Tuesday, February 18, 2014

Internal Combustion Engine

The engine of an automobile burns gasoline. The combustion produces expanding gases, which create the mechanical power used to move the vehicle. Generally speaking, the combustion can take place inside the engine, in the case of an internal combustion engine, or outside for an external combustion engine. Steam engine is an example of the latter. But internal combustion engine is more efficient, and is the type found in most automobiles.

The challenge of the engine is to sustain the transfer the energy from gasoline to kinetic energy of the vehicle. This repetitive mechanism is accomplished through the four-stroke combustion cycle, also known as the Otto cycle. Inside the cylinder of the engine is the piston, and its movement will direct the flow of the cycle. During the first step, known as the intake stroke, air and gasoline enters the engine, as the down movement of the piston opens up the intake valve, in order for the components to enter. Secondly, the upward movement of the piston then compresses this mixture of gasoline and gas. However, a mere compression does not start the reaction. During the third step, as the piston reaches the peak of its stroke, the spark plug gives off a spark that provides the activation energy necessary to finally ignite the gasoline. Finally, as the piston moves downward again, exhaust from the combustion leaves though a different value. While the movement of the piston is linear, it is helps to move the crankshaft, which is connected to the piston via the connecting rod. The rotational movement of the crankshaft is important, since it is then connected by gearing to the wheels of the automobile, which ultimately move in a rotational manner.

Various factors can go wrong in the engine, and tracing the steps of the Otto cycle reveals some of the reasons. To start off, the ingredients can be bad. The gasoline needs to have little impurity, such that it can burn. At the same time, the necessary amount of air is needed to supply enough oxygen for the combustion reaction. Once inside, lack of compression of spark also can be a source of problems. Compression can fail with leaky cylinders or valves not sealing properly, both of which prevents the pressure buildup from occurring. As for the spark, the wiring may be worn out or damaged.

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