Introduction
Propulsion, on an aircraft, is obtained by creating a force, called thrust, which results from the acceleration of a mass of air by a propeller (driven by a piston engine or a turboshaft engine), or by the combustion of an air/fuel mixture (turbojet engine or rocket engine). The power train, which usually includes one, two or four engines, is one of the main components of the aircraft. This characteristic is often used to classify aircraft: Mono, bi or quadrimo, bi or quadritoprop, mono, bi or quadrijet.
The single-flow turbojet engine, which appeared in the Second World War, has given rise to turboprop and turbofan derivatives (turbofan engines) used on almost all heavy or fast-moving aircraft (less than 800 km/h), civilian and military, as well as on fighter jets. There is also a hybrid between these two systems called “propfan”.
At the beginning of the 21st century, the propeller-driven piston engine remained the most widely used system in almost all light aircraft (ULMs, planes and light helicopters). It was supplanted by the turbine engine for heavy or rapid helicopters, civil and military (Petrescu et al., 2017 a-c; Aversa et al., 2017).
The thrusters are classified below according to their dilution ratio: The proportion between the thrust resulting from the acceleration of cold air and hot air. This classification has the merit of showing that a single principle is used for propulsion, even if it is declined in different technologies. That is why this article includes the propeller-driven motor, the ramjet and the pulsoreactor, which, although they have not undergone significant development, are part of the continuity of the presentation.
Methods and Materials
The piston engine allowed the first powered flight. The engine of the 1903 Wright Flyer had 4 cylinders in line. Some of the first planes were equipped with rotary star engines: The crankshaft was fixed and the engine + propeller assembly was rotating. This solution improved cooling but created a gyroscopic torque that was detrimental to the aircraft’s maneuverability. Military aircraft of the 1940s used water-cooled V-12 engines, such as the Rolls-Royce Merlin on the P-51 Mustang, or stationary two-row air-cooled 7- or 9-cylinder engines, the very famous R-2800 Double Wasp that equipped the P-47 Thunderbolt. Commercial aircraft of the 1950s were equipped with these star engines with up to four rows of 7 cylinders for the most powerful (3,550 hp).
The development of the high-power piston engine for aeronautics was completed in the late 1950s with the arrival of the turbojet engine. At present, the piston engine is only equipped with light aircraft and some very light helicopters for recreation and sports (eg Robinson R22).
The propeller transforms the mechanical energy of the engine into propulsive force. The crankshaft produces a propeller, which accelerates the air by about 10% on a cruise (if the plane flies at 200 km/h, the speed of the air behind the propeller is 220 km / h) more during the phase of acceleration on the ground and in climb. The thrust produced by the exhaust gases may be added to the traction produced by the propeller if the exhaust outlets are oriented correctly. The term “propellant exhaust pipes” is used. This system was almost systematically installed on all the hunters of the Second World War. oil mist collector