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How to make a helicopter quiet? Reveal the amazing innovations in modern helicopter noise reduction technology!
With the growth of air traffic and the emphasis on environmental protection, the noise problem of helicopters has become a challenge that needs to be solved urgently.The noise generated by the helicopter not only affects the quality of life of the flying community, but also causes trouble for its military and civilian applications.This article will explore the source of helicopter noise and its latest advances in noise reduction technology and reveal how these technologies can change our perception of helicopters.
Source of helicopter noise
The noise generated by helicopters can be divided into several unique sources, including:
- Thickness noise
- Load noise
- Blade vortex interaction noise
- Wide frequency noise
- High-speed impact noise
- Tail rotor noise
- Engine Noise
- Transmission Noise
Detailed description of various types of noise
Thickness noise is caused by the shape and movement of the rotor blades. This type of noise is mainly affected by the rotor and will propagate in the plane of the rotor.
Load noise is the acceleration of air caused by the movement of the rotor in the air, mainly under the rotor.This type of noise usually becomes more noticeable at low rotor speeds.
Blade vortex interaction noise occurs when the rotor blade approaches the vortex generated by the previous blade, which causes the load to change rapidly in a short period of time, resulting in a strong directional impact noise.
Technical methods to reduce noise
In terms of the design of a helicopter engine, nearly all engines are located above the fuselage compared to the aircraft, which will cause most engine noise to spread upwards.In addition, with the popularity of turbine engines, the impact of engine noise has been reduced.Today's research focuses on reducing noise from the main rotor and tail rotor.There are several effective noise reduction techniques, such as:
Use blade spacing adjustment techniques, such as installing the blade at different spacings, to diffuse noise, thereby reducing the spikes of noise intensity and its harmonics.
In the design of the tail rotor, the fan design (fenestron) that stores it into the tail steam wing can effectively reduce the noise of the helicopter in the city, and this type of design usually has 8 to 12 blades.
In addition, the helicopter design using the "tailless rotor" system can use airflow to control yaw, a technology that greatly improves the quietness of the helicopter.
Future challenges and opportunities
Although existing noise reduction technologies have made significant progress, further innovation is still needed to solve the problem of helicopter noise.The problem of noise not only affects the civilian field, but also in military applications, stealth characteristics are also crucial.With the advancement of technology, future helicopter design will surely incorporate more innovative elements to achieve the goal of completely silent.
In the future, will we be able to see a truly quiet helicopter?How will this change our lives and our environment?
