汽轮机的基本工作原理?
参考答案:
蒸汽通过喷嘴时,压力下降,体积膨胀形成高速气流,推动叶轮旋转而作功。
— I haven't seen Tom these days. Where is he?
— He _____ Japan.[ ]
A. has been to
B. has gone to
C. has been in
D. went to
柴油机冒黑烟是何原因?如何排除?