哈工程轮机英语--lesson 3

1、Lesson Three Text Diesel engine construction (II) Prof. Song Zhou New Words and Expressions in Text recess 凹槽，凹座，凹入处 dowel 销钉 pin 销子 caulk 敛(铆)缝，嵌塞 topmost 最上部 narrow 狭窄的 diagonal 对角的，斜的 overlap 重叠，搭接 joint 接合，接头 distributor 分配器 slightly 轻微地 round 圆的，使成圆形 film (油)膜 period 期间 opposite 在对面，与相对 diamete

2、r 直径 annular 环形的 ensure 保证，担保 assembly 组件，组装 component 部件 journal 轴颈 shoe 滑靴，滑块 horizontally 水平地 adequate 足够的，充分的 admit 允许进入，导入 duct 管道 scraper 刮子，刮油器 shim 垫片，调整片 thickness 厚度 adjustment 调整，调节 clearance 间隙 appropriate 适当的 channel 通道 crankpin 曲柄销 forge 锻造 shrink 红套 displace 错位，变位 carrier ring 承磨环 bui

3、ld-in 内装的，机内的，固定 top-bolt 锥体螺栓 white metal 白合金 telescope pipe 伸缩管，拉管 fitted bolt 拂配螺栓 A piston consists of a lower partpiston skirt(活塞裙活塞裙) of cast iron and an upper part or crown(活塞头活塞头) made of a special heat-resistant steel. They are bolted together and fixed to the piston rod. 1.Pistons and Pist

4、on rods Piston crown Piston skirt Piston rod Piston ring The position of the piston parts in relation to each other is secured by means of machine-turned recesses(凹槽凹槽) and a dowel pin(定定 位销位销) in the crown. Each piston is provided with five or six piston rings fitted in chromium plated grooves in t

5、he crown. The two or three topmost rings are narrow rings having diagonal cuts(斜切口式斜切口式), while the next two are broad and are provided with overlapping end joints. The lowest ring is an oil distributor ring. Diagonal cuts Overlapping end joint All the rings are slightly rounded on their external to

6、p and bottom edges to keep the oil film on the cylinder liner during the running-in period(跑合期、磨合跑合期、磨合 期期) for new piston rings. External top External bottom In order to control thermal stresses, thin-wall intensively cooled pistons(薄壁强制冷却式薄壁强制冷却式 活塞活塞) are used for some types of modern engines. In

7、 this case, the piston has an internal insert in the piston crown, which serves only to direct the cooling liquid flow and, thereby, to intensify the conventional cocktail shaker(振振 荡冷却荡冷却) effect. The piston rods are bored from the top flange to a point opposite the center of the crosshead(十字十字 头头)

8、. Through this bore, a long pipe is inserted which goes nearly to the bottom of the bore. Pipe The outside diameter of the pipe is less than the diameter of the bore, the result being that an annular space is formed between the piston rod and the pipe. Annular space The lower end of each piston rod

9、is reduced in diameter to fit a bore in the crosshead, this being secured to the piston rod by a nut. The piston rods are provided with dowel pins to ensure the c o r re c t a s s e m b l y o f t h e components. Piston rod Crosshead On each of the two journals of the crosshead, crosshead shoes(十十 字头

10、滑板字头滑板) are mounted which are guided in the built-in crosshead guides(十字头导板十字头导板) of the engine frame. Crosshead Crosshead shoe Engine frame Crosshead guide The position of the crosshead shoes on the crosshead is determined by dowel pins. The guide shoes are secured to the crosshead by means of tap-

11、 bolts(锥体螺钉锥体螺钉). The crosshead shoes are white metal lined(白合金衬里白合金衬里), grooves being cut horizontally in the face of the white metal to ensure an adequate supply of lubricating oil. The crosshead is short and rigid and the be ar ings are so constructed that the bearing pressure between the journal

12、 and bearing is distributed evenly over the entire length of the bearing. In order to improve the working conditions of the bearings, the bearing pressure is made smaller and the peripheral speed (is made) higher in later designs. The pistons are cooled by oil supplied from the forced lubrication sy

13、stem. The cooling oil is admitted through the pipe, from which the oil is led to the cooling spaces of the piston through telescopic pipes(伸缩管伸缩管) or articulated pipe(铰接管铰接管), and round the internal pipes of the piston rods. The cooling oil is conducted from the piston through the internal pipes of

14、the piston rods and the ducts in the crossheads, as well as the slotted pipes from which the oil is led to “control boxes” with sight glasses(观察镜观察镜) on the engine. Sealing between the crankcase and scavenging air boxes is achieved by means of the piston rod stuffing boxes, located in the bottom of

15、the scavenging air boxes. Each stuffing is provided with two sealing rings and three scraper rings. The sealing rings, which are mounted uppermost are in four parts and pressed together around the piston rods by means of coil springs(盘簧盘簧). Connecting Rod and Main Bearings The crosshead and crankpin

