Airborne particles and their adverse effects on air quality have been recognized by humans since ancient times. Current exhaust emission legislations increase the relative contribution of wear particles on the PM levels. Consequently, wear-based particle emissions from rail and road transport have raised concerns as ground transportation is developing quickly. Although scientific research on airborne wear-based particles started in 1909, there is almost no legislation that control the generation of wear-based particles. In addition, there is no accepted and approved standard measurement technique for monitoring and recording particle characteristics. The main objective of this study is to review recent experimental work in this field and to discuss their set-ups, the sampling methods, the results, and their limitations, and to propose measures for reducing these limitations.

One dimensional, linear, plane-wave modelling of silencer systems in the frequency domain provides an efficient means to analyse their acoustic performance. Software packages are available to analyse silencers within these modelling parameters; however, they are heavily restricted. The thesis develops an algorithm that increases the computational efficiency of the silencer analysis. The thesis concentrates on how data, within a software package, is stored, retrieved and analysed. The computational efficiency is increased as a result of the predictable patterns caused by the repetitive nature of exhaust system analysis. The work uses the knowledge gained from the construction of two previous algorithms of similar parameters; it isolates and maximises their advantages whilst minimising their associated disadvantages. The new algorithm is dependent on identifying consecutively sequenced exhaust components and sub-systems of such components within the whole exhaust system. The algorithm is further generalised to include multiple time-variant sources, multiple radiation points and exhaust systems that have a balance pipe. Another feature of the improved algorithm encompasses the option of modelling secondary noise sources such as might arise from flow generated noise or be included for active noise cancellation systems. The validation of these algorithmic techniques is demonstrated by comparison of the theoretical noise predictions with experimental or known results. These predictions are achieved by writing computational code using object orientated programming techniques in the language of c++ to implement the algorithms.

Orientador: Carlos Alberto Bandeira Guimarães / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-06T01:41:02Z (GMT). No. of bitstreams: 1 Lobkov_DmitriDmitrievich_M.pdf: 951415 bytes, checksum: 540ad2a18af759bf3bb0d0715b212f7f (MD5) Previous issue date: 2005 / Resumo: Neste trabalho se apresentam argumentos econômicos e de meio ambiente para o uso de GNC em ônibus de transporte público, na forma de gás-diesel. Assim, os objetivos deste trabalho são: Analisar e comparar a experiência real do uso de gás-diesel em outros países e também no Brasil, para oferecer alternativa de combustível Gás Natural Comprimido (GNC) para as empresas de transporte urbano. Fundamentar as vantagens econômicas de reduzir o consumo de combustível diesel em ônibus a gás-diesel, usando como combustível uma mistura de diesel e GNC. Fazer os cálculos de demanda crescente de GNC com a substituição de combustível diesel por GNC nos ônibus urbanos / Abstract: This work presents strong economical and enviromental arguments in favour of the use of CNG (Compress Natural Gas) in the passengers's public transport (buses). The main object of this work is to analyse and compare the real experience in the use of gas/diesel fuel in Brazil and in other countries in an attempt to give an alternative gas fuel system in the public transport. Also it establishes and explains the economical advantage in reducing the consume of diesel fuel in the gas/diesel buses, by the use of a diesel/CNG mixture. Finally, the calculations made show the increasing demand of CNG with the substitution of diesel fuel by CNG in the buses of the public transport / Mestrado / Geotecnia / Mestre em Engenharia Civil

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<p>This thesis contains three papers investigating problems of interest for noise control in ducts.</p><p>The first part of this thesis treats the sound propagation in rectangular ducts with flexible walls. Various experimental techniques are performed to measure the internal sound propagation and radiation to the surrounding. An analytical model is derived to calculate the coupled propagation wavenumber and radiated sound power. The two-port formalism is used.</p><p>The second part starts with the sound propagation in open ended circular straight pipe with airflow (a tailpipe). Various aspects such as: acoustic damping, reflection and transmission at the open termination are investigated. Sound absorption due to vorticity shed at the opening is also treated. The geometry of the opening is then modified (oblique cuts, diffusers) and comparisons with the reference straight pipe is made for the sound transmission and flow induced noise generation. The effect of an upstream bend close to the opening is also investigated.</p><p>In the third part the acoustic impedance of perforated plates are investigated. In particular the application to small perforation ratios ( ≈ 1% ) and holes or slits with apertures of sub-millimetre size, so called micro-perforated plates, are of interest. Linear and non-linear regimes are investigated. A model is derived to calculate the linear acoustic impedance of perforated elements.</p>

