermal efficiency (BTE) of a single cylinder direct injection (DI) diesel engine. The reference diesel fuel was blended with methanol
from 0 to 15% with an increment of 5%. The engine was run at constant
speed (2200 rpm) and four different loads (5 Nm, 10 Nm, 15 Nm, and 20 Nm)
for three different injection timings (15°, 20° and 25° CA BTDC). The original
injection timing of the test engine is 20° CA BTDC.
The BSFC is defined as the ratio of the fuel consumption to the brake
power. The effects of methanol–diesel fuel blends and injection timings on
the BSFC are shown in Figures 4.7 and 4.8 for different engine load and injection timing, respectively. The results showed that increasing methanol ratio
in the fuel blend caused it to increase in the BSFC. This behavior is attributed to lower heating value (LHV) per unit mass of the methanol, which is
noticeably lower than that of the diesel fuel as seen in Table 4.2. Therefore,
the amount of fuel introduced into the engine cylinder for a desired fuel
energy input has to be greater with the methanol. BSFC decreased about
two times as the engine load increased from 5 to 20 Nm constant load. This
decrease in BSFC could be explained by the fact that, as the engine load
increases, the rate of increasing brake power is much more than that of