问题 问答题

什么是轴流风机的逆流现象?

答案

参考答案:

风机发生喘振后,叶栅失去压缩气体的能力,如果风机出口管路的压力高于烟起出口压力,出口管路中的气体会进入压缩机,在风机中发生倒流,称为轴流风机的逆流现象,如果风机此时仍有动力推动,则原动机的功率在风机中变成倒流气体的摩擦热,很快就会使风机叶片膨胀,擦缸甚至熔化,转子飞逸,特别是主风管道中含有催化剂的高温气体的逆流对主风机的破坏性更大。

单项选择题

"What does the middleman do but add to the price of goods in the shops " Such remarks are aimed at the intermediate operations between manufacturers and final customers. This practice usually attracts a lot of attention from the public and the press and the operation most talked about is what is often called wholesaling.
The wholesaler buys goods in large quantities from the manufacturers and sells them in smaller parcels to retailers, and for this service his selling price to the retailer is raised several percent higher. But his job is made more difficult by retail demand not necessarily running level with manufacturers’ production. Because he adjusts or regulates the flow of goods by holding stock Until required, he frees the manufacturer, to some extent, from the effect on production of changing demand and having to bear the whole risk.
The manufacturer can then keep up a steady production flow, and the retailer has no need to hold heavy stocks, who can call on the wholesaler for supplies any time. This wholesale function is like that of a valve in a water pipe. The middleman also bears part of the risk that would otherwise fall on the manufacturer and also the retailer.
The wholesaler provides a purely commercial service, for which he is too well rewarded. But the point that is missed by many people is that the wholesaler is not just someone adding to the cost of goods. It is true one could eliminate the wholesaler but one would still be left with his function: that of making sure that goods find their way to the people who want them.

"Middleman" in the passage almost equals to all the following in meaning EXCEPT ______.

A.go-between

B.intermediary

C.manufacturer

D.wholesaler

单项选择题