主风机停机时为什么要首先切除系统(指切换主风机时)?
参考答案:
避免主风机停机对整个装置带来的压力波动;将主风机切除系统后可缓慢降低风机负载,对保护轴及轴瓦有利。
We will go for a picnic if it _____ tomorrow. [ ]
A. doesn't rain
B. wasn't rainy
C. won't rain
D. wasn't raining
正常发质的头发染发色彩如何选择?