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Fig. 5 — Final map of engine efficiency for the 2nd generation single cylinder engine in the DOE project [39]. Copyright © 2012 SAE International. Reprinted with permission.

Figure 5 — Final map of engine efficiency for the 2nd generation single cylinder engine in the DOE project [39]. Copyright © 2012 SAE International. Reprinted with permission.

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Fig. 2 — Forklift truck equipped with a HJICE, part of the demonstration activities within the Hydrogen Region Flanders — South-Netherlands project [21].
Fig. 2 — Forklift truck equipped with a HJICE, part of the demonstration activities within the Hydrogen Region Flanders — South-Netherlands project [21].
Fig. 3 — Hybrid light duty truck equipped with a 4L 91 kW hydrogen engine, demonstrated by Tokyo City University [3]. Permission to reproduce granted by copyright holder Tokyo City University.
Fig. 3 — Hybrid light duty truck equipped with a 4L 91 kW hydrogen engine, demonstrated by Tokyo City University [3]. Permission to reproduce granted by copyright holder Tokyo City University.
walls is a prerequisite for increasing efficiencies of hydrogen- fueled engines. Measurements of instantaneous heat flux through the combustion chamber wall, for stoichiometric PFI operation on hydrogen, gasoline and methane have shown that the heat fluxes recorded for hydrogen were much higher than for gasoline or methane [69-71]. This explains why, although combustion is much faster, the resulting efficiency is only as high or even lower for hydrogen compared to gasoline or methane (see also [49]), due to the higher heat losses. The balance becomes a lot better if lean mixtures are used, to take advantage of the wide flammability limits of hydrogen. For moderately lean mixtures, flame speeds remain higher than for gasoline or methane, while heat losses decrease substan- tially, leading to increased efficiencies. If part load points are
walls is a prerequisite for increasing efficiencies of hydrogen- fueled engines. Measurements of instantaneous heat flux through the combustion chamber wall, for stoichiometric PFI operation on hydrogen, gasoline and methane have shown that the heat fluxes recorded for hydrogen were much higher than for gasoline or methane [69-71]. This explains why, although combustion is much faster, the resulting efficiency is only as high or even lower for hydrogen compared to gasoline or methane (see also [49]), due to the higher heat losses. The balance becomes a lot better if lean mixtures are used, to take advantage of the wide flammability limits of hydrogen. For moderately lean mixtures, flame speeds remain higher than for gasoline or methane, while heat losses decrease substan- tially, leading to increased efficiencies. If part load points are
Fig. 7 — CFD results showing the mixture stratification at TDC resulting from two different nozzle geometries. Local equivalence ratios shown on 2 vertical planes and 1 horizontal plane, for a 2000 rpm and 13.5 bar bmep engine condition [39]. Copyright © 2012 SAE International. Reprinted with permission. Testing of the lean NO, trap continued on the final engine chosen within the project, a four cylinder 4.7 L heavy duty engine converted to naturally aspirated DI hydrogen opera- tion [24]. The engine equipped with the aftertreatment system is shown schematically in Fig. 9 and was run on the JEO5 test cycle. The aftertreatment system resulted in large reductions of NO, emissions. However, the transient testing also showed Also, as mentioned in the previous section, heat transfer models need to be improved. While this would allow a better prediction of how heat transfer affects efficiency, it is of even
Fig. 7 — CFD results showing the mixture stratification at TDC resulting from two different nozzle geometries. Local equivalence ratios shown on 2 vertical planes and 1 horizontal plane, for a 2000 rpm and 13.5 bar bmep engine condition [39]. Copyright © 2012 SAE International. Reprinted with permission. Testing of the lean NO, trap continued on the final engine chosen within the project, a four cylinder 4.7 L heavy duty engine converted to naturally aspirated DI hydrogen opera- tion [24]. The engine equipped with the aftertreatment system is shown schematically in Fig. 9 and was run on the JEO5 test cycle. The aftertreatment system resulted in large reductions of NO, emissions. However, the transient testing also showed Also, as mentioned in the previous section, heat transfer models need to be improved. While this would allow a better prediction of how heat transfer affects efficiency, it is of even
Fig. 8 — CFD results showing the ‘NO, potency’ at TDC resulting from two different nozzle geometries. As a measure of ‘NO,’ potency, the volumes are shown having local equivalence ratios of 0.5;4j2. 2000 rpm and 13.5 bar bmep engine condition [39]. Copyright © 2012 SAE International. Reprinted with permission.
Fig. 8 — CFD results showing the ‘NO, potency’ at TDC resulting from two different nozzle geometries. As a measure of ‘NO,’ potency, the volumes are shown having local equivalence ratios of 0.5;4j2. 2000 rpm and 13.5 bar bmep engine condition [39]. Copyright © 2012 SAE International. Reprinted with permission.
Fig. 9 — Schematic of final engine and aftertreatment system of the NTSEL project [24]. Copyright © 2010 SAE International. Reprinted with permission. (simulated) turbocharged lean engine operating strategy was chosen. The equivalence ratio was fixed at ¢ = 0.3 (A = 3.3), with throttling at engine loads below 4 bar bmep and turbo- charging at higher loads. The engine data was recalculated to a 3 L engine powering a passenger car and used in a vehicle simulation on the Urban Dynamometer Driving Schedule (part of the FTP cycle). NO, emissions were calculated to be within the SULEV II range, i.e. well below the target set by DOE, without any aftertreatment. Further calculations showed that downsizing the engine could result in increased efficiency while still meeting the DOE target for NO, emissions, albeit with a smaller margin. This again illustrates the trade-off between efficiency and NO, emissions. The authors suggest advanced powertrain layouts (hybridization) could be looked at in future to take full advantage of the high efficiency and ultra-low emissions regimes. An alternative approach was taken within the DOE project [40]. Based on the obtained engine data, discussed above, a
Fig. 9 — Schematic of final engine and aftertreatment system of the NTSEL project [24]. Copyright © 2010 SAE International. Reprinted with permission. (simulated) turbocharged lean engine operating strategy was chosen. The equivalence ratio was fixed at ¢ = 0.3 (A = 3.3), with throttling at engine loads below 4 bar bmep and turbo- charging at higher loads. The engine data was recalculated to a 3 L engine powering a passenger car and used in a vehicle simulation on the Urban Dynamometer Driving Schedule (part of the FTP cycle). NO, emissions were calculated to be within the SULEV II range, i.e. well below the target set by DOE, without any aftertreatment. Further calculations showed that downsizing the engine could result in increased efficiency while still meeting the DOE target for NO, emissions, albeit with a smaller margin. This again illustrates the trade-off between efficiency and NO, emissions. The authors suggest advanced powertrain layouts (hybridization) could be looked at in future to take full advantage of the high efficiency and ultra-low emissions regimes. An alternative approach was taken within the DOE project [40]. Based on the obtained engine data, discussed above, a
Fig. 10 — Control strategies for obtaining target power output while limiting NO, emissions [24]. Copyright © 2010 SAE International. Reprinted with permission.
Fig. 10 — Control strategies for obtaining target power output while limiting NO, emissions [24]. Copyright © 2010 SAE International. Reprinted with permission.
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