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Showing 1 to 7 of 7 for “"lined duct"”.
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Linear and weakly nonlinear boundary layer acoustics in a lined duct
… Acoustic linings are used in aircraft engine ducts to reduce the sound they produce. They typically consist of an array of Helmholtz resonators that are characterised by their impedance - a linear relationship between the acoustic pressure and acoustic normal velocity. However in aircraft …
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Investigation of the Herschel-Quincke tube concept in a rectangular lined duct
… liners is proposed for application in noise reduction of aircraft engines. The approach consists of installing Herschel-Quincke (HQ) tubes on lined rectangular ducts. An analytical model was developed to predict the effects of HQ tubes applied to rectangular lined ducts. The technique involves …
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Acoustic characteristics of fiberglass-lined circular ducts
Fiberglass lined circular ducts are circular ducts with an outer spiral metal shell. They are either dual-wall or single-wall. They have been acoustically treated and are intended to be used in heating, ventilation and air conditioning (HVAC) duct systems to reduce the amount of sound that is …
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Theoretical Modeling with Validation of a Combined HQ-Liner System for Turbofan Engine Noise Control
… circumferential arrays of HQ tubes on the lined sector of the inlet of a turbofan engine. A theoretical model is developed to predict the performance of this system assuming that the engine inlet is a circular lined duct with uniform mean flow. The tube-duct interfaces are modeled as finite …
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Compact Integrated Active-Passive Approach for Axial Fan Noise Control
… the installation of an axial fan into a short duct with both passive and active noise control functions. First, a systematic methodology for the analytical modeling of finite-length ducts with multiple discontinuities was formulated. The procedure involved the modeling of a duct as a collection …
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Mathematical modelling of noise generation in turbofan aeroengines using Green’s functions
… the Green’s function for pressure in a turbofan duct with swirling mean flow and secondly we investigate the effect of turbulence hitting an isolated aerofoil. The Green’s function allows engineers to calculate the noise from rotor-stator interaction in simple cases and can be used in beamforming …
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Active Control Of Noise Radiated From Personal Computers
… noise control technique based on folded lined ducts, integrating microphones and speakers, that were added to the PC air inlet and outlet. While the ducts were effective above 1000Hz, the use of a MIMO adaptive feedforward digital controller lead to significant noise reduction at the …