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  • 101.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Gventsadze, D.
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Kutelia, E
    Gventsadze, L.
    Tsurtsumia, O.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    A pin-on-disc investigation of nanoporous composite-based and conventional brake padmaterials focusing on airborne wear particles2011In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464Article in journal (Other academic)
  • 102.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Gventsadze, D.
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Kutelia, E.
    Gventsadze, L.
    Tsurtsumia, O.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    A pin-on-disc investigation of novel nanoporous composite-based and conventional brake pad materials focussing on airborne wear particles2011In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 44, no 12, p. 1838-1843Article in journal (Refereed)
    Abstract [en]

    Wear particles originating from disc brakes contribute to particulate concentration in the urban atmosphere. In this work novel nanoporous composite-based and conventional brake materials were tested against cast-iron discs in a modified pin-on-disc machine. During testing airborne wear particles were measured online and collected on filters, which were analysed using SEM and EDX. The morphology of airborne wear particles containing elements such as iron, oxygen, and copper is presented. These results show that two of the nanoporous materials generated 3-7 times less airborne wear particles than the conventional materials. Both the conventional and nanoporous materials displayed a bimodal number distribution.

  • 103.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Gventsadze, D
    Republic Dvali Institute of Machine Mechanics, Georgia.
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering (name changed to Building Service and Energy Systems 2012-03-01).
    Tsurtsumia, O
    Republic Center for Structure Researches of Georgian Technical University, Georgia.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    A pin-on-disc study of nanoporous composite-based and conventional brake pad materials focussing on airborne wear particles2010Conference paper (Refereed)
  • 104.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    A Pin-on-Disc Study Focusing on How Different Load Levels Affect the Concentration and Size Distribution of Airborne Wear Particles from the Disc Brake Materials2012In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 46, no 2, p. 195-204Article in journal (Refereed)
    Abstract [en]

    Airborne wear particles originating from disc brakes are one important contributor to the concentration of airborne particles in urban environments. It is therefore of interest to improve the knowledge of these particles. The purpose of this article is to investigate the concentration and size distribution of the airborne wear particles generated from the contact between a low-metallic pad material and a grey cast iron disc at different load levels. This is done on model level with a pin-on-disc machine that allows the cleanliness of the air surrounding the test specimens to be controlled, and thus the airborne portion of the wear particles to be studied separately. The concentration and size of airborne wear particles were measured online during testing with four particle instruments. In addition, airborne wear particles were collected on filters during the tests and afterward analysed using SEM. Trimodal size distributions with peaks around 280, 350 and 550 nm were registered during running-in for all load levels. After running-in bimodal size distributions with peaks around 350 and 550 nm were registered for all load levels with the exception of the highest load level where multimodal size distributions were registered. At the two highest load levels the concentration of ultrafine/fine particles showed an increase up to a factor hundred indicating a change in wear mechanism. SEM images show ultrafine, fine and coarse airborne wear particles.

  • 105.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Airborne Wear Particles Emissions ofCommercial Disc Brake Materials– Disc Brake Test Stand Simulations at LowContact Pressures and Rotors Pre-conditionedwith Rust2008Report (Other academic)
    Abstract [en]

    Most modern passenger cars have disc brakes on the front wheels, which unlike drum brakes are not sealed off to the ambient air. During braking, there is wear to both the rotor and the pads. This wear process generates particles, which may become airborne. A problem with measuring airborne wear particles in field tests is to distinguish them from the background noise. Therefore, a disc brake laboratory test stand that allows control of the cleanness of the surrounding air is used. With this test stand the number and size of the airborne wear particles from the pad to rotor contact can be measured online. In this technical report the results from two test series is presented. The first series were preformed at three brake cylinder pressure levels (1.2, 1.7 and 2.2 bar) and the rotors were pre-conditioned in a climate chamber with an oxide layer (e.g. rust). Ceramic NAO, NAO and low metallic type brake pads were tested. The second test series were conducted at three low brake cylinder pressure levels (0.1, 0.5 and 1 bar) with NAO and low metallic type brake pads, without any oxide layer. Promising results from the first test series indicate that this test stand can be used to study oxide layer removal from the rotor. The results are also promising for the ability to rank the number and size distribution from different pad rotor material combinations. The second test series shows that even at low pressures measurable levels of airborne particles are generated.