16、 bearings (曲柄销轴承曲柄销轴承) are made of cast steel and each consist of an upper and a lower part secured to the connecting rod by means of fitted bolts(拂配螺栓拂配螺栓), the nut of which are secured. The bearings have white metal bearing surfaces provided with lubrication grooves for the necessary supply of lub

17、ricating and cooling oil. Shims(垫片垫片,调整片调整片) of different thickness are inserted between the shells to enable adjustment of the bearing clearances (approx. 0.20-0.30mm). The main bearings, which support the crankshaft, each consist of two shells of cast steel with white metal bearing surfaces having

18、 lubricating grooves of an appropriate shape. The shells are secured by means of bearing caps and studs, the necessary clearance (approx. 0.30mm) being provided by means of shims of different thickness. All bearings are lubricated from the force-feed lubrication system of the engine, the oil being s

19、upplied partly through pipes to each main bearing cap and partly to the crosshead, from where the lubricating oil flows through channels to the crankpin bearings. 3. Crankshaft Flywheel 飞轮 曲柄销 Crankpin 曲柄臂 Crank throw(web) Main bearing journal 主轴颈 The crankshafts are built up types(组合式组合式). For semi

20、-built type(半组合式半组合式), the forged main bearing journals are shrunk(红红 套套) into cast steel crank throws with a crank journal and two crank throws as one unit. In the fully built type(全组合式全组合式), the crank throws are shrunk on to main journals and crank journals. The crank throws are displaced from eac

21、h other to obtain the same number of degrees between the different crank throws. The crankpin journals are provided with large bores for balancing purpose. Reading Material M.A.N. Marine diesel engine The latest large bore two stroke M.A.N. engine is the KSZ 90/160B series in cylinder numbers from 6

22、 to 12 and de v e l o pi n g 2 , 7 0 0 K . W. (3,672H.P.)/cyl. The engine operates at 122 rev/min. with an M.E.P.(mean effective pressure平均有效压力平均有效压力) of 13 bar and a mean piston speed of 6.5m/sec. The bedplate is of fabricated design and consists of two I- shaped longitudinal girders with transvers

23、e members into which the cast steel bearing housings are welded. The thrust bearing casing is incorporated into the bedplate. Columns(机架机架) have been replaced by frames constructed of box shaped longitudinal girders. The fabricated top and bottom sections run the full length of the engine and are mo

24、unted on the bedplate. Such an engine frame helps to stiffen the engine and so protect t h e b e a r i n g s f r o m t h e d e f o r m a t i o n f o r c e s transmitted(传递传递) via the ships double bottom. The cast iron guideways(导板导板) for the crosshead are attached to the top section and seal off the

25、 crankcase. The cylinder jackets are individual castings(铸件铸件) bolted together to form one continuous member. The one-piece cylinder liners are fitted into the jackets from the top and a cast steel strong back is fitted in way of the combustion space to help absorb gas forces. *The scavenge process

26、is the M.A.N. loop system(回流扫气系回流扫气系 统统) and the scavenge and exhaust ports are arranged in two tiers and are carried far around the liner. The vertical lands between the ports are cooled by water passing through cast in tubes and thence to passages arranged around the liner above the exhaust ports.

27、 Each cylinder cover is in two parts, the lower section is of special thin walled forged steel permitting the area in way of the c o m b u s t i o n g a s e s t o b e intensively cooled whilst absorbing thermal stresses and this is held in position by an upper supporting unit of cast iron, which tra

28、nsmits the gas forces to the cylinder jackets via long studs. The joint face between the cylinder cover and the liner is arranged as far away from the combustion process as possible. The gas loads on the engine structure are constrained(约束约束) by means of hydraulically(液压液压 的的) preloaded tie rods whi

29、ch connect the bedplate, frame sections and cylinder jackets into a single unit. The crankshaft is of the semi built type, with the journal being shrunk into the forged or cast steel crank throws. With the exception of the six- cylinder engine, it(crankshaft) is in two parts joined by fitted bolts.

30、The coupling flange(联接法兰联接法兰) for attachment to the propeller shaft also accommodates the turning gear(盘车机盘车机) and is integrally forged with the crankshaft. The aft end section also incorporates a thrust collar(推力推力 环环). The drive for the camshaft gear train is taken from a spur gear(正齿轮正齿轮) which f

31、or a six cylinder engine is at the coupling end and for 7 to 12 cylinder engines the drive is located in the middle of the engine. The piston crown is of forged steel and is designed for intensive cooling, the central supporting body is of cast steel and is mainly subjected to compressive stress. Th

32、e two components are bolted together and connected to the piston rod. A single piece piston skirt fitted with bronze(青铜青铜) rings guides the piston in the cylinder liner. The piston ring grooves for a standard engine are flame hardened(淬火，硬化淬火，硬化) against wear. The crosshead pin bearings are white me

33、tal lined shells lubricated by means of high- pressure pumps. T h e p i s t o n f o r c e s a r e transmitted over the entire length of the crosshead pin then to the connecting rod via the lower half single bearing shell. The principle of hydrostatic lubrication （液体静压润滑）（液体静压润滑） has been applied to

