And not just a fuel, but, indirectly, a technology: the internal combustion engine, without which mankind might have taken to the roads but never to the skies.

但这又不仅仅是一种新的燃料，而是一种新的技术：内燃机。没有内燃机，人类可能会拥有道路，但是不可能会飞向蓝天。

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Next, we can use a different and cleaner fuel for the internal combustion engine with other designs.

接下来，我们可以让内燃机使用不同的更清洁的燃料。

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More efficient internal-combustion engines will wring out mileage from every drop of fuel, and hybrid powertrains will combine an electric motor with a conventional engine.

更高效的内燃发动机将进一步节约油耗，混合动力装置把电动马达同传统引擎组合在一起。

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"Lots and lots of things are happening that indicate a worldwide interest, and most of the knowledgeable people are convinced that the next-generation replacement for the internal combustion engine is going to be a fuel cell, " Roan said.

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When the battery is depleted (or when driven at very high speeds), the premium-gas internal combustion engine powers the car, but its fuel mileage suffers from having to shove around 400lbs of batteries.

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The technology isn't new-a patent for a hydrogen internal combustion engine was issued in 1928, and a 20hp fuel-cell tractor was demonstrated in the late 1950s.

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