问题 问答题 简答题

为什么有焰燃烧时的火焰比无焰燃烧时稳定,不容易发生脱火?

答案

参考答案:

在扩散燃烧时,烧嘴出口附近的煤气和空气在混合过程中能形成各种浓度的可燃混合气体,其中包括火焰传播速度最大的气体,因而有利于构成稳定的点火热源;而无焰燃烧时,从烧嘴流出的是已经按照化学当量比例混合好的可燃气体,甚至是稍贫的气体(空气过剩系数大于1),这种气体由于受到燃烧后气体的冲淡,火焰传播速度显著下降,容易造成火焰的脱离和熄灭。

单项选择题

After winning a big game, athletes are often asked how they feel. Usually athletes say how (1) it is to win this big game. On the contrary, the fact is that losing a big game, or in my case, all the games, can be even harder.

From the spectators’ point of view, last year’s basketball (2) for my high school team was nothing (3) of an embarrassment. And (4) 0 and 20 is certainly nothing to be proud of, that season had a bigger impact on me than any other. As a team captain, I knew it probably wouldn’t be the (5) year, but did I ever think we would lose every game Of course not. Since six of our top players had graduated, it was clear that we were a (n) (6) team who would struggle. The struggle began earlier than expected, (7) , as our team center was suspended (禁赛) for the season, and two key members decided to (8) for some reason. At this point, dropping out probably passed through every player’s mind, but in the end, we all stuck if out, (9) to work still harder.

Then there came a time when even our (10) and given up on us. Personally, I felt like it was (11) worthwhile giving my all. I thought, if even the coach doesn’t believe in us, why should I But just as my hope began to (12) , a teammate called a meeting. He said," Nobody thinks we are going to win, but, as teammates and friends, we (13) it to each other to go all out every game. "

It was that moment that (14) me how to be a leader. It hit me that I certainly didn’t (15) the role. As a leader you can never quit (16) the team who looks up to you. It is one (17) to be named captain, feel great and go through the motions, but it is quite another to be a real captain and make sure everyone realizes their full (18) all the time.

I am sure it is great to go through without losing and bringing home awards. But in all honesty, I (19) the fact that my team lost every game last year. It may not help me to become a better basketball player, but it already has made me a better leader, and (20)

1().

A.exciting

B.pleasant

C.tough

D.significant

材料分析题