ENGINE

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ENGINE

This is the link of a video explaining how the 4 stroke spark-ignition engine works: (just a 9min video and has really good animation)

Converts power into Motion.
Or Converts Heat Energy into Mechanical Energy.

Types of engine:

  1. Internal Combustion Engine 
  2. External Combustion Engine
According to no. strokes:
  1. Two Stroke Engine 
  2. Four Stroke Engine
According to cycle used:
  1. Otto Cycle
  2. Diesel cycle 
  3. Dual cycle 
According to ignition:
  1. SI Ignition Engine (Spark ignition)
  2. CI Ignition Engine (Compression ignition)
  3. Hot Spot Ignition
According to fuel:
  1. Diesel Engine
  2. Petrol Engine
  3. Gas Engine (CNG, LPG)
  4. Alcohol Engine
According to the cooling system:
  1. Air Cooling System
  2. Water(liquid)Cooling System
According to Cylinder:
  1. Single Cylinder 
  2. Multi-Cylinder
According to Cumbustion Chamber:
  1. Open Chamber
  2. Divided Chamber

Parts of an Engine:



Cylinder Block:
It guides the piston, it is in direct contact with the combustion chamber.
Inside the cylinder block, water jackets are provided for flow of coolant/water through the block around the cylinder to cool the cylinders.
Made from cast iron. 


ENGINE CYLINDERS (CYLINDER BLOCK)

Gasket 

Pedestrial Bearing For Crank Shaft 




 Cylinder Head:
This provides an airtight sealing to the cylinder block. fits on the top end of the engine.
It consists of an inlet valve, exhaust valve, spark plug/injector etc.
Made from cast iron. 

Engine cylinders (CYLINDER HEAD) and Carburettor



Piston:
It transmits the power to the connecting rod and then to the crankshaft.
It should be light in weight, sufficient, strong to handle the gas pressure
Made from aluminium alloys.
PISTON


PISTON


Piston Rings:
(a)Compression ring:
It is used to provide a good sealing effect, to minimize the friction, minimize wear, transfer of heat from the piston to the cylinder.
(b)Oil ring:
To spread oil on cylinder walls for lubricating compression rings.
To regulate proper oil consumption and ensure oil is spread evenly on the cylinder walls also wipe off extra oil into the crankcase. 
*In the picture above. 


Connecting rod:
Transmit power from piston to the crankshaft i.e. reciprocating motion to rotating motion.
It has two ends one connected to the piston and one to the crankshaft.
*In the picture above.


Crank Shaft:
It transmits linear reciprocating motion to rotating motion. for this cranks are fixed at an offset from the central axis, so that the position of each piston is different at the given time (the motion of piston depends on the firing order). This helps to reduce heat production, faster cooling, produce more power in a given time.

CRANK SHAFT



Cam Shaft:
It controls the opening and closing of valves at proper timing. It is driven by timing belt drives by the crankshaft.
May be placed on the top or at the bottom of the cylindrical block according to the space provided.
CAMSHAFT

Valves :
Valves are provided for the intake of air (or air-fuel mixture) and to exhaust the burnt gases from the engine cylinder.

Flywheel:
It is designed to efficiently store rotational energy from the crank shaft and transmit it to the clutch plate. 
Flywheels help to resist changes in rotational speed by their moment of inertia.

  • When the piston reciprocates the motion during compression and exhaust produce less power and take less time to move from BDC (bottom dead centre) to TDC (top dead centre).         
  • Also during the power stroke of engine piston moves from TDC to BDC in less time.                                                             
  • This causes the crank shaft to rotate with varying speed according to each stroke of the piston.                                                    
  • So a flywheel is used to provide constant speed during all strokes. Hence there is no sudden increase or decrease in speed during the motion of the vehicle.
FLYWHEEL



Systems included in Engine
--------------------------------------
1.Throttle Body                                                                                                
2. Restrictor
        a.Orifice
        b.Convergent-Divergent Nozzle( venturi )                                        
3.Plenum
        a.Log Shaped Plenum
        b.Streamlined Plenum                                                                         
4.Runner
-------------------------------------
Exhaust System

1.Tail Pipe

2.Muffler
        a.Absorptive Type
        b.Reactive Type
        c.Combination Of Both
--------------------------------------------
Drive Train

1.Sprocket And Differential
--------------------------------------------
Engine Harness


STROKES OF A PISTON:
4 STROKE SI-ENGINE:
4 STROKE SI (SPARK IGNITION) ENGINE 

Engine cylinders and Carburettor
SI ENGINE


STROKE 1 (SUCTION):

The piston moves downwards till the BDC (Bottom Dead Center) that is the Bottom most point of the engine cylinder. Simultaneously the inlet valve is OPENED and the air is let inside the cylinder.
SUCTION STROKE


STROKE 2 (COMPRESSION):

When the piston reaches the BDC, Compression starts and the piston moves upwards. The inlet and exhaust valve is closed during the compression stroke. Compression of gas occurs in a specific ratio.
COMPRESSION STROKE

STROKE 3 (POWER):

Compression of air large amount of heat is generated. At that time fuel is injected/sprayed in the cylinder. Due to high-temperature fuel gets ignited and causes combustion (blast occurs in the cylinder above the piston). Due to high pressure generated the piston again moves to the BDC.
POWER STROKE

STROKE 4 (EXHAUST):

During this exhaust valve opens and the burnt gases are taken out of the engine cylinder. The piston moves upward till the TDC (Top Dead Centre)
EXHAUST STROKE

... and the cycle continues.

How does a vehicle start/move/function?

Following are the basic processes which take place in every vehicle:

Firing order:

The firing order is a sequence or the order of power delivery of each of cylinder in a multi-cylinder reciprocating internal-combustion engine. This is achieved by sparking of the spark plugs of a  gasoline internal-combustion engine in the correct order, or by the sequence of fuel injection with the help of a mechanical system in a Diesel engine.
e.g. for a 6 cylinder (CNG engine) 
15-36-24
16-35-24

1. Ignition system: (For petrol or gas engines)


  1. There is a carburettor which mixes air and fuel(gas)in the required ratio. (when the key is turned once). The ratio of gases is maintained by the L-series (sensor).                                                                                                                                      
  2. This mixture of gases is sent to engine cylinders                                                                                                                             
  3. When the vehicle is turned on by turning the key once more, the supply from the battery flows through the key and then to the starter.                                                                                                
  4. This starter consists of two coils:
  5. (a) Primary coil: Battery supply is given to the primary coil. this supply is given to the contact breaker circuit. It consists of cam lobe due to which the contact breaker point connects and disconnects. the contact breaker also consists of a condenser to prevent the contact point from damage due to heat production.   
  6. (b) Secondary coil: When the current flows through the primary winding due to the back emf large amount of current flows through the secondary coil. The secondary coil has the number of turns more than the primary coil. Hence the current flowing through the secondary coil is more than the battery supply.                                                                                                      
  7. Current from the secondary coil goes to the distributor. Rotor at the centre of the distributor rotates according to a given time interval.                                                                                                  
  8. When the rotor comes near the HT cable, high voltage passes from the distributor to the cable and to the spark plug.                            
  9. Hence according to the time interval, each cylinder in the engine is given the spark and power is generated due to combustion.
Distributer for CNG Engine

2. Ignition system: (Diesel engine)

* Content will be added soon 
FUEL INJECTOR