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Topic :- Diesel Engines

Topic :- Diesel Engines. contents. DEFINITION. INTRODUCTION. CLASSIFICATION. COMBUSION CYCLE. OPERATING-PRINCIPLE. FOUR STROKE ENGINE. INTAKE STROKE. COMPRESSION STROKE. POWER STROKE. EXHAUST STROKE. ENGINE STRUCTURE. EFFICIENCY. FUEL ECONOMY. DURABILITY. COMPRESSION RATIO.

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Topic :- Diesel Engines

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  1. Topic :- DieselEngines

  2. contents DEFINITION INTRODUCTION CLASSIFICATION COMBUSION CYCLE OPERATING-PRINCIPLE FOUR STROKE ENGINE INTAKE STROKE COMPRESSION STROKE POWER STROKE EXHAUST STROKE

  3. ENGINE STRUCTURE EFFICIENCY FUEL ECONOMY DURABILITY COMPRESSION RATIO ADVANTAGES OF A DIESEL ENGINE DISADVANTAGES OF A DIESEL ENGINE

  4. DieselEngines Definition :- Engine :-A machine that converts energy into mechanical force or motion .

  5. Introduction * A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel. The diesel engine is modeled on the Diesel cycle. The engine and thermodynamic cycle were both developed by Rudolf Diesel in 1897. * The diesel engine has the highest thermal efficiency of any regular internal or external combustion engine due to its very high compression ratio. Low-speed diesel engines often have a thermal efficiency which exceeds 50 percent. *The world's largest diesel engine is currently a Wärtsilä marine diesel of about 80 MW output.

  6. Gas Engine Diesel Engine Classifications 1. According to Fuel BMW 6-cylinder diesel engine Benz 6-cylinder diesel engine

  7. Four-stroke Engine Two-stroke Engine 2. According to “Stroke” Four-stroke Engine Two-stroke Engine

  8. Water-cooled Air-cooled 3. According to Cooling System A cylinder from an air-cooled engine Cooling system of a V-8 automotive spark-ignition engine

  9. The Combustion Cycle • The four-stroke combustion cycle of the diesel engine is composed of the intake stroke, compression stroke, power stroke, and the exhaust stroke. • The diesel engine operates through the motion of compression pistons in inside the cylinders of the engine. • Pistons inside the cylinders are connected by rods to a crankshaft.  As the pistons move up and down in their cylinders, they cause the crankshaft to rotate.  • The crankshaft’s rotational force is carried by a transmission to a drive shaft, which turns axles, causing the wheels to rotate.

  10. Operating Principle :- 1、Intake Stroke 2、Compression Stroke 3、Power Stroke 4、Exhaust Stroke

  11. 1. Intake Stroke :- Exhaust vale closes Piston moves downward Intake valve opens

  12. The Intake Stroke • During the intake stroke, the intake valve opens as the piston moves down to allow air into the cylinder. • The air is pushed by atmospheric pressure into the cylinder through the intake valve port.

  13. 2. Compression Stroke :- Piston moves upward Exhaust valve closes Intake valve closes

  14. The Compression Stroke • After the piston reaches its lower limit, it begins to move upward and as the piston moves up, the intake valve closes. • The exhaust valve is also closed, so that at this point in the cycle, the cylinder is sealed. • As the piston moves upward, the air is compressed and the compression of the air causes the pressure and the temperature of the cylinder to increase.

  15. 3. Power Stroke :- Piston moves downward Intake valve closes Exhaust valve opens near the bottom of the stroke

  16. The Power Stroke • As the piston reaches maximum compression of the air, diesel fuel is injected to the combustion chamber filled with compressed air. • The heat of the compressed air ignites the fuel spontaneously at the self-ignition temperature of the fuel. • As the cylinder pressure increases, the piston is forced down into the cylinder. • The power impulse is transmitted down through the piston, through the connecting rod, and to the crankshaft, which is rotated due to the force.

  17. 4. Exhaust Stroke :- Exhaust gases Intake valve opens just before the intake stroke Piston moves upward Exhaust valve opens

  18. The Exhaust Stroke • As the piston reaches the bottom of its stroke, the exhaust valve opens. • As the piston moves up on the exhaust stroke, it forces the burned gases out of the cylinder through the exhaust port. • Then as the piston reaches the top of its stroke, the exhaust valve closes, and the intake valve opens. • The cycle repeats again with the intake stroke.

  19. Efficiency • One positive aspect of the diesel engine is that they are thermally efficient. • The improved efficiency is caused by the relatively high compression ratios • The diesel engine is 54% thermally efficient, while gasoline engines are only 34%.   • As a result of diesel engines thermally efficiency, they are able to achieve better gas mileage because they produce greater horsepower output for fuel intake.

  20. Fuel Economy • One main reason for the diesel engine’s excellent fuel economy is that it burns more air than a fuel. • In a gasoline engine, it’s air intake is carefully restricted and controlled by the carburetor for a 15:1 air to fuel ratio. • However, in the diesel engine, the air intake is unrestricted.

  21. Durability • Diesel engines are also capable of running high miles without major engine work. • Truck diesel engines can run 250,000 or even 500,000 miles without major engine work. • In 1978, Mercedes-Benz launched a “Great Diesel Search” to find the highest mileage diesel in the United States. • Robert O’Reilly drove his 1957 Mercedes-Benz 180D 1,184,000 miles, 750,000 on its original engine. • Another owner drove his 1968 Mercedes-Benz 220 D 912,000 miles, 902,000 miles on its original engine.

  22. Compression Ratio • The diesel engine compresses at a very high ration of 14:1 to 25:1. • The higher the compression ratio, the more power is generated. • Knock is the term used to describe the auto ignition that occurs when a fuel ignites because the pressure in the cylinder is such that combustion occurs. • The knock limit of the fuel is determined by the point at which the engine begins to shake. • The higher the knock limit, the higher the compression ratio, the more power is generated.

  23. Advantages of a Diesel Engine • Low maintenance, greater efficiency, high power output, and better fuel economy under all types of loads. • Does not require a spark plug to ignite fuel, it relies on the spontaneous combustion through the heat of compression to ignite the diesel fuel. • Because of this type of combustion, a diesel engine are built more ruggedly and heavily built than the gas engine. • The ruggedness of the diesel engine gives a two to three times longer life than the gas engine, which has a life of around 100,000 miles.

  24. Disadvantages • Components of diesel engines are usually heavier that those of gasoline engines because of the additional structural strength needed to obtain the higher compression ratio and power output. • They can emit large amounts of ozone-forming constituents and particulates. • Because of diesel engines’ weight and compression ratio, they tend to have lower maximum RPMs than gasoline engines. • This makes diesel engines has high torque rather than high horsepower, and this tends to make cars with diesel engines slow in terms of acceleration.

  25. references • Sites :- • www.Wikipedia .com • www.Answers.com • www.howstuffswork.com • www.google images.com • www.britanica.com • www.arihant.com • Bing images.com

  26. Thank you sir AudiA6 Jetta Benz600

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