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Category Transport

What is the difference between petrol and a diesel engine?

            Engines that burn fuel inside them are called internal combustion engines. A petrol engine injects fuel into a cylinder and ignites it with a spark. The mixture of fuel and air explodes and drives a piston down the cylinder. The piston is connected to a crankshaft, which turns as the piston moves down. As the crankshaft continues to revolve, it pushes the piston up again.

            A diesel engine works in the same way, except that a spark is not needed to ignite the fuel. Instead, the engine is spun over by a starter. As the piston comes up the cylinder it compresses the mixture of diesel oil and air. Compressing the mixture heats it up and it explodes, driving the piston down.

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How do jet engines work?

            Like rockets, jet engines propel an aeroplane with a stream of hot gases. Unlike rockets, which produce hot gas as a result of burning an explosive mixture, jet engines burn fuel in the air that they draw in at the front of the engine?

            Air enters the front of the engine and is compressor wheel. Fuel is injected into the compressed air, burns fiercely and expands. The hot gas rushes out of the jet pipe at the rear of the engine. The hot gas passes through a turbine, which drives the compressor at the front of the engine.

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How does an aeroplane fly?

               As an aeroplane moves though the air, the air passes over the surface of the wings. These are shaped with a curved top surface and a flatter lower surface, which means that air passing over the top of the wing, has to travel a little faster than that below the wing. This lowers the pressure above the wing, while the air pressure below pushes up, and the end result is the lift that keeps the aeroplane in the air.

               The tail surfaces keep the wing at the proper angle to provide the right amount of lift. The power to propel the aeroplane can come from the engines or, in the case of gliders, from rising air currents.

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