Engines Essay, Research Paper

Engines

Engines are found all around our very day lives. They are found in our cars, trucks, vans and motorcycles. Almost all vehicles run on the basic combustion engine. An internal- combustion engine is any type of machine that gets mechanical energy from the expenditure of the chemical energy of fuel burned in a combustion chamber. There are four main types of internal- combustion engines, they are: the Otto – cycle engine, the diesel engine, the rotary engine and the gas turbine. The Otto-cycle engine is usually used in gasoline engines found in cars and airplanes. The diesel engine runs on a different principle and mainly uses oil as fuel. It is used in electric-generating and marine-power plants, in trucks, buses and some cars. Both diesel and Otto-cycle engines are made in two-stroke and four-stroke cycle models.

The first piston engine was developed in 1690 by a French physicist and inventor Denis Papin and it was used for pumping water. His first engine was a crude machine that used air. It was a single cylindered engine that also was used as a boiler. There was a small amount of water placed in the bottom of the cylinder and it was heated until steam was formed. The pressure that was made from the steam made the piston rise fitting in the cylinder, and after it was raised the heat was removed from the bottom of the cylinder. As the cylinder cooled, the steam condensed and the air pressure on the top of the piston pushed the piston down.

The main parts of an Otto-cycle engine and a diesel engine are the same. Their combustion chamber has cylinders that are closed at one end and in which a close-fitting piston slides. The outside of the piston is connected to a crankshaft by a connecting rod. The crankshaft changes the motion of the pistons in a rotary motion. Crankshafts have heavy flywheels and counterweights hooked on to them to keep the motion of the shaft smooth. An engine can have from 1 cylinder to 28 cylinders.

In every engine there is some sort of fuel system. If not the engine wouldn’t run. Vehicles have a gas tank, a fuel pump and a carburetor. Newer cars have a fuel injection system. In most engines with a carburetor, the fuel is sent to the cylinders through a branched pipe called the intake manifold. The fuel is sent to each cylinder and the wasted gases exhausted through mechanically operated poppet valves or sleeve valves. The valves are normally kept shut by the pressure of the springs and are opened at the right time during the operation cycle of the cam on a rotating camshaft that is geared to the crankshaft.

In all engines there must be a way of igniting the fuel in the cylinder. The high-voltage current is led to each cylinder by a rotary switch called the distributor. But the real ignition devise is the spark plug, it is an insulated conductor the wall of each cylinder. At the end of the spark plug there is a small gap between two wires. The current arcs that gap and burns the fuel in the cylinder.

Engines get really hot because of the heat from the combustion, every engine has to have some kind of cooling system. Some engines are cooled by air, in this system the outside surface of the cylinder are shaped in a series of radiating fins and a piece of metal to radiate heat from the engine. The other engines are water cooled, the water is pumped and circulated through the engine and coils of a radiator.

Ordinary Otto-cycle engines are four stroke. The pistons make four strokes, two toward the head of the cylinder and two away from it. In the first stroke, the piston moves away and opens the intake valve. In this stroke some fuel and air mixture is sucked into the combustion chamber. During the next stroke, the piston moves toward the head and compresses the fuel mixture in the head. When the piston gets to the end of the stroke the fuel mixture is ignited by the spark plug and burns. This puts pressure on the piston which is pushed away from the head in the third stroke. In the last stroke the exhaust valve opens and the gas is pushed out of the combustion chamber.

With the right design it is possible to operate an engine as a two stroke. With this cycle the engine has a power stroke every other stroke of the piston instead of every four strokes. The efficiency of such engines is less then that of four stroke engines.

Even though engines are a great help in our every day life they pose a danger to our environment. In 1985, the discovery of an “ozone hole” over Antarctica brought attention on the idea that humans can have a big impact on our environment. Our vehicles cause a part of the ozone depletion, the carbon dioxide that comes from the engines then out the exhaust and goes into the atmosphere. Engines are convenient but cause damage to our world.