Diesel Power Station

An alternator requires the mechanical energy as input further it is converted into electrical energy by it. In case of diesel power station, diesel engine acts as a prime mover which obtains its energy from a liquid fuel known as diesel oil and converts this energy into mechanical energy further which is provided to the alternator which is mounted on the same shaft as that of diesel generator. In case of diesel engine heat required for combustion of fuel is obtained by compression of air in the engine cylinder and then the fuel is injected in engine cylinder. The main difference between diesel power station and steam power station is that, in diesel power station, mechanical energy is generated using direct combustion of fuel under use, and in case of steam power stations first combustion of fuel under use is utilized to convert water into steam and then the steam at high pressure and temperature produces the mechanical energy. Diesel power plants are more advantageous than any other heat engine in the view of initial cost, quick starting and stopping time also, it doesn't require any warming up period. Therefore stand by losses are not present and hence has found increasing applications either as continuous or as a peak source of electric power.

Diesel Power Station (Source - Doosan.com)

Although steam power stations and hydroelectric power plant are invariably used to generate bulk power at cheaper costs, yet diesel power stations are finding favour at places where demand of power is less, sufficient quantity of coal and water is not available and the transportation facilities are inadequate. This plants are also standby sets for continuity of supply to important places such as hospitals, radio stations, cinema houses and telephone exchanges.

Block Diagram of Diesel Power Station

Essential element of Diesel Power Plant :-

1. Engine:- Engine is the main component of the diesel power plant, which develops mechanical power. Generally engine is directly coupled to the alternator. Internal combustion engine are used. An internal combustion engine is that produces power by burning fuel inside a combustion chamber within the engine. The fuel burns and the burnt fuel expands to do work on the moving part inside the cylinder called piston. This movement of piston rotates the flywheel and the engine is directly coupled with the generator. The gases after the expansion inside the chamber is exhausted into the atmosphere and passes through a silencer in order to reduce the noise.
2. Fuelling System:- It consists of storage tank, strainers, fuel transfer pump and all day fuel tank, heaters and connecting pipe work. To make the oil free from impurities it is passed through the strainers.The fuel oil is supplied at the plant site by rail and road. Heaters for oil may be required in winter season to heat the oil. Fuel is fired into the engine through fuel filter and fuel injection pump.
3. Air Intake System:- This consists of air filters, ducts and super charger.This system supplies necessary air to the engine for fuel combustion. It consists of ducts/pipes for the supply of fresh air to the engine manifold. Filters are provided to remove dust particles from the atmospheric air which is intended to supply to engine. 

   

   Air Intake System

4. Exhaust System:-  Exhaust system includes connecting ducts and silencers. This system leads the engine exhaust gas outside the building and discharges it into atmosphere. A silencer is usually incorporated to reduce the noise level. The exhaust system of the diesel power station performs three functions. First system, the exhaust system routes the spent combustion gases away from the engine, where they are diluted by the atmosphere. This keeps the area around the engine habitable. Second the exhaust system confines and routes the gases to the turbocharger, if used. Third, the exhaust system allows mufflers to be used to reduce the engine noise.
5. Cooling System:- Cooling system includes water circulating pumps, cooling towers or spray ponds and water filtration plant. The heat released by burning of fuel in the engine cylinder is partially converted into work. The remainder part of the heat passes through the cylinder wall, piston, rings etc. and may cause damage to the system. In order to keep the temperature parts of engine within the same operating limits, cooling is provided.
6. Lubricating System:- Lubricating system includes the oil pumps, oil tanks, filters, coolers, purifiers and connecting pipe work. Lubrication system reduces the friction of moving parts and reduce the wear and tear of the engine parts. The lubrication oil is drawn from the lubrication oil tank by the pump and is passed through filter to remove impurities. The clean lubrication oil is delivered to the points which require lubrication.

   

   Lubricating System (Source-IGNOU)

7. Engine Starting System:- Engine starting system includes storage battery compressed air tanks, self starters etc. The function of starting system is to start the engine from cold condition. The system enables the engine to route initially while starting until the firing starts and the unit runs on its own power.
8. Governing System:- The function of the governing system is to maintain the speed of the engine constant irrespective of the load on the plant. This is done generally by varying fuel supply to the engine according to the load. 

Major Components of Diesel Engine

To supply the diesel power station it is worth to know about the diesel engine i.e., its construction and working.

1. Cylinder:- It is the part of diesel engine in which combustion of fuel is taken place and power is developed. Therefore it is known as heart of the engine. Cylinder has consists of valves through which air and fuel are admitted and exhaust gases are discharged.
2. Piston:- Power developed by the burning of the fuel is transmitted by the piston to the crank shaft. Distance travelled by the piston from one end to another end is known as. Gas tight seal is required between piston and cylinder liner which is provided by the engine oil lubricated piston rings. 
3. Connecting rod and crankshaft:- Connecting rod mechanically connects the piston and crankshaft which transfers the mechanical power developed by the piston to the crankshaft. Thus mechanical power generated can be taken out from the crankshaft. 
4. Fuel Nozzle:- Fuel is delivered by the fuel nozzle in fine spray under pressure in diesel engines.  It mainly consists of fuel pump, fuel line and the injector.
5.  Camshafts:-  Camshaft is driven from the crankshaft by a timing gear on a chain. It mainly operates the intake valve and the exhaust valve through cam, cam followers, pushrods and rocker arms. 
6. CrankCase:- Crankcase holds the cylinder, piston and crankshaft.
7. Flywheel:- Fluctuations of the cyclic variations in speed is reduced by flywheel. It stores energy during power stroke and releases during the other stroke. Thus a constant torque is obtained at output.