dBA
Indicated efficiency
1.0
100
0.2
0.4
0.6
0.8
75
80
85
90
95
0.0
1.0
1.5
2.0
2.5
Indicated power - kW
3.0
70
3.5
Etai DME
Etai diesel
Noise -dB diesel
Noise -dB DME
188
Alternative Fuels for Transportation
Figure 6.11
The indicated thermal efficiency and engine noise of a 0.273 liter single cylinder diesel operating on diesel fuel and DME at a speed of 3000 rpm.
Figure 6.11 shows the indicated engine efficiency, Etai, (i.e., the efficiency of
production of work on the top of the piston) and engine noise as a function of
engine power. Contrary to expectations due to the longer duration of injection, the DME engine had the same efficiency as the diesel engine and operated with much less noise. The former is thought to be due to a lower heat
loss during DME combustion mentioned earlier. The lower noise is another
advantage of DME, and is due to good ignitability in a diesel engine. Because
it ignites more readily, less DME has been injected at the time of ignition
with the diesel engine, and the force of the initial DME combustion is less
than that of diesel.
Figure 6.12 shows the nitric oxide (NO x ) and smoke emissions of the DME
and diesel engines as a function of the engine power. Here the results are
very dramatic. There is no smoke (particulate emissions) from the combustion of DME. The values shown for DME are the detection limit from the
test method. Subsequent tests with many other engines verify that DME
combustion does not produce soot particles. A DME engine can emit small
amounts of particulate matter originating from the lubricating oil, as do all
other engines. With modern oil control techniques, these emissions are usually low enough not to need special control. It should be pointed out that
when the engine was operated on diesel fuel using the low injector opening
pressure, the smoke number was about twice as large as the values shown in
Figure 6.12. These values correspond to a very dark diesel exhaust, which is
completely unacceptable.
At the same time, the NO x emissions with DME are about 30% of those with
diesel fuel. In diesel fuel emissions research, the NO x /particulate trade-off
Indicated efficiency
1.0
100
0.2
0.4
0.6
0.8
75
80
85
90
95
0.0
1.0
1.5
2.0
2.5
Indicated power - kW
3.0
70
3.5
Etai DME
Etai diesel
Noise -dB diesel
Noise -dB DME
188
Alternative Fuels for Transportation
Figure 6.11
The indicated thermal efficiency and engine noise of a 0.273 liter single cylinder diesel operating on diesel fuel and DME at a speed of 3000 rpm.
Figure 6.11 shows the indicated engine efficiency, Etai, (i.e., the efficiency of
production of work on the top of the piston) and engine noise as a function of
engine power. Contrary to expectations due to the longer duration of injection, the DME engine had the same efficiency as the diesel engine and operated with much less noise. The former is thought to be due to a lower heat
loss during DME combustion mentioned earlier. The lower noise is another
advantage of DME, and is due to good ignitability in a diesel engine. Because
it ignites more readily, less DME has been injected at the time of ignition
with the diesel engine, and the force of the initial DME combustion is less
than that of diesel.
Figure 6.12 shows the nitric oxide (NO x ) and smoke emissions of the DME
and diesel engines as a function of the engine power. Here the results are
very dramatic. There is no smoke (particulate emissions) from the combustion of DME. The values shown for DME are the detection limit from the
test method. Subsequent tests with many other engines verify that DME
combustion does not produce soot particles. A DME engine can emit small
amounts of particulate matter originating from the lubricating oil, as do all
other engines. With modern oil control techniques, these emissions are usually low enough not to need special control. It should be pointed out that
when the engine was operated on diesel fuel using the low injector opening
pressure, the smoke number was about twice as large as the values shown in
Figure 6.12. These values correspond to a very dark diesel exhaust, which is
completely unacceptable.
At the same time, the NO x emissions with DME are about 30% of those with
diesel fuel. In diesel fuel emissions research, the NO x /particulate trade-off