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Lesson Two

Text Diesel Engine Construction (I)

 

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Bedplate( 机 座 ) and Frame( 机架 )The bedplate, which in most cases is of the welded design, is bolted to the seating which forms part of the double bottom of the ship.

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Cylinder block

A-Frame(Entablature)

Bedplate

Tie rod

Seating

Cylinder cover

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It is secured ( 固定 ) in the transverse( 横向的 ) direction by means of bolts known as side-chock bolts ( 侧楔螺栓 ) and in longitudinal( 纵向的 ) direction by means of end-chock bolt ( 端楔螺栓 ).

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The crankshaft rests( 放置、坐落 ) in bearing built into cross girders( 横梁 ) of the bedplate.

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Bearing

Cross girder

Housing

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These bearings, known as main bearings, each consist of two shells( 轴瓦 ) which are supported in housings( 轴承座 ) machined in the bedplate and secured by means of studs( 双头螺栓 )and bearing caps( 轴承盖 ).

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The thrust block or thrust bearing( 推力轴承 ), located at the aft end of the engine, may be integral with, or separate from, the bedplate.

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*On the flat( 平的 ) upper surface of the bedplate are arranged a number of A-shaped frames or entablatures( 机架 ) which may be manufactured of cast iron or fabricated steel( 结构钢 ).

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The frames are mounted on and bolted to the bedplate cross girders.

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At the top of the A-frames there is a strong cast iron frame called the scavenging air box, which is built of a number of sections provided with vertical flanges( 法兰 ) enabling them to be bolted together to form a block for 1-3 cylinders in front of the chain transmission, and a block with 4-6 cylinders aft of the chain transmission.

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The chain transmission, forming the connection between the crankshaft and the camshaft , is enclosed in a cast iron casing known as the chain drive casing.

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Cylinders and Covers

On top of scavenging air box is mounted a strong cast iron frame for each cylinder.

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These frames are known as cylinder blocks or cooling jackets( 冷却水套 ), which are provided with vertical flanges enabling them to be bolted together in the foremost and aftmost groups in the same way as the scavenging air boxes.

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The bedplate, frames and cylinder blocks are secured together by long tie-rods to achieve a greater rigid construction( 刚性结构 ) with less deformation( 变形 ) in service and lower vibration.

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The cylinder liners are made of alloyed cast iron and the cylinder surfaces are sometimes chromium-plated( 镀铬 ).

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The cylinder liners are extend somewhat down in the scavenging air box, and sealing between the liner and the top of the scavenging air box is achieved by the rubber rings fitted into the slots machine-turned( 机加工的 ) in the liners.

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In the part of the cylinder liner inside the scavenging air box there is a series of openings known as scavenging air ports.

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These ports are located at such a height that they are just exposed by the upper edge of the piston when the piston is in the bottom dead-center position.

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The ports are drilled in the liners at an angle of approx. 20°, the result being that the scavenging air is given a rotary movement.

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Each cylinder is closed at the top by a cylinder cover, made of a special heat-resistant steel ( 耐 热钢 ).

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The cover is mounted against a flat surface at the top of the cylinder liner and located on the liner by means of a machine-turned guide edge.

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A sealing ring is inserted in a groove turned in the conical( 园锥形的 ) part of the cover. The fitting of the sealing ring in the conical surface must be carried out with great care.

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The cylinder covers and the liners are bolted together by means of studs screwed into the cylinder frames.

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The cylinder liner has drillings for cylinder lubrication, and, in later types, has drillings for cooling water at the uppermost part of it.

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In each cylinder cover is a large central opening for mounting the exhaust valve, and two or three holes for the fuel valves.

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The cylinder cover is also provided with holes for: the starting valve; the safety valve; the indicator cock( 示功器旋塞 ); the cooling-water inlet and the cooling-water outlet to the exhaust valve cooling chamber.

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Reading Material

Sulzer Marine Diesel Engines

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Sulzer RND-M Engine

The RND-M Sulzer is a single acting slow speed ， two-stroke, reversible( 可倒转 ) engine.

