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1
Content available Aeroacoustical study of the serrated ventilation dampers
Kopania Joanna Maria, Bogusławski Grzegorz, Wójciak Kamil, Gaj Patryk
Vibrations in Physical Systems
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2022
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Vol. 33, nr 3
art. no. 2022313
EN
The serrated ventilation dampers for regulation of airflow volume were tested. The computer fluid flow analysis was conducted using the Comsol program. The nature of the flow through the serrated ventilation damper was analyzed to identify the different turbulence regions formed on the airflow field. Additionally, the aerodynamical and acoustical parameters of these blades of ventilation dampers with different serrated trailing and/or leading-edge were studied. The aeroacoustic studies were done in the reverberation room. The sound power level and loss coefficient were determined for the studied models.
2
Problem hałasu. Badania akustyczne rozprężania gazu w warunkach laboratoryjnych
Gaj Patryk, Karczewski Jacek, Kopania Joanna
Energetyka Cieplna i Zawodowa
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2022
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Nr 6
28--35
PL
Od czasu wynalezienia silników parowych rosnąca industrializacja powoduje zwiększenie wydajności produkcji zakładów przemysłowych. Jednakże rozwój technologii łączy się również z negatywnymi efektami. Należą do nich zanieczyszczenia lub zakłócenia środowiska pracy, co ma wpływ na nasze codzienne życie. Jednym z nich jest tak zwane „zatrucie hałasem”, czyli zwiększenie średniodobowego poziomu hałasu.
3
Content available Influence of shell shape on flow and acoustic parameters of a steam silencer
Gaj Patryk, Sobczak Krzysztof, Kopania Joanna, Wójciak Kamil
Archives of Thermodynamics
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2021
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Vol. 42, no 4
141--154
EN
Steam discharge produces noise due to rapid expansion and a temperature drop of ejected steam. This is why steam silencers are used to change one-stage into multi-stage expansion, which reduces the intensity of pressure and temperature drop during this process and shifts emitted noise into higher frequencies, which are easier to dampen. This paper presents a flow-acoustic numerical model of a steam silencer. It is meant to help to obtain a precise analysis of phenomena occurring in steam silencers and improve the process of designing this type of device. The model described in this paper was based on the parameters of a real working unit manufactured in the Institute of Power Engineering – Thermal Technology Branch. Most of the steam silencers are designed based on construction guidelines that have not been changed for a long time. This restrained an increase in the acoustics efficiency of the steam silencers. An improvement of their flow and acoustic properties allows for the development of smaller, more efficient, and lighter construction. The current version of the model was used for the analysis of flow and acoustic changes which occur after modifying the lower region of a shell of the steam silencer. The proposed modification allowed for a 19% increase in mass flow rate through the silencer and noise reduction in the low-frequency range.
4
Content available The impact of the damper blade position on the generated noise and pressure losses in plenum box with swirl diffusers
Wójciak Kamil, Gaj Patryk, Kopania Joanna, Bogusławski Grzegorz
Vibrations in Physical Systems
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2019
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Vol. 30, nr 1
art. no. 2019103
EN
The article presents the effect of setting the throttle in the plenum box with swirl diffuser on the generated noise and the pressure losses. The sound power levels of the source was determined using the precision method in the reverberation room in accordance with the PN-EN ISO 3741:2011 standard. The examination was carried out for damper blade position set vertically and horizontally for full opening and at a 45 degree angle in both directions. In order to confirm the universality of the conducted experiment, the tests were carried out for two different face swirl diffuser with different shapes of air control blades and holes in the plate and for different flow rates. The multi-criteria optimization methods were used to select the best throttle position.
5
Content available Noise radiation from circular rods at low-moderate Reynolds number
Kopania Joanna Maria, Bogusławski Grzegorz, Gaj Patryk, Wójciak Kamil
Vibrations in Physical Systems
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2019
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Vol. 30, nr 1
art. no. 2019116
EN
The well-known dominant sources of airframe noise are associated with unsteadiness of separated and/or vortical flow regions around the high-lift system (flaps, slats) and the aircraft undercarriage (landing gear). Current practical landing gear noise prediction models are individual component - based, which means that the various components are divided into groups according to the frequency range, in which they predominantly radiate noise. Since the far-field noise spectra are approximately Strouhal - based, the emitted frequency is assumed to be directly related to their size: the large elements are responsible for the low frequency region of the spectra, and the small components for the high frequency region. On the basis of such understanding of the noise generation mechanism, the special configurations that lead to considerable noise suppression were proposed. One element of these configurations are rods with different shape and cross section. In this work the situation when circular rods are in area of laminar-turbulent flow were analysed. The measurements were carried out for single circular rod with different diameters to study the noise effect depended on Reynolds number. Far field noise for broad range of Reynolds numbers was also examined depending on distance from the source of noise.
6
Content available Determination of sound power level by using a microphone array and conventional methods
Bogusławski Grzegorz, Kopania Joanna Maria, Gaj Patryk, Wójciak Kamil
Vibrations in Physical Systems
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2019
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Vol. 30, nr 1
art. no. 2019139
EN
Sound power is measured to make objective comparisons between the same type of products, but also because legislation requires it. To release a new product, it is often compulsory to certify it according to International Organization for Standardization (ISO) standards, and also with national and local regulations. Determining of sound power is not a straightforward process. Sound power can be determined through the measurement of sound pressure (series 3740 methods) or sound intensity (series 9614 methods). Selecting one of the above methods depends on the purpose of the test, as well as the available equipment, desired grade of accuracy, background noise level or the test environment. Nowadays the additional methods, such as microphone arrays are used to located of the noise source and determined of pressure sound level. But the results obtained with acoustic cameras cannot be, for now, used for legislative purposes (are not ISO compliant). In this work the differences in the determination of sound power level by using conventional ISO methods and microphone arrays are determined. The system composed of a loudspeaker and a fan were used as a sound source of the noise. Sound power levels according to ISO 3746 and ISO 9614-1 were determined and were compared with the developed method by using microphone arrays techniques.
7
Content available Assessment of sound absorbing properties of composite made of recycling materials
Gaj Patryk, Kopania Joanna, Wójciak Kamil, Bogusławski Grzegorz
Vibrations in Physical Systems
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2019
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Vol. 30, nr 1
art. no. 2019109
EN
In modern world we are searching methods to reuse most of industrial disposals produced during manufacturing. Some kinds of materials, like scraps from acoustic foam, however are not so easily utilized using recycling methods for its primary usage. Disposals produced during the manufacturing process can be compressed and reused as sound absorbing material. The purpose of this article is to examine sound absorbing properties of material made of acoustic foam disposals and compare it with sound protection materials, which are commonly used. Sound absorbing damping were tested using Kundt’s tube and reverberation room examination method. Tests were carried out according to standard PN-EN ISO 354:2005, for reverberation room examination, and according to Bruel&Kjaer electronic instruments technical manual for Kundt’s tube examination.
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