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40In current study, a bibliographical review concerning the usage of acoustic absorbers on buildings noise reduction is presented.
1. Sound Absorbing Materials
Porous materials obtained from synthetic fibres, such as mineral wool(fig.1) or glass wool(fig.2), are commonly used for thermal insulation and sound absorption, because of their high performance and low cost. Their diffuse-field sound absorption coefficient is very high at mid-high frequencies. On the other hand, they have several cons: they can be harmful for human health if their fibres are inhaled, since they can lay down in the lung alveoli, and can cause skin irritation (as stated by the European Council Directive on dangerous substances 67/548/EEC [9] and subsequent amendments). Hence such materials must be adequately overlaid if directly exposed to the air. Viscous losses convert acoustic energy into heat as sound waves travel through the interconnected pores (or fibers) of the material. Because motion of the air through the porous material is necessary to dissipate acoustical energy, a material tends to be ineffective when placed close to a rigid boundary (where the particle velocity is zero) [10]. Effectiveness of absorption is directly related to the thickness of the material; absorbers are most effective when their thickness is between one-fourth and one-half the wavelength of the sound, with the maximum performance where the thickness is one-fourth the wavelength. This means that sound absorbers do a very good job at high frequencies, which have short wavelengths [11, 12].
Fig. 1. Porous materials obtained from mineral wool [13].
Azimi, M., Azimi, M. 14
Noise Mitigation in Buildings Using Sound Absorbing Materials
Fig. 2. Porous materials obtained from glass wool [14].
A majority of sustainable materials for noise control can be divided into three main categories:
- Natural materials;
- Recycled materials;
- Mixed and composited materials.
There is a great variety of natural fibres which can be used for thermal and acoustical applications. These are commercially available in the form of coconut, kenaf, hemp, mineralized wood fibres (Fig.3) [15].
2. Building Noise Reduction
At the scale of materials and building, noise pollution is taken into account besides a number of sustainability aspects. Designing and improving acoustic environment, on the other hand, is linked to a choice of particular building techniques and materials that imply different environmental performance more than acoustic performance. An aware design should mediate between these issues, which are sometimes contradictory [16].
It is possible to obtain sufficient insulation against impact noises between different living units by interposing an element with the capacity of dampening vibrations between the sources of the noise and the adjacent structures. As circumstances or conditions change, this element may be applied in various points: Between loadbearing structure and the screed, or between the screed and the flooring, as well as directly underneath the floor by creating a false ceiling [17].
Brekreira et. Al [18] present the data elements to develop a new processing route to transform elastomeric waste residue (particulates) into acoustic and thermal insulation materials that can compete with commercial products.
Oldham et. Al [19] present an examination of the acoustical characteristics of a range of natural fibres which has confirmed their effectiveness as porous sound absorbers and also the limitations of current models for predicting their performance. Examination of the acoustical performance of materials consisting of different configurations of whole reeds and straws has revealed that these also possess considerable potential for application as broadband sound absorbers with particularly good low frequency absorption characteristics. They concluded that the combination of natural fibres and whole reeds offer the possibility of developing a range of sustainable absorbers which act very effectively across the complete audio frequency range.
Article written by Ballesteros, et al. [20] explains about the noise which turn out through the construction activities is one of the main acoustic polluting essence for society. However, there is no particular standard for this activity, which validates its own effluent factors that make it phenomenon different from other operations. This experimental information's on construction sites have been measured through four averaging and integrating sound level meters with spectrum analyzer included and a sound calibrator. The factors of sound emission for experimental data has been differentiate as five stages (excavation stage, frameworks, installation stage, roof stage, stage of walls) each stage have been analyzed and compared with the standard level. The comparison among the values is to characterize the noise emission of the construction process. These stages of the construction process cannot be reasonably enviable regarding the spectra, except for the excavation stage, given that the only staggering thing is effect of the peak at low frequency. The results show that the measures for controlling the noise and the analysis of the acoustic impact which such activity produce in the concern specified area.
Conclusion
Many public housing sites are subject to severe noise impact from various sources many recycled materials, such as waste rubber, metal shavings, plastic, textile agglomerates can be used. It can be useful to mix various recycled materials of different grain size to obtain the desired performance. For this purpose a binder needs to be added in proper proportions. This paper presents a brief review about acoustic absorbers and their usage for building noise reduction.
References
1. Gorji-Bandpy, M., Azimi, M. (2012) «Technologies for Jet Noise Reduction in Turbofan Engines», Aviation, DOI:10.3846/16487788.2012.679770.
2. Gorji-Bandpy, M., Azimi, M. (2012) «Airframe Noise Sources and Reduction Technologies in Aircraft», Noise and Vibration Worldwide, Vol.43, No.9, pp.29-36.
3. Gorji-Bandpy, M., Azimi, M. (2013) «Passive Techniques for fan noise reduction in new turbofan engines: review», Journal of Science and Technology Review, Vol.6, Issue.1, pp.59-61.
4. Azimi, M., Ommi, F. (2012) «Using Microjets as an Efficient Technique for Jet Noise Reduction in High-Bypass Turbofan Engines», Journal of Mechanical Engineering and Technology, Vol.2, Issue.1, pp.49-53.
5. Gourdom, P.G., Arnavd, L. (2011) «Acoustical Properties of Material made of Vegtable Particles with Several Scales of Porosity», Applied Acoustics, Vol.72, pp.249-259.
6. Yang, H.S., Kim, D.J., Kim, H.J. (2003) «Rice straw-wood particle composite for sound absorbing wooden construction materials », Applied Acoustics, Vol.86, pp. 117-121.
