four stroke engine
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Joined: Oct 2010
21-10-2010, 12:48 PM
Need seminar and presentation on four stroke engine
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Joined: Sep 2010
22-10-2010, 09:42 AM
Today, internal combustion engines in cars, trucks, motorcycles, aircraft, construction machinery and many others, most commonly use a four-stroke cycle. The four strokes refer to intake, compression, combustion (power), and exhaust strokes that occur during two crankshaft rotations per working cycle of the gasoline engine and diesel engine.
The cycle begins at Top Dead Center (TDC), when the piston is farthest away from the axis of the crankshaft. A stroke refers to the full travel of the piston from Top Dead Center (TDC) to Bottom Dead Center (BDC). (See Dead centre.)
1. INTAKE stroke: On the intake or induction stroke of the piston , the piston descends from the top of the cylinder to the bottom of the cylinder, reducing the pressure inside the cylinder. A mixture of fuel and air is forced by atmospheric (or greater) pressure into the cylinder through the intake port. The intakevalve(s) then close.
2. COMPRESSION stroke: With both intake and exhaust valves closed, the piston returns to the top of the cylinder compressing the fuel-air mixture. This is known as the compression stroke.
3. POWER stroke.: While the piston is close to Top Dead Center, the compressed air–fuel mixture is ignited, usually by a spark plug (for a gasoline or Otto cycle engine) or by the heat and pressure of compression (for a diesel cycle or compression ignition engine). The resulting massive pressure from thecombustion of the compressed fuel-air mixture drives the piston back down toward bottom dead center with tremendous force. This is known as the powerstroke, which is the main source of the engine's torque and power.
4. EXHAUST stroke.: During the exhaust stroke, the piston once again returns to top dead center while the exhaust valve is open. This action evacuates the products of combustion from the cylinder by pushing the spent fuel-air mixture through the exhaust valve(s).
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Joined: Nov 2012
03-12-2012, 11:35 AM
Four Stroke engine
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An Engine is a device or motor that coverts thermal energy to mechanical energy, or an engine is a mechanical device that produces some form of output from a given input.In an engine the linear motion of the pistons is converted into rotational motion by the crankshaft There are two types of engines; Two stroke engines (petrol engine) and Four stroke engines (petrol and diesel engines). Two stroke engines are built for high speed and performance while Four stroke engines are fuel efficient. Four stroke engines are more preferred than Two stroke engines.
A stroke is a single action of certain engines, or A Stroke is a half revolution of an engine during which the piston travels from one extreme of its range to the other.
TYPES OF ENGINES
Four Stroke engine
An internal combustion engine (type of engine in which burning of fuel takes place within the engine)in which the entire engine cycle is completed in four piston strokes. In this type of engine with a single intake of fuel the engine can run four strokes [3+1(fuel intake)]. Four stroke engine includes the following strokes;
1. Intake or Suction Stroke
2. Compression Stroke
3. Power or Combustion Stroke
4. Exhaust stroke
Four stroke engine can be further divided on the bases of fuel, i.e. Four Stroke Diesel engine and Four Stroke Petrol engine.
a) Four stroke Petrol engine
The four stroke internal combustion engine which uses petrol as the burning fuel is known as four stroke petrol engine. The fuel actually used in the engine is the mixture of petrol and air (oxygen, used to ignite petrol).
The cycle begins at top dead center (TDC), when the piston is farthest away from the axis of the crankshaft.
Intake or Suction Stroke
The piston starts at TDC, the intake valve opens and the piston moves down to let the engine to take in a cylinder-full of fuel (mixture of air and petrol). This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work. The piston is connected to crankshaft with the help of connecting rod. This crankshaft is further transforms the mechanical work into desired output.
Four stroke Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to a petrol engine, which uses the Otto cycle, in which a petrol and air mixture is ignited by a spark plug. The major difference between the petrol and diesel engine is that diesel engines do not have spark plugs.
Like in the petrol engine, cycle begins at top dead center (TDC), when the piston is farthest away from the axis of the crankshaft.
Intake or Suction Stroke
The piston starts fromTDC, the intake valve opens pushing air into the chamber and the piston moves down. The piston is connected to crankshaft with the help of connecting rod. This crankshaft further transforms the mechanical work into desired output.
Then in the compression stroke the pistonmoves back up to the extreme top position ,which compress theair which results in increase in pressure and temperature. The use or benefit of compression is to make the explosion more powerful.
Power or Combustion Stroke
Then in the Power stroke, the compressed air with very high temperature is brought in contact with the diesel, which is injected through the ignition pipe called as fuel injector. After this blast occurs in the chamber which builds up huge pressure.The resulting pressure of burning fuel pushes the piston back to the extreme end or down position.