  • 106.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Size, Shape, and Elemental Composition of Airborne Wear Particles from Disc Brake Materials2010In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 38, no 1, p. 15-24Article in journal (Refereed)
    Abstract [en]

    During braking, both the rotor and pads experience wear, generating particles that may become airborne. In field tests, it is difficult to distinguish these particles from others in the surrounding environment, so it is preferable to use laboratory test stands to study the amount of airborne wear particles generated. The purpose of this work is to investigate the possibility of separate, capture, and analyze airborne wear particles generated by a disc brake in a disc brake assembly test stand. This test stand used allows the cleanliness of the air surrounding the test specimens to be controlled and thus the airborne portion of the wear particles to be studied separately. One pair each of low-metallic (LM) and non-asbestos organic (NAO) brake pads was tested against grey cast iron rotors. Before testing, the elemental contents of the brake materials were analyzed using glow discharge optical emission spectroscopy (GDOES). The concentration and size of airborne wear particles were measured online during testing. In addition, airborne wear particles were collected on filters during the tests and afterward analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The analyzed wear particles contained elements such as iron, titanium, zinc, barium, manganese, and copper. Both the low-metallic and non-asbestos organic type of brake pads tested display a bimodal size distribution with peaks at 280 and 350 nm. Most of the airborne particles generated have a diameter smaller than 2.5 mu m.

  • 107.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Applied Mechanical Engineering (KTH Södertälje).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Jansson, Anders
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Airborne Wear Particles Emissions fromCommercial Disc Brake Materials– Passenger Car Field Test2008Report (Other academic)
    Abstract [en]

    Most modern passenger cars have disc brakes on the front wheels, which unlike drum brakes are not sealed off to the ambient air. During braking, there is wear to both the rotor and the pads.

    This wear process generates particles, which may become airborne. In field tests it is difficult to distinguish these particles from others in the surrounding environment. It may be preferable to use laboratory test stands where the cleanness of the surrounding air can be controlled. The validity of these test stands has to be verified by comparison with field tests and therefore a test series has been conducted. These tests were performed in Stockholm, Sweden, in urban traffic.

    Low metallic type brake pads and gray cast iron rotors were tested. The results indicate that this test methodology can be used to study the number and mass concentrations as well as size distributions of particles generated from car disc brakes. Overall, the measured mean particle number and mass diameters of the airborne particles were 0.39 μm and 1.5 μm, respectively.

  • 108.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    A pin-on-disc study of automotive disc brake materials focusing on airborne wear particles2010In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897Article in journal (Other academic)
  • 109.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Söderberg, Anders
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering (name changed to Building Service and Energy Systems 2012-03-01).
    Jansson, Anders
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    A pin-on-disc simulation of airborne wear particles from disc brakes2010In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 268, no 5-6, p. 763-769Article in journal (Refereed)
    Abstract [en]

    A novel test method was used to study the concentration and size distribution of airborne wearparticles from disc brake materials. A pin-on-disc tribometer equipped with particle countinginstruments was used as test equipment. Material from four different non-asbestos organic(NAO) pads and four different low metallic (LM) pads were tested against material from greycast iron rotors. The results indicate that the low metallic pads cause more wear to the rotormaterial than the NAO pads, resulting in higher concentrations of airborne wear particles.Although there are differences in the measured particle concentrations, similar size distributionswere obtained. Independent of pad material, the characteristic particle number distributions ofairborne brake wear particles have maxima around 100, 280, 350, and 550 nm.

