Abstract
One of the main comfort issue affecting the passenger comfort into a turboprop aircraft fuselage is the propeller tonal noise and the related vibrations. It is well known that propeller rotation during flight generates the main noise sources, depending upon its rotational angular velocity, number of blades, power at shaft generating aircraft thrust and blades geometry. Thanks to the progress behind the control systems of the blades rotations, an innovative highly selective DVA has been conceived. The purpose of the research activity has been improving the performances of the standard passive tonal noise control system used for the BPF tuned noise and vibration attenuation in turboprop aircraft. Due to specific commercial need, the use of bi-tuned frequency can lead at a passive noise reduction at two RPM regimes. Generally, the turboprop aircrafts use only two RPM regimes: 100% at take-off, climb and approach, 86% during cruise, climb and descent. An innovative passive bi-tonal device capable to be tuned at two different frequencies in order to optimize the fuselage noise reduction at two different flight regimes (100% and 86%), has been designed and numerically verified. The functional effectiveness of the bi-frequential tuned device has been analysed by finite elements simulations on a linear beam, representative of the turboprop fuselage frame. The outcomes achieved within this activity encourage the advancement of this research sector, as a support to the needs of the turboprop aeronautical industry. According to the long experience gained by the research group, the proposed multifunctional concept can be a valid technology solution ready to be manufactured as well as validated in flight.
Highlights
It is well known that propeller rotation during flight generates the main noise sources, depending upon its rotational angular velocity, number of blades, power at shaft generating aircraft thrust and blades geometry
An innovative passive bi-tonal device capable to be tuned at two different frequencies in order to optimize the fuselage noise reduction at two different flight regimes (100% and 86%), has been designed and numerically verified
The propeller rotation during flight generates the main noise sources depending upon its rotational angular velocity, number of blades, power at shaft generating aircraft thrust and blades geometry
Summary
The propeller rotation during flight generates the main noise sources depending upon its rotational angular velocity, number of blades, power at shaft generating aircraft thrust and blades geometry. The higher noise levels generated are concentrated at first Blade Passing. In addition to the tuned ones, the passengers comfort can be affected by other noise sources (Figure 1) that act with as broadband components; they are mainly linked e.g. with the blades shape, the developed engine power and the Turbulent Boundary Layer (TBL) [1-2]. These Broadband components have, generally, lower single frequency amplitude but are distribute over a wide frequency range covering all audible range, being more important at frequencies lower than 1000 Hz
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