问题 问答题 简答题

润滑油中混入水分对压缩机有何危害?

答案

参考答案:

①混入水分的油,水与油形成一种乳化物,这将大降低润滑油的粘性。

②如润滑油在压缩机气缸润滑,如果混入水分,则润滑油在压缩过程,升温升压,从而使部分水分形成蒸汽,冲破气缸的润滑油膜,加速气缸的磨损。由以上两种危害我们知道,润滑油中混入水分将造成润滑油的性能降低,起不到应有的润滑效果,损坏设备,运动机件。

阅读理解

When you cough or sneeze, please turn your head away from others and cover your mouth with the full part of your hand. Afterwards, you should say,” Excuse me.” This is a rule I set for my students

It is so simple, but many kinds have never been told to do this. In fact, I notice adults cough and sneeze in public without putting a hand over the mouth. I hate traveling by subway(地铁) in New York during cold and flu season, because it is certain that someone is going to stand right behind me and cough or sneeze on my neck.

One important thing I point out to the kids is that after they sneeze or cough on their hand, they should wash their hands as soon as possible. Otherwise, they will be passing those germs(病菌) along to everything and everyone they touch.

In order to help the kids remember this rule, I tell them about an old story. It says that when you sneeze, evil spirits jump into your body. If you don’t cover your mouth, the spirits will enter, but if you cover your mouth, you will keep them out, We say “God bless you” when someone sneezes, and in Germany you should say “Gesundheit”. That means “Good health to you. “ Both expressions are said just in case you didn’t cover your mouth in time and the spirits were able to enter your body. The kids love finding out the origins(起源) of these expressions and it encourage them to put the advice to use more often.

小题1:The writer of this article must be _______ .

A.a reporter

B.a teacher

C.a doctor

D.an officer小题2: What does the underline word ‘this” mean?

A.Don’t cough or sneeze in front of people.

B.Don’t stand beside someone who coughs or sneezes.

C.Many people cough or sneeze on the underground train.

D.Cover your mouth when coughing or sneezing and say sorry.小题3:After coughing or sneezing on their hand, students are advised to _______.

A.say “God bless you”

B.wash their hands as soon as possible

C.go to see a doctor as soon as possible

D.go home and have a good rest小题4: According to the article, the writer would like the kids _______.

A.to be polite to adults

B.to be in better health

C.to have good manners

D.to do well in exams

单项选择题