http://ntrs.nasa.gov/archive/nasa/ca...1977016170.pdf
SUIMMARY OF RESULTS
Apparent flame speed and energy balance measurements were used to explain performance and emissions differences between gasoline and gasoline enriched by bottled hydrogen and hydrogen produced by a methanol reformer.
For a single load and engine speed condition, a multicylinder engine operating with lean mixture ratios with and without hydrogen addition gave the following results:
1. Adding small amounts of hydrogen to gasoline produced efficient lean operation by increasing the apparent flame speed and reducing ignition lag.
2. The actual minimum energy consumption was the same for gasoline and hydrogen-gasoline, although the minimum-energy-consumption equivalence ratio decreased from 0.79 to 0.67.
3. Exhaust emissions levels followed the classical trends with changing equivalence ratio. Oxides-of-nitrogen emission levels at the minimum-energy-consumption equivalence ratios were appreciably lower for hydrogen-gasoline than for gasoline. At the same equivalence ratio, in the range of practical interest, NOx emissions were higher for hydrogen-gasoline than for gasoline because of hydrogen's higher peak combustion temperatures.
4. Gasoline with reformed hydrogen gave the highest NOx emission levels. The reformer must produce gas at a high enough temperature to avoid water or methanol condensation. The high inlet temperature can cause higher peak combustion temperatures and, therefore, higher NOx emission levels.
5. The hydrocarbon emission levels of hydrogen-gasoline did not follow the trends reported from lower-compression-ratio engines, in that hydrocarbon emission levels were lower with hydrogen enrichment at equivalence ratios above 0.80. Hydrocarbon emission levels were somewhat higher for hydrogen-gasoline at minimum-energyconsumption equivalence ratios. However, the combustion process for gasoline with bottled hydrogen produced the lowest carbon monoxide emission levels.
6. The steam reformation of methanol is potentially an energy-conserving way to produce onboard hydrogen. A closed-loop control system is required to maintain engine reformer stability and to optimize the total performance and efficiency of the combined reformer -engine system.
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