SVIBOR - Project code: 2-05-408

MINISTRY OF SCIENCE AND TECHNOLOGY

Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69
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Project code: 2-05-408


MEASUREMENT METHODS FOR ROTATING ACOUSTIC SOURCES


Main researcher: BAJIĆ, BRANKO (78490)



Assistants
Type of research: applied
Duration from: 04/01/92.

Papers on project (total): 8
Papers on project quoted in Current Contents: 1
Institution name: Brodarski institut, Zagreb (192)
Department/Institute: Special Technology Department
Address: Av. V. Holjevca 20
City: 10000 - Zagreb, Croatia
Communication
E-mail: bajic@irs.hrbi.hr
Fax: 385 (0)1 6550-947
Phone: 385 (0)1 6551-022

Summary: For a class of rotating sources of airborn or hydroacoustical noise, important in various applications, the possibilities of space-time signal processing methods have been investigated. The final aim to develop measurement methods which will furnish the estimates of a free-field source signature, extracting it from input signals corrupted by disturbances and reflections, while providing selectivity in the analysis of source spatial distribution. The classification of the methods has been founded by theoretical means, numerical simulation and experiments. The dependence of the gain in signal-to-noise ratio and efficiency of the free-field extraction and spatial resolution on the algorithm's parameters, have been established. The effects of signal degradation due to random inhomogeneities of a medium have been investigated, as well as the problems of implementation of the methods. The procedure for the measurement system optimisation has been founded. The methods have been applied to the case of screw propeller cavitation noise and cavitation erosion in hydro-turbines.

Keywords: noise, acoustical source, rotating source, space-time signal processing, correlation methods, signal decorrelation, random inhomogeneities, polarity-coincidence correlation, relay correlation, cavitation, erosion, turbine

Research goals: 1.To evaluate the classification scheme of space-time signal processing methods which extract the free field of a rotating acoustical source from reflections and correlated and uncorrelated disturbances, providing spatial resolution of a contribution arising from various parts of a source. 2.To establish the methods for evaluation of a detailed description of the source parameters: total averaged source strength, source strength as a function of a source angular position, dependence of the spatial distribution of the averaged source strength volume density on the source angular position, or the same function averaged over the angular position of the source. 3.To investigate the mechanisms of reflection reduction, and for the chosen methods, develop the ways for their optimisation. 4.To investigate the problems of implementation of these methods. 5.To investigate the effects of signal degradation caused by random inhomogeneities in a medium. 6.To develop a measuring system realizing the chosen methods. 7.Experimental verification of the measuring system in real conditions. 8.To apply the results to the propeller cavitation and cavitation in a hydro-turbine.


COOPERATION - PROJECTS


  1. Name of project: 1 KRO ENG1 Acoustical Diagnosis of Cavitation
    Name of institution: Oskar-von-Miller-Institut, Technische Universitaet Muenchen
    City: D-82432 - Obernach/Walchensee, Njemačka


COOPERATION - INSTITUTIONS


  1. Name of institution: Oskar-von-Miller-Institut, Technische Universitaet Muenchen
    Type of institution: University/Faculty
    Type of cooperation: Joint project
    City: D-82432 - Obernach/Walchensee, Njemačka

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Last update: 10/16/95
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