considered to threaten ship safety).另一方面，不依赖于实际操作模式的状态监控系统和评估系统会选择柴油机保护模式（当这种选择不会危及船舶安全的时候）。
The fruit of MAN B&W Diesel's and Sulzer's R&D is now available commercially, their respective electronically-controlled ME and RT- flex engines being offered alongside the conventional models and increasingly specified for a wide range of tonnage. 现在，MAN B&W和Sulzer的开发研究成果已经开始商业化，它们各自的电子控制的ME和RT- flex机型和传统机型一起使用，越来越多地用在各种吨位的船上。
Research and development by Mitsubishi, the third force in low speed engines, has successfully sought weight reduction and enhanced compactness while retaining the performance and reliability demanded by the market. 低速柴油机的第三方力量——三菱的研究已经成功发现市场需要柴油机重量降低和增加紧凑性的同时继续保持良好的性能和可靠性The Japanese designer's current UEC-LS type engines yield a specific power output of around three times that of the original UE series of the mid-1950s. 日本的设计者现在设计的UEC-LS 型柴油机所产生的功率系数大约是原来20世纪50年代所产UE 系列柴油机的三倍。The specific engine weight has been reduced by around 30 per cent over that period and the engine length in relation to power output has been shortened by one-third. Mitsubishi strengthened its long relationship as a Sulzer licensee in 2002 by forging a joint venture with the Wartsila Corporation to develop a new 500 mm bore design to be offered in two versions: a 'mechanical' RTA50C and an 'electronic' RT-flex 50C. 柴油机的比重已经比那个时期大约下降30%，与功率输出相关的长度已经下降了三分之一。由于Sulzer执照持有者在2002年与Wartsila公司合资发展新的500mm缸径的柴油机，这种柴油机有两种形式：一种是机械式的RTA50C，一种是电子式的RT-flex 50C，所以三菱公司加强了它的长期关系
LESSON 12
Gas-Diesel And 2 Dual-Fuel Engines
气体—柴油和双燃料发动机
Growing opportunities for dual-fuel and gas-diesel engines in land and marine power markets have stimulated designs from leading medium speed and low speed engine builders. 对于双燃料和气体—柴油发动机来说，在陆地和海洋动力的市场中，不断增加的机会激励了设计重要的中速和低速发动机的制造商。Development is driven by the increasing availability of gaseous fuels, the much lower level of noxious exhaust emissions associated with such fuels, reduced maintenance and longer intervals between overhauls for power plant. 使用气体燃料的不断增加驱动了它们的发展，相关燃料的有毒排放物越少，那么维修就会减少并且动力装置的大修间隔就会变长。
Valuable breakthroughs in mainstream markets have been made since 2000 with the specification of LNG-burning engines for propelling a small Norwegian double-ended ferry, offshore supply vessels and a 75 000 cube LNG carrier.在主流市场里，有价值的突破性进展自从2000年就已经开始，特别是燃烧液化天然气的发动机用来推动小型的挪威首尾同型渡船，近海供应船和75 000立方的液化天然气船。
Natural gas is well established as a major contributor to the world's energy needs. 天然气已经被充分证明是世界能源需求的一个主要贡献方。It is derived from the raw gas from onshore and offshore fields as the dry, light fraction and mainly comprises methane and some ethane.它是来自于陆地和近海区域的原料气体，干燥，轻馏分并且主要由甲烷和一些乙烷组成。 It is
available directly at the gas field itself, in pipeline systems, condensed into liquid as LNG or compressed as CNG.它可以直接被气田区域本身使用，在管路系统里被冷凝成液体作为液化天然气或者压缩成压缩天然气。
Operation on natural gas results in very low emissions thanks to the clean-burning properties of the fuel and its low content of pollutants. 对天然气的使用会导致非常低的排放物，由于燃料干净的燃烧特性以及低含量的污染物。Methane, the main constituent, is the most efficient hydrocarbon fuel in terms of energy content per amount of carbon; operation on natural gas accordingly reduces emissions of another key pollutant--carbon dioxide--by over 20 per cent compared with operation on diesel fuel. 在热碳比方面，主要的组成成分甲烷是最有效的碳氢化合物燃料；使用天然气会相应的降低另外一种主要污染物的排放—二氧化碳—与使用柴油相比会降低20%。Natural gas has very good combustion characteristics in an engine and, because it is lighter than air and has a high ignition temperature, is also a very safe fuel. 天然气在发动机里有非常良好的燃烧特性，因为它比空气轻并有一个高的发火温度，同时也是一种非常安全的燃料。