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The individual cylinder running gear is made up of a piston ，piston rod and connecting rod joining the single throw( 曲柄 ) of crankshaft.

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The bedplate is fabricated as a double wall design with longitudinal box section girders. A-frames are mounted on the bedplate and support the entablature and cylinder block ．

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The complete assembly of bedplate ， A-frames and cylinder block are held together by tie rods to form a rigid structure.

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To resist crankshaft-loading transverse bending( 弯曲 ) the main bearing keep( 主轴承盖 ) are held down by jack-bolts( 液 压 撑 杆 螺栓 ).

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This strong structure is necessary to withstand the combustion loads which pass via the cylinder head to the engine structure ．

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keep

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The crankshaft is semi-built( 半总成式 ) with the crankwebs( 曲柄臂 ) being designed to partially balance the rotating masses ．

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The cylinder cover is made in single piece and contains the central fuel injector ， the starting air valve ， relief valve( 安全阀 ) and indicator cock ．

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Exhaust gas driven turbo-chargers operating on the constant pressure system supply scavenge air.

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Loop type scavenging is employed and an electrically driven automatically operating auxiliary blower is provided for slow speed and maneuvering operations.

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Lubricating oil is supplied to a low and a medium pressure system. The low-pressure system supplies the main and other bearings. The crosshead( 十字头 ) bearings are supplied by the medium pressure system.

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Articulated pipes( 铰链管 ) supply the oil to the crosshead bearings. Water-cooling is used for cylinder jackets and heads and also the pistons. Telescopic pipes( 伸缩管，套管式 ) provide the water to the pistons.

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Fuel injection uses the Jerk pump( 高压喷射泵 ) system and a Woodward type hydraulic governor( 液压调速器 ) is used to control engine speed.

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The RL engine is based on the RND-M and provides, with its increased piston stroke, a higher output and lower engine speed. New features include a single wall bedplate with integral thrust block.

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Also the piston crown( 活 塞头 ) and other main components of the combustion chamber are bore cooled( 钻孔冷却 ), i.e. by water circulating in holes bored close to the hot surfaces.

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Sulzer RTA Engine

The Sulzer RTA 84C is a typical modern slow-speed, two-stroke, crosshead type, long stroke engine.

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It has a bore of 840 mm, a stroke of 2,400 mm and an operating speed of 100r/min. It is available with between four and twelve cylinders and is particularly produced for the large, fast container ship( 集装箱船 ) market.

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Its design and construction is similar to other engines in the RTA series 2 which offer a number of cylinder sizes down to 380 mm.

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A deep single wall-box type bedplate fabricated from welded steel plates and castings, and substantial( 坚固的 ) welded ‘A’ frames surmounted( 安在…顶上 ) by cast iron cylinder jackets bolted together to form a cylinder block, together give rigid overall construction.

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The structure is pre-stressed( 预加应力 ) by long vertical tie bolts.Cylinder liners are of alloy cast iron. A stiff( 硬的 ) collar at the upper end resists the heavy gas load; this lands on the cylinder jacket.

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It is bore cooled with water flow rates regulated to maintain correct temperatures throughout the liner. The lower end is uncooled within the scavenge space. Multi-level cylinder lubrication is used to reduce liner wear rates.

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The solid forged steel( 整体锻钢 ) cylinder cover is bore cooled to reduce thermal stress( 热应力 ) and to conduct heat from the fuel injector pockets( 腔 ).

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A centrally positioned large exhaust valve cage( 腔 ) has its valve seat intensively( 强烈的、集中的 ) cooled, taking water from the cover.

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The valve is manufactured of Nimonic( 镍铬钛合金 ) 80 A alloy and is rotated by vanes( 叶 片 式 旋 阀器 ) fitted to its spindle( 阀杆 ). It is opened by hydraulic pressure from a cam driven actuator( 驱动器、执行器 ) and is closed under the action of an air spring.

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The piston has an alloy steel crown and has five compression rings fitted in chromium plated grooves. There is a short cast iron skirt( 裙部 ).

