问题 问答题 简答题

为什么双层汽缸的汽轮机,可以缩短启动和停止时间?

答案

参考答案:

由于采用了双层结构的汽缸,每个缸的内外壁压差和温差都可大大降低,汽壁和法兰就可做的薄些,整个单位热容就小,机组的加热和冷却过程可以加快,缩短启停时间。对由此而产生的热应力和热膨胀,热变形的承受承受能力大大增强,另外,因高、中压内缸直接与高温蒸汽相接触,因此,采用了一种综合性比较强的珠光体热强钢(国产机组ZG15M01V)能够承受由于蒸汽温度的交变而引起的热冲击,所以,大容量机组采用这样的汽缸结构,对启动和停机时汽缸的加热和冷却都是很有利的。

多项选择题
阅读理解

阅读理解。

     Many Chinese have been greatly shocked by the traffic accident caused by the drunk driver Sun

Weiming, who has killed five and injured some others in Chengdu, Sichuan. However, such a case is not

rare.    

     Today, traffic accidents may have been regarded as a social problem. The car has killed and disabled more people in its brief history than any bomb or weapon ever invented. Much of the blood on the street

flows actually from rude behavior of drivers who refuse to respect the legal and moral rights of others. In

fact, the enemies of society on wheels are rather harmless but just ordinary people acting carelessly, you

might say. But it is a principle both of law and common morality that carelessness is no excuse when one's actions could bring death or damage to others. A minority of the killers go even far beyond carelessness

that can be imagined.    

     Researchers have estimated that as many as 80 percent of all automobile accidents can be attributed to the psychological condition of the driver. Emotional upsets can change drivers' reactions, slow their

judgment, and make them blind to the dangers that might otherwise be evident. The experts warn that it is

vital for every driver to make a conscious effort to keep his/her emotions under control.    

     Yet the irresponsibility that accounts for much of the problem isn't only put upon drivers. Street walkers regularly ignore or break traffic regulations. They are blamed in most vehiclewalker accidents, and many

cyclists even believe that they are not subject to the basic rules of the road.    

     Significant legal advances have been made towards safer driving in the past few years. Safety standards for vehicles have been raised both at the point of manufacture and through regular road inspections. In

addition, speed limits have been lowered. Due to these measures, the accident rate has decreased. But the accident experts still worry because there has been little or no improvement in the way drivers behave. The only real and lasting solution, say the experts, is to make people believe that driving is a skilled task

requiring constant care and concentration. Those who fail to do all these things present a threat to those

with whom they share the road.

1. Traffic accidents may be regarded as a social problem because _____.  

A. auto driving has become dangerous and harmful in today's society  

B. people usually pay no attention to law and morality when driving  

C. they have caused serious psychological problems among drivers  

D. the car has killed and disabled more people than any weapon in history

2. Who are NOT mentioned to be responsible for the road accidents in the passage?  

A. Careless bicycleriders.  

B. Careless people walking in the street.  

C. Irresponsible auto drivers.  

D. Irresponsible auto manufacturers.

3. By discussing solutions to traffic accidents,  the author seems to be _____.

A. doubtful and hopeless  

B. angry and disappointed

C. objective and concerned

D. anxious and annoyed

4. The author writes this passage to _____.  

A. show his worries about drunk driving  

B. help protect street walkers from car accidents  

C. discuss traffic problems and possible solutions  

D. warn auto drivers to refuse drunk driving