Wartsila's dual-fuel (DF) four-stroke engines can be run in either gas mode or liquid-fuelled diesel mode. 瓦锡兰双燃料四冲程发动机可以在气体模式或者液体燃料柴油模式下工作。In gas mode the engines work according to the lean-burn Otto principle, with a lean premixed air-gas mixture in the combustion chamber.(Lean burn means the mixture of air and gas in the cylinder has more air than is needed for complete combustion, reducing peak temperatures). 在气体模式下发动机根据稀薄燃烧的奥拓原理工作，在燃烧室里有稀薄的预先混合的空气—天然气混合物。（稀薄燃烧表示为了燃烧完全，降低最高燃烧温度，气缸里空气和天然气的混合物中的空气比需要的空气量更多。 Less NOx is produced and efficiency increases during leaner combustion because of the higher compression ratio and optimized injection timing. A lean mixture is also necessary to avoid knocking (self-ignition).在稀薄燃烧过程中，由于高的压缩比和优化的喷射定时，氮氧化物的产生量更少，效率变高。稀薄混合物也需要避免敲缸（自燃）。
The gas is fed into the cylinder in the air inlet channel during the intake stroke. 在吸气行程过程中。天然气通过空气道供给到气缸中。Instead of a spark plug for ignition--normally used in lean-burn gas engines--the lean air-gas mixture is ignited by a small amount of diesel fuel injected into the combustion chamber. 在正常情况下，稀薄燃烧的天然气发动机使用火花塞点火，但是稀薄的空气—天然气混合物是通过喷射进入燃烧室内少量的柴油点燃的。This high energy source ensures reliable and powerful ignition of the mixture, which is needed when running with a high specific cylinder output and lean air-gas mixture. 这种高的能量源保证混合气体被可靠并且强力的点燃，对于气缸输出与稀薄空气—天然气混合物之间的高比值发动机是必须的。To secure low NOx emissions it is essential that the amount of injected diesel fuel is very small. The Wartsila DF engines therefore use a 'micro-pilot' injection, with less than 1 percent diesel fuel injected at nominal load, to achieve NOx emissions approximately one-tenth those of a standard diesel engine.为了获得低的氮氧化物排放，喷射的柴油必须是少量的。因此瓦锡兰的DF型发动机使用“微量控制”喷射，喷入低于标准柴油机中正常载荷下消耗柴油的1%，获得大约十分之一的氮氧化物排放量。
When the DF engine is running in gas mode with a pre-mixed air-gas mixture the combustion must be closely controlled to prevent knocking and misfiring. 当DF型柴油机使用预先混合的空气—天然气混合物在气体模式下工作时，必须精密控制来防止敲缸和发火失败。The only reliable way to effect this, says Wartsila, is to use fully electronic control of both the pilot fuel injection and the gas admission on every cylinder head. 瓦锡兰公司说，为了实现这一点，只有
一个可靠的方法就是在每个气缸头上使用全电子控制的燃料预先喷射和天然气输入。The global air-fuel ratio is controlled by a waste gate valve, which allows some of the exhaust gases to bypass the turbine of the turbocharger. This ensures that the ratio is of the correct value independent of changing ambient conditions, such as the temperature.总的空气—燃料比是通过一个废气闸阀，允许一些排气经过涡轮增压器的涡轮机旁通。这样保证比率是一个准确的数值，不依赖于环境条件的变化，比如温度。
The quantity and timing of the injected pilot fuel are adjusted individually together with the cylinder-specific and global air-fuel ratio to keep every cylinder at the correct operating point and within the operating window between the knock and misfire limits. 引燃燃料的数量和定时是单独调整，与单位气缸和总的空气—燃料比一起保证每个气缸在合适的工作点上并且位于敲缸和发火失败的工作区间之间。This is the key factor for securing reliable operation in gas mode, automatically tuning the engine according to varying conditions, Wartsila explains.瓦锡兰解释到，这是保证在气体模式下可靠运行的关键因素，根据变化的情况自动地对发动机调整。 In diesel mode the engine works according to the normal diesel concept using a traditional jerk pump fuel injection system: diesel fuel is injected at high pressure into the combustion chamber just before the top dead centre.在柴油模式下，根据正常的柴油观点，柴油机使用一个传统的高压燃油喷射泵的燃油喷射系统工作：柴油在上止点前被高压喷射进入燃烧室。 Gas admission is de-activated but the pilot fuel remains activated to ensure reliable pilot ignition when the engine is transferred to gas operation.当发动机转变到气体模式运行时，进入的气体是没有活性的，但是引燃燃料能够保持能量确保可靠的引燃。
