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86 Victor Pantilie et al.
Another influence factor is the excess air-fuel ratio. On gasoline BSFC
decreases when λ increased from 0.8 to 0.9. On hydrogen BSFC decreases when
the excess air-fuel ratio increased from 1 to 1.5 and when the dosage is leaner
the BSFC has a slight increase (Fig. 3).
Fig. 3 – Brake specific fuel consumption diagram.
The NOx emissions level on gasoline increases with the increasing excess
air-fuel ratio from 0.8 to 0.9, but decreases when the engine is supercharged due
to the timing adjustment which decreased to avoid detonation (Fig. 4).
Fig. 4 – Gasoline NOx emissions diagram.
When hydrogen was used the NOx emissions level had a different
behaviour (Fig. 5). When normal intake was used the maximum was reached at
λ=1.3 with more than 5000 ppm.
When the engine was supercharged with 1.3 bar supercharge pressure the
maximum emissions level was reached at λ=1.4 and when the engine was