  • 110.
    Wahlström, Jens
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Söderberg, Anders
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olander, Lars
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering (name changed to Building Service and Energy Systems 2012-03-01).
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    A disc brake test stand for measurement of airborne wear particles2008Conference paper (Refereed)
  • 111.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Toward Industrialized Retrofitting: Accelerating the Transformation of the Residential Building Stock in Sweden2013Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Energy utilization issues are becoming increasingly important around the world. Existing residential and building service sectors represent a large part of total energy utilization, and the corresponding operational costs and environmental impacts are high. Retrofitting is considered an effective way to accelerate the sustainable transformation of the existing building stock. In Sweden, 1945–1975 was a boom period for the construction of residential buildings. After 40–70 years of use, large contingents of buildings need to be systematically retrofitted. In the past, most Swedish buildings were retrofitted individually, and occasionally in small clusters. Cost-effective retrofitting for large-scale implementation has not yet been substantially attained. Standardizing and industrializing the retrofitting process is expected to produce the following benefits: availability of standardized toolkits based on building typologies; simplified and more efficient decision-making process; lower retrofitting costs; shorter project durations; greater resource-efficiency; lower environmental impact; and higher profitability.The overall aim of the present study is to contribute to the knowledge regarding industrialized retrofitting toolkits in Swedish residential buildings and evaluate the various toolkits. More specifically, the study aims to analyze the energy demand saving potential of different retrofitting measures and long-term profits based on the typology of residential buildings. Based on a systematic set of building properties and classification of existing residential types in Sweden, four slab houses (lamellhus) were selected as the major sub-types of building stock for the demonstration cases. The case buildings were constructed between 1945 and 1975 and are currently used as single-family houses, multi-family houses, or apartment blocks. The main approaches applied to model the retrofitting profits were Consolis Energy +, parametric-based sensitivity analysis, and life-cycle-based economic assessment.Based on the theoretical modeling and analytical results from the case studies, it was found that the energy-saving potential is strongly dominated by the building type, which affects the design of retrofitting toolkits and defines life cycle costs. The results show that improving the efficiency of heat recovery in exhaust ventilation systems is an effective retrofitting measure for energy demand savings in the studied building types. However, the efficiency of other measures is highly dependent on the typology of the buildings. From an economic perspective, toolkits that include all of the possible retrofitting measures may not lead to larger expected reduction in LCC compared to standard retrofits that only include the most sensitive parameters. In addition, the impacts of energy price changes to the LCC in the future are highly diverse in different types of residential buildings. Developing systematic retrofitting guidelines for Swedish residential buildings requires both further research and a close collaboration between all stakeholders involved in the retrofitting process.

  • 112.
    Yunkai, Yang
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Numerical study on flow and pollutant dispersion inside street canyons2013Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This thesis analyzes the characteristics of flow pattern and vehicle-emitted pollutant dispersion in roughness surface layer. In an urban environment, wind flow and transported-pollutant source interfere strongly with buildings and other roughness elements on the surface ground, which results in complex characteristics of flow pattern and pollutant dispersion in 3D circumstances. The present study intends to simplify the research domain and investigate the fundamental modeling problems that exist in the field. The current physical research topic is restricted to 2D street canyon in equilibrium conditions. The study is motivated by the fact that characteristics of flow pattern and pollutant distribution inside street canyons are important for public health. The research has applied the computational fluid dynamics (CFD) methodology. To date, insights have typically focused on idealized street canyons without strictly limited boundary conditions and turbulence models. Those approaches face challenges related to their applicability to real urban scenarios or the reliability of prediction results.

    The thesis examines the influence of grid density, turbulence models and turbulent Schmidt number on pollutant distribution at windward and leeward surfaces of street canyon. Since numerical results usually are validated with wind-tunnel measurement data, the results between full-size model and wind-tunnel model are compared in order to test the Reynolds number effect. The lack of measurement data means that the morphometric method is used to generate upcoming wind profile, including the mean vertical velocity and turbulence parameters. The thesis also analyzes the potential errors brought by the method (Scenario A).

    Based on the evaluated numerical model, the thesis continues to study the impacts of surrounding buildings and geometry of street canyon on flow and pollutant distribution inside street canyons. The effect of wind on pollutant distribution inside street canyons was also investigated (Scenario A). Furthermore, the influence of roof shape and configuration of street canyon on characteristics of flow and pollutant distribution is also systematically studied, with the results shown in scenario B.

    The main conclusions of the thesis are that the uncertainty of numerical results derives from different aspects. Wind profile in the inlet profile generated by morphometric method brings major error to the simulation results. Current turbulence models cannot compromise the simulation results between flow field and pollutant distribution field. Ignored small-scale obstacles also need to be handled carefully. Numerical results revealed that flow and pollutant distribution inside street canyons are mainly dominated by the geometry of the street canyon itself. Medium-spaced surrounding buildings are also better able to transport pollutant out of the street canyon. Through systematic analysis, roof shape is proven to have a significant effect on flow and pollutant distribution inside a street canyon. The major impact is altered turbulence intensity depth and strength of shear layer inside the street canyon, which is important for pollutant removal process out of the street canyon.

    In the future, advanced turbulence models accompanied by small-obstacle effect models need to be developed in order to reliably simulate flow and pollutant dispersion simultaneously. Based on the advanced turbulence model, simulation of flow and pollutant dispersion in a complex 3D environment is essential in the next steps for the purpose of engineering application. Accurate vertical wind profile provided for inlet profile is another interesting direction for further development.

    Keywords: Flow; Pollutant dispersion; CFD; Street canyon; Reliability

123 101 - 112 of 112
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