The gas pressure in the engine is less than 4 bars at full load, making a single-wall pipe design acceptable if the engine room is arranged with proper ventilation and gas detectors. 假如机舱布置有合理的通风和气体检测器，发动机内的气体压力在全负荷下低于4巴，就可以设计制作一个值得接受的单壁管道。The gas valve on every cylinder head is a simple and robust, electronically-controlled solenoid valve, promising high reliability with long maintenance intervals.每个气缸头上的气阀是简单和坚固的，是一个电子控制式的电磁阀，可以确保很长维修间隔内的可靠性高。
The pilot fuel system is a common rail system with one engine-mounted high pressure pump supplying the pilot fuel to every injection valve at a constant pressure of 900 bars. Due to the high pressure a double-walled supply system is used with leak fuel detection and alarms.引燃燃料系统是在一个普遍的共轨系统上有一个机器，这个机器上安装有高压油泵以900巴的恒定压力供给引燃燃油到每个喷射阀。由于压力高，使用一个双壁的带有燃料泄漏检测和报警的供给系统。 The injection valve is of twin-needle design, with the pilot fuel needle electronically controlled by the engine control system.喷射阀是双针阀设计，通过柴油机的控制系统对引燃燃料的针阀进行电子控制。 It is important that the injection system can reliably handle the small amount of pilot fuel with minimum cycle-to-cycle variation. The main needle design is a conventional system in which mechanically-controlled pumps control the injection.非常重要的是喷射系统能够在最低限度的循环变化下，可靠的处理少量的引燃燃料。主要的针阀结构是一个常规的系统，在系统内由机械装置控制的泵来控制喷射。
Other main components and systems are similar to designs well proven over a decade on Wartsila standard diesel engines, further underwriting high reliability of the dual-fuel engines.其它的主要部件和系统与过去十年间瓦锡兰经过广泛设计验证的柴油机相似，从而进一步保证双燃料发动机的可靠性。
LESSON 13
Exhaust Emissions And Control 废气排放和控
制
Marine engine designers in recent years have had to address the challenge of tightening controls on noxious exhaust gas emissions imposed by regional, national and international authorities responding to concern over atmospheric pollution.近些年船用柴油机设计者不得不集中精力应对严格控制有毒废气排放物的挑战，这些控制是各地区、国家和世界的权力机构为防止大气污染所提出的强制要求。
Exhaust gas emissions from marine diesel engines largely comprise nitrogen, oxygen, carbon dioxide and water vapor, with smaller quantities of carbon monoxide, oxides of sulphur and nitrogen, partially reacted and non-combusted hydrocarbons and particulate material 船用柴油机的废气排放物的组成主要由有氮、氧、二氧化碳和水蒸气，少量的一氧化碳、硫氧化物和氮氧化物，部分反应但没有燃烧的碳氢化合物和颗粒物质。
Nitrogen oxides (NOx)--generated thermally from nitrogen and oxygen at high combustion temperatures in the cylinder--are of special concern since they are believed to be carcinogenic and contribute to photochemical smog formation over cities and acid rain (and hence excess acidification of the soil). 氮氧化物是由氮和氧在汽缸中高温条件下热反应所生成的，由于它们被认为有致癌性、会导致城市上空光化学烟雾的I形成和酸雨（使土壤过度酸化），所以被特别的关注。Internal combustion engines primarily generate nitrogen oxide but less than 10 per cent of that oxidizes to nitrogen dioxide the moment it escapes as exhaust gas.内燃机主要产生一氧化氮，但是当废气被排出去的时候仅有不到10%的一氧化氮被氧化成二氧化氮。
Sulphur oxides (SOx)--produced by oxidation of the sulphur in the fuel--have an unpleasant odor, irritate the mucus membrane and are a major source of acid rain (reacting with water to form sulphurous acid). 硫氧化物由燃油中的硫氧化而来，有难闻的气味，刺激黏膜还是酸雨的主要来源（与水反应形成硫酸）Acid deposition is a trans-boundary pollution problem: once emitted, SOx can be carried over hundreds of miles in the atmosphere before being deposited in lakes and streams, reducing their alkalinity.酸的沉降是一个跨地域的污染问题，一旦产生后，硫氧化物可以被空气携带几百英里，然后沉降到湖里河里，降低它们的碱度。
Sulphur deposition can also lead to increased sulphate levels in soils, fostering the formation of insoluble aluminum phosphates which can cause a phosphorous deficiency. 硫的沉积导致土壤中硫酸盐含量提高，促进了不溶性磷酸铝的形成，这样就导致土壤中磷酸盐的缺乏。Groundwater acidification has been observed in many areas of Europe; this can lead to corrosion of drinking water supply systems and health hazards due to dissolved metals in those systems. 在欧洲的许多地区已经发现地下水的酸化，导致饮用水供应系统的腐蚀，由于金属溶解在系统里又对健康造成伤害。Forest soils can also become contaminated with higher than normal levels of toxic metals, and historic buildings and monuments damaged.有毒金属的含量超过正常水平，森林的土壤也会被污染。历史建筑和遗迹也会遭到破坏。
