104
Alternative Fuels for Transportation
increases as the methanol content was increased in the fuel blend (Nwafor,
Rice, and Ogbonna 2000).
4.7.2 engine emissions Tests
Engine emissions can be divided into two groups: regulated and unregulated emissions. Regulated emissions are carbon monoxide (CO), nitrogen
oxides (NO x ), and unburned fuel or partly oxidized hydrocarbons (HC).
The levels of these emissions are specified by legislations. Unregulated
emissions include polycyclic aromatic hydrocarbons (PAHs), methane,
aldehydes, carbon dioxide (CO 2 ), other trace organic emissions, and carbon
deposits.
Chao et al. (2000) studied the effect of a methanol-containing additive
(MCA) on the emissions of carbonyl compounds (CBCs) generated from a
heavy-duty diesel engine. When either 10 or 15% MCA was used, the emission factors of the CBCs acrolein and isovaleraldehyde increased by at least
91%. Song et al. (2008) studied dual-fuel operation on a DI, four stroke,
single-cylinder, water-cooled diesel engine. In that work, an electronically controlled low-pressure common rail system was employed to deliver
methanol to the inlet port, while the engine’s original high-pressure diesel
injection system was used to deliver a suitable quantity of diesel fuel for
ignition. The experimental results showed that smoke was reduced significantly, while a modest reduction in NO x was observed under the dual-fuel
conditions. The equivalent BSFC was improved under high-load operating
conditions. Especially, the dual-fuel engine showed a better fuel economy
when run at a high rate of methanol addition. However, unburned HC
and CO emissions for dual-fuel operation increased when methanol was
added. Song et al. (2008) claimed that it is better for the dual-fuel engine
to run with a high rate of methanol under high-load operating conditions
and with pure diesel under low-load operating conditions. In this case, an
improved thermal efficiency as well as an increased alternative ratio could
be reached.
Huang et al. (2004a) used various blend rates of methanol–diesel fuels in
the engine tests. The results indicated that the increase of methanol content
decreased smoke number (SN) and CO and UHC emissions but increased
BSFC and NO x emissions. Cheng et al. (2008a) researched the effects of the
fumigation methanol on the engine performance, emissions, and particulates. In that study, the fumigation methanol was injected to top up 10, 20,
and 30% of the power output under different engine operating conditions.
The experimental results showed that there is a decrease in the BTE when
fumigation methanol is applied, except at the highest load of 0.67 MPa. At
low loads, the BTE decreased with the increase in fumigation methanol; but
at high loads, it increased with the increase in the fumigation methanol. The
fumigation methanol resulted in a significant increase in UHC, CO, and NO x
emissions.
Alternative Fuels for Transportation
increases as the methanol content was increased in the fuel blend (Nwafor,
Rice, and Ogbonna 2000).
4.7.2 engine emissions Tests
Engine emissions can be divided into two groups: regulated and unregulated emissions. Regulated emissions are carbon monoxide (CO), nitrogen
oxides (NO x ), and unburned fuel or partly oxidized hydrocarbons (HC).
The levels of these emissions are specified by legislations. Unregulated
emissions include polycyclic aromatic hydrocarbons (PAHs), methane,
aldehydes, carbon dioxide (CO 2 ), other trace organic emissions, and carbon
deposits.
Chao et al. (2000) studied the effect of a methanol-containing additive
(MCA) on the emissions of carbonyl compounds (CBCs) generated from a
heavy-duty diesel engine. When either 10 or 15% MCA was used, the emission factors of the CBCs acrolein and isovaleraldehyde increased by at least
91%. Song et al. (2008) studied dual-fuel operation on a DI, four stroke,
single-cylinder, water-cooled diesel engine. In that work, an electronically controlled low-pressure common rail system was employed to deliver
methanol to the inlet port, while the engine’s original high-pressure diesel
injection system was used to deliver a suitable quantity of diesel fuel for
ignition. The experimental results showed that smoke was reduced significantly, while a modest reduction in NO x was observed under the dual-fuel
conditions. The equivalent BSFC was improved under high-load operating
conditions. Especially, the dual-fuel engine showed a better fuel economy
when run at a high rate of methanol addition. However, unburned HC
and CO emissions for dual-fuel operation increased when methanol was
added. Song et al. (2008) claimed that it is better for the dual-fuel engine
to run with a high rate of methanol under high-load operating conditions
and with pure diesel under low-load operating conditions. In this case, an
improved thermal efficiency as well as an increased alternative ratio could
be reached.
Huang et al. (2004a) used various blend rates of methanol–diesel fuels in
the engine tests. The results indicated that the increase of methanol content
decreased smoke number (SN) and CO and UHC emissions but increased
BSFC and NO x emissions. Cheng et al. (2008a) researched the effects of the
fumigation methanol on the engine performance, emissions, and particulates. In that study, the fumigation methanol was injected to top up 10, 20,
and 30% of the power output under different engine operating conditions.
The experimental results showed that there is a decrease in the BTE when
fumigation methanol is applied, except at the highest load of 0.67 MPa. At
low loads, the BTE decreased with the increase in fumigation methanol; but
at high loads, it increased with the increase in the fumigation methanol. The
fumigation methanol resulted in a significant increase in UHC, CO, and NO x
emissions.