正常情况下，发动机缸内都喷的是汽油，柴油，天然气，甲醇等可燃烧的液体，同样正常的发动机的燃烧应该如下面的动图所展示的，喷如汽油等可燃烧的液体，然后点火燃烧做功。那为什么要往气缸内喷水呢? 发动机气缸内喷水是有宝马首先提出来的，宝马在 ...

This is the VOA Special English Education Report. Now, we continue our discussion from last week about the pay for professors in the United States. We looked at the averages. Today we narrow that to ...