34、the crosshead using high-pressure lubricators. This is achieved by means of high pressure pumps with two plungers and rods operated by the oscillating(振荡振荡) movement of the connecting rod, high pressure oil is delivered to the lower part of the crosshead bearing, the pumps press oil into the bearing

35、 when the load on the shell is at its lowest. This ensures that the oil film is maintained at all times and on all loads between the journal and the shell. Scavenging of the cylinder liner is on the loop scavenge system and constant pressure of the exhaust gas is used to drive the turbochargers. Dur

36、ing running up(起动起动) and in the lower partial load range the turbochargers are assisted by electrically driven auxiliary blowers connected before the compressors of the main blowers. In the upper power range the a u x i l i a r y b l o w e r s a r e disconnected. Diffusers(扩压器扩压器) are fitted in the

37、exhaust system and facilitate charge removal and scavenging in each cylinder. The diffuser also prevents pressure pulse from one cylinder interfering with another during operation. B. MAN-B&W MC ENGINE MAN-B&W K 90MC-C engine is a large crosshead type two- stroke engine with a bore of 900 mm, a 2,30

38、0 mm stroke and an operating speed of 104 r/min. It is constructed with between six and twelve cylinders. Developed as one of the extensive range of the manufacturers MC engines, it is of the power and speed best suited to large, fast container ships. The increase in running speed is obtained by a s

39、light decrease in engine stroke. High thermal efficiency is maintained by an increase in mean effective pressure(M.E.P). Construction can be considered generally as typical for the whole range. The engine bedplate is of rigid box form,fabricated from steel plates with main bearing supports of cast s

40、teel . Welded Aframes are assembled into a frame box which contains the crankcase, the crosshead guides and also supports the wheels for the chain drive of the camshaft. A cast iron cylinder frame accommodates the scavenge space between the cylinder jacket and the diaphragm(横隔板）横隔板）, both of which a

41、re water-cooled. Long pre-stressed tie bolts are fitted between the top of the frame and the underside of the bedplate girders. The cylinder liner is of alloy cast iron, its upper flange lands on top of the frame and has bore cooling. It is secured by a forged steel cylinder cover which is also bore

42、 cooled and shaped internally to accommodate most of the combustion space. Cylinder lubricating oil is injected at one level in the liner. P i s t o n h a v e a c h r o m e - molybdenum alloy steel(铬钼合铬钼合 金钢）金钢） crown with hard chrome- surfaced(plated)（表面镀铬）（表面镀铬） ring grooves in which four compress

43、ion rings are fitted. In this particular model a protective layer of inconel(铬镍铬镍 铁合金）铁合金） is welded to part of the crown surface to prevent high temperature corrosion. The piston is oil cooled, oil being supplied by a telescopic pipe to the crosshead and then through the piston rod. It is returned

44、from the crosshead to a slotted pipe in the crankcase. A short cast iron skirt is added. The crown is bolted to the piston rod at an inner support ring. Surface hardening reduces wear on the piston rod at the diaphragm gland. The rod is bolted at the top of a cylindrical crosshead which is of large

45、diameter and incorporates a full-length bottom half-bearing shell. Floating guide shoes are attached at each end. The crankshaft may be either semi-built up or of welded construction, with large journal and pins. All crankcase bearings are of white metal. Main bearings have thick(wall) shells, crank

46、pin(bottom end)and crosshead(top end ) bearing have thin-wall shells. White metal is used for the guide surface. The exhaust valves are operated by hydraulically under oil pressure from cam-timed actuated pistons. They have air compressed springs which allows them to be rotated by vanes. The valve s

47、pindles are usually manufactured by the hot isostatic(均均 衡的衡的) pressure(HIP) method热均压热均压 法法, a compound Nimonic(镍铬钛合镍铬钛合 金金) and austenitic(奥氏体的奥氏体的) steel part construction. Valve housing（阀壳）（阀壳） is cooled at its seat and spindle guide bush （导套）（导套） but its upper duct is uncooled to avoid low temp

48、erature corrosion. Fuel pumps are cam driven and timed by the plunger helix(螺旋螺旋 槽槽). An adjustable barrel(套筒套筒) allows variable ignition timing to maintain combustion efficiency at low speed and can be adjusted to match the ignition quality of fuels. Pumping timing is changed for astern operation b

49、y a link connected at the cam roller guide which is activated by compressed air. Each pump supplies three identical fuel injectors for the corresponding unit. Injectors are uncooled but they circulate hot fuel directly while their needle valves are in the closed position. The engine operates with a

50、constant pressure system, with uncooled turbochargers. Two auxiliary blowers are fitted to operate at low charge air pressure or at low engine revolutions. A number of waste heat recovery(余热回收装置余热回收装置) and power take-off systems(取力系统取力系统) can be operated under running conditions. c. VIBRATION DAMPER 减振器减振器 The vibration damper serves to reduce the torsional(扭转扭转 的的)vibration generated by the crankshaft. The damper consists of a h