Aircraft piston engine: overview, device and characteristics

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

For a long time, from the end of the 19th century to the middle of the 20th century, the piston aircraft engine remained the only engine that provided aircraft flights. And only in the forties of the last century, he gave way to engines with other principles of operation - turbojet. But despite the fact that piston engines have lost their positions, they have not disappeared from the scene.

Modern Applications for Reciprocating Engines

Currently, aviation piston engines are used mainly in sports aircraft, as well as in small aircraft made to order. One of the main reasons that engines of this type are used very little is that the ratio of unit power to unit mass of a piston engine is significantly less compared to gas turbines. In terms of speed, piston engines cannot compete with other engines used in the aircraft industry. Moreover, their efficiency does not exceed 30%.

Types of piston aircraft engines

Piston aircraft engines differ mainly in the order of the cylinders in relation to the crankshaft. As a result, there are a fairly large number of different types of piston motors. The most widely used are the following:

• V-shaped engines;
• reciprocating radial engine where the cylinders are arranged in a star pattern;
• boxer engine, its cylinders are in-line.

V-engines

They are the most famous and used types of internal combustion engines in the aircraft industry and beyond. Their name is associated with the characteristic arrangement of the cylinders in relation to the crankshaft. At the same time, they have a different level of inclination in relation to each other. It can range from 10 to 120 degrees. Such motors work on the same principles as other internal combustion engines.

The advantages of engines with a V-shaped arrangement of cylinders include their relative compactness while maintaining power performance, as well as the ability to obtain a decent torque. The design allows to achieve significant shaft accelerations due to the fact that the inertia created during operation is much higher than that of other types of internal combustion engines. Compared to other types, these are characterized by the smallest height andlength.

Motors of this type have a high rigidity of the crankshaft. This provides greater structural strength, which increases the life of the entire engine. The operating frequencies of such motors differ in large ranges. This allows you to quickly gain momentum, as well as work steadily at limit modes.

The disadvantages of piston aircraft engines with a V-engine include the complexity of their design. As a result, they are much more expensive than other types. Moreover, they differ in rather big width of the engine. Also, V-shaped motors are characterized by a high level of vibration, difficulties in balancing. This leads to the fact that it is necessary to specially weight their various parts.

Aircraft Radial Piston Engine

At present, radial piston engines are again in demand in aviation. They are actively used in sports aircraft models, or in those made to order. All of them are small in size. The device of an aviation piston engine of a radial type, unlike other motors, lies in the fact that its cylinders are located around the crankshaft at equal angles, like radial rays (asterisks). This gave him the name - star-shaped. Such motors are equipped with an exhaust system that diverges in radial beams. Moreover, an engine of this type can have several stars - compartments. This is possible due to the fact that the crankshaft is increased in length. As a rule, radial engines are made with an odd number of cylinders. This allows a spark to be applied to the cylinder throughone. But they also make radial engines with an even number of cylinders, but their number must be more than two.

The biggest disadvantage of radial engines is the possibility of oil penetrating the lower cylinders of the engine when the aircraft is parked. This problem quite often leads to the occurrence of an instantaneous water hammer, which leads to the breakdown of the entire crank mechanism. To prevent such problems before starting the engine, a constant check of the condition of the lower cylinders is required to ensure that there is no oil penetration to them.

The advantages of radial engines include their small size, ease of operation and decent power. Usually they are installed on sports model aircraft.

Opposed Aircraft Piston Engine

At present, boxer aircraft engines are beginning to experience their rebirth. Due to the fact that they are small in size and relatively light in weight, they are placed on light sport aircraft. They are able to develop sufficient power and provide very high speeds.

Boxer engines have several types of designs:

1. Motor made according to the "boxer" method (Subaru). In such engines, the pistons of cylinders located opposite each other move equidistantly. This results in one being at top dead center and the other at bottom dead center every cycle.

2. engines,equipped with an OROS device (Opposed Piston Opposed Cylinder). In such motors, the cylinders are located horizontally in relation to the crankshaft. Each of them contains two pistons, which move towards each other during operation. The far piston is connected to the crankshaft by a special connecting rod.

3. An engine made on the basis of the principle applied in the Soviet 5TDF engine. In such a product, the pistons move towards each other, working in pairs in each individual cylinder. When both pistons reach top dead center, fuel is injected between them. Engines of this variety can operate on various types of fuel, from kerosene to gasoline. To increase the power of boxer engines, they are supplied with a turbocharger.

The main advantage in boxer-type engines is compactness, small dimensions. They can be used on very small aircraft. Their power is quite high. They are now increasingly being used in sports aircraft.

The main drawback is high fuel consumption and especially engine oil. In relation to engines of other types, boxer engines consume fuel and lubricants twice as much. They require constant oil changes.

Modern aircraft engines

Modern piston aircraft engines are very complex systems. They are equipped with modern units and assemblies. Their work is provided and controlled by modern systems and devices. Due to the applicationadvanced technology, the weight characteristic of the engine is significantly reduced. Their capacities have increased, which contributes to their widespread use in light-engine and sports aviation.

Aviation oils

Oil in reciprocating aircraft engines operates under rather difficult conditions. These are high temperatures in the areas of the piston rings, on the internal parts of the pistons, on the valves and other components. Therefore, in order to ensure the high-quality operation of the motor under conditions of significant temperatures, pressures, loads, they use high-viscosity oils, which are subjected to special cleaning. They must have high lubricity, remain neutral to metals and other structural materials of the engine. Aviation oils for piston engines must be resistant to oxidation when exposed to high temperatures, not to lose their properties during storage.

Domestic piston aircraft engines

The history of the production of piston engines in Russia begins in 1910. Mass production began during the First World War. In the Soviet Union, Soviet piston aircraft engines of their own design began to be created in 1922. With the growth of industrial production, including aviation, the country began to mass-produce piston engines of 4 manufacturers. These were the engines of V. Klimov, A. Shvetsov, plant number 29, A. Mikulin.

After the war, the process of modernization of the aviation of the USSR begins. Aircraft engines for new aircraft are designed and built. The reactiveaircraft construction. In 1947, all military aircraft operating at high speeds switched to jet propulsion. Piston aircraft engines are used only in training, sports, passenger and military transport aircraft.

The largest piston aircraft engine

The most powerful piston aircraft engine was created in the USA In 1943. It was called the Lycoming XR-7755. It was a thirty-six-cylinder engine. Its working volume was 127 liters. He was able to develop a power of 5000 horsepower. Designed for the Convair B-36 aircraft. However, the series did not go. Was created in two copies, as prototypes.