A diesel engine (also known as a compression-ignition engine) is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber.
Difference between diesel and petrol engine:
The only difference between Diesel Engine and Petrol Engine is the way through which combustion of fuel take place. In Petrol Engine combustion of fuel takes place by first compressing it and then igniting it from a spark plug. In Diesel Engine combustion of fuel starts automatically when it take it into contact with highly compressed air.
4- Stroke diesel engine cycle:
1-2 Isentropic Compression 2-3 Constant P Heat Add 3-4 Isentropic Expansion 4-1 Constant V Heat Reject
………… P-V diagram ………….
…………. T-S diagram …………..
Efficiency of diesel engine:
Thermal efficiency of 4 Stroke diesel engine can be calculated as follows.
If
qin = net heat input
qout = net heat output
Then
Thermal Efficiency = (qin - qout ) / qin
Superiority of diesel engine over petrol engine:
Diesel engine is superior than petrol engine because Cost of diesel is low, Compression ratio is too much high, Diesel cycle is more realistic than Otto cycle etc.
Strokes of 4 stroke diesel engine:
1- Intake Stroke
2- Compression Stroke
3- Power Stroke
4- Exhaust Stroke
Intake Stroke:
This is the first movement of the piston. This is a downward motion of the piston that develops a vacuum in the cylinder. This vacuum pulls the air and fuel mixture into the cylinder through the open intake valve.
Compression Stroke:
During this second stroke, all valves are closed. This allows all of the piston's force to be used to compress the air and fuel mixture. As it is compressed, the mixture becomes more dense creating a more potent mixture for detonation.
Power Stroke:
Just before the piston reaches top dead center, the mixture is ignited due to high compression. The third stroke, the power stroke harnesses the energy of the explosion by allowing the piston to be forced downward from top dead center. This linear motion is changed to rotational motion by the crankshaft.
Exhaust Stroke:
The last stroke is the exhaust stroke. During this last upward movement of the piston the exhaust valve is open. The piston forces all of the burned gasses from the previous explosion out of the cylinder. The cycle is completed and can begin again.
Parts of 4 stroke diesel engine:
Base
That is the lower portion of 4 stroke diesel engine and is used to envelope the sump.
Sump
That is used for the lubrication management of the engine. It is the limited space that is used to collect the lubrication liquid.
Fins
These are used to manage the temperature inside the engine.
Water hollow space
That is the space around the cylinder in which cooling fluid circulates, which cools the burnt air-fuel mixture inside the cylinder.
SUMP FINS
Driving Shaft
The shaft which is driven by expansion of piston is known as driving shaft
Fly Wheel
That is a rotating mechanical device which stores the energy.
Connecting Rod
It changes reciprocatory motion of piston into rotating motion of flywheel.
Cylinder
The potion in which diesel cycle executes is known as cylinder.
Driving Shaft Flywheel Connecting Rod
Piston
The device which compress the air-fuel mixture inside the cylinder is known as piston.
Intake Valve
The valve through which fuel enters the cylinder is known as intake valve.
Exhaust Valve
The valve through which fuel leaves the cylinder is known as exhaust valve.
Valve Springs
The springs which impel the valves to retain their original positions after their displacement directed by timing gears.
Piston Valve Spring
Cap
The cap with which valve springs are fixed.
Rocker Arm Nut
The nut with which a lever is attached, which transmits the motion
of cam to valve.
Air Filter
It filters the air which enters the cylinder of engine.
Intake Manifold
The path through which air – fuel mixture enters the cylinder.
Exhaust Manifold
The path through which air – fuel mixture exhausts to surrounding
Cap Nut Filter Manifold
Glow Plug
A glow plug is a device, used to pre ignite the fuel in engine.
Injector
That is a device which injects fuel inside the cylinder of engine.
Timing Gears
The gears which control the timing of intake and exhaust valve.
Pre-Combustion Chamber
The chamber in which air and fuel mix with each other just before combustion.
Plug Gears
Injection Pump Body
Part of the engine which controls the injection of fuel into the cylinder.
Cam Shaft
it controls the movement of valves by taking driving force from crankshaft.
Tappet
A lever or projecting arm that moves or is moved by contact with another part, usually to transmit motion, as between a driving mechanism and a valve.
Barrel
Hollow cylinder of engine
Piston Spring
The spring which moves piston to and fro.
Cam tappet spring
Sector Gear
The gear system which deals with proper fuel ignition process.
Flow Rod
The rod whose movement cause gears to rotate.
Pressure Valve
The valve which adjusts the pressure of air – fuel mixture is known as pressure valve
Pressure Valve Spring
The springs which impel the pressure valve to retain their original positions after their displacement.
flow rod
Fuel Piping
The piping through which fuel is directed to cylinder
Exhaust Piping
The pipe through which burnt air-fuel mixture exhausts.
Fuel piping Exhaust pipe
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