The components of the air inlet and exhaust system
control the quality of air and the amount of air that is
available for combustion. The air inlet and exhaust
system consists of the following components:
• Air cleaner
• Turbocharger
• Aftercooler
• Inlet manifold
• Cylinder head, injectors, and glow plugs
• Valves and valve system components
• Piston and cylinder
• Exhaust manifold
Air is drawn in through the air cleaner into the air inlet
of the turbocharger (9) by the turbocharger
compressor wheel (8). The air is compressed and
heated to about 150 °C (300 °F) before the air is
forced to the aftercooler (5). As the air flows through
the aftercooler the temperature of the compressed air
lowers to about 50 °C (120 °F). Cooling of the inlet air
increases combustion efficiency. Increased
combustion efficiency helps achieve the following
benefits:
• Lower fuel consumption
• Increased power output
• Reduced particulate emission
From the aftercooler, air is forced into the inlet
manifold (4). Air flow from the inlet manifold to the
cylinders is controlled by inlet valves (10). There is
one inlet valve and one exhaust valve for each
cylinder. The inlet valves open when the piston
moves down on the intake stroke. When the inlet
valves open, cooled compressed air from the inlet
port is forced into the cylinder. The complete cycle
consists of four strokes:
• Inlet
• Compression
• Power
• Exhaust
On the compression stroke, the piston moves back
up the cylinder and the inlet valves (10) close. The
cool compressed air is compressed further. This
additional compression generates more heat.
Note:
If the cold starting system is operating, the glow
plugs (3) will also heat the air in the cylinder.
Just before the piston reaches the Top Center (TC)
position, fuel is injected into the cylinder. The air/fuel
mixture ignites. The ignition of the gases initiates the
power stroke. Both the inlet and the exhaust valves
are closed and the expanding gases force the piston
downward toward the Bottom Center (BC) position.
From the BC position, the piston moves upward. This
initiates the exhaust stroke. The exhaust valves open.
The exhaust gases are forced through the open
exhaust valves into the exhaust manifold.
Exhaust gases from exhaust manifold (1) enter the
turbine side of the turbocharger in order to turn
turbocharger turbine wheel (7). The turbine wheel is
connected to the shaft that drives the compressor
wheel. Exhaust gases from the turbocharger pass
through exhaust outlet (6), a silencer, and an exhaust
pipe.
Turbocharger
Illustration 8
g00302786
Turbocharger
(1) Air intake
(2) Compressor housing
(3) Compressor wheel
(4) Bearing
(5) Oil inlet port
(6) Bearing
(7) Turbine housing
(8) Turbine wheel
(9) Exhaust outlet
(10) Oil outlet port
(11) Exhaust inlet
The turbocharger is mounted on the outlet of the
exhaust manifold in one of two positions on the right
side of the engine, toward the top of the engine or to
the side of the engine. The exhaust gas from the
exhaust manifold enters the exhaust inlet (11) and
passes through the turbine housing (7) of the
turbocharger. Energy from the exhaust gas causes
the turbine wheel (8) to rotate. The turbine wheel is
connected by a shaft to the compressor wheel (3).
As the turbine wheel rotates, the compressor wheel is
rotated. This causes the intake air to be pressurized
through the compressor housing (2) of the
turbocharger.
14
UENR0617
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