Ändra sökning
Avgränsa sökresultatet
1234567 101 - 150 av 1078
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 101.
    Bergström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Shape verification aimed for manufacturing process control2011Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 49, nr 3, s. 403-409Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We describe a method to verify the shape of manufactured objects by using their design model. A non-contact measuring method that consists of a stereo-camera system and a single projected fringe pattern is used. The method acquires one image from each camera. Additional shape information from the design model is also used. This surface-measurement method gives an accuracy of about 45 µm. Deviations from the design model within ±1.6 mm can be correctly detected. The measured surface representation is matched to the design model using the ICP-method. Fast performance has been considered adapting the method for on-line use.

  • 102.
    Bhaduri, Basanta
    et al.
    National University of Singapore.
    Quan, Chenggen
    National University of Singapore.
    Tay, Cho Jui
    National University of Singapore.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Simultaneous measurement of translation and tilt using digital speckle photography2010Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 49, nr 18, s. 3573-3579Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A Michelson-type digital speckle photographic system has been proposed in which one light beam produces a Fourier transform and another beam produces an image at a recording plane, without interfering between themselves. Because the optical Fourier transform is insensitive to translation and the imaging technique is insensitive to tilt, the proposed system is able to simultaneously and independently determine both surface tilt and translation by two separate recordings, one before and another after the surface motion, without the need to obtain solutions for simultaneous equations. Experimental results are presented to verify the theoretical analysis.

  • 103.
    Bhaduri, Basanta
    et al.
    National University of Singapore.
    Tay, C.J.
    National University of Singapore.
    Quan, C.
    National University of Singapore.
    Niu, H.
    National University of Singapore.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Two wavelength simultaneous DSPI and DSP for 3D displacement field measurements2011Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 284, nr 10-11, s. 2437-2440Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel optical system is proposed that implements digital speckle pattern interferometry (DSPI) and digital speckle photography (DSP) simultaneously using two wavelength illumination of an object for simultaneous measurement of all three components of the displacement vector field. A collimated red light illuminates both the object and a reference surface in a DSPI configuration which is sensitive to out-of-plane displacement field while a blue light illuminates the object in a DSP configuration which is sensitive to in-plane displacement fields. A color 3-CCD camera records the red and blue lights individually through its red and blue channels, respectively. Two reference images and one image in the deformed state of the object are required for quantitative measurement. Experimental results are presented to validate the system.

  • 104.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Forsmo, S.P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Consideration of X-ray microtomography to quantitatively determine the size distribution of bubble cavities in iron ore pellets2013Ingår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 233, s. 312-318Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    X-ray microtomography data of iron ore green pellets of approx. 12 mm in diameter were recorded using a commercial instrument. The reconstructed volume after thresholding represented a unique dataset consisting of a three-dimensional distribution of equiaxed objects corresponding to bubble cavities. This dataset was used to successfully validate a stereological method to determine the size distribution of spherical objects dispersed in a volume. This was achieved by investigating only a few cross-sectional images of this volume and measuring the profiles left by these objects in the cross-sectional images. Excellent agreement was observed between the size distribution of the bubble cavities obtained by directly classifying their size in the reconstructed volume and that estimated by applying the aforementioned stereological method to eight cross-sectional images of the reconstructed volume. Subsequently, we discuss the possibility of calibrating X-ray tomography data quantitatively using the size distribution of the bubble cavities as a figure of merit and the results obtained by applying the stereological method to SEM images as reference data. This was justified by considering the validity of the stereological method demonstrated by tomography, the accurate thresholding made possible by back-scattered electron imaging and the solid reproducibility of the results obtained by SEM. Using different threshold values for binarization of the X-ray microtomography data and comparing the results to those obtained by SEM, we found that X-ray microtomography can be used after proper calibration against SEM data to measure the total porosity of the bubble cavities but can only provide a rough estimate of the median diameter because of the limited resolution achieved in this study.

  • 105.
    Bilal, Ahmed
    et al.
    College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, China.
    Xie, Qiancheng
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    The Numerical Study of Open Channel Junctions with Extreme Confluence Angles for Surface Flow without Wall Roughness2019Konferensbidrag (Refereegranskat)
  • 106.
    Bin Asad, S M Sayeed
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Laser Based Flow Measurements to Evaluate Hydraulic Conditions for Migrating Fish and Benthic Fauna2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Hydropower is one of the main sources for Sweden’s energy, which is clean and renewable. It is a clean energy source because no fuels are burned which does not pollute the air and it is a renewable energy source as it only uses natural water cycle for generating energy. However, hydropower has some consequences in nature, such as creating dams in rivers and changing water flow directions, which alters the natural behaviour of the river. These problems are mostly studied from a biological point of view but more detailed studies are required from a fundamental fluid mechanics point of view. For instance, fish migrates when an ecological imbalance is created and one of the reasons for this imbalance is having dams for hydropower that alter the natural flow of the river. This flow alteration of the river flow has other environmental effects such as flow alteration changes benthic (bottom) structure of the riverbed or stream that affects the fish and invertebrates. Fishes, as well as invertebrates, are adapted for different flows and habitats but flow alteration affects their life cycles. Therefore, flow measurements when the flow is altered due to the hydropower are one of the important issues concerning environmental problems. These flow measurements in the lab scale can increase the understanding of what happens in a river when the flow is altered.

