Page 32 - Mechatronics with Experiments

JWST499-c01
18 JWST499-Cetinkunt Printer: Yet to Come October 9, 2014 7:39 254mm×178mm
MECHATRONICS
Ambient
air inlet
EGR
cooler
EGR Trap Turbine
valve
wheel Turbine exhaust
gas outlet
Ambient Turbo charger
air
section Exhaust
back pressure
valve Exhaust gas inlet
Waste gate Compressed
Compressor Turbine valve Ambient air discharge
air inlet
Compressor
Cool Inter wheel
air/water cooler

Engine block
Intake manifold
Cylinders Exhaust
gas

Exhaust manifold

FIGURE 1.18: Engine and its surrounding sub-systems: intake manifold, exhaust manifold,
turbo charger with waste-gate valve, charge (inter) cooler, exhaust gas recirculation (EGR), trap
or catalytic converter.

exhaust valves, and a fuel injector. The power obtained from the combustion process is
converted to the reciprocating linear motion of the piston. The linear motion of the piston is
converted to a unidirectional continuous rotation of the crankshaft through the connecting
rod. In the case of a spark ignited engine (gasoline engine), there would also be a spark
plug to generate ignition. The compression ratio of diesel engines is in the range of 1:14 to
1:24, while gasoline engine compression ratio range is about half of that.
Normally, there are multiple cylinders (i.e., 4, 6, 8, 12) where each cylinder operates
with a different crankshaft phase angle from each other in order to provide non-pulsating
power. An engine’s power capacity is determined primarily by the number of cylinders,
volume of each cylinder (piston diameter and stroke length), and compression ratio. Fig-
ure 1.18 shows the engine block and its surrounding sub-systems: throttle, intake manifold,
exhaust manifold, turbo charger, charge cooler. In most diesel engines there is not a physical
throttle valve. A typical diesel engine does not control the inlet air, it takes the available air
and controls the injected fuel rate, while some diesel engines control both the inlet air (via
the throttle valve) and the injected fuel rate.
The surrounding sub-systems support the preparation of the air and fuel mixture
before the combustion and exhausting of it. Timing of the intake valve, exhaust valve, and
injector is controlled either by mechanical means or by electrical means. In completely
mechanically controlled engines, a mechanical camshaft coupled to the crankshaft by
a timing belt with a 2:1 gear ratio is used to control the timing of these components
which is periodic with two revolutions of the crankshaft. Variable valve control systems