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A piston engine aircraft.
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A piston engine aircraft.

A piston engine aircraft.

 

History piston engines has for several decades more than the history of the aviation. They moved from the place of the first car took to the skies the first plane and the first helicopter, there were two world wars, and is still used in 99.9% of cars in the world. However, aviation piston engines today almost completely driven turbine engines and are used for personal or small-size sports aircraft.

This was due to the fact that even the most simple and inefficient gas turbine engine has a high power density (power per unit weight of the engine unit) than most modern piston and aviation weight - an extremely important parameter. In addition, the gas turbine engine more versatile and can move the plane by jet, only this fact allowed the aircraft to reach speeds in 2, 3 4 times or even higher than the speed of sound.

piston engine photosBut back to the piston engines. How are they arranged? The scheme demonstrates the device of a cylinder of a four-stroke gasoline engine for air cooling: 1 - inlet pipe (supply of fuel-air mixture to the cylinder), 2 - cylinder wall (in this case ribbed from the outside, to increase the cooled area, since the cylinder is air-cooled) 3 - piston (reciprocating motion ensures mixture intake, its compression, energy generation and further exhaust of exhaust gases), 4, 5 - connecting rod and crankshaft (conversion of reciprocating Torque, 6 - spark plug (gives a spark that ignites the mixture), 7 - exhaust pipe (exhaust gas outlet), 8 - intake and exhaust valves ("open" the cylinder for the input of the mixture (inlet) and the exhaust gas outlet (Exhaust), seal the cylinder during compression and ignition.It should be noted that only an example of the design is shown, but its variations can be significant, for example, the cylinders of diesel engines do not have spark plugs, and if the engine of liquid cooling is absent But there are channels for running the coolant, etc. By the number of cycles (the actions occurring alternately in the engine cylinder) distinguish 3 engine type - two-stroke, four-stroke and six-stroke. The most widely used four-stroke engine, four of its bars are shown in the diagram.

piston engine

The efficiency of most modern piston engines does not exceed 25-30%, ie really about 70% of the total energy produced during combustion of the fuel is converted into heat, which is necessary to remove from the engine. The cooling system is a very important component in the power plant and largely determines its characteristics. By type of heat output (otherwise cooling) engines are divided into the air and fluid type.

piston engine

And if air cooling is practically not used in cars, because of its low efficiency at low speeds and its complete absence when stopped, in piston aircraft, air cooling engines are very, very widely used, because they have a number of advantages over liquid-cooled engines. Namely, a smaller mass, correspondingly a greater specific power and a simpler, and therefore more reliable, design. In addition, due to the large force of the incident flow during the flight, the cooling efficiency is usually sufficient for the normal operation of the engine.

 

Most piston engines - multi-cylinder, it is necessary to increase the capacity and overall efficiency. In this regard, they are classified by location of the crankshaft relative to the cylinders. At the peak of its development, aircraft engines had to 24 cylinders, and some non-serial items and more. And the main, the most widely used options for the location of cylinders is V-shaped, in-line and star.

aircraft engine smokes

It is easy to distinguish them, because if you look from the front, they look like the letter V in the first case, one row (column) - in the second case, and the star (or if there are a large number of cylinders - more a saucer) in the third. Traditionally, the first two types use a liquid cooling system, while the latter is air-cooled. Accordingly, in addition to the above advantages and disadvantages of engines by the type of their cooling, it can also be added that the in-line engines are compact, they can be installed in an inverted position, but in the presence of a large number of cylinders, they are very long.

V-shaped have 2 cylinders in a row, respectively, they are half as long as in-line, but less compact, although they can also be installed in an inverted position, have a larger frontal section, and therefore a greater drag. Star-shaped, or radial engines, have cylinders located around the crankshaft, respectively, they are the most cumbersome, they simply have a huge frontal cross-section and drag, but due to this they can effectively be cooled by the oncoming flow and have very small length indices.

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