    Flow characteristic measurements can provide quantitative information on the velocity distribution in the altered flow. Recent studies suggest that turbulence created due to flow alteration has a major effect on fish migration, for example, attracting fishes to enter fishway. This is why obtaining flow information from well-defined turbulent flows, such as flow past cylindrical objects is one of the prime objectives of work. However, flow alteration due to the dam for hydropower production has a significant environmental effect on the river ecosystem. Lotic species often adapt to prevailing flow conditions; and as a crude example, two species of caddis larvae: Hydropsyche instabilis and Plectrocnemia conspersa respectively are found to thrive on fast and slow-moving water flows. For some instances, changes in river velocity may merely mean the relocation of one species whilst the flourishing of another. Therefore, flow measurement in stones embedded riverbed in lab scale is another important objective of this work.

    Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) have become the most popular and promising techniques for these types of non-contact flow measurements. PIV techniques are used to visualize and measure the flow characteristic in a selected area while LDV techniques are suited for point-based measurement.  The works included in this thesis are reviewing PIV techniques previously used in fish movement related studies, LDV measurements both at upstream (bow wake) and downstream wake of vertical cylindrical obstructions, Computational Fluid Dynamics (CFD) simulations to supplement wake information and PIV measurements over the horizontal semicircular cylinders to explore wall shear stress. Apart from this, flow visualization was also included in this work. The results from all these works can be useful to evaluate hydraulic conditions for migrating fish and benthic fauna.

  • 107.
    Bin Asad, S M Sayeed
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Andersson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Study the Flow behind a Semi-Circular Step Cylinder (Laser Doppler Velocimetry (LDV) and Computational Fluid Dynamics (CFD))2017Ingår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 10, nr 3, artikel-id 332Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laser Doppler Velocimetry (LDV) measurements, flow visualizations and unsteadyReynolds-Averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) simulations havebeen carried out to study the turbulent wake that is formed behind a semi-circular step cylinder ata constant flow rate. The semi-circular cylinder has two diameters, a so-called step cylinder. Theresults from the LDV measurements indicate that wake length and vortex shedding frequency varieswith the cylinder diameter. This implies that a step cylinder can be used to attract fish of differentsize. By visualizations of the formation of a recirculation region and the well-known von Kármánvortex street behind the cylinder are disclosed. The simulation results predict the wake length andshedding frequency well for the flow behind the large cylinder but fail to capture the dynamics ofthe flow near the step in diameter to some extent and the flow behind the small cylinder to a largerextent when compared with measurements.

  • 108.
    Bin Asad, S M Sayeed
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Andersson, Anders G.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Experimental study of the flow past submerged half-cylinders2017Ingår i: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 1851, artikel-id 020001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This investigation studies the details of the flow behind and over two identical semicircular cylinderspositioned in tandem. Laser Doppler Velocimetry (LDV) measurements are carried out in a laboratory waterflume using two different gap ratios (Sp/d = 1 and Sp/d = 0.5; where Sp indicates distance between the cylindersand d indicates cylinder diameter) under two different flow situations. These LDV measurement are used toderive velocities, formation length and Power spectral density for the various flow conditions. Flowvisualizations are also added in this investigation. The results indicate that the flow is significantly affected dueto gap ratios.

  • 109.
    Bin Asad, S M Sayeed
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Andersson, Anders G.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hellström, J. Gunnar I.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Leonardsson, Kjell
    Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden.
    Wall shear stress measurement on curve objects with PIV in connection to benthic fauna in regulated rivers2019Ingår i: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 11, nr 4, artikel-id 650Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The flow characteristics in the vicinity of a set of half-cylinders of different sizes simulating benthic objects were studied experimentally using particle image velocimetry (PIV). The cylinders were mounted on the bottom of an open channel, and the influence of the flow speed on the distribution of the shear stress along the bottom geometry was investigated. Of special interest was how the shear stress changes close to the wall as a function of the flow speed and cylinder arrangement. It was found that the shear stress varies significantly as a function of position. This implies habitat heterogeneity allowing benthic invertebrates with different shear stress tolerance exists when the bottom consists of differently sized stones. It was also shown that direct measurements of near wall velocity gradients are necessary to accurately calculate the wall shear stress for more complex geometries.

