On a turbocharged diesel engine (Fig. 3), the
turbocharger supplies air under pressure to the intake
manifold which provides a greater amount of air to the
combustion chamber. The fuel injection system is
calibrated to inject the correct amount of fuel for the
increased volume of air.
2. Fuel Injector
The turbocharger, in addition to exhaust volume
and velocity, depends upon exhaust heat. Under loaded
conditions at maximum fuel delivery, the turbocharger
becomes very efficient and supplies the increased air
volume needed to support proper combustion (Fig. 4).
Since the turbine speed is governed by the
exhaust energy of the engine at any speed, the
turbocharger delivers the correct volume of air at any
throttle position. Also, less air resistance at higher
elevations allows the turbocharger to spin faster and
maintain correct air delivery, thereby avoiding the power
loss and excessive smoking that occurs on naturally
aspirated and supercharged engines at high altitude.
Fig. 4. Turbocharger Cycle
Compressor Wheel Speed Increases as
Exhaust Expansion Increases.
Increased Fuel Consumption Requires
Greater Air Intake.
Exhaust Temperature Increased with
Greater Fuel Consumption.
Increased Exhaust Temperature Results in
Greater Expansion within Turbine Housing.
turbocharger are as follows:
The engine exhaust is directed into the turbine housing
(Fig. 5). As the exhaust passes through the nozzle ring
vanes, it gains velocity and strikes the turbine wheel
vanes. This action spins the turbine wheel shaft to which
the compressor wheel is attached.
As the compressor wheel turns, it draws air from the air
cleaner into the compressor housing, compresses it and
forces it into the intake manifold. This provides a greater
volume of air in the combustion chamber. Because a
greater volume of air
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