Introduction to Internal Combustion Engine
Heat engine:
A heat engine is a device which transforms the chemical energy of a fuel into thermal energy and uses this energy to produce mechanical work. It is classified into two types-
(a) External combustion engine
(b) Internal combustion engine
External combustion engine:
Internal Combustion Engine:
C – crankshaft
E – exhaust camshaft
I – inlet camshaft
P – piston
R – connecting rod
S – spark plug
V – valves. red: exhaust, blue: intake.
W – cooling water jacket
In this engine, the combustion of air and fuels take place inside the cylinder and are used as the direct motive force. It can be classified into the following types:
1. According to the basic engine design- (a) Reciprocating engine (Use of cylinder piston arrangement), (b) Rotary engine (Use of turbine)
2. According to the type of fuel used- (a) Petrol engine, (b) diesel engine, (c) gas engine(CNG, LPG), (d) Alcohol engine (ethanol, methanol etc.)
3. According to the number of strokes per cycle- (a) Four stroke and (b) Two stroke engine
4. According to the method of igniting the fuel- (a) Spark ignition engine, (b) compression ignition engine and (c) hot spot ignition engine
5. According to the working cycle- (a) Otto cycle (constant volume cycle) engine, (b) diesel cycle (constant pressure cycle) engine,
6. According to the number of cylinder- (a) Single cylinder and (b) multi-cylinder engine
7. Method of cooling- water cooled or air cooled
8. Cylinder Arrangement-Vertical, horizontal, inline, V-type, radial, opposed cylinder or piston engines.
Main components of reciprocating IC engines:
Cylinder: It is the main part of the engine inside which piston reciprocates to and fro. It should have high strength to withstand high pressure above 50 bar and temperature above 2000°C. The ordinary engine is made of cast iron and heavy duty engines are made of steel alloys or aluminum alloys. In the multi-cylinder engine, the cylinders are cast in one block known as cylinder block.
Cylinder head: The top end of the cylinder is covered by cylinder head over which inlet and exhaust valve, spark plug or injectors are mounted. A copper or asbestos gasket is provided between the engine cylinder and cylinder head to make an air tight joint.
Piston: Transmit the force exerted by the burning of charge to the connecting rod. Usually made of aluminium alloy which has good heat conducting property and greater strength at higher temperature.
> Compression ring is upper ring of the piston which provides air tight seal to prevent leakage of the burnt gases into the lower portion.
> Oil ring is lower ring which provides effective seal to prevent leakage of the oil into the engine cylinder.
Connecting rod:
It converts reciprocating motion of the piston into circular motion of the crank shaft, in the working stroke. The smaller end of the connecting rod is connected with the piston by piston pin/wrist pin/gudgeon pin and bigger end of the connecting rod is connected with the crank pin.
Crankshaft: It converts the reciprocating motion of the piston into the rotary motion with the help of connecting rod. The special steel alloys are used for the manufacturing of the crankshaft. It consists of eccentric portion called crank.
Crank case: It houses cylinder and crankshaft of the IC engine and also serves as sump for the lubricating oil.
Flywheel:
It is big wheel mounted on the crankshaft, whose function is to maintain its speed constant. It is done by storing excess energy during the power stroke, which is returned during other strokes (Suction, compression and exhaust).
Terminology used in IC engine:
1. Cylinder bore (D): The nominal inner diameter of the working cylinder.
2. Piston area (A): The area of circle of diameter equal to the cylinder bore.
3. Stroke (L): The nominal distance through which a working piston moves between two successive reversals of its direction of motion.
4. Dead centre: The position of the working piston and the moving parts which are mechanically connected to it at the moment when the direction of the piston motion is reversed (at either end point of the stroke).
(BDC): Dead centre when the piston is nearest to the crankshaft.
(TDC): Dead centre when the position is farthest from the crankshaft.
