而且气门头部容易被经过的高温气体烧蚀，活塞顶部也可能会碰到气门使发动机严重损坏。

Also the valve heads will be liable to be burnt by the passing hot gases, and there is the likelihood of the piston crown touching an open valve, which can seriously damage the engine.

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此外气门头易于被通过的热气体燃烧，这有可能使活塞频繁冲击打开的气门，使发动机严重损坏。

Also the valve heads will be liable to be burnt by the passing hot gases, and there is the likelihood of the piston crown touching an open valve, which can seriously damage the engine.

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灰云让航班不得不滞留在地面，是因为火山灰会阻塞飞机的发动机并且导致严重损坏。

The reason why the dust cloud has grounded planes is because volcanic ash can clog up aeroplane engines and cause serious damage

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