3.3.4. Variations in injection timi

3.3.4. Variations in injection timing
Several tests are performed on the PFI-HICE to study the in-
fluence of hydrogen injection timing on cycle variation. The
test conditions are shown in Table 7.
The COVimep varies with hydrogen injection timing as
shown in Fig. 8.
Fig. 8 illustrates that the COVimep of the PFI-HICE is almost
unchanged at a hydrogen injection timing of 360 to 360 CA
at 3500 rpm; this result is maintained at 1.5%. However, the
COVimep of the PFI-HICE substantially changes with hydrogen
injection timing at 800 rpm, especially during the intake process
from opening to closing of the intake valve. The COVimep
increases from 4% to 8% because the turbulence of the mixture
is very weak at idle conditions, and hydrogen injection
imposes a marked effect on fresh air mass flow. No backfire is
observed possibly because no hot point forms in the cylinder.
The combustion process is therefore stable.