英國學(xué)生科學(xué)讀本 Lesson 94 一副風(fēng)箱(2)

for when you shut the bellows, the valve cannot close the air-hole because of your finger, and most of the air then escapes through this hole instead of going out through the nozzle.

因?yàn)? 當(dāng)你關(guān)閉風(fēng)箱把手時, 你的手指使得閥門無法關(guān)閉空氣進(jìn)出的圓孔, 那么大部分空氣也就通過這個孔逃了出去而不是通過噴嘴透出。

Every one knows that we use the bellows to make the fire burn more brightly. But how do they do this ? It is by causing more air to pass among the hot coals. Air is a mixture of several gases, and one of these gases—oxygen —is necessary for making the coals burn.

大家都知道, 我們使用風(fēng)箱來增強(qiáng)火焰的燃燒。然而, 這其中的原理是什么呢? 因?yàn)槲覀兇偈垢嗟目諝獯┻^了炙熱的火炭?？諝馐且环N混合氣體, 而這其中的氧氣則是煤炭燃燒的關(guān)鍵所在。

If your mother has no bellows, what does she do when she wants the fire to burn more brightly ? She opens either the door or the window, to let more air into the room, or she stirs the fire with the poker, to let the air pass freely among the coals.

如果你的母親沒有風(fēng)箱, 那么當(dāng)她希望讓火焰更旺時會怎么做呢? 她會打開門或者窗戶, 使得房間中的空氣更加充沛;或者, 她會使用撥火棍來攪動火堆, 促使空氣能夠大量穿過火炭。

Have you ever watched a blacksmith working at his forge ? He needs a very hot fire to heat the iron bars which he makes into horse-shoes and many other things; and he could not have this without using bellows. If you look carefully, you will see that there is a difference between the bellows of the blacksmith's forge and those which you use for your kitchen fire. The air comes out of your kitchen bellows in puffs, but it comes out of the blacksmith's bellows in a steady stream.

你有沒有看到過鐵匠在鍛造工廠的工作情景? 要制造馬蹄鐵或者其他諸多鐵制產(chǎn)品, 需要極為炎熱的火焰來加熱鐵條, 而風(fēng)箱就必不可少。如果你仔細(xì)觀察的話, 就會發(fā)現(xiàn), 鍛造工廠所用的風(fēng)箱與你家廚房里的有所不同。廚房風(fēng)箱吹出的風(fēng)一陣一陣, 而鐵匠的風(fēng)箱卻能持續(xù)不斷地吹出風(fēng)來。

If we were to take a common pair of bellows, and hinge the lower board of another pair to their under side, in the same way as the two boards are hinged together, we should then have bellows somewhat like those of the blacksmith. The middle board is fixed; the under board is worked by a handle; and the top board is free to rise when air is forced in.

如果我們拿起一副日常家用的風(fēng)箱, 將它上方的木片與另一幅風(fēng)箱的下方木片固定在一起——就好似一副風(fēng)箱中兩塊木片的固定方式一樣——就可以得到一個類似于鐵匠使用的風(fēng)箱了。中間的木片固定不動;下方的木片通過把手進(jìn)行移動, 而上方的木片則能夠在空氣流入時自由抬起。

When the blacksmith works his bellows, air is sent from the lower chamber into the upper chamber in puffs, and is then driven out through the nozzle by the weight of the uppermost board. But air can be sent in through the valve faster than it can escape through the nozzle, and before the first puff is forced out, more air has been received from the chamber below. Thus there is a steady stream of air sent through the fire, instead of a series of puffs.

當(dāng)鐵匠使用風(fēng)箱時, 空氣通過下氣室一陣一陣地進(jìn)入上氣室;然后, 在最上層木片的重力作用下通過噴嘴透出。然而, 通過閥門流入的空氣比噴嘴流出的空氣數(shù)量更多, 當(dāng)?shù)谝魂嚳諝馍形赐赋鰰r, 下氣室又送來了更多空氣。結(jié)果, 燃燒的火焰就能不停地得到新鮮空氣。

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