FLOCON - Adaptive and Passive Flow Control for Fan Broadband Noise Reduction
Overview
Background & policy context:
Air traffic is predicted to grow by 5% per year in the short and medium term. Technology advances are required to achieve this growth with acceptable levels of noise. FLOCON addresses this issue by reducing fan noise at the source through the development of innovative concepts based on flow control technologies. FLOCON aimed primarily at reducing fan broadband noise. This is one of the most significant noise sources on modern aircraft and FLOCON provides one essential element of a wider effort by the industry to achieve established targets for noise reduction.
Objectives:
Previous attempts at reducing broadband noise were inhibited by a limited understanding of the dominant mechanisms and a lack of high-fidelity numerical models. These issues have been addressed in the ongoing PROBAND FP6 project. In FP7, FLOCON moved beyond the scope of PROBAND to the development of specific concepts for reducing broadband noise in aero-engine fan stages.
FLOCON demonstrated methods capable of reducing fan broadband noise from aero-engines at source by 5dB at approach and take-off conditions, contributing to the European objective of reducing aircraft external noise per operation by 10dB by 2020.
To achieve this, FLOCON:
- designed noise-reduction concepts and associated devices able to reduce fan broadband noise from aero engines;
- assessed the noise reduction concepts by conducting lab-scale experiments;
- complemented the experiments by numerical simulations that are assessing the capability of currently available numerical tools to design low broadband noise treatments and configurations;
- developed understanding of the mechanisms involved and extrapolate the results to the aero engine environment using state-of-the-art numerical methods;
- selected the best concepts by balancing noise benefit and integration impact.
Methodology:
In FLOCON, a wide range of concepts was considered and developed to Technology Readiness Level 4 (laboratory-scale validation):
- Rotor trailing edge blowing;
- Rotor tip vortex suction;
- Rotor overtip treatments;
- Rotor and stator leading and trailing-edge treatments;
- Partly lined stator vanes.
Experiments were performed on two rotating rigs, supported where possible by more detailed measurements on a single airfoil and a cascade. Numerical methods were used to optimise the concepts for experimental validation and to extrapolate the results from laboratory scale to real-engine application.
The impact of scaling from lab- to engine-relevant operating conditions were assessed, as well as the side/complementary effect of broadband noise reduction features on fan-tone noise. Generally speaking, FLOCON increased the understanding of the flow physics and broadband noise generation and control mechanisms.
The potential benefit of each concept was assessed, including any associated penalties (weight, complexity and aerodynamic performance). Recommendations were made as to which concepts could be integrated into new engine designs and which will require further validation at industrial rig or full engine-scale. Any developments required in enabling technologies were also identified.
Share this page