General occurrence in the internal combustion engine
During the combustion process, the combustion gases try to expand and exert force on the bottom of the piston. This force is known as gas force. The direction of the force moves the piston from top dead centre to the bottom dead centre whereby causing some transformation of energy.
Chemical energy stored in fuel (1) :- This chemical energy stored in fuel undergoes an incomplete combustion and in this process, the energy is converted by combustion phenomena, some gases get lost due to the incomplete combustion.
Heat Energy (1) to (2) :- There are several heat losses due to the various reasons.
- Radiation
- Cooling
- Exhaust gases
- Power at piston due to (1)-(2)-(3) ( Indicated power)
- frictional loss [ piston sliding of piston with respect to cylinder walls]
- pumping loss or adverse pressure difference q
- Power at Crankshaft (1)-(2)-(3)-(4)
- power at crankshaft are not fully utilized l, so therefore there are frictional losses between the crankshaft and the bearing.
- the unaccounted losses (power to run auxiliary devices example Air conditioning set.
- Useful power at crankshaft (1)-(2)-(3)-(4)
This power is utilized to run an automobile, known also as brake, shaft and delivered power. The inlet valves and the exhaust valves are operated with the help of the camshaft, this camshaft is utilized to operate the vehicle mechanism. The camshaft is attached to the crankshaft with the help of gear mechanism are supported by some bearing ( frictional losses between camshaft and bearing occurred ).
At this point in time, the energy remain conserved while converting energy from one form to another.
Assuming a four cycle with this parameters.
a. Suction (180°)
b. Compression ( 180°)
c. Expansion/power (180°)
d. Exhaust stroke ( 180°)
One power cycle of 4- stroke engine constitute of 720° of crank rotation which means it is 2 crank cycles which is equal to 1 power cycle.
So therefore N which is rpm is crank cycle/ min
n = N/2
n= N= 2 stroke.