When the engine is cold, for example, then the mixture must be rich ( have a high proportion of fuel).

例如，当发动机冷车时，就必须提供较浓的混合气（具有较高的燃油比例）。

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The mixture must be of varying degrees of richness to suit engine operating conditions. It must be rich (have a higher percentage of fuel) for starting, acceleration, and high-speed operation.

混合气的浓度比例可以改变，以适应发动机的运行状况。汽车在启动、加速和高速行驶时，需要含燃油浓度较高的混合气；

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In a two-stroke gasoline engine, exhaust gas pollution is especially severe when it burns rich mixture of blended fuel.

二冲程汽油机排气污染严重，尤其是燃烧混合油、浓混合气时有害物排放量大。

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That mixture is then fed into a fuel reformer that turns it into a hydrogen-rich gas.

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