Machinery: existing ships
機械：現有船舶

It is assumed in the following that the engine onboard has a reasonable lifetime left and that engine modification can be justified compared to a new complete installation. As the reduction techniques in question are described in detail in Appendix 3 the next sections focus more on a possible applicability on existing ships of measures described above.
這是假設在下面的發動機板載有一個合理的壽命，與一個新的完整的安裝相比，該引擎的修改可以是合理的。由于減少技術問題附錄3中詳細介紹了接下來的章節中更注重對現有船舶上述措施可能的適用性。

Efficiency improvement of machinery on existing ships can be divided into different categories.
Improvements may vary from minor modifications to the most extensive, reflecting both the magnitude of improvement and the costs:
提高現有船舶機械效率，可以分為不同的類別。改進可能會有所不同，從最廣泛的小的修改，反映出改進和成本的幅度：

•  Fuel injection can be modified so that the amount of fuel is injected over a shorter period of time. The cost involved by fuel injection modification is moderate. Fuel consumption can be reduced in the range about 2-4 g/kWh by applying this measure.
對燃料噴射的量進行修改，以便在一個較短的時間內注入。燃油噴射修改所涉及的費用適中。

• A replacement of an old turbo charger with a new modern normally requires some adaptations for the new one to fit in. The effect on the engine overall efficiency is in the same magnitude as for the simple rate shaping described above. Retrofit of a turbo charger installation represents a significant cost, and hence the payback should be quite clear before applying this measure.
渦輪增壓器安裝改造代表一個顯著的成本，因此應用此措施前，投資回收期應該是相當清楚的。

•  Engine efficiency rating implies quite extensive modifications, including an engine upgrade with a set of changes. For implementation of this measure, the mechanical strength of the engine has to allow for increased peak pressure (10-15 bar   http://ukthesis.org/dissertation_sample/   ).

Of the measures discussed in this part efficiency rating is the most extensive and thereby most expensive. Compared to the alternatives efficiency rating is found to be the measure that pays off with highest efficiency gain. A reduction in specific fuel consumption in the magnitude of 8-10 g/kWh may be achieved for medium speed engines. A slight increase in NOx has to be encountered.
大小為8-10克/千瓦時的特定燃料消耗的減少，可以實現中速發動機。氮氧化物略有增加會遇到。

Timing retard:
正時延遲

Retarded fuel injection timing is the simplest way to reduce NOx from a ship diesel engine. This measure can be implemented without hardware modification or extra cost. Retarded timing alone have a negative effect on fuel consumption (specific CO2 increases). Reduction of the NOx emission level in the range of 6-8 g/kWh is possible, but at a cost of an increased fuel consumption of 5-7 g/kWh. Most measures imply retrofit and engine modifications aiming for an improved combustion in order to reduce CO2 and NOx emissions. The possible measures descried in the following are all primarily for NOx reduction and imply additional or modified equipment installed.
大部分措施意味著改造和引擎的修改，旨在改善燃燒，以減少二氧化碳和氮氧化物排放量。可能在下面描述的措施中都主要用于NOx還原，意味著額外的或修改過的安裝設備。

Low NOx combustion:
低NOx燃燒

Some engine manufacturer can offer retrofit/upgrading packages for ”low NOx combustion” without increase of fuel consumption. A low NOx combustion upgrade on an existing engine implies to some extent engine component retrofit. The reduction of NOx emission is in the range of 4-6 g/kWh [Wärtsilä NSD, 1997].

Water injection:
Water injection to reduce NOx is an effective measure (50-60% NOx reduction) which can be retrofitted on existing engines. The main components are the combined injector, common rail water supply system and electronically control system. Retrofit cost figures are estimated to approximately 25 USD pr. kilowatt. The operating cost inclusive maintenance is about 4-5 % of fuel costs [Wärtsilä NSD, 1998, Diesel & Gas Turbine, 1999].

Emulsion:
乳液

Fuel emulsion (adding water in fuel) is a NOx reduction measure where the necessary equipment can be installed on existing engines. The reduction potential without penalty on fuel efficiency is in the range of 20-25%.
乳化燃料（燃料中加入水）是一個必要的設備，可以安裝在現有發動機的NOx還原措施。在未經燃油效率罰款的還原電位是在20％至25％的范圍內。

Humid Air Motor (HAM):
Implementation of the HAM technique on existing engines can result in up to 60% reduction of
NOx emission level. The technique is however new and the long-term operational effect is not fully proven. In existing ship it is in most cases difficult to install the HAM equipment, mainly because of the rearrangement of the air supply system to the engine and the additional space required. Most engines have a turbo-charger and aftercooler system that is heavily integrated and matched for the specific engine. Engine manufacturers may be reluctant to modify this original integrated system solution [Bunes et .al, 1998, Munters Europa 1998].

Miller Cycle:
The Miller principle and measures as described on new engines are also valid for existing engines.#p#分頁標題#e#

Exhaust Gas Re-circulation (EGR):
Several problems need to be addressed and solved before EGR will be an applicable measure for existing or new ships. The main challenge is the re-entrance of particulates damaging for the engine, especially when running on HFO and therefore very limited application is foreseen
[EPA 1998, DNV, 1998].

SCR:

A properly operating SCR installation can remove up 95 % of NOx components from the exhaust. It can be installed on existing machinery as retrofit packages, which includes the reactor, urea storage/dosing and control system. For installation on an existing ship there are some practical limitations due to the need for space. Although the reactor can replace the exhaust silencer it can be rather costly to install. In addition to the space for the reactor, there is also need for storage space for urea.
一個正常操作的SCR安裝，可以去除高達95％的氮氧化物組件排氣。它可以安裝在現有的機械改裝套件，其中包括在反應器中，尿素存儲/定量給料和控制系統。

CO and HC
Efforts on upgrading an existing engine normally also pay off with minor reductions on CO and HC emissions. In the overall perspective these gains are very small as the CO and HC emissions from the diesel combustion process are very low initially.  Due to this reduction measures for CO and HC have not been further assessed in this report.

SOx
氧化硫

The SOx emissions are related to the quality of the fuel. Only a dramatic turnover from high sulphur to low sulphur fuel oil can have a major impact on SOx emissions from the existing fleet.
SOx的排放與燃料的質量。只有一個戲劇性的營業額從高含硫量的低硫燃料油，對現有車隊中的SOx的排放有重大影響。

Table 5-7 - Emission reduction in existing ships – applicability
表5-7 - 現有船舶減排適用性

Figure 5-4 above compares NOx reduction measure and cost for new ships. The figure is to a large extent valid also for similar measures on existing ship machinery for the techniques that is possible to implement. The NOx/CO2 trade off (Figure 5-5) will also be valid for measures on existing machinery systems.
NOx/CO2對現有的機械系統，權衡（圖5-5）有效的措施。

Table 5-8 summarises the potential for fuel savings on existing ships by machinery measures.
表5-8總結了通過機械措施，現有船舶節省燃油的潛力。

Table 5-8 – CO2 reduction potential in existing ships - machinery measures
表5-8 - 現有船舶CO2減排潛力 - 機械措施