DIESEL ENGINE

Diesel Engine Is a type of internal-combustion engine in which heat caused by air compression ignites the fuel. At the instant fuel is injected into a diesel engine’s combustion chambers, the air inside is hot enough to ignite the fuel on contact. Diesel engines, therefore, do not need spark plugs, which are required to ignite the air-fuel mixture in gasoline engines. Diesel engines burn a petroleum product similar to kerosene, jet fuel, and home heating oil.


Diesel engines are more efficient and less expensive to operate than gasoline-powered engines, partly because diesel fuel costs less. Diesels consume less fuel and emit fewer waste products. A disadvantage of the diesel engine is the production of sooty, smelly smoke, but modern diesels generally run cleaner and with less odor than older models.

German engineer Rudolf Diesel invented the diesel engine in the 1890s. The engines initially used powdered coal for fuel. By 1897 Diesel had built a compression-ignition engine that ran on kerosene.

Diesel engines were more efficient than the steam engines of the 1800s and became popular. They were also big and heavy, suitable mostly for the shipping and railroad industries. They are still the engines of choice for heavy transportation and industry. Most modern buses, trucks, trains and ships are powered by diesels. These engines have become popular in some automobiles as well.

Main parts of internal-combustion engine : The four-stroke internal-combustion engine is used in most cars and trucks powered by gasoline or diesel. This illustration shows the parts of the engine that make the four-stroke cycle work. The starter moves the crankshaft to begin the four-stroke cycle to produce power. In gasoline engines, the battery supplies power to the spark plugs. The carburetor and intake manifold supply air and fuel. In many modern cars, a computer controls the amount of fuel injected instead

How four-stroke Engines works The cylinders contain pistons that move up and down. In a gasoline engine, a spark plug ignites a compressed mix of gasoline and air inside each cylinder. In a diesel engine, the diesel and air ignite without a spark plug. The hot expanding gas pushes back the piston in the cylinder, creating the power stroke in the cycle and moving the crankshaft.

Frist stroke Intake of fule and air : In the first part of the cycle, the piston moves down. In a gasoline engine, this stroke draws in a mix of gasoline and air from the carburetor through the intake valve at the top of the cylinder. In a diesel engine, only air is drawn in.

Second stroke compression : In the second part of the cycle, the intake valve closes and the piston rises. In a gasoline engine, this compresses the mix of gasoline and air. In a diesel engine, the air is first compressed and diesel fuel is injected directly into the cylinder at the end of the compression.

Third stroke Combustion : Combustion occurs during the third stroke. In a gasoline engine, an electric spark from the spark plug ignites the compressed mix of gasoline and air. The resulting explosion pushes the piston back as the burning gas expands, turning the crankshaft. The motion of the piston transforms chemical energy in the fuel into mechanical energy.In a diesel engine, the mix of diesel and air ignites spontaneously because the air became much hotter when it was compressed.

Forth stroke Exhaust : The gases left by the burned fuel are pushed out of the cylinder as the piston rises again. An exhaust valve at the top of the cylinder opens to let the fumes escape. When the valve closes, the piston can move down to start the intake cycle again.

Forth-stoke cycle : Many improvements have been made to the four-stroke engine since its invention in the 19th century. Recent improvements include fuel injection in place of a carburetor system. A computer controls the exact amount of fuel sprayed into the cylinder for more power and better fuel efficiency, as well as smoother operation and reduced exhaust emissions.