Hydrocarbons (HC)--created by the incomplete combustion of fuel and lube oil, and the evaporation of fuel--have an unpleasant odor, are partially carcinogenic, smog forming and irritate the mucus membrane (emissions, however, are typically low for modern diesel engines.)燃油和润滑油的不完全燃烧以及燃油蒸汽生成碳氢化合物，它有难闻的气味、部分致癌性，能形成油
雾，刺激黏膜（现代柴油机的排放物低）
Carbon monoxide (CO)--resulting from incomplete combustion due to a local shortage of air and the dissociation of carbon dioxide--is highly toxic but only in high concentrations.局部缺少空气所造成的不完全燃烧和二氧化碳的分解都会产生一氧化碳，浓度较高时一氧化碳有高毒性。
Particulate matter (PM) is a complex mixture of inorganic and organic compounds resulting from incomplete combustion, partly unburned lube oil, thermal splitting of HC from the fuel and lube oil, ash in the fuel and lube oil, sulphates and water. 颗粒物质是不完全燃烧的无机化合物和有机化合物的混合物，其中包括部分未燃烧的润滑油，燃油和润滑油碳氢化合物的热分裂，燃油和润滑油中的灰分，硫酸盐和水。More than half of the total particulate mass is soot (inorganic carbonaceous particles), whose visible evidence is smoke. 颗粒物质一半以上是烟灰（无机碳颗粒），能够看见的证据是烟。Soot particles (unburned elemental carbon) are not themselves toxic but they can cause the build-up of aqueous hydrocarbons, and some of them are believed to be carcinogens. 灰颗粒（未燃烧的碳）本身没有毒性，但是它们能够形成水溶性的碳氢化合物，这多少被认为有致癌性。Particulates constitute no more than around 0.003 per cent of the engine exhaust gases.颗粒物组成大约不超过柴油机排气的0.003%。
Noxious emissions amount to 0.25-0.4 percent by volume of the exhaust gas, depending on the amount of sulphur in the fuel and its lower heat value, and the engine type, speed and efficiency. 有毒排放物的量是废气排放量的0.25-0.4%，主要取决于燃油里的含硫量、燃油的低热值，还有柴油机的类型、转速和效率。Some idea of the actual pollutants generated is provided by MAN B&W Diesel, which cites an 18 V 48/60 medium speed engine in NOx-optimized form running at full load on a typical heavy fuel oil with 4 per cent sulphur content. MAN B&W 柴油机厂提供了实际实际污染物的产量，数据来源于一台18 V 48/60型带有优化氮化物形成的中速柴油机，全负荷燃烧含硫量为4%的典型重油。A total of approximately 460 kg of harmful compounds are emitted per hour out of around 136 tones of exhaust gas mass per hour. 每小时排放接近460 kg 的有害化合物，大约136 t的废气。Of the 0.35 per cent of the exhaust gas formed by pollutants, NOx contributes 0.17 per cent, sulphur dioxide 0.15 per cent, hydrocarbons 0.02 percent, carbon monoxide 0.007 per cent and soot/ash 0.003 per cent.废气的0.35%由污染物质组成，氮氧化物的量为0.17%，二氧化硫的量为0.15%，碳氢化合物的量为0.02%，一氧化碳的量为0.007%，烟灰/灰分的量为0.003%。
Carbon dioxide: some 6 per cent of the exhaust gas emissions from this engine are carbon dioxide. Although not itself toxic, carbon dioxide contributes to the greenhouse effect (global warming) and hence to changes in the Earth's atmosphere. 这种机型废气排放物中6%是二氧化碳，尽管它本身没有什么毒性但是二氧化碳会引起温室效应（全球变暖），也会改变在地球大气中的比例。The gas is an inevitable product of combustion of all fossil fuels, but emissions from diesel engines--thanks to their thermal efficiency--are the lowest of all heat engines. 二氧化碳是石油燃料不可避免的燃烧产物，但是由于柴油机热效率高，所以它的排放物是所有热机中最低的。A lower fuel consumption translates to reduced carbon dioxide emissions since the amount produced is directly proportional to the volume of fuel used, and therefore to the engine or plant efficiency. 低的燃油消耗就会降低二氧化碳的排放，因为产生二氧化碳的量正比于消耗燃油的量，柴油机或装置的效率 As a rough guide, burning one tone of diesel fuel produces approximately three tones of carbon dioxide.一个粗略的指导意见是，燃烧一吨的船用燃料油就会产约三吨的二氧化碳。
International concern over the atmospheric effect of carbon dioxide has stimulated measures