  • 110.
    Bin Asad, S M Sayeed
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Andersson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hellström, Gunnar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    A Review of Particle Image Velocimetry for Fish Migration2016Ingår i: World Journal of Mechanics, ISSN 2160-049X, E-ISSN 2160-0503, Vol. 6, nr 4, s. 131-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Understanding the flow characteristic in fishways is crucial for efficient fish migration. Flow characteristic measurements can generally provide quantitative information of velocity distributions in such passages; Particle Image Velocimetry (PIV) has become one of the most versatile techniques to disclose flow fields in general and in fishways, in particular. This paper firstly gives an overview of fish migration along with fish ladders and then the application of PIV measurements on the fish migration process. The overview shows that the quantitative and detailed turbulent flow information in fish ladders obtained by PIV is critical for analyzing turbulent properties andvalidating numerical results.

  • 111.
    Bin Asad, S M Sayeed
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Andersson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hellström, Gunnar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Velocity distribution measurements in a fishway like open channel by Laser Doppler Anemometry (LDA)2016Ingår i: / [ed] Dancova, P; Vesely, M, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Experiments in an open channel flume with placing a vertical half cylinder barrier have been performed in order to investigate how the upstream velocity profiles are affected by a barrier. An experimental technique using Laser Doppler Velocimetry (LDV) was adopted to measure these velocity distributions in the channel for four different discharge rates. Velocity profiles were measured very close to wall and at 25, 50 and 100 mm upstream of the cylinder wall. For comparing these profiles with well-known logarithmic velocity profiles, velocity profiles were also measured in smooth open channel flow for all same four discharge rates. The results indicate that regaining the logarithmic velocity profiles upstream of the half cylindrical barrier occurs at 100 mm upstream of the cylinder wall.

  • 112.
    Broberg, Patrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Imaging and analysis methods for automated weld inspection2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    All welding processes can give rise to defects, which weakens the joint and can eventually lead to the failure of the welded structure. In order to inspect welds for detects, without affecting the usability of the product, non-destructive testing (NDT) is needed. NDT includes a wide range of different techniques, based on different physical principles, each with its advantages and disadvantages. The testing is often performed manually by a skilled operator and in many cases only as spot-checks. Today the trend in industry is to move towards thinner material, in order to save weight for cost and for environmental reasons. The need for inspection of a larger portion of welds therefore increases and there is an increasing demand for fully automated inspection, including both the mechanised testing and the automatic analysis of the result. Compared to manual inspection, an automated solution has advantages when it comes to speed, cost and reliability. A comparison of several NDT methods was therefore first performed in order to determine which methods have most potential for automated weld inspection. Automated analysis of NDT data poses several difficulties compared to manual data evaluation. It is often possible for an operator to detect defects even in noisy data, through experience and knowledge about the part being tested. Automatic analysis algorithms on the other hand suffer greatly from both random noise as well as indications that originate from geometrical variations. The solution to this problem is not always obvious. Some NDT techniques might not be suitable for automated inspection and will have to be replaced by other, better adapted methods. One such method that has been developed during this work is thermography for the detection of surface cracks. This technique offers several advantages, in terms of automation, compared to existing methods. Some techniques on the other hand cannot be easily replaced. Here the focus is instead to prepare the data for automated analysis, using various pre-processing algorithms, in order to reduce noise and remove indications from sources other than defects. One such method is ultrasonic testing, which has a good ability for detecting internal defects but suffers from noisy signals with low spatial resolution. Work was here done in order to separate indications from corners from other indications. This can also help to improve positioning of the data and thereby classification of defects. The problem of low resolution was handled by using a deconvolution algorithm in order to reduce the effect of the spread of the beam.The next step in an automated analysis system is to go beyond just detection and start characterising defects. Using knowledge of the physical principles behind the NDT method in question and how the properties of a defect affect the measurement, it is sometimes possible to develop methods for determining properties such as the size and shape of a defect. This kind of characterisation of a defect is often difficult to do in the raw data, and is therefore an area where automated analysis can go beyond what is possible for an operator during manual inspection. This was shown for flash thermography, where an analysis method was developed that could determine the size, shape and depth of a defect. Similarly for laser ultrasound, a method was developed for determining the size of a defect.

