Diesel engine power plant

DIESEL ENGINE POWER PLANT

The Diesel Power Plant is a fossil-fuel plant, since diesel is a fossil-fuel.

1. LAYOUT OF DIESEL ENGINE POWER PLANT (Fig. 7)

1. Diesel Engine: (Refer Chapter 11 - Internal Combustion Engines)

Diesel Engine is also known as Compression Ignition Engine. It is classified as Two Stroke Engine and Four Stroke Engine. According to the number of cylinders, diesel engines are classified as Single Cylinder and Multi-cylinder Engines. Diesel Engines may have more than one cylinder such as 4, 6, 8, etc. Normally, multi-cylinder two stroke diesel engines are used in diesel power plants.

See Fig. 7, showing the layout of a Diesel Power Plant. In the diesel engine, air admitted into the cylinder is compressed. The compression ratio is 12 to 20.

At the end of the compression stroke, the fuel (diesel) is injected. It burns and the burning gases expand and do work on the piston. The engine is directly coupled to the electric generator. The gases are then exhausted from the cylinder to the atmosphere.

2. Engine Starting System

This includes Air Compressor and Starting Air Tank. The function of this system is to start the engine from cold by supplying compressed air.

3. Fuel System

Pump draws diesel from the Fuel Storage Tank and supplies it to the small Day Tank through the Filter. Day tank supplies the daily-fuel-need of the engine. The day tank is usually placed high so that diesel flows to engine under gravity. Diesel is again filtered in the Filter inside the engine before being injected into the engine by the Fuel Injection Pump. The fuel is supplied to the engine according to the load on the plant.

4. Air Intake System

Air Filter is used to remove dust from the incoming atmospheric air. Air filter may be of dry type, which is made up of felt, wool or cloth. In oil bath type of filter, the air is swept over a bath of oil so that dust particles get coated.

5. Exhaust System

In the exhaust system, Silencer (Muffler) is provided to reduce the noise produced by the engine.

6. Engine Cooling System

Temperature of burning gases in the engine cylinder is 1500°C to 2000°C. Water is circulated inside the engine to keep the temperature at a reasonable level. The hot water from the engine is cooled in a Spray Tank and re-circulated using Pump.

7. Engine Lubricating System

Lubrication is essential to reduce friction and wear of the engine parts such as cylinder walls and piston. Engine Lubricating System includes Lubricating Oil Cooler and Oil Pump. [Oil pump is not shown.] Lubricating oil which gets heated due to the friction of the moving parts is cooled before re-circulation.

8. Governing System

The function of the governing system is to maintain the speed of the engine constant, irrespective of load on the plant. This is done generally by varying fuel supply to the engine according to the load.

2. ADVANTAGES OF DIESEL ENGINE POWER PLANT

1. Plant Layout: Plant layout is simple. Hence, it can be quickly installed and commissioned, while the erection and starting of a steam power plant or hydro-plant takes a fairly long time.

2. Quick Starting: Quick starting and easy pick-up of loads are possible in a very short time.

3. Location: Location of the plant is near the load center.

4. Plant Operation: The plant operation is easy and requires minimum labour.

5. Part Load: Efficiency at part loads does not fall so much as that of a steam plant.

6. Varying Load: It can respond to varying loads without any difficulty.

7. Fuel Handling: Fuel handling is easier and no problem of ash disposal exists.

8. Size: The plant is smaller in size than steam power plant for the same capacity.

9. Space Required: The space required for diesel plant is considerably less than thermal plant. Therefore, cost of foundation and building is less.

10. High Overall Efficiency: Diesel plants operate at high overall efficiency than steam plants.

11. No Skilled Labours: Skilled labours are not required.

12. Reliability in Operation: Diesel plant is more reliable compared to other plants.

3. DISADVANTAGES OF DIESEL ENGINE POWER PLANT

1. Plant Capacity: Plant capacity is limited to about 50 MW of power.

2. Expensive Fuel: Diesel fuel is much more expensive than coal.

3. Maintenance Cost: The maintenance and lubrication costs are high.

4. Overloading: Diesel engines are not guaranteed for operation under continuous overloads, while steam turbines can work under 25% of overload continuously.

5. Noise Pollution: The noise is a serious problem in diesel plants.

6. Life: Life of the diesel plant is less when compared to thermal plant.

4. APPLICATIONS

1. Small and Medium Capacity: Diesel power plants in the range of 2 to 50 MW capacity are used as central stations for small or medium power supplies.

2. Standby Plants: They can be used as standby plants to hydro-electric power plants. If the water available is not sufficient due to reduced rain fall, a diesel station supplies power in parallel with hydro-station. The use is made temporarily till the water is available to take the full load.

3. Emergency Plants: The plants used for emergency purposes are also standby units, normally idle. But, they are used where power interruption would mean financial loss or danger in key industrial processes, tunnel lighting and operation theatres of hospitals. They are also used for telecommunication and water supply under emergency conditions.

4. Peak Load Plants: They can be used as peak load plants in combination with thermal or hydro-plants.

5. Mobile Power Generation: They are quite suitable for mobile power generation. They are used where electric line service is unavailable. They are widely used in transportation systems such as automobiles, railways, air planes and ships.

6. Diesel-Generating Set: Nowadays, power cut has become a regular feature for industries. The only solution to tide over this difficulty is to install diesel-generating sets. Small supply units for commercial purposes and public utilities, viz., cinema hall, hospital, shopping complex, etc., are commonly used in practice.

7. Starting Station: The diesel plants are used to run the auxiliaries for starting the large steam plants.