Fig. 2 also shows the brake thermal efficiency contours of the
DMDF engine. It is observed that for all the MSP (containing neat
diesel operation, 0 MSP), the BTE is improved with increasing
engine load. But as the MSP increases at a given engine load, the
change in BTE is not uniform. Compared with neat diesel combustion,
the BTE of DMDF is reduced at low engine load when fumigation
methanol is increased. At low engine load, the cooling effect,
together with the leaner air/methanol mixture, result in poorer
combustion and thus reduce the BTE with more fumigation methanol.
At medium load, the BTE slightly drops at first and then
increases with the increment of MSP. The homogeneous air/methanol
mixture burns with a higher rapid rate of heat release, which
might increase the BTE at high MSP. At high engine load, the higher
in-cylinder gas temperature, the longer the ignition delay and the
combustion of the diesel fuel in a richer air/methanol mixture
resulted in the improvement of BTE.
Fig. 2 also shows the brake thermal efficiency contours of theDMDF engine. It is observed that for all the MSP (containing neatdiesel operation, 0 MSP), the BTE is improved with increasingengine load. But as the MSP increases at a given engine load, thechange in BTE is not uniform. Compared with neat diesel combustion,the BTE of DMDF is reduced at low engine load when fumigationmethanol is increased. At low engine load, the cooling effect,together with the leaner air/methanol mixture, result in poorercombustion and thus reduce the BTE with more fumigation methanol.At medium load, the BTE slightly drops at first and thenincreases with the increment of MSP. The homogeneous air/methanolmixture burns with a higher rapid rate of heat release, whichmight increase the BTE at high MSP. At high engine load, the higherin-cylinder gas temperature, the longer the ignition delay and thecombustion of the diesel fuel in a richer air/methanol mixtureresulted in the improvement of BTE.
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