Transcript Diesel Engine 4 Stroke Cycle model

Diesel Engine 4 Stroke Cycle
model
Direct Injection
Load ‘Diesel 4S cycle.ppt’ as well and then run this presentation in
‘Slide Show’ mode to see the Animated sequence at the end
4 STROKE DIESEL ENGINE
Direct Injection
•This is a simplified model of a single cylinder Diesel engine to show the
principal parts, their relationships to each other and how the engine works.
•Is not based on any real engine, but is generally representative of real
engines. Most real engines are made up of several of this unit sharing a single
flywheel and cam shaft drive e.g. Three, four and six cylinder engines.
•Many minor details and some components are left out for clarity, for example
the bearings, exhaust pipe silencer, air intake filter and the fuel injection pump.
THE CONSTRUCTION OF THE ENGINE
Inside the solid body of
the Engine are a number
of fast moving parts
Cam-shafts
Moving parts
Crank-shaft
Bolts and fixings
omitted for clarity
Cam Shaft Drive. The cam-shaft drive arrangement is simply
represented by a box. In reality there would be a chain drive or a
gear train between the crank-shaft and the cam-shafts.
The Names of the Main Moving parts
Piston
Cam-Shafts
Valve Spring
Piston
Ring
Valves
Gudgeon
Pin
Connecting Rod
Crank-Shaft
Bolts and fixings
omitted for clarity
FlyWheel
Some stationary parts
Fuel
Injector
Cylinder
Head Cover
Cylinder
Head
Timing Case
Sump
Bolts and fixings are
omitted for clarity
(holds lubricating oil)
Engine block
Cylinder Head, Cylinder and Piston
Piston, a cylindrical part made to
be a close, but free running, fit in
the Cylinder of the Block.
The Cylinder Head sits on the top of the
Block to close off the top of the Cylinder.
It also carries the Valves, Fuel Injector
and the Inlet and Exhaust passages
The Piston Rings fit in
grooves on the
Piston. They seal the
Piston to be ‘gas tight’
in the Cylinder of the
Block
Block, a large strong
lump of metal that is
the main structural
member of the engine
Cylinder, a
large round
hole bored
straight and
parallel through
the Block
Bolts and fixings are
omitted for clarity
PISTON, CRANK SHAFT & FLY-WHEEL
• The Connecting Rod is inserted into a large recess
in the bottom of the Piston
Piston
•The Piston is attached to swivel on the ‘little end’ of
the Connecting Rod by the Gudgeon Pin through the
side of the Piston.
Gudgeon pin
•The ‘Big end’ of Connecting Rod fits onto the ‘throw’
of the Crank Shaft. (this end is usually split in half and bolted
‘Little End’
together for assembly purposes)
•The Connecting Rod connects the linear ‘up and
down’ motion of the Piston within the Cylinder with
the circular rotary motion of the Crank Shaft.
Connecting Rod
•The Fly-Wheel is attached to the end of the CrankShaft and serves to store the pulses of energy from
the Power Strokes, delivering energy to the other 3
strokes, and power to whatever the engine is driving.
‘Big End’
‘Throw’
FlyWheel
Crank Shaft
VALVES
One set of a Cam and a Valve controls the Inlet flow of fresh air into the Cylinder.
The other set controls the burnt Exhaust Gases out of the Cylinder. Both these
Valves are spring loaded to shut and seal the Cylinder during the Compression and
Power strokes. They open into the Cylinder, so that they are held closed by the high
pressures during the Compression and Power strokes.
Bump, or lobe, on the Cam pushes the Valve
open during part of the rotation of the Cam
Exhaust Cam
& Valve
Spring
Inlet Cam
& Valve
Inlet
Passage
Exhaust
Passage
INJECTOR
•The Fuel Injector is connected to a
high pressure pump that is not
illustrated.
•It sprays a small amount of diesel
fuel into the Cylinder at the end of
the Compression Stroke and
beginning of the Power Stroke.
•The fuel is sprayed through several
very small holes at very high
pressure in order to form a fine mist
of droplets of fuel that will ignite
easily and burn quickly in the hot air.
Nozzle tip with several
small holes for fuel spray
The 4 Stroke COMBUSTION CYCLE
•The Diesel Engine 4 Stroke cycle consists of four distinct stages carried out whilst
the engine Crank Shaft does two complete turns (or as we say, two revolutions).
•The Cams rotate once every two turns of the Crank Shaft, i.e. once per complete 4
stroke cycle.
•A ‘stroke’ is a movement of the Piston from one end of the Cylinder to the other end.
1st Stroke - INDUCTION. Fresh air is drawn into the Cylinder through the open Inlet
Valve by the Piston descending. The Inlet Valve closes when the Piston reaches
bottom of Cylinder, trapping the fresh air in the Cylinder.
2nd Stroke - COMPRESSION. The Air is squeezed as the Piston rises, reaching
about 40 bar pressure. The air gets very hot (about 700° C) because of the work
done to it by the Piston. Diesel fuel is started to be Injected into the Cylinder as
the Piston gets near to the top.
3rd Stroke - POWER. Fuel is injected into the Cylinder for a short while as the Piston
is near the top. The fuel spray ignites and burns in the hot air, creating even
higher pressures and temperatures in the cylinder. The pressure of the hot gases
push the Piston down, delivering power to the crank-shaft and fly wheel.
4th Stroke - EXHAUST. The Exhaust Valve opens and the rising Piston pushes the
burnt gases out of the Cylinder. When the Piston gets near the top the Exhaust
Valve closes and the Inlet Valve opens, ready to draw fresh air in again.
ANIMATION
• Click here to run the animated Diesel engine combustion
sequence.
(this link will only work if you run the presentation in ‘Slide Show’ mode with ‘Diesel 4S cycle.ppt in the same directory as this file)
End of Show