INTRODUCTION TO INTERNAL COMBUSTION
Combustion is a chemical reaction that take place in every fuel with the pressure of
air. Combustion can be classified as internal combustion and external combustion.
ENGINE CHARACTERISTICS
Internal combustion applies to most engine big or small. An internal combustion engine
is a heat engine that convert chemical energy in a fuel into a mechanical energy usually made
available on a rotating shaft. Chemical energy of the fuel in first converted to thermal energy by
means of combustion or oxidation with air inside the engine. This thermal energy raises the
temperature and pressure of the gasses within the engine, and the pressure gas then expands
against the mechanical mechanism of the engine. This expansion is converted by the mechanical
linkages of the engine to a rotating crankshaft which is the output of the engine. The crankshaft
in turn is connected to a transmission to transmit the rotating mechanical energy to the desired
final use.
Internal-combustion engines are the most broadly applied and widely used power-
generating devices currently in existence. Examples include gasoline engines, diesel
engines, gas-turbine engines, and rocket-propulsion systems.
Internal-combustion engines can be delineated in terms of a series of thermodynamic events.
In the continuous-combustion engine, the thermodynamic events occur simultaneously as the
oxidizer and fuel and the products of combustion flow steadily through the engine.
ENGINE PARAMETER
WORK
Work is produced inside each engine cylinder as gas pressure pushes the piston
downward during the expansion stroke. Pressure data for the gas in the cylinder over the
operating cycle of the engine can be used to calculate this work transfer from the gas to the
piston. Work is the result of a force acting through a distance. Force due to gas pressure on the
moving piston generates the work in an ICE cycle.
Work can be expressed in:
W =∫ PdV
Where;
P = pressure in combustion chamber
dV = differential volume displaced by the piston
, Indicated work – pressure inside the cylinder combustion chamber with respect to its
volume.
Brake work – work delivered by the crankshaft which is less than indicated work, it is
because of mechanical friction and parasitic load of the engine.
The relationship between this types of work can be expressed in:
w b=wi−wf
Where; wf = specific work lost due to friction and parasitic loads
TORQUE
Torque is a turning or twisting force and is a measure of an engine’s ability to rotate the
wheels. Torque is measured either by Foot X Pound or Kilogram X Meter. The torque is initially
produced by the piston. The force is then delivered to the crank and then to the transmission and
on to the wheels. In an piston engine, the combustion forces the piston to go downwards, pushing
the connecting rod that forces the crank to rotate.
The torque exerted by the engine is: T = Fb
POWER
Is defined as the rate of work of an engine. If n is the number of revolutions per cycle and
N is the engine speed. It can be computed through brake power and indicated power
The power delivered by engine is, product of torque and angular speed: P = 2πNT
1. Indicated Power
( imep ) LAnK bp
ip= =
60 ηm
Where ip = indicated power (kW)
Imep = indicated mean effective pressure (KN/m2)
L = length of stroke (m)
Combustion is a chemical reaction that take place in every fuel with the pressure of
air. Combustion can be classified as internal combustion and external combustion.
ENGINE CHARACTERISTICS
Internal combustion applies to most engine big or small. An internal combustion engine
is a heat engine that convert chemical energy in a fuel into a mechanical energy usually made
available on a rotating shaft. Chemical energy of the fuel in first converted to thermal energy by
means of combustion or oxidation with air inside the engine. This thermal energy raises the
temperature and pressure of the gasses within the engine, and the pressure gas then expands
against the mechanical mechanism of the engine. This expansion is converted by the mechanical
linkages of the engine to a rotating crankshaft which is the output of the engine. The crankshaft
in turn is connected to a transmission to transmit the rotating mechanical energy to the desired
final use.
Internal-combustion engines are the most broadly applied and widely used power-
generating devices currently in existence. Examples include gasoline engines, diesel
engines, gas-turbine engines, and rocket-propulsion systems.
Internal-combustion engines can be delineated in terms of a series of thermodynamic events.
In the continuous-combustion engine, the thermodynamic events occur simultaneously as the
oxidizer and fuel and the products of combustion flow steadily through the engine.
ENGINE PARAMETER
WORK
Work is produced inside each engine cylinder as gas pressure pushes the piston
downward during the expansion stroke. Pressure data for the gas in the cylinder over the
operating cycle of the engine can be used to calculate this work transfer from the gas to the
piston. Work is the result of a force acting through a distance. Force due to gas pressure on the
moving piston generates the work in an ICE cycle.
Work can be expressed in:
W =∫ PdV
Where;
P = pressure in combustion chamber
dV = differential volume displaced by the piston
, Indicated work – pressure inside the cylinder combustion chamber with respect to its
volume.
Brake work – work delivered by the crankshaft which is less than indicated work, it is
because of mechanical friction and parasitic load of the engine.
The relationship between this types of work can be expressed in:
w b=wi−wf
Where; wf = specific work lost due to friction and parasitic loads
TORQUE
Torque is a turning or twisting force and is a measure of an engine’s ability to rotate the
wheels. Torque is measured either by Foot X Pound or Kilogram X Meter. The torque is initially
produced by the piston. The force is then delivered to the crank and then to the transmission and
on to the wheels. In an piston engine, the combustion forces the piston to go downwards, pushing
the connecting rod that forces the crank to rotate.
The torque exerted by the engine is: T = Fb
POWER
Is defined as the rate of work of an engine. If n is the number of revolutions per cycle and
N is the engine speed. It can be computed through brake power and indicated power
The power delivered by engine is, product of torque and angular speed: P = 2πNT
1. Indicated Power
( imep ) LAnK bp
ip= =
60 ηm
Where ip = indicated power (kW)
Imep = indicated mean effective pressure (KN/m2)
L = length of stroke (m)
