问题 问答题 简答题

影响充气效率的因素有哪些?是如何影响的?

答案

参考答案:

1.进气终了压力Pa:Pa值越大,ηv越大;

2.进气终了温度Ta:Ta上升,ηv下降;

3.压缩比ε与残余废气系数γ:ε增加,ηv略有上升,γ增加,ηv下降;

4.配气定时:合理的配气定时可使ηv增大;

5.进气状态:进气温度Ts升高,ηv增加,进气压力Ps下降,Pa随之下降,且Pa/Ps的比值基本不变,对ηv影响不大。

阅读理解

阅读理解。

                                                                 How to Become Cleverer

      Once a boy came to ask a fisherman how to become cleverer, because his mother always called him

"foolish boy".

      "That's easy," answered the fisherman. "I know one way to make you become cleverer."

      "Really?"

      "Of course. It is said a fish head is good for brain. If you eat one, you'll become cleverer indeed. Pay

only three pounds for one fish head." The boy paid him three pounds and the fisherman cut off a fish head

and handed it to him.

      A raw fish head is not good-not even for a hungry boy to eat but the boy ate it up in two gulps.

      "Do you feel anything?" asked the fisherman. 

      "Not in my head," said the boy.

      The boy lay on the ground and thought. "One whole fish costs only two pounds. I had paid him three

pounds for the fish head. Why couldn't I have the whole fish for soup, a head for brain and one pound left

over?" He jumped up and shouted at the fisherman. "You thief! You are fooling me!" The fisherman laughed,

saying, "The fish head works now, you see."

1. The boy ate up the raw fish head only in two gulps, because he _____. [ ]

A. enjoy it

B. wanted to taste it

C. took it as a good medicine

D. was a foolish boy

2. The boy came to the fisherman in order to _____. [ ]

A. buy a fish head

B. ask the fisherman a question

C. buy a whole fish

D. A and C

3. The boy paid three pounds. He should have had _____. [ ]

A. a whole fish

B. a fish head and one pound back

C. a whole fish and one pound back

D. a whole fish, a fish head and one pound back

4. _____ helped the boy become cleverer. [ ]

A. A good meal

B. The raw fish head

C. Nothing

D. What had happened

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