7. Schiavi, A., Pavoni Belli, M., Corallo, M., Russo, F. (2006), «Acoustic Performance characterization of Euronoise» Tampere, Finland.
Azimi, M., Azimi, M. Noise Mtigation in Buildings Using Sound Absorbing Materials
8. El Hajji, N., Mboumba-Mamboundou, B., Dheilly, R.M., Aboura, Z., Benzeggagh, M., Queneudec, M. (2011) «Development of Thermal insulating and Sound Absorbing agro-sourced materials from Auto Linked Flax-Tows», Industrial Crops and Products, Vol.34, pp. 921-928.
9. Dangerous Substances Directive (67/548/EEC), available at: http://en.wikipedia.org/wiki/Dangerous_Substances_Directive_%2867/548/EEC%29 (accessed May 20, 2015).
10. Japan Sustainable Building Consortium. (2003), Manual of Comprehensive Assessment System for Building Environment Efficiency.
11. Beranek LL, Ver IL. (1996), Noise and vibration control engineering. New York:
Wiley.
12. Kibert, C.J., (1994) «Establishing Principles and a Model for Sustainable Construction», Proceedings: the First International Conference on Sustainable Construction, 6-9 November, Tampa, Florida, U.S.A.
13. Available at http://en.wikipedia.org/wiki/File:Rockwool_4lbs_per_ft3_fibrex5.jpg.
14. Available at : http://upload.wikimedia.org/wikipedia/commons/0/0c/CSIRQ ScienceImage 2175 Installing Insulati on_Batts.jpg.
15. Pervaiz M., Sain, M.M. (2003) «Carbon Storgae Potential in Natural Fiber Composites», Conservation and Recycling, Vol.39, pp.325-340.
16. Pederson, D. (2004) «Acoustic performance of building elements with organic insulation materials», 33rd Internoise, Prague.
17. Toyoda, E., Sakamoto, S., Tachibana, H. (2004) «Effects of room shape and diffusing treatment on the measurement of sound absorption coefficient in a reverberation room», Acoustical Science and Technology, Vol.25, No.4, pp.255-265.
18. Benkreira, H., Khan, A., Horoshenkov, K.V. (2011) «Sustainable acoustic and thermal insulation materials from elastomeric waste residues», Chemical Engineering Sciences, Vol.66, No.18, pp.4157-4171.
19. Oldham, D., Egan, C.A., Cookson, R.D., (2011) «Sustainable acoustic absrbers from the biomass», Vol.72, pp.350-363.
20. Ballesteros, M.J., Fernandez, M.D., Quintana, S., Ballesteros, J.A., Gonzales, I. (2010) «Noise emission evolution on construction sites, Measurement for controlling and assessing its impact on the people and on the environment», Vol.45, No.3, pp.711-717.
Устройство для снижения вибрации и шума в трубопроводных системах энергетических установок. Разработка и исследование
1 2* Чернов Н.С. , Мурановский В.П.
1 К.т.н., доцент, Тольяттинский государственный университет, Самарская область, г. Тольятти, Белорусская, д. 14, РФ Начальник КБ, ООО Волжский машиностроительный завод (ВМЗ), Самарская область, г. Тольятти, Северная ул., д. 111, РФ
Аннотация
Рассмотрены проблемы и пути снижения колебаний давления и вибрации в трубопроводных системах энергетических установок. Описаны теоретические основы виброгашения. Рассмотрена разработанная авторами конструкция устройства для снижения шума и вибрации в трубопроводных системах. Исследована и экспериментально проверена проблема снижения колебания давления и шума в сравнении с зарубежными аналогами, приведены показатели эффективности приведенного устройства. Применение разработанного и внедренного устройства для снижения колебаний давления в трубопроводных системах энергетических установок позволяет значительно снизить вибрацию, повысить эффективность, надежность и ресурс работы промышленного оборудования.
Ключевые слова: вибрация, шум, пульсации давления, трубопроводные системы, измерительные приборы.
Development and research of the device for reduction of vibration and noise in piping
systems of power plants
Chernov N.S.1, Muranovskiy V.P.2
'Candidate of technical Sciences, associate Professor, Togliatti State University, Togliatti, Russia 2 Head of the design Bureau, OOO Volga Machine Works (VMW), Togliatti, Russia
Abstract
In this article were researched the problems and ways for reducing the pressure of fluctuations and vibration in piping systems ofpower plants. Also in this paper were described the theoretical basics of vibration damping. We considered the design of device for reducing noise and vibration in piping systems, which were designed by authors. In this work were studied and experimentally verified the problem of reducing vibrations pressure and noise in comparison with foreign counterparts, were showed indicators of effectiveness of the device. This device allows reducing the vibration significantly, improving efficiency and reliability and life operation of industrial equipment.
Key words: vibration, noise, pressure pulsations, pipeline systems, measuring instruments.
Введение
Надежность работы энергетических установок (ЭУ) и технологического оборудования (ТО) в значительной степени зависит от динамических свойств трубопроводных систем [1 ].
Возникающие при работе ЭУ низкочастотные пульсации давления при подаче теплоносителя по трубопроводу, являются источником интенсивной вибрации и могут вызвать разрушение трубопроводов и агрегатов, выход из строя измерительных приборов, а также могут приводить к аварии с тяжелыми последствиями [2].
Вибрации и шум являются наиболее распространенными и неблагоприятными вредными факторами, возникающими при эксплуатации ЭУ и ТО. Вибрация
E-mail: [email protected] (Чернов Н.С.), [email protected] (Мурановский В.П.)
