问题 问答题 简答题

发动机为什么要进行曲轴箱通风?

答案

参考答案:

发动机工作时,肯定有一部分可燃混合气和燃烧后的废气经活塞环漏到曲轴箱内。这些气体在曲轴箱内会产生如下不良后果:

(1)漏入的可燃混合气和废气冷却,凝结成水、汽油等,使润滑油变稀,性能变坏。

(2)废气中的二氧化硫遇水后生成亚硫酸再遇到氧气便生成硫酸,这些酸性物质在润滑系中即使量较少,也会使零件受到腐蚀。

(3)漏入的可燃混合气不回收利用,对耗油不利。

(4)漏入曲轴箱内的气体,使曲轴箱内压力增高,发动机容易产生漏油现象。

(5)漏入曲轴箱内的气体,如不充分利用,跑到大气中去,使空气污染。所以,曲轴箱必须进行通风。

多项选择题
阅读理解

阅读理解。

     If women are mercilessly exploited (剥削) year after year, they have only themselves to blame, because

they tremble at the thought of being seen in public in clothes that are out of fashion. They are always taken

advantage of by the designers and the big stores. Clothes which have been worn only a few times have to be

put aside because of the change of fashion. When you come to think of it, only a woman is capable of standing

in front of a wardrobe packed full of clothes and announcing sadly that she has nothing to wear.

     Changing fashions are nothing more than the intentional creation of waste. Many women spend vast sums

of money each year to replace clothes that have hardly been worn. Women who cannot afford to throw away

clothing in this way, waste hours of their time changing the dresses they have. Skirts are lengthened or

shortened; necklines are lowered or raised, and so on.

     No one can claim that the fashion industry contributes anything really important to society. Fashion

designers are rarely concerned with primary things like warmth, comfort and durability (耐用). They're only

interested in outward appearance and they take advantage of the fact that women will put up with any amount

of discomfort, as long as they look right. There can hardly be a man who hasn't sometime in his life smiled at

the sight of a woman shaking in a thin dress on a winter day, or picking her way through deep snow in high-

heeled shoes.

     When comparing men and women in the matter of fashion, the conclusions to be drawn are obvious. Do

the constantly changing fashions of women's clothes, one wonders, reflect basic qualities of instability (不稳

定)? Men are too clever to let themselves be cheated by fashion designers. Do their unchanged styles of dress

reflect basic qualities of stability and reliability? That is for you to decide.

1. Designers and big stores always make money _____. [ ]

A. by mercilessly exploiting women workers in the clothing industry

B. because they are capable of predicting new fashions

C. by constantly changing the fashions in women's clothing

D. because they always improve quality of women's clothing

2. The writer would be less critical (批评) if fashion designers placed more stress on the _____ of clothing. [ ]

A. cost

B. appearance

C. comfort

D. suitability

3. According to the passage, which of the following statements is TRUE? [ ]

A. New fashions in clothing are created for the commercial exploitation of women.

B. The constant changes in women's clothing reflect their strength of character.

C. The fashion industry makes an important contribution to society.

D. Fashion designs should not be encouraged since they are only welcomed by women.

4. By saying "the conclusions to be drawn are obvious", the writer means that _____. [ ]

A. women's changeableness in their choice of clothing is often laughed at

B. women are better able to put up with discomfort

C. men are also exploited greatly by fashion designers

D. men are more reasonable in the matter of fashion