1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
g/km
HC
NO
CO
1.57
x
1.06
0.174
0.199
0.38
0.21 0.19
0.25 0.18
0.022
0.21 0.21
NG
λ = 1 (HCNG15)
λ = 1 Opt
λ = 1 Opt
(HCNG15)
(HCNG10)
280
Alternative Fuels for Transportation
1.2
1
0.8
0.6
0.4
0.2
0
g/km
1.06
0.21 0.21
0.99
0.07
0.54
0.8
0
0.57
NOx
CO HC
NG
λ = 1.4 Opt (HCNG15) λ = 1.4 Opt (HCNG10)
Figure 9.19
Emissions produced on the ECE15 driving cycle with stoichiometric mixtures (left) and lean
(right) for HCNG10 and HCNG15. (From Ortenzi, F., Chiesa, M., and Conigli, F., Experimental
Tests of Blends of Hydrogen and Natural Gas in Light Duty Vehicles, HYSYDays-Turin, 2nd World
Congress of Young Scientists on Hydrogen Energy Systems, 2007.)
For lean burn mixtures the emissions present two different behaviors: the
CO emissions are always lower for blends with 10% and 15% of H 2 by volume.
Nevertheless, concerning the NO x emissions, the values are lower than those
using pure CNG, but not as good as stoichiometric values. Furthermore, HC
emissions increase for the lower combustion quality due to lean mixture.
It is interesting to note that operating the vehicle with the O 2 sensor disabled, the fuel system had not been able to adjust the blend to an “objective”
value: in all the unsteady conditions (especially in acceleration phases) any
variation toward leaner mixtures had led to higher HC emissions and richer
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
g/km
HC
NO
CO
1.57
x
1.06
0.174
0.199
0.38
0.21 0.19
0.25 0.18
0.022
0.21 0.21
NG
λ = 1 (HCNG15)
λ = 1 Opt
λ = 1 Opt
(HCNG15)
(HCNG10)
280
Alternative Fuels for Transportation
1.2
1
0.8
0.6
0.4
0.2
0
g/km
1.06
0.21 0.21
0.99
0.07
0.54
0.8
0
0.57
NOx
CO HC
NG
λ = 1.4 Opt (HCNG15) λ = 1.4 Opt (HCNG10)
Figure 9.19
Emissions produced on the ECE15 driving cycle with stoichiometric mixtures (left) and lean
(right) for HCNG10 and HCNG15. (From Ortenzi, F., Chiesa, M., and Conigli, F., Experimental
Tests of Blends of Hydrogen and Natural Gas in Light Duty Vehicles, HYSYDays-Turin, 2nd World
Congress of Young Scientists on Hydrogen Energy Systems, 2007.)
For lean burn mixtures the emissions present two different behaviors: the
CO emissions are always lower for blends with 10% and 15% of H 2 by volume.
Nevertheless, concerning the NO x emissions, the values are lower than those
using pure CNG, but not as good as stoichiometric values. Furthermore, HC
emissions increase for the lower combustion quality due to lean mixture.
It is interesting to note that operating the vehicle with the O 2 sensor disabled, the fuel system had not been able to adjust the blend to an “objective”
value: in all the unsteady conditions (especially in acceleration phases) any
variation toward leaner mixtures had led to higher HC emissions and richer