2014中石油職稱英語考試新版通用選讀文章6

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　6.Carbon-based Alternative 碳基替代燃料

　　1.Although recent years have seen substantial reductions in noxious pollutants from individual motor vehicles, the number of such vehicles has been steadily increasing. Consequently, more than 100 cities in the United States still have levels of carbon monoxide, particulate matter, and ozone (generated by photochemical reactions with hydrocarbons from vehicle exhaust) that exceed legally established limits. There is a growing realization that the only effective way to achieve further reductions in vehicle emissions-short of a massive shift away from the private automobile- is to replace conventional diesel fuel and gasoline with cleaner-burning fuels such as compressed natural gas. liquefied petroleum gas, ethanol, or methanol.

　　1、盡管近幾年來私人機(jī)動(dòng)車輛排放的有害污染物已有相當(dāng)程度的減少，但這類車輛的數(shù)量卻仍在穩(wěn)定地增長(zhǎng)。因此，美國(guó)100多個(gè)城市仍然存在著超過法律限定的一氧化碳、懸浮顆粒物和臭氧(由于車輛排出氣體中碳?xì)浠衔锝?jīng)過光化反應(yīng)產(chǎn)生)。人們逐漸認(rèn)識(shí)到實(shí)現(xiàn)車輛尾氣排放更進(jìn)一步減少的唯一有效方法--大規(guī)模消減私人小汽車除外--是用燃燒更為清潔的燃料，如壓縮天然氣、液化石油氣、乙醇或甲醇代替?zhèn)鹘y(tǒng)的柴油和汽油。

　　2.All of these alternatives are carbon-based fuels whose molecules are smaller and simpler than those of gasoline. These molecules burn more cleanly than gasoline, in part because they have fewer, if any, carbon-carbon bonds and the hydrocarbons they do emit are less likely to generate ozone. The combustion of larger molecules, which have multiple carbon-carbon bonds involves a more complex series of reactions. These reactions increase the probability of incomplete combustion and are more likely to release uncombusted and photochemically active hydrocarbon compounds into the atmosphere. On the other hand, alternative fuels do have drawbacks. Compressed natural gas would require that vehicles have set of heavy fuel tanks- a serious liability in terms of performance and fuel efficiency-and liquefied petroleum gas faces fundamental limits on supply.

　　2、所有這些替代物都是碳基燃料，它的分子要比汽油的小而簡(jiǎn)單。這些分子要比汽油燃燒得更為清潔，部分是因?yàn)樗麄兲?碳鍵較少，而且即使會(huì)釋放出碳?xì)浠衔?，也不太可能?huì)成為臭氧。較大分子的燃燒，由于它們具有多重碳-碳，伴隨著更為復(fù)雜的一系列反應(yīng)。這些反應(yīng)增加了不完全燃燒得可能性并且易于放出未燃燒的、易起光化反應(yīng)的碳?xì)浠衔镝尫诺酱髿庵?。從另一方面來說，替代燃料也有缺點(diǎn)。壓縮天然氣要求車輛有一套沉重的燃料箱--在外觀和燃料效率方面有嚴(yán)重的不利之處--并且液化石油氣面臨著基本的供應(yīng)量限制。

　　3.Ethanol and methanol, on the other hand, have important advantages over other carbon-based alternative fuels: they have higher energy content per volume and would require minimal changes in the existing network for distributing motor fuel. Ethanol is commonly used as a gasoline supplement, but it is currently about twice as expensive as methanol, the low cost of which is one of its attractive features. Methanol’s most attractive feature, however, is that it can reduce by about 90 percent the vehicle emissions that form ozone, the most serious urban air pollutant.

　　3、從另一個(gè)方面來看，乙醇和甲醇具有由于其他碳基替代燃料的重要優(yōu)勢(shì)：它們?cè)趩挝蝗萘肯掠懈叩哪芰亢?，并且只需要在現(xiàn)存的配送燃料的網(wǎng)絡(luò)中做很小的變更。乙醇通常用作汽油的補(bǔ)充燃料，但它現(xiàn)在的價(jià)格是甲醇的兩倍，后者的低成本是具有吸引力的特征之一。不過，甲醇最吸引人的特征是它能夠?qū)⑿纬沙粞醯能囕v尾氣這一嚴(yán)重的城市空氣污染減少90%。

　　4.Like any alternative fuel, methanol has its critics. Yet much of the criticism is based on the use of "gasoline clone" vehicles that do not incorporate even the simplest design improvements that are made possible with the use of methanol. It is true, for example, that a given volume of methanol provides only about one-half of the energy that gasoline and diesel fuel do; other things being equal, the fuel tank would have to be somewhat larger and heavier. However, since melhanol-fueled vehicles could be designed to be much more efficient than "gasoline clone" vehicles fueled with methanol they would need comparatively less fuel. Vehicles incorporating only the simplest of the engine improvements that methanol makes feasible would still contribute to an immediate lessening of urban air pollution.

　　4、像任何替代燃料一樣，甲醇也有對(duì)其的批評(píng)意見。然而，大部分批評(píng)都是針對(duì)“克隆汽油車”的，這些車并沒有為使用甲醇而做出哪怕最簡(jiǎn)單的設(shè)計(jì)上的改進(jìn)。這些批評(píng)意見是對(duì)的，舉例來說，一定容量的甲醇只能供給汽油和柴油燃料所能供給的能力的一伴。在其他條件相同時(shí)，不得不將車輛的燃料箱做的較大和較沉些。然而，因?yàn)闊状嫉能囕v可以被設(shè)計(jì)成比燒甲醇的“克隆汽油車”更有效率的車輛，所以它們只需要比較少的燃料。車輛只要包含為使用甲醇而作的發(fā)動(dòng)機(jī)方面最簡(jiǎn)單的改進(jìn)，也將為迅速減輕城市空氣污染做出貢獻(xiàn)。