The engine or power unit provides power to drive the vehicle. Internal combustion engine (briefly written as I.C. engines) are employed in automobiles as power units. Since the air-fuel mixture is burned inside the engine cylinder to develop power, so these are known as internal combustion engines. Following are the two types of I.C. engines commonly used in automobiles:
l . Petrol engines.
In petrol engines (also known as spark Ignition engines or S.I. engines), the air-fuel (petrol) mixture is supplied to the engine cylinder during the *suction stroke. The mixture is now compressed during the compression stroke and thus the pressure and temperature is raised. The mixture is ignited with the help of a spark plug just before the compression is complete. It results in the sudden rise of pressure, due to the expansion of the combustion of the products in the engine cylinder. This sudden rise of pressure pushes the piston with great force and rotates the crankshaft, which in turn, drives the vehicle. The burnt gases are exhausted from the engine cylinder, so as to make space available for the fresh air-fuel mixture.
( Note: The petrol engines work on Otto cycle. It is also known as constant volume cycle as the heat is received and rejected at a constant volume.)
2. Diesel engines.
In diesel engines (also known as compression ignition engines or C.I. engines), the pure air is drawn into the engine cylinder during the suction stroke. It is now compressed as a result of which the pressure and temperature of air increases considerably (the actual value depends upon the compression ratio, which is about 14 to 25). Before the piston just completes the compression stroke, the fuel oil (diesel) is injected into the engine cylinder through the injector nozzle. At this moment, the temperature of compressed air is sufficiently high to ignite the fuel.
It suddenly increases the pressure and temperature of the products of combustion. The fuel oil is assumed to be burnt at constant pressure. Due to the increased pressure, the piston is pushed down with a great force and rotates the crankshaft which, in turn, drives the vehicle. The movement Of the piston push out the products of combustion from the engine cylinder into the atmosphere
( Note: The diesel engines work on diesel cycle. It is also known as constant pressure cycl combustion takes place at constant pressure. )
l . Petrol engines.
In petrol engines (also known as spark Ignition engines or S.I. engines), the air-fuel (petrol) mixture is supplied to the engine cylinder during the *suction stroke. The mixture is now compressed during the compression stroke and thus the pressure and temperature is raised. The mixture is ignited with the help of a spark plug just before the compression is complete. It results in the sudden rise of pressure, due to the expansion of the combustion of the products in the engine cylinder. This sudden rise of pressure pushes the piston with great force and rotates the crankshaft, which in turn, drives the vehicle. The burnt gases are exhausted from the engine cylinder, so as to make space available for the fresh air-fuel mixture.
( Note: The petrol engines work on Otto cycle. It is also known as constant volume cycle as the heat is received and rejected at a constant volume.)
2. Diesel engines.
In diesel engines (also known as compression ignition engines or C.I. engines), the pure air is drawn into the engine cylinder during the suction stroke. It is now compressed as a result of which the pressure and temperature of air increases considerably (the actual value depends upon the compression ratio, which is about 14 to 25). Before the piston just completes the compression stroke, the fuel oil (diesel) is injected into the engine cylinder through the injector nozzle. At this moment, the temperature of compressed air is sufficiently high to ignite the fuel.
It suddenly increases the pressure and temperature of the products of combustion. The fuel oil is assumed to be burnt at constant pressure. Due to the increased pressure, the piston is pushed down with a great force and rotates the crankshaft which, in turn, drives the vehicle. The movement Of the piston push out the products of combustion from the engine cylinder into the atmosphere
( Note: The diesel engines work on diesel cycle. It is also known as constant pressure cycl combustion takes place at constant pressure. )
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