Internal combustion engine and its types
An internal combustion engine is one in which the fuel is burnt within the engine. Most of the cases it is of reciprocating type. Combustion of the fuel and the conversion of the heat energy from combustion to mechanical energy takes place within the cylinders. Internal combustion engines can be of the rotary type, such as the gas turbine and the rotary engine. Reciprocating internal combustion engines may be of the spark-ignition or
compression-ignition type.
Spark-ignition engines use gaseous or volatile distillate fuels and work on a modified Otto cycle. They operate on the two or four-stroke cycle.
Compression-ignition engines may also be of either two or four-stroke cycle type. They use distillate liquid fuels or, where conditions allow, a blend of distillate and residual fuels. This type of engine is usually designed to operate on the dual combustion cycle or a modification of it. In some cases the cycle is such that the whole of combustion takes place at constant volume.
Some engines are designed for dual-fuel operation and may use either liquid or gaseous fuel. When gaseous fuel is used a small amount of liquid fuel is injected to initiate combustion.
CLASSIFICATION OF INTERNAL COMBUSTION ENGINES
Internal combustion engines may be classified as given below :
1. According to cycle of operation :
(i) Two stroke cycle engines
(ii) Four stroke cycle engines.
2. According to cycle of combustion :
(i) Otto cycle engine (combustion at constant volume)
(ii) Diesel cycle engine (combustion at constant pressure)
(iii) Dual-combustion or Semi-Diesel cycle engine (combustion partly at constant volume and partly at constant pressure).
3. According to arrangement of cylinder :
(i) Single cylinder engine. Engine has one cylinder and piston connected to the crankshaft.
(ii) In-line or straight engines. Cylinders are positioned in a straight line one behind the other along the length of the crankshaft.
(iii) V-engine
- An engine with two cylinder banks (i.e., two-in-line engines) inclined at an angle to each other and with one crankshaft.
- Most of the bigger automobiles use the 8-cylinder V-engine (4-cylinder in-line on each side of V)
(iv) Opposed cylinder engine
- Two banks of cylinders opposite each other on a single crankshaft (a V-engine with 180° V).
- These are common on small aircraft and some automobiles with even number of cylinders from two to eight or more.
(v) W-engine
- Same as V-engine except with three banks of cylinders on the same crankshaft.
- Not common, but some have been developed for racing automobiles.
(vi) Opposed piston engine
- In this type of engine there are two pistons in each cylinder with the combustion chamber in the centre between the pistons.
- A single combustion process causes two power strokes, at the same time, with each piston being pushed away from the centre and delivering power to a separate crankshaft at each end of this cylinder.
(vii) Radial engine
- It is an engine with pistons positioned in a circular plane around the central crankshaft. The connecting rods of the pistons are connected to a master rod which, in turn, is connected to the crankshaft.
- In a radial engine the bank of cylinders always has an odd number of cylinders ranging from 3 to 13 or more.
- Operating on a four-stroke cycle, every other cylinder fires and has a power stroke as the crankshaft rotates, giving a smooth operation.
- Many medium and large size propeller-driven aircraft use radial engines. For large aircraft two or more banks of cylinders are mounted together, one behind the other on a single crankshaft, making one powerful smooth engine.
- Very large ship engines exist with upto 54 cylinders, six banks of 9 cylinder each.
4. According to their uses :
(i) Stationary engine
(ii) Portable engine
(iii) Marine engine
(iv) Automobile engine
(v) Aero engine etc.
5. According to the speed of the engine :
(i) Low speed engine
(ii) Medium speed engine
(iii) High speed engine.
6. According to method of ignition :
(i) Spark-ignition engine
(ii) Compression-ignition engine.
7. According to method of cooling the cylinder :
(i) Air-cooled engine
(ii) Water-cooled engine.
8. According to method of governing :
(i) Hit and miss governed engine
(ii) Quality governed engine
(iii) Quantity governed engine.
9. According to valve arrangement :
(i) Over head valve engine
(ii) L-head type engine
(iii) T-head type engine
(iv) F-head type engine.
10. According to number of cylinders :
(i) Single-cylinder engine
(ii) Multi-cylinder engine.
11. According to air intake process :
(i) Naturally aspirated. No intake air pressure boost system.
(ii) Supercharged. Intake air pressure increased with the compressor driven off the engine crankshaft.
(iii) Turbocharged. Intake air pressure increased with the turbine-compressor driven by the engine exhaust gases.
(iv) Crankcase compressed. Two stroke-cycle engine which uses the crankcase as the intake air compressor. Limited development work has also been done on the design and construction of four-stroke cycle engines with crankcase compression.
#Internal combustion engine
12. According to fuel employed :
(i) Oil engine
(ii) Petrol engine
(iii) Gas engine
(iv) Kerosene engine
(v) LPG engine
(vi) Alcohol-ethyl, methyl engine
(vii) Duel fuel engine
(viii) Gasohol (90% gasoline and 10% alcohol).
13. Method of fuel input for S.I. engines :
(i) Carburetted
(ii) Multipoint port fuel injection. One or more injectors at each cylinder intake.
(iii) Throttle body fuel injection. Injectors upstream in intake manifold.
# Internal combustion engine
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