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Description
The fans in the cooling system contribute significantlyto the noise emissions of heavy construction equipmentsuch as rotary drilling rigs. Protective grilles are usedto prevent people and animals from coming into con-tact with the rapidly rotating fan blades. It is knownfrom the relevant literature that such protective grilleson axial fans can increase the fan’s radiated soundpower by several decibels. In this study, we thereforesystematically investigate the acoustical influence ofprotective grilles mounted on the pressure side of thefan of a cooler-fan combination used in constructionmachinery. Four typical protective grilles with sig-nificantly different geometries are used. The grillesare first acoustically characterized in an aeroacousticwind tunnel under low-turbulence flow conditions andthen mounted on the pressure side of the cooler. Thecooler, which is installed in an axial-fan test rig, isacoustically measured at various operating points ofthe axial fan. It is found that the grilles have no significantinfluence on the sound emissions of the overall systemat any of the feasible operating points. A similarityanalysis leads to the hypothesis that pressure-side pro-tective grilles primarily influence the emitted soundspectrum in low-pressure axial fans.