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A piston engine aircraft.
Articles
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 engine. How do they work? Но вернемся к поршневым двигателям. Как же они устроены? На схеме продемонстрировано устройство цилиндра четырехтактного бензинового двигателя воздушного охлаждения: 1 – впускной патрубок (подача топливно-воздушной смеси в цилиндр), 2 – стенка цилиндра (в данном случае ребристая с внешней стороны, для повышения охлаждаемой площади, поскольку цилиндр имеет воздушное охлаждение), 3 – поршень (возвратно-поступательным движением обеспечивает впуск смеси, ее сжатие, получение энергии и дальнейший вывод отработанных газов), 4, 5 – шатун и коленвал (преобразование возвратно-поступательного импульса в крутящий момент), 6 – свеча зажигания (дает искру, которая поджигает смесь), 7 – выхлопной патрубок (вывод отработанных газов), 8 – впускной и выпускной клапаны («открывают» цилиндр для входа смеси (впускной) и выхода отработанных газов (выпускной), герметизируют цилиндр во время сжатия и воспламенения. Следует отметить, что изображен лишь пример конструкции, но ее вариации могут быть значительными, к примеру цилиндры дизельных двигателей не имеют свечей зажигания, а если двигатель жидкостного охлаждения – отсутствуют «ребра», но присутствуют каналы для прогона охлаждающей жидкости и т.д. По количеству тактов (действия, происходящие поочередно в цилиндре двигателя) различают 3 типа двигателя – двухтактный, четырехтактный и шеститактный. Наиболее широко используемым является четырехтактный двигатель, четыре его такта показаны на схеме. It should be noted that only shows a construction example, but its variations may be considerable, for example cylinders diesel engines do not have a spark plug, and if the engine cooling liquid - there are no "edges", but there are channels for cooling fluid runs, etc. According to the number of cycles (actions taking place alternately in the cylinder) distinguish 3 engine type - two-stroke, four-stroke and shestitaktny. The most widely used is the four-stroke, four of its stroke 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 the air-cooled cars almost never used because of its low efficiency at low speeds and its complete absence when you stop, the piston aircraft engines are air-cooled and is very widely used, as have several advantages over liquid-cooled engine. Namely less weight, respectively, high specific power and more simple, and hence more reliable design. Furthermore, because of the great strength of the incident flow during flight, the cooling efficiency is usually sufficient for normal engine operation.

 

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, as seen from the front, and they look like the letter V in the first case, one row (column) - In the second case, and the star (or in the presence of a large number of cylinders - rather saucer) in the third. Traditionally, the first two types use liquid cooling system, while the latter - the air. Accordingly, in addition to the above advantages and disadvantages of the type of engine cooling, we can add that line engines are compact, can be installed upside down, but in the presence of a large number of cylinders, they get very much longer.

V-shaped cylinder 2 are in a row, respectively, they have twice shorter than the row, but less compact, though can also be mounted in inverted position are more frontal cross section, and hence more drag. The star, or radial engines have cylinders, bred around the crankshaft, respectively, they are more bulky, are still just a huge frontal section and drag, but because it can be effectively cooled by running stream and have a very minor performance length.

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