Fig. 8 shows the accumulated heat releases of DME and ULSD fuels
according to the various injection timings. As illustrated in Fig. 8, the
advanced ignition of DME shows an early increasing of the
accumulated heat releases and the fast burning by the fast
evaporation and high cetane number caused the sudden increase,
comparing those of ULSD. On the other hand, at the same engine load
conditions, the most dominant factor determining the cumulative
heat release is the homogeneity of the fuel-air mixture in the
premixed zone because the total heat release is influenced by the
premixed combustion phase [27]. In this view point, the ignition
timing is also important factor on the cumulative heat release.
Therefore, the cumulative heat release of DME fuel at the same
injection timing is slightly higher than that of ULSD.