Lesson 14 Internal Combustion Engine The Diesel Part B

Contents Diesel Engine Construction ---- Structural Components ---- Moving Components New Words & Expressions

Diesel Engine Construction Structural Components Bedplate & Frame, Cylinder Block, Cylinder Head/Assembly, Crankcase, Oil sump Moving Components Piston, Piston Rings, Piston Pin, Connecting Rod, Crankshaft, Flywheel, Valves, Camshaft & Cams

Diesel Engine Construction

Structural Components Cylinder Block Part of engine frame that contains cylinders in which piston moves Supports liners & head

Structural Components Bedplate and Frame The bedplate, which in most cases is of the welded design, is bolted to the seating which forms a part of the double bottom of the ship. It is secured in the transverse direction by means of bolts known as side-chock bolts and in longitudinal direction by means of end- chock bolts.

Structural Components

Structural Components On the flat upper surface of the bedplate are arranged a number of A-shaped frames or entablatures which may be manufactured of cast iron or fabricated steel. The frames are mounted on and bolted to the bedplate girders.

Structural Components At the top of the A-frames there is strong cast iron frame called the scavenging air box, which is built of a number sections provided with vertical flanges 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. 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.

Structural Components

Structural Components Cylinder Cover Each cylinder is closed at the top by a cylinder cover, made of special heat-resistant steel. 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.

Structural Components Cylinder Cover In each cylinder cover is a large central opening for mounting the exhaust valve, and two or three holes for the fuel valves. The cylinder cover is also provided with holes for: the starting valve; the safety valve; the indicator cock; the cooling water inlet and the cooling water outlet to the exhaust valve cooling chamber.

Structural Components Cylinder Head/Assembly Serves to admit, confine, and release fuel/air Cover to cylinder block Supports valve train Crankcase Engine frame section that houses the crankshaft Oil sump Reservoir for collecting and holding lube oil

Moving Components Three Groups – according to motion Reciprocating only (pistons and valves) Reciprocation & rotary (connecting rods) Rotary only (crankshafts and camshafts)

Moving Components Piston Piston Ring A piston consists of a lower part-piston skirt of cast iron and an upper part or crown made of a special heat-resistant steel. They are bolted together and fixed to the piston rod. Piston Ring Transfer heat from piston to cylinder Seal cylinder & distribute lube oil

Moving Components Piston Ring Each piston is provided with five or six piston rings fitted in chromium- plated grooves in the crown. The two or three topmost rings are narrow rings having diagonal cuts, while the next two are broad and are provided with overlapping end joints. The lowest ring is an oil distributor ring.

Moving Components Piston Pin Connecting Rod Pivot point connecting piston to connecting rod Connecting Rod Connects piston & crankshaft reciprocating & rotating motion

Moving Components Piston Compression Rings Piston Pin Oil Rings Connecting Rod

Moving Components Valves Camshaft & Cams Intake: open to admit air to cylinder Exhaust: open to allow gases to be rejected Camshaft & Cams Used to time the addition of intake and exhaust valves Operates valves via pushrods & rocker arms

Moving Components

Moving Components Main Bearing The main bearings, which support the crankshaft, each consist of two shells of cast steel with white metal bearing surfaces having 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 thicknesses.

Moving Components

Moving Components

Moving Components Crankshaft The crankshafts are built up types. For the semi-built type, the forged main bearing journals are shrunk into cast steel crank throws with a crank journal and two throws as one unit. In the fully built type, the crank throws are shrunk on to main journals and crank journals.

Words & Expressions bedplate n. 底座 frame n. 机架, 机座 weld v. 焊接 bolt n. 螺栓 liner n. 衬套 extend v. 延伸, 伸展 slot n. 槽、缝 secure v. 固定 transverse a . 横向的,横断的

Words & Expressions chock n. 楔形物 longitudinal a. 纵向的 bearing n. 轴承 stud n. 双头螺栓 thrust n. 推力 locate v. 定位；位于… camshaft n. 凸轮轴 enclose v. 封闭 jacket n. 夹层，水套 conical a. 圆锥的, 圆锥形的

Words & Expressions recess n. 凹槽，凹座 dowel n. 定位销 pin n. 销子 caulk v. 嵌塞 diagonal a. 对角的，斜的 overlap v. n. 重叠，搭接 joint n. v. 接合，接头 distributor n. 分配器 film n. 油膜

Words & Expressions diameter n. 直径 annular a. 环形的 ensure v. 保证，担保 assembly n. 组件，组装 component n. 部件 journal n. 轴颈 shoe n. 滑块 duct n. 管道 scraper n. 刮刀，刮油器

Words & Expressions shim n. 垫片，调整片 adjustment n. 调整，调节 clearance n. 间隙 channel n. 通道 crankpin n. 曲柄销 forge v. 锻造 shrink v. 红套 displace v. 错位，变位 machine-turned 车削的，车制的 dowel pin 定位销

Assignments What is bedplate? Where is the scavenging box? There are many valves in the cylinder cover. What are they? Which ring of the piston is the lowest? What is the function of the compression shims?