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2025-03-24 01:45本頁(yè)面
【正文】 四個(gè)行程，兩個(gè)離缸蓋最近，另外兩個(gè)離缸蓋距離最遠(yuǎn)?；钊谶@個(gè)過(guò)程中的運(yùn)動(dòng)，使得燃料和空氣進(jìn)入燃燒室混合。當(dāng)活塞上行到最高點(diǎn)時(shí)，燃燒室的體積達(dá)到最小，火花塞就會(huì)點(diǎn)燃混合氣體，燃燒產(chǎn)生的膨脹壓力會(huì)作用在活塞上，使活塞遠(yuǎn)離缸蓋，這就是第三個(gè)行程。 發(fā)動(dòng)機(jī)的效率會(huì)受到很多因素的限制，例如 冷卻損失以及摩擦損失?，F(xiàn)在發(fā)動(dòng)機(jī)的壓縮比一般在 810 之間。現(xiàn)在，好的發(fā)動(dòng)機(jī)的效率在 20％ 25％，也就是說(shuō)，只有這部分能量真正用于產(chǎn)生機(jī)械能量。大多數(shù)柴油機(jī)都是采用四沖程，但卻與奧托式四沖程不一樣。其次，在壓縮時(shí)，活塞將空氣壓縮到比先前小很多倍的體積，并在這個(gè)過(guò)程中使空氣的溫度達(dá)到 440℃（等同于華氏 820℉）。 一些發(fā)動(dòng)機(jī)上設(shè)有電子噴射輔助系統(tǒng)，在發(fā)動(dòng)機(jī)發(fā)動(dòng)直到加熱完成期間進(jìn)行燃油噴射。第四個(gè)沖程跟奧托式四沖程發(fā)動(dòng)機(jī)一樣，都是排氣過(guò)程。事實(shí)上，現(xiàn)在發(fā)動(dòng)機(jī)中，基本的效率都不會(huì)超過(guò) 40％。但是也有一些柴油機(jī)的轉(zhuǎn)速達(dá)到了 2021 轉(zhuǎn)每分鐘。 好的設(shè)計(jì)一般采用奧托式循環(huán)或者二沖程的方式來(lái)代替四沖程的方式。 二沖程的有點(diǎn)在于，縮短了燃料壓縮的時(shí)間，并且減少了燃料的浪費(fèi)以及用半個(gè)沖程完成了四沖程發(fā)動(dòng)機(jī)的一個(gè)壓縮沖程。 在二沖程循環(huán)中，燃料和空氣的混合氣體在活塞在汽缸中下行時(shí)進(jìn)入曲軸箱。這是活塞在燃?xì)鈮毫Φ淖饔孟孪滦?，廢棄就會(huì)從排氣口由汽缸內(nèi)向外排出去。在這種發(fā)動(dòng)機(jī)上，活塞和汽缸被一個(gè)在橢圓形燃燒室里旋轉(zhuǎn)的三角轉(zhuǎn)子所代替。 混合氣體通過(guò)轉(zhuǎn)子的旋轉(zhuǎn)得到壓縮，最后被火花塞點(diǎn)燃。循環(huán)過(guò)程中，轉(zhuǎn)子 的旋轉(zhuǎn)一周，會(huì)出有三個(gè)沖程，而且在轉(zhuǎn)子的正反兩面產(chǎn)生壓力。另外，它簡(jiǎn)單的結(jié)構(gòu)使得生產(chǎn)成本低， 冷卻系統(tǒng)質(zhì)量輕，另外它的重心低，使得他的安全性得到了增加。很多美國(guó)的汽車制造商都很看好這個(gè)項(xiàng)目。日本的汽車制造商 — 馬自達(dá)，繼續(xù)了改善轉(zhuǎn)子發(fā)動(dòng)機(jī)燃油經(jīng)濟(jì)性的設(shè)計(jì)和研發(fā)。 它的特點(diǎn)在于在一個(gè)汽缸中有兩個(gè)燃燒室，當(dāng)沖入的混合氣體過(guò)多是，備用燃燒室就會(huì)將多余的混合氣體儲(chǔ)存起來(lái)。這樣最高火焰溫度 就會(huì)比較合適 ，從而很好的限制 NOx 化合物的生成量以及 CO 和 HC 的排放量。 Rocket. The Ottocycle engine, named after its inventor, the German technician Nikolaus August Otto, is the familiar gasoline engine used in automobiles and airplanes。 that is, in a plete power cycle, its pistons make four strokes, two toward the head (closed head) of the cylinder and two away from the head. During the first stroke of the cycle, the piston moves away from the cylinder head while simultaneously the intake valve is opened. The motion of the piston during this stroke sucks a quantity of a fuel and air mixture into the bustion chamber. During the next stroke, the piston moves toward the cylinder head and presses the fuel mixture in the bustion chamber. At the moment when the piston reaches the end of this stroke and the volume of the bustion chamber is at a minimum, the fuel mixture is ignited by the spark plug and burns, expanding and exerting a pressure on the piston, which is then driven away from the cylinder head in the third stroke. During the final stroke, the exhaust valve is opened and the piston moves toward the cylinder head, driving the exhaust gases out of the bustion chamber and leaving the cylinder ready to repeat the cycle. The efficiency of a modern Ottocycle engine is limited by a number of factors, including losses by cooling and by friction. In general, the efficiency of such engines is determined by the pression ratio of the engine. The pression ratio (the ratio between the maximum and minimum volumes of the bustion chamber) is usually about 8 to 1 or 10 to 1 in most modern Ottocycle engines. Higher pression ratios, up to about 15 to 1, with a resulting increase of efficiency, are possible with the use of highoctane antiknock fuels. The efficiencies of good modern Ottocycle engines range between 20 and 25 percent— in other words, only this percentage of the heat energy of the fuel is transformed into mechanical energy Theoretically, the diesel cycle differs from the Otto cycle in that bustion takes place at constant volume rather than at constant pressure. Most diesels are also fourstroke engines but they operate differently than the fourstroke Ottocycle engines. The first, or suction, stroke draws air, but no fuel, into the bustion chamber through an intake valve. On the
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