1, the development history of propellers

Aerospace propeller is a type of engine output power into thrust/A power device for tension. since1903Since the Wright brothers invented the "Flyer One", the development of aviation propeller technology has been closely related to the development of aircraft.

Figure 1 General aviation aircraft Figure 2 Typical drone

The development of propeller technology can be traced back to ancient bamboo dragonfly toys in my country. exist16centuryLeonardo DavinciThe device for generating lift was created based on the Archimedes spiral surface principle. Of course, early devices only reflected the basic characteristics of propellers.

exist19In the middle of the world, two basic theories of propellers were proposed: momentum theory (18652019) and the theory of lemon (1878Year). Momentum theory reveals the relationship between the rate of change of the fluid momentum flowing through the paddle disc and the propeller tension. The flange theory directly studies the local interaction between fluid and solid, thereby determining the aerodynamics between the blade and the fluid. However, both theories are still insufficient to support the design and performance analysis of propellers.

Figure 3 Schematic diagram of momentum theoryFigure 4 Schematic diagram of the theory of lemon

20At the beginning of the century, propellers were designed as wooden propellers designed according to experience. exist1917Year,F.Through a large number of wind tunnel tests, data are summarized, and the aerodynamic performance of propellers is studied by introducing a dimensional analysis method. It is proposed that the propeller efficiency η is the forward ratio λ and Mach numberMaand Reynolds numberReFunctions with equal parameters. A set of propeller design methods is summarized, and the designed propeller effect is achieved70%That's all.

20th century30The era is a period of vigorous development of propellers. The development of metallurgical technology and the adoption of more advanced blade stress analysis technology and testing technology, aluminum alloy blades have been widely used. The structural form of propeller has also gradually developed from a constant-mode propeller to a hydraulic constant-speed variable-game propeller. The continuous adjustment of the pitch angle makes it a good balance between the power absorbed by the propeller and the output power of the engine, and can maintain relatively good propeller efficiency in all flight stages.

During World War II, the significant increase in aircraft flight speed and engine power promoted the further development of propeller technology. During this period, countries developed a series of advanced low-speed laminar flow wings (e.g.NACA-16series, propeller aerodynamic theory has been further improved, and strip analysis method has become a standard theory.

20century50In the mid-year period, the continuous development and improvement of turbojet engine technology was gradually promoted from the military to the civilian field, which brought certain resistance to the development of propellers. Except in special aircraft fields (such as short-range take-off and landing, long-distance flight, etc.), the application of propellers has gradually decreased.

20world70In the early years, a global oil crisis broke out, and propeller technology regained attention because the power unit form of engine plus propeller could significantly reduce fuel consumption. Aviation research institutions in the UK, the United States and other countries have taken the lead in carrying out a lot of work in improving the aerodynamic performance of the blades. With the help of wind tunnel tests, a series of new propellers-specific airfoils have been developed one after another. Propellers with new airfoils are constantly used on regional passenger planes, business planes and small aircraft.

2, the development of advanced aviation propeller technology

(1) Research on advanced aerodynamic performance

In order to improve the aerodynamic performance of the propeller. The United Kingdom, the United States and other countries have successively carried out special airfoil development. USANASADeveloped with HamiltonHS-1、HS-2Airfoil series, British Aviation Research Association (WE BUY) developed with Daodi CompanyNow-dAirfoil series. As a supercritical airfoil, it can meet the aerodynamic and use requirements of the aircraft. Have a relatively lift coefficient and a relatively tightening level.

Figure 5 Aerodynamic characteristics of air propeller wings (Ma=0.3)

(2) Advanced composite material paddle manufacturing technology

Due to the advantages of composite materials in weight, structural damping, damage safety and maintenance. The development of composite propellers is an inevitable trend. However, there are many key technologies in the structural design, strength calculation, material selection, process molding and non-destructive testing of composite material blades. Britain, the United States, Russia and other countries have been in the world60According to the study, the corresponding research was carried out. For example, the design of the overall strength of the blade is complex due to its influencing factors and complete theoretical calculations are very difficult. Therefore, establishing the blade strength test capability is essential in the blade design. In addition to a large amount of basic research, the development of composite material propellers also requires special attention to process molding and experimental technology, and requires complete sets of process equipment and complete strength experimental equipment, such as fiber wrappers, material prepreg equipment, vacuum suction casting molding equipment, blade vibration fatigue test bench, torsion fatigue test bench and environmental test bench. Composite propeller blades have become an important symbol of advanced propeller technology.

(3) Multiple functional adjustment and control technologies

In order to improve the safety, reliability and comfort of civil aircraft. The functions of the advanced propeller adjustment and control system are more complete. In addition to the typical constant speed variable distance adjustment, feathering, and return paddles, the anti-pad function is also added to shorten the sliding distance. To reduce noise level, a propeller phase synchronizer is added to accurately adjust the number of revolutions and phases of the propeller to realize noise phase interference technology.

Figure 6 Advanced composite propellerFigure 7 Electric constant speed controller

In recent years, with the full permission digital electronic control system (Fadec) has made propeller adjustment form an integral part of the control of the engine and aircraft, and the aircraft's flight quality, fuel consumption, noise, safety and trustworthiness have been improved. There are information that it is beneficial toFadecWith the development of the system, the noise and fuel consumption of the aircraft have been significantly reduced after the integrated matching of the paddle flying and engine. Taking a turboprop regional passenger plane as an example, the noise in the cabin after optimization matching is lower than that of76db, the flight speed can reach676km/hThe fuel consumption rate is only for jet aircraft80%。

Conclusion

According to non-statistics, there are currently70The remaining major regional passenger aircraft, among which propeller aircraft are59species, about84%, in terms of number of frames,92%. According to statistics, it is being used and developed9There are total of straight-line passenger planes above seats48, among which propeller aircraft accounts for a proportion of87.5%,have42There are so many species. In terms of agricultural and forestry aircraft, there are approximately2.6More than 10,000 aircraft, almost all of which are powered by propeller. In addition, propellers also account for a large proportion of general aviation, trainers, military transport aircraft, early warning aircraft, reconnaissance aircraft and ground-effect aircraft. In addition to large military transport aircraft, early warning aircraft and medium-level trainers, the power devices that drive propellers are mainly piston aircraft engines.

Advanced aviation heavy oil piston engines match the power solution of fully authorized digital control of constant speed variable pitch propellers, which will give existing piston-powered aircraft a new improvement in handling, economy, comfort and safety.