Ch. 9 - INTAKE & EXHAUST Flashcards
Combustion requires three things:
Air, fuel, and heat.
What are the six basic components of intake and exhaust systems?
Pre-cleaner, air filters, filter service indicator's, turbo chargers, intake and exhaust manifolds, mufflers.
What is the flow of air intake and exhaust systems?
Pre-cleaner, air filters, turbo charger, intake manifold and cylinder heads, combustion chamber, exhaust manifold.
What does a blower do?
The blower compresses the air and forces it into an air box or manifold, which surrounds or is attached to the cylinders of an engine. Thus, more air under constant pressure is available as required during the cycle of operation.
What is scavenging?
The increased amount of air, a result of blower action, fills the cylinder with a fresh charge of air.
During the process, the increased amount of air helps to clear the cylinder of the gases of combustion. This process is called scavenging.
The air forced into the cylinder is called scavenge air, and the ports through which it enters are called scavenge ports.
What are the three types of air intake systems for Diesel engines?
Naturally aspirated, supercharged, and turbo charged.
When does scavenging occur?
In a 2-stroke, the process takes place during the latter part of the down stroke (expansion) and the early part of the upstroke (compression).
In a 4-stroke, scavenging takes place when the piston is nearing and passing TDC during the latter part of an upstroke (exhaust) and the early part of a down stroke (intake).
How does a turbo charger work?
Air is forced into the combustion chamber under a greater pressure.
EXHAUST gases from the engine drive the turbo charger, therefore no power it’s taken from the engine’s output.
Sometimes referred to as centrifugal blowers.
How does a supercharger work?
Air is forced into the combustion chamber under a greater pressure.
Instead of being powered by exhaust gases from the engine (as is the case with turbo chargers), a supercharger is powered from the engine’s OUTPUT.
What are the three types of superchargers?
Roots type (blower)
Screwtape
Centrifugal
What is a roots type blower?
A positive displacement air pump.
A fixed volume of air is moved with every rotation of the rotors.
The compression process is external to the blower.
As volume of air present in the intake manifold increases, air pressure increases accordingly.
What is a screw type supercharger?
Similar in function to a roots blower.
Relies on internal compression.
Operates by pulling air through a pair of mesh lobes resembling a set of worms gears.
Air is trapped in pockets by rotor lobes. As air pockets decrease in size, air moves from fill side to discharge side. As air pockets shrink, air is squeezed into a smaller space.
What is a centrifugal type supercharger?
Similar in nature to a turbo charger.
The century forgot type supercharger is mechanically driven by the engine crankshaft rather than exhaust gases.
Why do we need super chargers?
Because in order to have more power, we need more burning of fuel, and to have that we need more air to compress.
The supplying of more air to the combustion spaces than can be supplied through the action of atmospheric pressure and piston action is called supercharging.
Supercharging is done with the exhaust ports or valves closed, a condition that enables the blower to force air under pressure into the cylinder and thereby increase the amount of air available for combustion.
How does supercharging affects the intake and exhaust valves?
The intake and exhaust valves are open much longer and a supercharged engine, and the compression and power events are shorter, permitting a longer period for scavenging.
