Sem 4, PCT Presentation, K. J. Somaiya College of Engineering
Transcript of Internal Combustion Engines - Construction and Working (All you need to know, more than what you...
AND THEIRAPPLICATIONS
APRESENTATIONBySEMECHANICALA4 SEPTEMBER 2008
An Introduction The internal combustion (IC) engine converts
chemical energy into useful mechanical energy by burning fuel.
Chemical energy is released when the fuel-air mixture is ignited by
the spark in the combustion chamber. The gas produced in this
reaction rapidly expands forcing the piston down the cylinder on
the power stroke.
The crankshaft, sometimes casually abbreviated to crank, is the
part of an engine which translates reciprocating linear piston
motion into rotation.To convert the reciprocating motion into
rotation, the crankshaft has "crank throws" or "crankpins"
In a reciprocating piston engine, the connecting rod or conrod
connects the piston to the crank or crankshaft.The connecting rod
was invented sometime between 1174 and 1200
The camshaft is an apparatus often used in piston engines to
operate poppet valves.It consists of a cylindrical rod running the
length of the cylinder bank with a number of oblong lobes or cams
protruding from it, one for each valve.
A spark plug is an electrical device that fits into the
cylinder head of internal combustion engines and ignites compressed
aerosol gasoline by means of an electric spark. Internal combustion
engines can be divided into spark-ignition engines, which require
spark plugs to begin combustion, and compression-ignition engines
(diesel engines), which compress the air and then inject diesel
fuel into the heated compressed air mixture where it
auto-ignites.
Spark plug gapping: The centre electrode (dark rod) is a
cylindrical rod, and the top ground electrode (a hook) has square
edges. When regapping, the hook is raised or lowered to adjust the
gap, often to 0.035 to 0.050 inches.The main issues with spark plug
gaps are: Narrow-Gap risk: spark might be too weak/small to ignite
fuel; Narrow-Gap benefit: plug always fires on each cycle; Wide-Gap
risk: plug might not fire, or miss at high speeds; Wide-Gap
benefit: spark is strong for a clean burn.A properly gapped plug
will be wide enough to burn hot, but not sowide that it skips or
misses at high speeds, causing that cylinder to drag,or the engine
to begin to rattle.
The drivetrain is the mechanical path by which the enginesends
power to the wheels (i.e. provides drive). The drivetrain includes
a gearbox, a power transmissionor transfer system i.e. chain and
sprocket or drive shaft,a differential, axles, CV joints, wheels
and tyres and finallythe braking system.
Turbochargers are a type of forced induction system which
hasits compressor powered by a gas turbine running off the
exhaustgases from the engine.The purpose of a turbocharger is to
increase the mass of airentering the engine to create more power.
The compressor whichdrives the turbocharger is powered by a turbine
driven by theengines own exhaust gases.
A carburettor is a device that blends air and fuel for
aninternal combustion engine. It was invented by Karl Benzbefore
1885 , patented in 1886. It is colloquially called a carb
Fuel injection is a system for mixing fuel with air in
aninternal combustion engine. It has become the primary systemused
in automotive engines, having almost completely
replacedcarburettors in the late 1980s.
TYPICAL EFI (ELECTRONIC FUEL INJECTION) COMPONENTS Injectors
Fuel Pump Fuel Pressure Regulator ECM - Engine Control Module;
includes a digital computer and circuitry to communicate with
sensors and control outputs. Wiring Harness Various Sensors (Some
of the sensors required are listed here.) o Crank/Cam Position:
Hall effect sensor o Airflow: MAF sensor, sometimes inferred with a
MAP sensor o Exhaust Gas Oxygen: Oxygen sensor, EGO sensor, UEGO
sensor
An internal combustion engine would not run for even a
fewminutes if the moving parts were allowed to make metal-to-metal
contact. The heat generated due to the tremendousamounts of
friction would melt the metals, leading to thedestruction of the
engine. To prevent this, all moving parts rideon a thin film of oil
that is pumped between all the moving partsof the engine.Once
between the moving parts, the oil serves two purposes.One purpose
is to lubricate the bearing surfaces. The otherpurpose is to cool
the bearings by absorbing the friction-generated heat. The flow of
oil to the moving parts isaccomplished by the engines internal
lubricating system.
A Rotary Engine is an internal combustion engine, like the
enginein your car, but it works in a completely different way than
theconventional piston engine.In a piston engine, the same volume
of space (the cylinder)alternately does four different jobs:
intake, compression,combustion and exhaust.A rotary engine does
these same four jobs, but each onehappens in its own part of the
housing. Its kind of like having adedicated cylinder for each of
the four jobs, with the pistonmoving continually from one to the
next.The rotary engine (originally conceived and developed by
Dr.Felix Wankel) is sometimes called a Wankel engine, or
Wankelrotary engine.
One cycle shownSame process occurring for all sides of body
A
Engines based on the two-stroke cycle use two strokes (oneup,
one down) for every power stroke. Since there are nodedicated
intake or exhaust strokes, alternative methodsmust be used to
scavenge the cylinders. The most commonmethod in spark-ignition
two-strokes is to use thedownward motion of the piston to
pressurize fresh chargein the crankcase, which is then blown
through the cylinderthrough ports in the cylinder walls.
Engines based on the five-stroke cycle are a variant of the
four-stroke cycle. Normally, the four cycles are intake,
compression,combustion, and exhaust. The fifth cycle added by
Delautour isrefrigeration. Engines running on a five-stroke cycle
are claimed tobe up to 30% more efficient than equivalent
four-stroke engines.The six stroke engine captures the wasted heat
from the four-stroke Otto cycle and creates steam, which
simultaneously coolsthe engine while providing a free power stroke.
This removes theneed for a cooling system making the engine lighter
while giving40% increased efficiency over the Otto Cycle. Beare
HeadTechnology combines a four-stroke engine bottom-end with
aported cylinder which closely resembles that of a two-stroke:
thus,4+2 equals a six-stroke cycle. It has an opposing piston that
acts inunison with auxiliary low pressure reed and rotary valves,
whichallows variable compression and a range of tuning
options.