2.1 COMPONENTS OF A SIMPLE DIESEL ENGINE



The simple diesel engine has a cylinder, a piston, a connecting rod, and a crankshaft. The end of the cylinder is sealed with a cylinder head. The piston which is sealed to the cylinder wall by piston rings is connected to the crankshaft by a connecting rod and a piston pin. This arrangement allows the piston to return to the top of the cylinder, making continuous rotary motion of the crankshaft possible. Because of the powerful impulses on the piston as the fuel is burned in the cylinder, a heavy flywheel blends together the power impulses into one continuous motion of the crankshaft.


For each cylinder the cylinder head has an inlet valve port that allows maximum amount of air into the cylinder. An exhaust valve port allows the burned gases to flow out. The head is sealed to the cylinder block with a head gasket. The openings of the valves is controlled by the camshaft.


2.2 DETAILS OF DIESEL ENGINE MAIN COMPONENTS


The detail cross section of a in line and v shape diesel engine are shown in more details in Fig A. I and A.2 -in the Appendix A. The individual components are discussed below.


a) Cylinder Block and Oil Pan

The cylinder block forms the framework of a liquid cooled diesel engine. It is generally a engine
unit made from cast iron. The air cooled diesel engine usually has a separate cast iron crankcase and individual cylinder blocks. The cylinder block has openings for the cylinder sleeve (cylinder liner), oil and water passages, and bores for the crankshaft and camshaft bearings. The upper half of a water cooled cylinder block contains the water jackets. ackets. The lower half of the cylinder block house the crankshaft and camshaft followers and pushrods are located is called the crankcase. An oil pan which is bolted to the crankshaft, forms the oil reservoir for the lubrication system.


b) Piston and Piston Rings
The piston and the piston rings act as a piston pump while moving up and down in the cylinder sleeve. Piston are made from aluminium or cast iron alloy. Piston rings are made from cast iron alloy and compression rings commonly chrome plated. Two main functions of the piston and piston rings are to seal the lower side of the combustion chamber and to transmit the pressure of compression and combustion via the piston pin and connecting rod to the crankshaft. They also transmit heat to the cylinder walls and into the water jacket.


C) Connecting Rod
The connecting rod is made from drop-forged, heat-treated steel and is the link between the crank-shaft and the piston. It is bored at each end, and in the upper bearing bore (piston pin bore) a bushing is inserted in which the piston pin is placed. The lower bearing bore (crankpin connecting-rod bore), is split half by the connecting-rod cap. One-half of the connecting road bearing fits tightly into the rod cap, and the other half fits into the connecting rod. When the connecting, rod is bolted to the crankshaft connecting-rod journal and the crankshaft rotates, the connecting rod and piston move up and down.

d) Cylinder Sleeve
The cylinder sleeve (cylinder liner) foinis the combustion chamber walls. When the cylinder sleeve is in direct contact with the coolant it is referred to as a wet sleeve. When the cylinder sleeve is indirectly in contact with the coolant (that is, the sleeve is enclosed in the cylinder) it is referred to as a dry sleeve. It is through the cylinder sleeve contact with the coolant or the cylinder block that effective cooling is achieved. Wet sleeves have special sleeve seal which seal the coolant at the lower end of the cylinder sleeve and block. The accurately machined surfaces of the sleeve flange, cylinder block, and cylinder-head gaskets form the seal at the cylinder block surface (top deck).

e) Crankshaft
The crankshaft is made of forged steel and has precision machined and hardened main bearings and connecting-rod journals (Fig. 8-2). The off-set cranks of the crankshaft are C, (Fig
for proper weight distribution to ensure even force during rotation. Some crankshafts use conterbalance weights (or a gear train) to achieve balancing. weight
shaft rotates in its main bearings and lubricating oil from the drilled passages within ZD ZD
the cylinder block feeds the main bearings. Drilled passages in the crankshaft pass lubricating oil to the connecting-rod journals. A crankshaft thrust bearing is used to prevent excessive end movement.


f) Flywbeel
The flywheel serves three purposes. First, through its inertia, it reduces vibration by smoothing out the power stroke of the cylinders. Second, it is the mounting surface of the clutch pressure plate and the friction surface for the clutch. (When a fluid clutch is used, the impeller is splined or bolted to the flywheel.) Third, the "shrunk-. on" flywheel ring gear is used for transmitting cranking motor power to the crankshaft.

g) Vibration Damper
A vibration damper is a unit which counteracts the twisting or torsional vibration caused by force variations (usually from about 3 to 10 tons [2,724 to 9,080 kg]) on the piston and subsequently the crank. Torsional vibration is rythmic force which occurs within every power stroke. The application of force, and its absence a split second later, cause the crankshaft to be alternately twisted out of alignment and then snapped back into place. If preventive measures were not taken against this, the engine would run rough and the crankshaft could break.
Vibration dampers of the viscous or rubber-element design are fastened to the front of the cranking-shaft (Fla. 8-3). Since torsion vibration differs with engine design, vibration dampers are constructed to suit specific engines.

h) Timing Gears, Camshaft and Valve Mechanism
The timing gears (see Fig. 8-5) transmit rotary motion to the camshaft and at the same time maintain a fixed relation between the crankshaft and camshaft. The camshaft rotates on friction bearings in the crank-case. The rotary motion of the camshaft is transmitted to the followers, thereby causing the followers and push-rods to move up and down, the rocker aLHIS to pivot, and the valves to open and close. On engines where the camshaft is located above the valve stem (overhead), the cam lobes open and close the valves by directly pushing each valve's cam follower