| Mixtures of hydrogen and natural gas (hythane) are considered viable alternative fuels to gasoline due to lower overall pollutant emissions. However, as with all compressed gas vehicles, hythane vehicles have less comparable range due to low energy density.;To date, vehicle engines have run on hythane using a fixed hydrogen fraction and air-to-fuel ratio but it is possible to leverage greater advantage from H2 addition. Hydrogen posses unique lean-bum characteristics which make it possible to control power by the air-to-fuel ratio. In this manner, it is possible to decrease fuel consumption by varying the mixture strength of hydrogen in methane, and varying the air-to-fuel ratio during a driving cycle, without decreasing engine power. Cumulative production of CO2 , CO, and NO can be reduced, but production of unburned hydrocarbons increases due to operation near the partial bum limit. Hydrogen can also be produced on-board by the electrolysis of water, from engine power, and from regenerative braking power. This has the potential to increase engine efficiency, reduce storage requirements and recycle energy. This study presents the results of a one-cylinder engine test with mixtures of hydrogen in methane of 0%, 20%, 40% and 60% by volume. Each fuel was tested at speeds of 700RPM and 900RPM, full & part loads, and equivalence ratios from stoichiometric to the partial bum limit. These engine results are applied to three different driving cycles where engine speed and power requirements are changing. Optimum operating systems are identified given a specified quantity of hydrogen on-board. Furthermore, a simulated electrolyser operating from engine power and regenerative power is determined to offer no advantage. |
