问题 问答题 简答题

介绍直流燃烧器的两种布置形式。

答案

参考答案:

均等配风直流燃烧器:一二次风口交错布置,相邻喷口间间距较小。适用于易着火的煤种,如烟煤、褐煤及挥发分产率较高的贫煤等煤种。

分级配风直流燃烧器:数个一次风口集中布置,一二次风喷口中心间距较大。适用于着火较为困难的煤种,如无烟煤、贫煤和劣提高蒸汽品质的途径质煤等。这些煤种若使一二次风混合过早,会使火焰温度降低,造成着火不稳。故将二次风分级送入,有效推迟一二次风的混合,保证煤粉既稳定着火又完全燃烧。

阅读理解

阅读理解。

     In most situations, light helps us see. But nowadays humans are using too much of it so that it is in fact

a kind of pollution.

     When it comes to looking at the night sky, too much light makes it difficult for us to watch some of life's

most wonderful sights: stars, planets and even galaxies (星系).

     According to scientific research, about 2, 500 stars can be seen by the human eye without using any

special equipment (设备). But because of light pollution, you can only see 200 to 300 stars from today's

countryside, and no more than ten stars from a city. In most big cities, people cannot see the sky filled with

stars like they did in their childhood.

     Light pollution affects more than just our view of sky. Research shows that lots of nighttime light can

harm wildlife, too.

     When birds fly to another place over cities, they sometimes get lost by the brightness and fly in circles

(圈) until they drop from tiredness. Sea turtles (海龟) need dark beaches for laying eggs, but they can't find

their ideal places because of those bright lights.

     Too much light at night may even affect human health, but scientists are not sure of that. They are still

learning more.

     In order to prevent things from going worse, governments and some organizations are working to reduce

light pollution. Many cities and towns have taken action to reduce the use of lights at night. Lights are used

only when and where they are truly needed. They also shine lights down at the ground instead of up into the

sky and use lower brightness levels.

     Hopefully, in the near future, humans can enjoy the clear and beautiful sky again and all the wildlife will

live a peaceful and undisturbed life, too.

1. Why does the writer think that too much light is a kind of pollution? [ ]

A. Because there are fewer and fewer stars.

B. Because human health has been affected.

C. Because too much light is a waste of energy.

D. Because some of the wildlife can be harmed.

2. Which of the following is NOT mentioned (提到) in this passage?[ ]

A. The problems that light pollution has caused.

B. The reason why humans use too much light.

C. The ways that light pollution can be reduced.

D. The reason why fewer stars can be seen than before.

3. Which of the following is true according to the passage?[ ]

A. There are about 2,500 stars in the sky.

B. Humans want to do nothing to reduce light pollution.

C. Sea turtles always get lost and die from tiredness.

D. Something has been done to reduce light pollution.

单项选择题