Motor vehicles are a major source of gaseous and particulate matter pollution in urban areas, particularly of ultrafine sized particles (diameters < 0.1 µm). Exposure to particulate matter has been found to be associated with serious health effects, including respiratory and cardiovascular disease, and mortality. Particle emissions generated by motor vehicles span a very broad size range (from around 0.003-10 µm) and are measured as different subsets of particle mass concentrations or particle number count. However, there exist scientific challenges in analysing and interpreting the large data sets on motor vehicle emission factors, and no understanding is available of the application of different particle metrics as a basis for air quality regulation. To date a comprehensive inventory covering the broad size range of particles emitted by motor vehicles, and which includes particle number, does not exist anywhere in the world. This thesis covers research related to four important and interrelated aspects pertaining to particulate matter generated by motor vehicle fleets. These include the derivation of suitable particle emission factors for use in transport modelling and health impact assessments; quantification of motor vehicle particle emission inventories; investigation of the particle characteristic modality within particle size distributions as a potential for developing air quality regulation; and review and synthesis of current knowledge on ultrafine particles as it relates to motor vehicles; and the application of these aspects to the quantification, control and management of motor vehicle particle emissions. In order to quantify emissions in terms of a comprehensive inventory, which covers the full size range of particles emitted by motor vehicle fleets, it was necessary to derive a suitable set of particle emission factors for different vehicle and road type combinations for particle number, particle volume, PM1, PM2.5 and PM1 (mass concentration of particles with aerodynamic diameters < 1 µm, < 2.5 µm and < 10 µm respectively). The very large data set of emission factors analysed in this study were sourced from measurement studies conducted in developed countries, and hence the derived set of emission factors are suitable for preparing inventories in other urban regions of the developed world. These emission factors are particularly useful for regions with a lack of measurement data to derive emission factors, or where experimental data are available but are of insufficient scope. The comprehensive particle emissions inventory presented in this thesis is the first published inventory of tailpipe particle emissions prepared for a motor vehicle fleet, and included the quantification of particle emissions covering the full size range of particles emitted by vehicles, based on measurement data. The inventory quantified particle emissions measured in terms of particle number and different particle mass size fractions. It was developed for the urban South-East Queensland fleet in Australia, and included testing the particle emission implications of future scenarios for different passenger and freight travel demand. The thesis also presents evidence of the usefulness of examining modality within particle size distributions as a basis for developing air quality regulations; and finds evidence to support the relevance of introducing a new PM1 mass ambient air quality standard for the majority of environments worldwide. The study found that a combination of PM1 and PM10 standards are likely to be a more discerning and suitable set of ambient air quality standards for controlling particles emitted from combustion and mechanically-generated sources, such as motor vehicles, than the current mass standards of PM2.5 and PM10. The study also reviewed and synthesized existing knowledge on ultrafine particles, with a specific focus on those originating from motor vehicles. It found that motor vehicles are significant contributors to both air pollution and ultrafine particles in urban areas, and that a standardized measurement procedure is not currently available for ultrafine particles. The review found discrepancies exist between outcomes of instrumentation used to measure ultrafine particles; that few data is available on ultrafine particle chemistry and composition, long term monitoring; characterization of their spatial and temporal distribution in urban areas; and that no inventories for particle number are available for motor vehicle fleets. This knowledge is critical for epidemiological studies and exposure-response assessment. Conclusions from this review included the recommendation that ultrafine particles in populated urban areas be considered a likely target for future air quality regulation based on particle number, due to their potential impacts on the environment. The research in this PhD thesis successfully integrated the elements needed to quantify and manage motor vehicle fleet emissions, and its novelty relates to the combining of expertise from two distinctly separate disciplines - from aerosol science and transport modelling. The new knowledge and concepts developed in this PhD research provide never before available data and methods which can be used to develop comprehensive, size-resolved inventories of motor vehicle particle emissions, and air quality regulations to control particle emissions to protect the health and well-being of current and future generations.

This thesis contains three papers investigating problems of interest for noise control in ducts. The first part of this thesis treats the sound propagation in rectangular ducts with flexible walls. Various experimental techniques are performed to measure the internal sound propagation and radiation to the surrounding. An analytical model is derived to calculate the coupled propagation wavenumber and radiated sound power. The two-port formalism is used. The second part starts with the sound propagation in open ended circular straight pipe with airflow (a tailpipe). Various aspects such as: acoustic damping, reflection and transmission at the open termination are investigated. Sound absorption due to vorticity shed at the opening is also treated. The geometry of the opening is then modified (oblique cuts, diffusers) and comparisons with the reference straight pipe is made for the sound transmission and flow induced noise generation. The effect of an upstream bend close to the opening is also investigated. In the third part the acoustic impedance of perforated plates are investigated. In particular the application to small perforation ratios ( ≈ 1% ) and holes or slits with apertures of sub-millimetre size, so called micro-perforated plates, are of interest. Linear and non-linear regimes are investigated. A model is derived to calculate the linear acoustic impedance of perforated elements. / QC 20101111