问题 问答题 简答题

多级凝汽式汽轮机最末几级为什么要采用去湿装置?

答案

参考答案:

多级凝汽式汽轮机的最末几级蒸汽温度很低,一般均在湿蒸汽区工作。湿蒸汽中的微小水滴不但消耗蒸汽的动能形成湿汽损失,还将冲蚀叶片,威胁叶片安全。因此必须采取去湿措施,以保证凝汽式汽轮机膨胀终了的允许湿度。大功率机组采用中间再热,对减少低压级叶片湿度带来显著的效果。当末级湿度达不到要求时,应加装去湿装置和提高叶片的抗冲蚀能力。

阅读理解

V Reading

Ellas’ story

My name is Ellas .I am a poor black worker in South Africa .The time when I first met Nelson Mandela was a very difficult period of my life .I was twelve years old . It was in 1952 and he had opened a black law firm to advise black poor people on their problems .

I began school at six . The school where I studied only two years was three kilometers away. I had to leave, because my family could not continue to pay the school fees and the bus fare .I could not read or write. After trying hard ,I got a job in a gold mine, This was a time when one had got to have a passbook to live in Johannesburg. Sadly I did not have this passbook because I was not born there and I was worried about whether I would be out of work.

The day when Nelson Mandela told me what to do and helped me was one of the happiest days of my life .He told me how to get the correct papers so I could stay in Johannesburg .I never forgot how kind he was and when he organized the ANC Youth League ,I joined it as soon as I could .He said:

“The last thirty years have seen the greatest number of laws stopping our rights and progress, until today we have reached a stage where we have almost no rights at all.”

It was the truth .Black people has no vote and could not choose who ruled them .The parts of town where they lived were places decided by white people .They could not get jobs they wanted .The places there they were sent to live were the poorest areas in South Africa .No one could grow food there .In fact as  Nelson Mandela said:

“…we were put in a position in which we had either to accept we were less important ,or fight the Government .We chose to attack the law .We first broke the law in a way which was peaceful ;when this was not allowed… only then did we decide to answer violence with violence.”

As a matter of fact, I do not like violence… but in 1963 I helped him blow up some government buildings .It was very dangerous because if I was caught I could be put in prison for years .But I was happy to help because I knew it was to realize our dream of making black and white people equal.

1 Read the text and answer the following questions.

1) When and where was the writer born?

2) What difficulty did he meet when he worked in a gold mine in Johannesburg?      

3 )why did Mandela organize the ANC Youth League?      

4 )What position were the black in and what did they do

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