Prime Mover
原动机
电气英语
The source for power is most often a generator set driven by a combustion engine which is fueled with diesel or heavy fuel oil. Occasionally one can find gas engines , and also gas turbines, steam turbines or combined cycle turbines, especially for higher power levels, in light high-speed vessels, or where gas is a cheap alternative (e.g. waste product in oil production, boil-off in LNG carriers, etc.).
译文：动力源通常来源于内燃机驱动的发电机组，该内燃机以柴油或重质燃油为燃料。偶尔，人们也会发现燃气发动机，以及燃气轮机、蒸汽轮机或联合循环涡轮机，尤其是在轻型高速船舶上，或在天然气是廉价替代品的地方（例如，石油生产中的废品、液化天然气运输船中的汽化物等）。
In a diesel-electric propulsion system, the diesel engines are normally medium to high-speed engines, with lower weight and costs than similar rated low speed engines that are used for direct mechanical propulsion. Availability to the power plant is of high concern, and in a diesel electric system with a number of diesel engines in a redundant network; this means high reliability but also sophisticated diagnostics and short repair times.
译文：在柴油-电力推进系统中，柴油发动机通常为中高速发动机，与用于直接机械推进的类似额定低速发动机相比，其重量和成本更低。发电厂的可用性备受关注，在柴油电力系统中，冗余网络中有多台柴油发动机；这意味着高可靠性，但也意味着诊断较复杂和维修时间短。
The combustion engines are continuously being developed for higher efficiency and reduced emissions, and at present, a medium speed diesel engine has a fuel consumption of less than 200g per produced kWh at the optimum operation point as seen in Fig.1-1. Even though this is regarded to be a high utilization factor of fuel, it represents only about 40% of the energy in the fuel, the rest of the energy being removed by the exhaust or heat dissipation.
译文：内燃机正在不断开发以提高效率和减少排放，目前，在图1-1所示的最佳运行点，中速柴油发动机每生产千瓦时的燃料消耗量小于200g。尽管这被认为是一个高燃料利用率，但它仅代表燃料中约40%的能量被利用，其余的能量则通过排气或散热被浪费了。
Fig.1-1 Example fuel consumption for a medium speed diesel engine
图1-1中速柴油发动机的燃油消耗示例
Moreover, the efficiency drops fast as the load becomes lower than 50% of MCR (Max Continuous Rating). At this working condition, the combustion is inefficient, with high NOx and SOx content, and with a high degree of soothing which increases the need for maintenance. In a diesel electric system with several diesel engines it is hence an aim to keep the diesel engines loaded at their optimum operating conditions by starting and stopping generator sets dependent on the load, with an aim to keep the average loading of each running diesel engine closest possible to its optimum load point.
译文：此外，当负载低于MCR（最大连续额定值）的50%时，效率迅速下降。在这种工况下，燃烧效率低，NOx和SOx含量高，且具有高度的舒缓作用，这增加了维护成本。因此，在具有多个柴油发动机的柴油电气系统中，其目的是通过根据负载启动和停止发电机组，使柴油发动机保持在其最佳运行条件下，以使每个运行柴油发动机的平均负载尽可能接近其最佳负载点。
01
New Words and Expressions
combustion [kəmˈbʌst∫ən] n. 燃烧，发火，点火
diesel[ˈdiːzəl] n. 柴油机，内燃机
turbine[ˈtəːbin,-bain] n.（涡）轮机，叶轮机，汽轮机，透平机
redundant[riˈdʌndənt] adj. 过多的，冗余的，冗长的（文章等）；累赘的
diagnostics[ˌdaiəgˈnɔstiks] n. 征候，特征
sophisticated[səˈfistikeitid] adj. 复杂的，尖端的，高级的；微妙的
emission[iˈmi∫ən] n. 发出，发射，射出，放射；传播
utilization[ˌjuːtilaiˈzei∫ən] n. 利用；效用
dissipation [ˌdisiˈpei∫ən] n. 消散，分散
02
Notes
（1）“…as seen in Fig…” as（表示方式、程度、情况等）如同；像；按照
例如：
1）I work as others do.
我跟别人一样工作。
2）I remember it as it were but yesterday.
我想起这件事就仿佛是昨天发生的一样。
3）Parks are to the city as lungs are to the body.
公园对于都市来说就如同肺部对于身体一样。
“as”在英语里是一个比较常见、用法繁多的词。本课 “as” 的用法比较集中，为方便学习，特把几种基本用法归纳如下:
1）引出同位语，常与 “such” 连用
We call such metals as copper and silver good conductors.
我们称这些金属，例如铜和银，为良导体。
There are different forms of energy, such as heat energy, sound energy and electric energy.
有各种不同的能，例如热能、声能和电能。
2）用做介词
Electronics is regarded as an applied science.
电子学被认为是一门应用科学。
Electricity is especially convenient as a source of mechanical power.
电作为机械的动力源特别方便。
3）用做关系代词或关系副词，引出定语从句
This is the same material as is used in the diode.
这和用在二极管中的材料是一样的。
I want to get such a tool as he is using.
我想得到一把像他正在使用的那种工具。
He repaired the machine in the same way as we did.（这句“in the same way”所代替的是介词短语“as”，而该介词短语在主句中作状语，所以“as”作关系副词。）他采取和我们同样的方法修理机器。
4）用做从属连词，引出时间、原因、方式、比较等状语从句
As the piston moves down, the pressure in the cylinder decreases.（时间状语从句）
当活塞下移时，汽缸里的压力就减小。
As the question is of importance, we should tell the chief engineer at once.（原因状语从句）
因为这个问题很重要，所以我们必须立即告诉轮机长。
Light waves are different in frequency just as sound waves are.（方式状语从句）
正如声波一样，光波也有不同的频率。
This generator is as effective as that one (is).（比较状语从句）
这台发电机和那台发电机效率一样。
（2）“…to its optimum load point” to（表示范围、程度）到，达到；……到，……得。
例如：
1）The room was hot to suffocation.
房间热得闷人。
2）to his name be it said
（虽说是敌人然而）真是名不虚传。
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