https://acoustique.ec-lyon.fr/publi/roger_jsv05.pdf

Back-scattering correction and further extensions of amiet's trailing-edge noise model. Part 1: theory

An experimental study is described to investigate the negative effects of the tip clearance gap on the aerodynamic and acoustic performance of axial turbomachines. In addition to the increased broadband levels reported in the literature when the tip clearance is enlarged, significant level increases were observed within narrow frequency bands below the blade passing frequency. Measurements of the pressure and velocity fluctuations in the vicinity of the blade tips reveal that the tip clearance noise is associated with a rotating flow instability at the blade tip, which in turn is only present under reversed flow conditions in the tip clearance gap. A turbulence generator inserted into the tip clearance gap is found to be effective in eliminating the tip clearance noise and in improving the aerodynamic performance.

Experimental study of tip clearance losses and noise in axial turbomachines and their reduction

Fused Deposition Modeling is an Additive Manufacturing technology able to fabricate prototypes, tooling and functional parts without geometrical complexity limitations Despite of the potential advantages of this technology, a limiting aspect of its industrial diffusion is the obtainable accuracy The literature highlighted that significant deviations from the nominal values are observed: these deviations are not constant over all the part surfaces but strictly depend upon the process parameters, ie the layer thickness and the deposition angle This involves poor surface quality: the parts could not satisfy the design specifications nor assure the functionality and the assembly fit with other components The aim of this work is the development of a design for manufacturing methodology able to improve the dimensional accuracy obtainable by this technology It operates in the design model step performing a virtual model preprocessing: an anisotropic offset is applied to the surfaces, defined by a mathematical formulation, in order to compensate for the abovementioned dimensional deviations This way, without to eliminate the physical sources of the errors, it is possible to obtain a part with dimensional values very close to nominal ones This method does not require any additional resources for its application such as preliminary artifact construction and measurements A design for manufacturing to improve FDM part accuracy is proposedA redesign of the solid allows compensating for the dimensional deviationThe model surfaces are modified by means of an anisotropic offsetThe proposed method is applied to parts defined by a mathematical formulationThe method is validated through the application to three mechanical components

Yoshio Kodama

Papers

Generation of Electric Power from a Thermal Spring

Turbulent Noise Generated by a Jet Fan