Aircraft refers to equipment flying in and out of the earth’s atmosphere. Generally, aircraft are classified into four categories according to their flight environment and working methods: aircraft, spacecraft, rockets, and missiles.
An aircraft refers to an aircraft flying in the atmosphere. Aircraft are divided into aerostatic aircraft (also known as aircraft that are lighter than air) and aerodynamic aircraft (also known as aircraft that are heavier than air) according to the principle of flight. Aerostatic aircraft rely on the static buoyancy of the air to fly into the air, including balloons and airships; aerostatic aircraft rely on the aerodynamic force generated by their relative motion with the air to fly into the air, including airplanes, helicopters, gliders, rotorcraft, and ground-effect aircraft.
A spacecraft refers to an aircraft that mainly flies in the outer space of the atmosphere. The flying principle of a spacecraft is: get the necessary speed to enter the space outside the atmosphere under the push of a launch vehicle, and then complete the orbital motion similar to celestial bodies under the action of gravity, such as artificial earth satellites, space probes, manned spacecraft, space stations and Space shuttle and so on.
Both rockets and missiles are single-use aircraft. A rocket is an aircraft powered by a rocket engine that can fly in the atmosphere or outside the atmosphere. According to its purpose, it can be divided into three types: uncontrolled rockets, sounding rockets and launch vehicles; missiles are missiles with warheads. , Relying on its own power plant to advance, the guidance system controls its flight trajectory, guides the target and destroys the target aircraft, according to the combat mission can be divided into tactical missiles and strategic missiles.
An aero engine is a power device that generates thrust, pull or lift on an airplane and makes the airplane fly. It is called the primary energy source of the airplane. Aeroengines are mainly gas turbine engines, including turbojet engines, turbofan engines, turboprop engines and turboshaft engines. The secondary energy of the aircraft refers to the energy required for the operation of the aircraft or engine equipment. The secondary energy sources of modern aircraft include hydraulic energy, pneumatic energy and electric energy. The retracting and unfolding of the aircraft landing gear, the opening and closing of the cabin door and the control of the aircraft control surface all currently use hydraulic actuators. The hydraulic actuation mechanism has the advantages of large output, fast response, small volume and stable work. The work of the hydraulic actuation mechanism requires a high-pressure hydraulic source, a pressure accumulator, and the corresponding infusion pipeline to control and protect the valve, that is, a hydraulic energy system is required. The braking of wheels and the transmission of ammunition mostly use pneumatic energy. The anti-icing of the wings and the temperature adjustment of the cockpit are realized by extracting the air pressurized by the engine compressor in many airplanes. In addition, there are a large number of equipment on the plane that work on electrical energy. The coexistence of three secondary energy sources on modern aircraft has caused the aircraft’s internal pipelines and circuits to cross vertically and horizontally and become intricate, and the aircraft’s manufacturability, maintainability and reliability have been reduced.
Since the 1970s, electrical technology has undergone breakthrough developments, mainly in terms of new electrical materials, electrical devices, and microcomputers. (EHA) and other new actuating mechanisms can replace hydraulic and pneumatic actuating mechanisms, so that electric energy can replace centralized hydraulic and pneumatic energy, laying the foundation for the unification of the three types of secondary energy sources on the aircraft to electric energy, and promoting multi-electricity / Development of all-electric aircraft.
Multi-electric aircraft refers to an aircraft that uses electrical energy to partially replace secondary energy such as hydraulic energy and pneumatic energy; all-electric aircraft refers to an aircraft that uses electrical energy to replace secondary energy such as hydraulic energy and pneumatic energy.
The multi-electric/all-electric aircraft simplifies the internal structure of the engine and the aircraft, removes the centralized hydraulic source and hydraulic pipelines in the aircraft, and deletes part of the pneumatic pipelines, which significantly improves the reliability of the aircraft, improves the maintainability, and reduces the fuel. Consumption and emission of pollutants simplifies ground support equipment and is a global optimization technology for aircraft. The development of multi-electric/all-electric aircraft is an important contribution of electrical technology to aviation technology. In the second half of the 20th century, electrical technology has developed rapidly. New soft magnetic materials, high energy product permanent magnetic materials and high-temperature high-strength insulating materials are integrated Circuits, microcomputers, and solid-state power electronic devices were born one after another, so brushless motors, solid-state non-contact electrical appliances, and power electronic converters came out one after another. Aircraft electrical systems have also been greatly developed, creating conditions for the birth of more electric aircraft. . The birth and development of multi-electric airplanes, in turn, put forward new requirements for electrical technology, which requires further improvement of the power density of motors and electrical energy conversion devices, improvement of electrical energy conversion efficiency, and improvement of electrical equipment reliability and environmental adaptability.
The key technologies of multi-electric/all-electric aircraft are:
(1) High-power power generation and start-up power generation technology;
(2) Efficient power conversion technology;
(3) Distributed solid-state power distribution technology;
(4) High torque and fast response electromechanical actuator technology;
(5) Efficient motor technology;
(6) High-speed communication bus technology.
Modern spacecraft are all sent to a predetermined orbit by a launch vehicle, and the launch vehicle is the primary energy system of the spacecraft. Spacecraft must have special secondary energy when it orbits, and the secondary energy commonly used by spacecraft is electric energy. The artificial earth satellites launched earlier use chemical power sources (primary batteries or accumulators), and later solar cell power sources; fuel cells and accumulators are used in spacecraft and space shuttles; nuclear power sources are used in space probes and some military satellites .