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Old 04-20-2012, 06:39 PM   #40 (permalink)
t vago
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Originally Posted by tangomar View Post
Apple? Meet orange!

Fig. 1 displays the variation of engine brake thermal efficiency with excess air ratio under various hydrogen addition fractions at 800rpm. It shows that the brake thermal efficiency of the original engine is
reduced sharply with the increase of excess air ratio. This phenomenon demonstrates that the lean combustion technology is not suitable to be applied on the low speed conditions of a pure gasoline fuelled SI engine, since the lean mixture is hard to be burned well under large resodual gas fraction and low combustion temperature. Especially when excess air ratio exceeds 1.43, it can be clearly seen that the original engine thermal efficiency decreased dramatically, which is attributed to the misfire of the mixture in the cylinder.
While this is certainly true from a thermodynamics standpoint, the article neglects to mention the fuel savings due to not having to generate a strong intake vacuum. Nor does the article address partial load conditions, which is where an engine would be the vast majority of its operational time. Just because something is very efficiently using fuel, it doesn't mean that it's getting good fuel economy.

Furthermore, the article kind of buries the fact that NOx emissions increased over no hydrogen being added.
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