- Four-stroke spark-ignition engine: The cross section of a four-stroke spark-ignition engine is shown in Fig. 10.3. The major components of the engine are as follows:
- Cylinder block: It is the main supporting structure for the various components. The cylinder head is mounted on the cylinder block. The bottom of the cylinder block is called the crank case. The lubricating oil is kept in the crank case sump.
- Cylinder: It is a cylindrical vessel in which the piston reciprocates.
Figure 10.3 Cross-section of a spark-ignition engine - Piston: It is a cylindrical component fitted into the cylinder forming the moving boundary of the combustion system.
- Combustion chamber: It is the space between the cylinder and the piston top where combustion takes place.
- Inlet manifold: It is the pipe through which air or air-fuel mixture is drawn in the cylinder.
- Exhaust manifold: It is the pipe through which the products of combustion escape into the atmosphere.
- Inlet and exhaust valves: The valves are used for regulating the incoming charge into the cylinder (inlet valve) or discharging the products of combustion (exhaust valve) from the cylinder.
- Spark plug: It is a component to initiate the combustion process in SI engine.
- Carburettor: It is used for mixing fuel and air in correct proportion in SI engine.
- Connecting rod: It is used to interconnect the piston and the crank to transmit force from the piston to the crankshaft.
- Crankshaft: It is used to convert reciprocating motion of the piston into rotary motion of the output shaft.
- Piston rings: They provide a tight seal between the piston and the cylinder wall.
- Gudgeon pin: It connects the small end of the connecting rod to the piston.
- Camshaft: It is a shaft on which cams are mounted to operate the valves. It is driven from the cam shaft by gears.
- Flywheel: It absorbs surplus energy during working stroke and delivers during idle stroke.
- Four-stroke compression-ignition engine: Except for the spark plug and carburettor, all other components are the same as for the SI engine. It also requires a fuel pump and fuel nozzle. Figure 10.4 shows outline of a CI engine.
Figure 10.4 Outline of diesel engine - Two-stroke SI engine: In the case of two-stroke engine, the valves are replaced by the exhaust port and the transfer port. The charging of the cylinder with the air-fuel mixture takes place through the carburetor and ignition by a spark plug. Other components are same as for a four-stroke engine.
- Two-stroke CI engine: Here, the carburettor and the spark plug are replaced by a fuel pump and fuel nozzle. All other components are same as for two-stroke SI engine.
CONSTRUCTION FEATURES
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