Working of Engine Alternator

What is the Working principal of Engine Alternator?

How many parts of Diesel Engine?

Working of Engine Alternator

Various forms of standby AC supply arrangements are available, out of which the Engine Generator sets are most common. This consists of two separate machines, an Engine and the other a Generator or Alternator.
An Engine is a machine which converts the natural forms of fuel energy into mechanical energy. A Generator is an Electromagnetic machine which converts mechanical energy into Electrical energy. A Diesel Engine in an internal combustion engine (Engine which burns fuel inside the engine) which operates on liquid fuel. It depends on heat developed by compressing air to ignite fuel, which is forced into the combustion chamber at the instant of maximum compression and heat.

2. Construction of Internal Combustion Engines

The different parts of an internal combustion engine may be grouped as ‘ Stationary parts’ and ‘moving parts’. Stationary parts, are the parts are the Frame work, Crank Case, cylinder block, cylinder head etc. and the moving parts are the piston, connecting rod, crankshaft, camshaft, valve gear etc.
Diesel cycle
All diesel engines are four stroke engines only. These four strokes are Suction stroke, Compression stroke, Power stroke, and Exhaust stroke.
Suction stroke
Exhaust valve closes and inlet valve opens. The piston moves from top dead centre (TDC) towards bottom dead centre (BDC). Partial vacuum is created in the cylinder. The filtered air comes through inlet port.
Compression stroke
Inlet valve closes and exhaust valve remain closed. The piston moves from BDC to TDC. The air is compressed and the temp of the air raises to about 1000 F or 540 C.

Power stroke
Both the valves remain closed. Fuel is injected in the form of very fine spray through injector. Fuel ignites due to temperature . Due to heavy expansion, the piston moves towards the BDC and the energy is stored in the fly wheel.
Exhaust stroke

The exhaust valve opens and the inlet valve remains closed. The piston moves from BDC to TDC. The exhaust gases are expelled outside and the engine is ready for next cycle of operation.

Exhaust stroke



Various forms of standby power supply arrangements are available in our Department. The Diesel Engine Alternator sets are most common among them. Engine Alternator set consists of two separate machines, an Engine and the other an alternator or Generator.

An Engine is a machine which converts natural form of energy into mechanical energy.

An Alternator or Generator is an electro-magnetic machine which converts mechanical energy to electrical energy.

A Diesel engine is an “Internal Combustion” engine (engine which burns fuel inside the engine), which operates on liquid fuel. It depends on Heat developed by compressing air to ignite the fuel, which is forced into the combustion chamber at the instant of maximum compression and heat. Due to high compression the air charge reaches a much higher temperature-high enough to cause the injected fuel to vaporizes and ignite spontaneously. This is “Compression Ignition”, the essential feature of Diesel engine. Working of Engine Alternator, Working of Engine Alternator, Working of Engine Alternator, Working of Engine Alternator

Types of Diesel Engine Alternator

Diesel Engine Alternators are available from 3.5 KVA to 250 KVA Capacity, say, 3.5 KVA, 5.5 KVA, 7.5 KVA are available for single phase power supply and 10.5 KVA, 15 KVA, 33 KVA, 100 KVA, 150 KVA, 200 KVA, 250 KVA are available for three phase power supply.

Stationary parts

  • Bed Plate : Bottom most part made of cast iron.
  • Crank case : It is fixed above the Bed plate and as a sump, the lubricating oil is stored. The crank shaft is inside the crank case.
  • Cylinder Block: It is fixed above the crank case either the cylinder or cylinder with sleeve will be there inside.
  • Cylinder head : It is the upper fitting of the cylinder block which closes it. The inlet valve, the exhaust valve and the fuel injector are fitted on the cylinder head.
  • Rocker box : It is above the cylinder head and it contains rocker arms which are used for operating the valves.
  • Inlet Manifold : Through which air is sucked into engine.
  • Exhaust Manifold : Through which burnt out gases are thrown out.
  • Air Filter : It sucks the natural air, filters it and then passes the clean air to the combustion chamber. It may be dry or wet

Wet type filter

  • Silencer or Muffler: Sudden expansion of exhaust gases produce noise. Muffler changes the velocity of the exhaust gases and reduces the pressure in steps.
  • Asbestos rope : The exhaust pipe near the engine is covered by “Asbestos rope” to prevent accidental burning.
  • Radiator : It cools the engine by water. It consists of upper tank, lower tank, overflow pipe and water drain cock.
  • Fuel Tank : It supplies the filtered fuel into fuel pump. It is having pre filter, ceramic filter and fine filter. Big fuel tanks have fuel level indicator also. It has drain cock. In smaller fuel tank “Dipstick” is used for fuel level. It has “min” & “max” mark on it.
  • Fuel pump: It accurately meters the fuel required and inject the fuel at the proper timings through fuel injector.
  • Fuel Injector : It supplies the fuel into combustion chamber at the correct time, in the form of fine mist/spray at a high pressure (Say 150 kg/

Moving parts

  • Piston: It is sliding in a cylinder and performs all the strokes. Its functions are:


(i) To suck the air.

(ii) to compress the charged air.

(iii) To receive the pressure of the gases while they are expanding.

(iv) To expand the air. It has compression rings and oil rings.

  • Connecting Rod: It connects the piston to the crank shaft. The function is to transmit the force in either direction form the piston to the crank on the crank shaft.

connecting rod

  • Crank Shaft: The engine power is tapped out from the Crank shaft only in multi-cylinder engine. It will be a “zigzag shoed” shaft to which all the pistons are attached through the connecting rods.

Crank Shaft

  • Fly wheel: This is the heavy wheel attached to the one end of the crank shaft. It stores up the surplus energy of the Power stroke and returns this stored energy during other strokes.
  • Cam Shaft: This is driven by the crank shaft. It controls and operates the fuel injection pump. It also opens the inlet and exhaust valves at the appropriate time.
  • Valve Gear : This is the gear wheel of crank shaft which drives the cam shaft via spur gear.
  • Spur Gear : This is the gear connected to the cam shaft. Spur gear’s and valve gear’s teeth are so arranged that the cam shaft rotates only once for every two rotations of the crank shaft.

Parts in a valve fitting

  • Governor : It regulates the amount of Fuel supplied at each stroke and this controls the engine speed and power. A “Spring guarded governor” is commonly used in diesel engines.

Governor of Diesel engine

  • External Governor Lever: Small diesel engines are stopped by operating the “external Governor Lever” by hand.
  • Decompression Lever: It is used to leak the compression pressure of Air inside the cylinder to some extent for making “ easy manual (starting) cranking” while starting the small capacity engines.

Crank shaft with crank case

  • Meters:

  1. Speed Meter: It measures the speed of the engine. The speed should not exceed 1500 RPM. Speed adjusting knob is there to adjust the low or high speed.
  2. Water temperature Meter : The temperature of the water in the cooling system should not exceed 90º C. If it exceeds, an alarm will come; then stop the engine for 15-20 minutes.
  3. Oil temperature Meter: The oil temperature should not exceed 60º C.
  4. Oil pressure Meter: The oil pressure should not go below 2.5 kg/cm square. It should not go above 6 kg/cm square.

Fuel system of Diesel Engines

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