Discover the secret of the noise produced by innovative aircraft engines

Scientists from the University of Bristol have uncovered the mystery behind the noise generated by advanced aircraft engines integrated into the airframe and equipped with an innovative energy-saving design.

The scientists' research, published in the journal Fluid Dynamics and Gas Mechanics, shows for the first time how noise from these engines, technically known as boundary layer absorption (BLI) fans, is generated and propagated.

In this regard, the study describes the aeroacoustic characteristics of the fan absorbing the boundary layer.

BLI propellers are similar to the large engines found on modern aircraft, but are partially integrated into the main body of the aircraft rather than placed under its wings. Since they suck air from the body surface, they operate less intensively, which reduces fuel consumption.

The researchers were able to identify some sources of noise emanating from the air fan, the rotating propeller, and the air passing over the curved surface of the aircraft fuselage.

Scientists discovered that the noise pattern changes depending on the amount of thrust achieved by the propeller. In the case of high thrust, the noise is similar to the sound recorded in fans that do not contain ventilation ducts. However, as the thrust decreases, the noise characteristics change due to increased noise from the ventilation duct itself.

The scientists pointed out that their research addresses the problem of persistent noise, which was a major obstacle to obtaining aircraft license certificates, by revealing the physical processes that lead to noise generation in such configurations.