4. Conclusions
1. One hundred fifty cycles are sufficient for studying the
cycle variations in HICEs.
2. The COVimep of HICEs decreases as fueleair ratio increases
at 1000e5000 rpm, especially when the COVimep is less than
5% at a fueleair ratio greater than 0.2. Engine speed has
little effect on the COVimep of HICEs. The variation trend of
COVimep with fueleair ratio tends to be the same at different
speeds.
3. COVimep decreases as fueleair ratio increases. The best
ignition advance angles that correspond to the minimum
COVimep also decrease with increasing fueleair ratio. The
effect of ignition advance angle on COVimep diminishes with
a richer mixture, and COVimep gradually varies with ignition