MTBE (Methyl Tertiary Butyl Ether) blended diesel fuel, and DME (Dimethyl E
ther) with the homogeneous charge compression ignition (HCCI) system are ve
ry attractive for NOx and PM (particulate matters) reductions in DI diesel
engines, while their effects on combustion and odorous emissions are not cl
ear. In this study, a few percent MTBE blended in diesel fuel gives a lower
HCHO (formaldehyde) and an improved exhaust odor than with neat diesel fue
l, while over 10% blend, a very low boiling point MTBE forms an overlean mi
xture and diminishes the positive effect of the O-2 content of MTBE. The st
udy of DME achieved a 100% DME combustion, and hybrid combustion of DME and
diesel fuel with HCCI system. Two peaks in heat release during combustion
appear in DME and hybrid-operation under an ultra-lean engine operation. Al
though the homogeneous DME mixture allows the ultra-lean engine operation,
it also gives a very strong exhaust odor together with higher HCHO and THC
(total hydrocarbon).