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STUDY ON DIESEL POWER PLANT

INTRODUCTION

• (^) Diesel power plants produce power in the range of 2 to 50MW, are used as central stations for supply authorities and work.
• (^) They are used as standby sets for continuity of supply such as hospitals, telephone exchanges, radio stations, cinema theatres and industries.
• (^) They are suitable for mobile power generation and widely used in railways and ships.
• (^) Used as Peak Load Plants, Mobile Plants, Stand By Units, Emergency Plants, Starting Stations, Central Stations, Industries where power requirement is small 500kW

TWO TYPE DIESEL CYCLE ENGINE

• FOUR STROKES

• TWO STROKES

1.Suction Stoke: With the movement of piston from TDC to BDC, inlet valve opens and air at atmospheric pressure is drawn inside the engine.(5-1)

2. Compression stroke: It raises pressure to about 35kg/cm2. and temp 600deg C. piston moves from BDC to TDC(1-2)
3. Expansion or Working Stroke: Fuel injection starts at or near end of compression stroke. Fuel starts burning at constant pressure. (2-3) High air temperature caused by compression ignites fuel. Burning mixture expands, pushing piston down on working stroke. At 3 fuel supply is cut. Hot gases expand to point 4 (3-4)
4. Exhaust stroke: The piston moves from BDC to TDC and exhaust gases escape to atmosphere through exhaust valve. When piston reaches TDC exhaust valve closes and cycle is complete.

PV DIAGRAM OF FOUR STROKE ENGINE

PHASES IN CI ENGINE COMBUSTION

• IGNITION DELAY PERIOD

• PERIOD OF RAPID OR UNCONTROLLED

COMBUSTION

• PERIOD OF CONTROLLED COMBUSTION

• AFTER BURNING

• (^) Due to the delay period the pressure reached during second stage will depend up on the duration of delay period.
• (^) The longer delay will cause rough running and may cause diesel knock.
• (^) Delay period should be as short as possible both for the sake of smooth running and in order to maintain control over the pressure changes.
• (^) But , some delay period should be necessary other wise the droplets would not disappear in the air for complete combustion.

PERIOD OF RAPID OR UNCONTROLLED

COMBUSTION

• (^) It is the second stage of combustion in C.I engine.
• (^) This period is counted from end of the delay period to the point of maximum pressure on the indicator diagram.
• (^) The rise of pressure is rapid because during the delay period the droplets of fuel have had time to spread themselves over a wide area and they have fresh air all around them.
• (^) About 1/3 of heat is evolved during this period

AFTER BURNING

• (^) The combustion continues even after the fuel injection is over , because of poor distribution of particles
• (^) This burning may be continue in the expansion stroke up to 70 to 80(deg) of crank revolution from TDC.
• (^) The total heat evolved by the entire combustion process is 95 to 97%; 3 to 5% of heat goes as un burnt fuel in exhaust.

GENERAL LAYOUT

ENGINE:IT IS THE MAIN COMPONENT OF THE PLANT AND IT IS DIRECTLY

COUPLED TO THE GENERATOR.

AIR INTAKE SYSTEM:AIR FILTERS ARE USED IN ORDER TO REMOVE THE

DUST AND DIRT FROM THE INCOMING AIR AS THEY MAY CAUSE WEAR OF

THE ENGINE.

Exhaust System:

● (^) It discharges the engine exhaust to the atmosphere. ● (^) The exhaust system is provided with a muffler or silencer which is used to reduce the exhaust pressure and noise which may result if gases are discharged directly into the atmosphere. ● (^) The exhaust system should have flexible tubing system in order to account the effects of expansion due to high temperature and also isolate the exhaust system from the engine vibration.