问题 问答题 简答题

造成上下汽缸温差大的原因有哪些?

答案

参考答案:

引起上下汽缸温差大的原因有以下几方面:

(1)上下汽缸的质量、散热面积不同,使得在相同的加热或冷却条件下,上缸温度高,下缸温度低。

(2)在汽缸内蒸汽向上流动,凝结水流到下缸,产生上下缸温差。同时在汽缸大气空间中空气由下向上流动,造成汽缸的冷却条件不同,进一步导致上下缸温差的产生。

(3)由于汽缸保温不良,如下汽缸保温工艺差,运行中与汽缸脱离,使保温层与汽缸之间存在间隙,流入空气使下汽缸散热比上汽缸快。

(4)在给汽缸法兰、螺栓加热时。上法兰相对于下法兰过热,也是汽缸发生热变形弯曲的原因之一。

(5)由于汽缸疏水不畅,使得启停时上下汽缸温差的加剧。

(6)采用喷嘴调节的汽轮机,当调速汽门开启的顺序不当时,会造成部分进汽,使上下汽缸温度不均匀。

阅读理解

In Daniel Gilbert’s 2006 book "Stumbling(跌撞) on Happiness," the Harvard professor of psychology looks at several studies and concludes that marital(婚姻的) satisfaction decreases after the birth of the first child and increases only when the last child has left home. He also declares that parents are happier grocery shopping and even sleeping than spending time with their kids.

The most recent comprehensive study on the emotional state of those with kids shows us that the term "bundle of joy" may not be the most accurate way to describe our kids. "Parents experience lower levels of emotional well-being, less frequent positive emotions and more frequent negative emotions than their childless peers," says Florida State University’s Robin Simon, a sociology professor.

Simon received plenty of hate mail in response to her research,which isn’t surprising. Her findings shake the very foundation of what we’ve been raised to believe is true. In a recent NEWSWEEK Poll, 50 percent of Americans said that adding new children to the family tends to increase happiness levels. But which parent is willing to admit that the greatest gift life has to offer has in fact made his or her life less enjoyable?

Is it possible that American parents have always been this disillusioned(有幻觉的)? In pre-industrial America, parents certainly loved their children, but their kids also served a purpose—to work the farm, contribute to the household. Today, we have kids more for emotional reasons, but an increasingly complicated work and social environment has made finding satisfaction far more difficult. Raising children has not only become more complicated, it has become more expensive as well. The National Marriage Project’s 2006 report says that parents have significantly lower marital satisfaction than nonparents because they experienced more single and child-free years than previous generations.

As for those of us with kids, all the news isn’t bad. Parents still report feeling a greater sense of purpose and meaning in their lives than those who’ve never had kids. And there are other rewarding aspects of parenting that are impossible to quantify.

小题1:.

What’s the main idea of the book Stumbling on Happiness?

A.Parents are happier shopping than looking after their children.

B.Once they have children, the couples can never be as happy as before.

C.Compared with their childless peers, parents are leading a sad life.

D.The adding of children at home brings down marital satisfaction.小题2:.

. What can we infer from Para.3?

A.The Newsweek Poll shows that people think Prof. Simon’s finding is right.

B.Many people can’t accept the fact that they are not happy with their children.

C.It isn’t surprising that Professor Simon’s controversial research made her famous.

D.Simon’s findings are based on the belief passed down from generation to generation.小题3:.

What can we learn about American’s families in the past?

A.People had very good parents-children relationship in the family.

B.Having children could be partly out of some practical purposes.

C.Parents loved their children but they still asked them to work a lot.

D.Children had to work very hard to make their parents love them.小题4:.

What’s the author’s opinion about having children?

A.The author doesn’t think having children is a good thing to the family.

B.The author feels children make the life of a family happy.

C.The author thinks parenting can still be rewarding in a certain way.

D.The author believes that parents sacrifice a lot for having children.

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