The combustion performance test under different injection parameters was carried
out on an inline 6-cylinder spark-ignition (SI) methanol engine, and the
influence mechanism of injection parameters on methanol evaporation, mixing,
combustion and emission was revealed through simulation. The results indicate
that compared to the low-flow nozzle scheme (14*D0.26), when adopting the
high-flow nozzle scheme (16*D0.30), the injection duration is shorter. The
evaporation rate of methanol in the intake port is increased, the amount of
methanol droplets and wall-attached liquid film in the cylinder is reduced, and
the temperature in the cylinder is elevated. Moreover, the changes are more
significant under high-load operating conditions. The change in the methanol
charge rate during the intake process leads to a slightly higher inhomogeneity
of the in-cylinder mixture. The relatively high temperature in the cylinder and
the appropriate increase in the mixture concentration on the exhaust side are
conducive to accelerating the combustion in the early and middle stages. The
CA0-10 is shortened, and the CA50 is advanced, which improves the combustion
performance under different loads. The brake thermal efficiency (BTE) is
increased by 0.53% to 1.27%. Moreover, as the load increases, the increase in
BTE becomes more significant. In terms of emission performance, adopting the
16*D0.26 nozzle scheme reduces the amount of methanol in the piston crevice,
weakens the crevice effect, and reduces HC emissions by 56.3% to 68.5% under
different loads. However, the relatively rich mixture in the combustion chamber
on the exhaust side leads to an increase in CO emissions. In conclusion,
adopting the high-flow nozzle scheme can lead to a relatively small increase in
CO emissions while significantly reducing HC emissions, reducing the liquid film
in the cylinder, and obtaining a relatively high BTE. Moreover, it is possible
to adjust the injection phase more flexibly under high-load operating
conditions.