问题 问答题 论述题

汽轮机的OPC和AST保护是如何实现的?

答案

参考答案:

汽轮机的OPC和AST保护是通过DEH控制器所控制的OPC-AST电磁阀组件实现的。

OPC-AST电磁阀组件由两只并联布置的的超速保护电磁阀(20/OPC-1、2)及两个逆止阀和四个串并联布置的自动停机危急遮断保护电磁阀(20/AST-1、2、3、4)和一个控制块构成超速保护-自动停机危急遮断保护电磁阀组件,这个组件布置在高压抗燃油系统中。它们是由DEH控制器的OPC部分和AST部分所控制。

正常运行时两个OPC电磁阀是失电常闭的,封闭了OPC母管的泄油通道,使高压调节汽阀执行机构活塞杆的下腔建立起油压,当转速超过103%额定转速时,OPC动作信号输出,这两个电磁阀就被励磁打开,使OPC母管油经无压回油管路排至EH油箱。这样相应的调节阀执行机构上的卸载阀就快速开启,使各高压调节阀迅速关闭。

四个串并联布置的AST电磁阀是由ETS系统所控制,正常运行时这四个AST电磁阀是带点关闭的,封闭了AST母管的泄油通道,使主汽门执行机构和调节阀门执行机构活塞杆的下腔建立起油压,当机组发生危急情况时,AST信号输出,这四个电磁阀就失电打开,使AST母管油液经无压回油管路排至EH油箱。这样主汽门执行机构和调节阀门执行机构上的卸荷阀就快速打开,使各个汽门快速关闭。

四个AST电磁阀布置成串并联方式,其目的是为了保证汽轮机运行的安全性及可靠性,AST/1和AST/3、AST/2和AST/4每组并联连接,然后两组串联连接,这样在汽轮机危急遮断时每组中只要有一个电磁阀动作,就可以将AST母管中的压力油泄去,进而保证汽轮机的安全。在复位时,两组电磁阀组的电磁阀,只要有一组关闭,就可以使AST母管中建立起油压,使汽轮机具备起机的条件。

AST油和OPC油是通过AST电磁阀组件上的两个逆止阀隔开的,这两个逆止阀被设计成:当OPC电磁阀动作时,AST母管油压不受影响;当AST电磁阀动作时,OPC母管油压也失去。

单项选择题
阅读理解

We can make mistakes at any age. Some mistakes we make are about money. but most mistakes are about people. "Did Jerry really care when I broke up with Helen?" "When I got that great job, did Jim, as a friend, really feel good about it? Or did he envy my luck?" "And was Paul friendly just because I had a car? " When we look back, doubts like these can make us feel bad.

But when we look back, it is too late.

Why do we go wrong about our friends, or our enemies? Sometimes what people say hides their real meanings. And if we do not really listen, we miss the feeling behind the words. Suppose someone tells you, "You're a lucky dog!"(你真幸运!) Is he really on your side? If he says, "You're a lucky guy!", that is being friendly. But "a lucky dog?" There is a bit of envy in those words. What he may be saying is that he does not think you deserve your luck.

"Just think of all the things you have to be thankful for" is another phrase that says one thing and means another. It could mean that the speaker is trying to get you to see your problem. But this phrase contains the thought that your problem is not at all important.

How can you tell the real meaning behind someone's words? One way is to take a good look at the person talking. Do his words fit the way he looks? Is what he says shown by the tone of voice? The look in his eyes? Stop and think. The minute you spend thinking about the real meaning of what people say to you may save your another mistake.

57.When the writer recalls(回想) some of the things that happened between him and his friends, he _______.

A. feels happy, thinking how nice his friends were to him

B. feels he might not have understood his friends' true feelings

C. think it a mistake to have broken up with his girl friend

D. is sorry that his friends let him down

58.When the writer talks about someone saying, "You're a lucky dog!", he is saying that

_____.    

A. the speaker is just friendly

B. this sentence suggests the same as "You're a lucky guy!"

C. the word "dog" should not be used to apply to people

D. sometimes the words show that the speaker is a bit envious

59.This passage tries to tell you how to ______.

A. avoid mistakes about money and friends

B. get an idea of friendly people

C. avoid mistakes in understanding what people tell you

D. keep people friendly without trusting them

60.The writer suggests that ______ be trusted.

A. everybody   B. nobody    C. all the people  D. all the people not