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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) of cast iron and an upper part or crown(活塞头) made of a special heat-resistant steel. They are bolted together and fixed to the piston rod.,1.Pistons and Piston rod
4、s,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) and a dowel pin(定位销) in the crown.,Each piston is provided with five or six piston rings fitted in chromium plated grooves in the crown. Th
5、e two or three topmost rings are narrow rings having diagonal cuts(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 top and bottom edg
6、es to keep the oil film on the cylinder liner during the running-in period(跑合期、磨合期) for new piston rings.,External top,External bottom,In order to control thermal stresses, thin-wall intensively cooled pistons(薄壁强制冷却式活塞) are used for some types of modern engines.,In this case, the piston has an inte
7、rnal insert in the piston crown, which serves only to direct the cooling liquid flow and, thereby, to intensify the conventional cocktail shaker(振荡冷却) effect.,The piston rods are bored from the top flange to a point opposite the center of the crosshead(十字头). Through this bore, a long pipe is inserte
8、d 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 is reduced in diameter to fit a bore in the
9、 crosshead, this being secured to the piston rod by a nut. The piston rods are provided with dowel pins to ensure the correct assembly of the components.,Piston rod,Crosshead,On each of the two journals of the crosshead, crosshead shoes(十字头滑板) are mounted which are guided in the built-in crosshead g
10、uides(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-bolts(锥体螺钉).,The crosshead shoes are white metal lined(白合金衬里), groove
11、s 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 bearings are so constructed that the bearing pressure between the journal and bearing is distributed evenly over the entire length of the bearing.,In orde
12、r 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 system.,The cooling oil is admitted through the pipe, from which the oil is led to
13、the cooling spaces of the piston through telescopic pipes(伸缩管) or articulated pipe(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 the piston rods and the ducts in the crossheads, as well as the slotted pipes from whic
14、h the oil is led to “control boxes” with sight glasses(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 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).,Connecting Rod and Ma