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The piston is oil cooled using both the ‘shaker( 震荡 , 摇杆 )’ method and small jets( 射流 ) to propel oil into bore holes close to the underside of the crown and behind the ring grooves.

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Oil for cooling is supplied and returned through a bore in the piston rod from swinging( 摇摆 ) links at the crosshead.

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The single piece crosshead has the piston rod bolted to its upper surface and a continuous full-length lower half ( 全支承式 ), top end bearing, which is of white metal and lubricated with high pressure oil.

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Guide shoes( 导块，滑块 ) are attached to each end of the crosshead.A semi-built up crankshaft( 半套合式 , 半总成式 ) has slim( 细的 ) webs to allow large bearing areas; main bearing caps are secured by jackbolts from the engine frames ．

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The main camshaft is gear driven and is fitted with servomotors( 伺服马达 ) to re-time fuel pump cams and the air start distributor( 起动空气分配器 ) when operating the engine astern( 向后 ) ．

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Fuel pumps are of the cam-driven valve-timed type ， with variable ignition timing(VIT 机构 ,可变点火定时 ) to adjust timing and maintain efficient combustion at low speed.

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Each pump supplied three uncooled fuel injectors placed symmetrically( 对称地 ) in each cover ．Hot fuel oil circulates the valves when not injecting ．

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The engine has through-scavenge( 直流扫气 ) and constant pressure turbocharging with a high efficiency ， uncooled turbocharger supplemented at very low speeds by two constant speed ， electric driven auxiliary air blowers ．

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END

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1. There be/stand( 站立 )/lie( 平放 )/

appear( 出现 )/occur( 发生 )/ exist( 存在 ) 倒装句：例：There stands a large hydroelectri

c power station on the river.

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2. Here/There/Thus/Then/Hence 开头的句子中，主语是名词，而谓语用Come, go 一类的动词时，整个句子应采用完全倒装语序。例：Here comes our English teacher.

Listen, there goes the bell.

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3. “ 衔接”倒装：有时，为了衔接而将谓语中的分词置于句首，从而引起倒装。这种句子的主语往往带有较长的后置定语，倒装语序使句子显得更加平衡。例：Punched on the tapes are a number ofholes which mean binary 1’s for the computer.

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4. “ 强调”倒装：为了强调，将句末的状语提到句首，引起主谓语倒装。In this design are involved a number of complicated problems which should be solved first.

5. “ 祝愿”倒装：表示祝愿的句子习惯用倒装语序。Long live the people!May you succeed!

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6. Only/Often/Not only/Not until等为句子开头时，常采用倒装语序。Only after a programme is prepared in every detail, can the electronic computer understand the problem it is to solve.

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7. Never/Hardly/Seldom/Little/In no case/In no way/By no means/At no time 等含有否定意思的词语开头时，须采用部分倒装语序。Ｎ ever has a machine been so efficient and accurate as the electronic computer.从没有一台机器象…In no way can theory be separated frompractice.理论决不能脱离实践。

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8. “ 省略”倒装：前一句子谓语中的情况也同样适用于后一句子时，后面的句子就可以用 so( 肯定 ) 或 nor( 否定 ) 等开头，并采用倒装语序，句子且为省略句。Production is going up steadily, and so is the people’s standard of living.Wood cannot conduct electricity, nor can stone.

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9. “ 虚拟“倒装：在虚拟条件句中，如果谓语含有 had/were/should 等时，可以省略连词 if ，而采用倒装语序来表示虚拟的条件。Had we known about the method, we should have applied it earlier.我们如果知道这个方法，早就用了。

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10. 强调结构的倒装：强调主语、宾语或状语，通常采用一种惯用结构 It is(was) …that.Mr. Green has been teaching us English for a long time.It is Mr. Green that (or who) has been teaching us English for a long time.

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They did not begin to learn English until last year.It was not until last year that they began to learn English.( 在 not… until 句子中强调时间状语时使用）一直到去年他们才开始学习英语。

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The old scientist has been working at this problem for ten years.It is ten years since the old scientist began to work at this problem.( 强调时间状语是 for a long time 一类的短语时采用）