Авіаційно-космічна техніка та технологія (Aug 2020)
CURRENT STATE OF THE PROBLEM OF THE DEVELOPMENT OF ACOUSTIC LINERS FOR GAS-TURBINE ENGINES
Abstract
A review of current international aviation noise requirements is provided. It is shown that international requirements for aircraft noise levels are constantly increasing. The rapid growth of the international fleet leads to an increase in the number of take-offs and landings of aircraft at airports, and as a result, the problem of aircraft noise still relevant. To reduce noise levels at airports, various methods are used, one of which is the operational limitations of aircraft concerning the levels of noise they create. In European Union countries there are operational restrictions for aircraft meeting the requirements of Chapter 3 with a noise margin of less than 10 EPNdB. For already established aircraft that have passed certification, again it is necessary to look for methods to reduce noise. The main type of aircraft in operation in the world is an aircraft with turbofan engines. For such an aircraft, the main sources of noise during take-off will be the noise of the fan and jet, while landing, the noise of the landing gear, flaps, slats, and fan noise. When choosing a method of reducing aircraft noise, it should determine the source that most affects the overall noise level. It has been determined that fan noise is one of the main sources of noise. Acoustic liners constructions are widely used to reduce the noise level created by the fan. They are one of the most priority areas for reducing fan noise. Achievements in the use of acoustic liners to decrease the noise of domestic aircraft An-124-100, An-148-100 are considered. It is noted that due to the increasing requirements for aircraft noise, it is necessary to use new acoustic liners with improved sound-absorbing properties. It was determined that it is possible to improve the sound-absorbing properties of the acoustic liners by expanding the frequency range of sound absorption of such structures. Modern methods for improving the acoustic properties of the acoustic liners are presented: the use of multilayer resonant acoustic liners makes it possible to customize the design for an increased number of calculation parameters; the use of modified variants of the acoustic liners core such as corrugated core, oversized perforated core; the use of porous and porous fiber materials in the design of the acoustic liners to provide additional sound-absorbing ability, the use of low-frequency acoustic liners to reduce the noise of promising turbofan engines with a high and ultra-high bypass ratio.
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