问题 问答题 论述题

何谓滑参数停机?它有什么优缺点?

答案

参考答案:

滑参数停机是指在调速汽门全开状态下,借助锅炉降低蒸汽参数以逐渐降低负荷,汽轮机金属温度也随着相应降低,直至负荷到零为止。发电机解列后,还可继续降低蒸汽参数以降低汽轮机的转速,直到转子静止。

滑参数停机的优点:由于滑参数停机是采用低参数、大流量的蒸汽使汽轮机各受热部件得到均匀的冷却,而且金属温度可以降低到较低水平,故大大缩短了汽缸的冷却时间。另外,还可以利用锅炉的余热发电,利用低参数、大流量的蒸汽对汽轮机的通流部分进行清洗。在条件许可的情况下,高、低压加热器及除氧器均可以进行随机滑停,提高热效率,减少汽水损失。

滑参数停机的缺点:在停机过程中比额定参数停机较容易出现大的负胀差,对锅炉运行操作要求很严格,汽温均匀下降很难控制。在汽轮机方面操作和调整频繁,如监视不严格,容易产生水冲击和受热部件过冷却,造成设备损坏。

写作题
完形填空。
     Jim Green has been in China for more than two years. He has been to many interesting  1  in Beijing, but
he has not yet been to many other parts of  2 . Last week he went to Mount Emei in Sichuan with his  3 .
     Many people like to travel by  4 , but the Greens think that travelling by train is the best. It is much  5  and
far more enjoyable than a rushed journey by air. They had a won-derful train ride to Chengdu  6  they went on
to Mount Emei by bus.
     The train was quite nice and tidy, and there weren't too many people in  7  sleeping car. The Greens could
stand up and  8  around. It was a long journey,  9  none of them felt tired. They kept  10  the beautiful things
out of the window. They talked, laughed and played cards. The conductor kept coming to give them hot water
and  11   them newspapers. People nearby  12   with each other. A young man tried to speak English with Mr
and Mrs Green. Jim thought the train was like a big moving party. He went to sleep quite  13 . He enjoyed
listening to the sound of the running train and then fell asleep. When Jim woke up the next morning, the train
was already  14   Chengdu. His train ride seemed really  15 , but his memory (记忆) of the pleasant journey
will last long.
( )1. A. schools 
( )2. A. England 
( )3. A. friends 
( )4. A. air     
( )5. A. cheaper 
( )6. A. before  
( )7. A. my      
( )8. A. sit     
( )9. A. and     
( )10. A. looking
( )11. A. reading
( )12. A. talked 
( )13. A. early  
( )14. A. beside 
( )15. A. quick  
B.  places   
B.  America  
B.  classmates
B.  bus      
B.  dearer   
B.  when     
B.  your     
B.  walk     
B.  so        
B.  drawing  
B.  buying   
B.  spoke     
B.  late     
B.  to       
B.  slow     
C. villages
C. China   
C. father  
C. train   
C. dirtier 
C. after   
C. our     
C. run     
C. also    
C. watching
C. selling 
C. told    
C. easily  
C. past    
C. short   
D. cities  
D. the world
D. family  
D. ship    
D. quicker 
D. while   
D. their   
D. dance   
D. but     
D. getting                                        
D. writing 
D. said    
D. hard    
D. near    
D. long    
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