Component s of Diesel Power Plants–Lecture Notes

Component s of Diesel Power Plants

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1. Engine

2. Air Intake System

3. Engine Starting system

4. Fuel System

5. Exhaust System

6. Cooling System

7. Lubricating System

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Engine:

· It’s the main component of plants which develops power.

· Types : Two stroke, Four strokes.

· Air is passed into the cylinder, fuel is also injected.

· The fuel is burned and bring gases expand and do work on piston.

· Shaft of engine is coupled to generator. Burned gases are exhaust to atmosphere.

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Air intake system:

· Removes dust from atmospheric air & supplies fresh air to engine.

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· Types of filters :

1. Dry or oil bath filter.

2. Oil immersed type of filter.

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Precaution’s for location:

1. Should not be located inside engine room.

2. Air intake line should not be too small or too long.

3. Air should not be taken from a confined space.

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Engine Starting System:

Used to start the engine in cold conditions by supplying air.

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Starting methods:

1. Auxiliary engine.

2. Self-starters

3. Compressed air system.

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Auxiliary engine:

Auxiliary engine located close to main engine and driven through clutch and gears. Clutch is disengaged and engine is started.

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Self-Starters:

Used in small diesel engines. Motor draws heavy current & designed to work continuously for 30sec after which it is cooled.

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Compressed Air System:

Used in large diesel engines.

Compressed air supplied from air tank.

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Fuel System:

Contains:

· Storage Tank

· Fuel pump

· Strainers

· Meters

· Day Tanks (Supplies daily fuel need of engines and contains min 8hours of oil requirement)

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1.Fuel Injection system:

Functions:

1. Filters fuel.

2. Measures correct quantity of fuel to be injected.

3. Time the fuel injection.

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Types:

1. Individual pump injection system.

2. Common rail injection system.

3. Distributor.

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Individual Pump Injection System:

· Individual pump is connected to each fuel nozzle.

· Nozzles contain delivery value actuated by oil pressure.

· High cost of manufacture.

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Common rail injection system:

· Single pump supplies fuel to header.

· Control valve is present to set the amount & time of injection of fuel.

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Distributor System:

There os a pressure pump which meters the fuel & time of injection. Fuel enters the distributor blocks. From there fuel is distributed to cylinders in correct order.

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2.Fuel Pump :

· Measures & delivers correct quantity of fuel at high pressure to injector.

· It consists of plunger. When it moves down , oil comes into the barrel through ports SP & Y when it moves up, fuel gets compressed and lifts delivery value & fuel flows to injected through passage (p).

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3.Fuel Injection:

· Delivers fuel into combustion chamber where fuel is mixed with air.

· Fuel from pump enters through passage and lifts nozzle value. Fuel travels down nozzle & injected to cylinder. The injection pressure can be adjusted by adjusting the screw present above the spring.

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Exhaust System:

Discharge engine exhaust to atmosphere. Includes silencers & connecting ducts.

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Lubricating System:

It is used to reduce friction of moving parts & reduce wear & tear of the engine.

Contains:

· Oil pumps

· Oil tanks

· Filters

· Coolers & pipes.

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Types:

1. Wet sump lubrication system

i)Splash System

ii)Semi pressure system

iii)Fuel pressure system

2. Dry sump lubrication system.

3. Mist sump lubrication system.

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Splash System:

· Used in 4 stroke stationary engines.

· Bottom of sump contains lubricating oil. Scoop is located at the bottom which splashes oil from all the parts.

· Suitable for low & medium speed engines.

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Semi pressure System:

· Combination of splash & pressure systems.

· Oil is pumped from the sump through a filter and fed to main bearings.

· Less cost.

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Full pressure system:

· Oil is pumped from sump through filter under pressure to various parts for lubrication.

· Oil is supplied to big end & small end bearings.

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Dry sump lubrication system:

· Used in two stroke cycle engines.

· Mixture of oil & fuel is induced through carburetor & is vaporized.

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Cooling System:

Carries heat generated inside engine cylinder.

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Methods:

1. Air cooling

2. Liquid cooling

i)Thermo-syphon cooling

ii)Forced or pump cooling

iii)Cooling with thermostatic regulator.

iv)Pressurized water cooling.

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Air cooling:

· Engine is cooled by atmospheric air, which flows around engine.

· Used in scooters , motor cycles.

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Advantage:

1. No danger of coolant leakage.

2. Simple design.

3. Less weight.

4. Easy installation.

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Disadvantage:

1. Non uniform cooling.

2. Less output.

3. More maintenance.

4. Used in small engines only.

5. Noisy operation.

6. More maintenance.

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Liquid Cooling:

Thermo Siphon Cooling:

· Hot water goes up and cold water comes down due to density without any pump.

· Top of radiator is connected to top of water jacket by a pipe & bottom of radiator to bottom of water jacket.

· Water travels down the radiator across which air is passed to coal it. Simple, Cheap , but slow cooling.

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Forced cooling by pump:

· Pump forces water to circulate to engine.

· It may cause over cooling which causes corrosion.

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Thermostatic Cooling:

· Thermostat maintains desired temperature to increase heat transfer in radiator.

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Pressurized water cooling:

High water pressure is maintained to increase heat transfer in radiator.

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Evaporative Cooling:

Water is allowed to evaporate by absorbing latent heat of evaporation from the cylinder walls.

The temperature of cooling water is allowed to reach 100c.

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Governing System:

It is used to regulate the speed of the engine. This is done by varying the fuel supply according to the engine load.

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