  • 113.
    Broberg, Patrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Towards automation of non-destructive testing of welds2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    All welding processes can give rise to defects that will weaken the joint and can lead to failure of the welded structure. Because of this, non-destructive testing (NDT) of welds have become increasingly important to ensure the structural integrity when the material becomes thinner and stronger and welds become smaller; all to reduce weight in order to save material and reduce emissions due to lighter constructions.Several NDT methods exists for testing welds and they all have their advantages and disadvantages when it comes to the types and sizes of defects that are detectable, but also in the ability to automate the method. Several methods were compared using common weld defects to determine which method or methods were best suited for automated NDT of welds. The methods compared were radiography, phased array ultrasound, eddy current, thermography and shearography. Phased array ultrasound was deemed most suitable for detecting the weld defects used in the comparison and for automation and was therefore chosen to be used in the continuation of this work. Thermography was shown to be useful for detecting surface defects; something not easily detected using ultrasound. A combination of these techniques will be able to find most weld defects of interest. Automation of NDT can be split into two separate areas; mechanisation of the testing and automation of the analysis, both presenting their own difficulties. The problem of mechanising the testing has been solved for simple geometries but for more general welds it will require a more advance system using an industrial robot or similar. Automation of the analysis of phased array ultrasound data consists of detection, sizing, positioning and classification of defects. There are several problems to solve before a completely automatic analysis can be made, including positioning of the data, improving signal quality, segmenting the images and classifying the defects. As a step on the way towards positioning of the data, and thereby easing the analysis, the phase of the signal was studied. It was shown that the phase can be used for finding corners in the image and will also improve the ability to position the corner as compared to using the amplitude of the signal. Further work will have to be done to improve the signal in order to reliably analyse the data automatically.

  • 114.
    Bruzelius, F
    et al.
    Volvo Technology.
    Svendenius, J
    Haldex.
    Yngve, S
    Volvo Cars.
    Olsson, G
    Saab Automobile.
    Casselgren, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Andersson, M
    Volvo Technology.
    Rönnberg, J
    Saab Automobile.
    Löfving, S.
    Evaluation of tyre to road friction estimators: test methods and metrics2010Ingår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 5, nr 2-3, s. 213-236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The tyre to road contact friction is one of the most important properties when it comes to manoeuvrability of ground vehicles and information, to driver and vehicle, is of vital importance in critical situations. Different characteristics of different friction estimation methods make it hard to determine and compare performance of estimators. This article is an attempt to define and evaluate the performance of tyre to road friction estimators. The objective of the performance evaluation is to define and grade the performance of estimators based on all sorts of approaches and combinations of these. The result may be used in the context of benchmarking as well as a tool in the development process of the estimator. The test methods and metrics presented are illustrated with a comparative study of three different estimation approaches.

  • 115.
    Bucur, Diana
    et al.
    POLITEHNICA University of Bucharest.
    Dunca, Georgiana
    POLITEHNICA University of Bucharest.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Clinoiu, C.
    POLITEHNICA University of Bucharest.
    Isbşoiu, E.C.
    POLITEHNICA University of Bucharest.
    Simultaneous transient operation of a high head hydro power plant and a storage pumping station in the same hydraulic scheme2014Ingår i: 27th IAHR Symposium on Hydraulic Machinery and Systems, IAHR 2014: Montreal, Canada, 22 - 26 September 2014 / [ed] C. Deschenes, IOP Publishing Ltd , 2014, artikel-id 42015Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents an on-site experimental analysis of a high head hydro power plant and a storage pumping station, in an interconnected complex hydraulic scheme during simultaneous transient operation. The investigated hydropower site has a unique structure as the pumping station discharges the water into the hydropower plant penstock. The operation regimes were chosen for critical scenarios such as sudden load rejections of the turbines as well as start-ups and stops with different combinations of the hydraulic turbines and pumps operation. Several parameters were simultaneously measured such as the pumped water discharge, the pressure at the inlet pump section, at the outlet of the pumps and at the vane house of the hydraulic power plant surge tank. The results showed the dependence of the turbines and the pumps operation. Simultaneous operation of the turbines and the pumps is possible in safe conditions, without endangering the machines or the structures. Furthermore, simultaneous operation of the pumping station together with the hydropower plant increases the overall hydraulic efficiency of the site since shortening the discharge circuit of the pumps.

  • 116.
    Bucur, Diana Maria
    et al.
    University POLITEHNICA of Bucharest.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Dunca, Georgiana
    University POLITEHNICA of Bucharest.
    Maximum pressure evaluation during expulsion of entrapped air from pressurized pipelines2017Ingår i: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 10, nr 1, s. 11-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pressurized pipeline systems may have a wide operating regime. This paper presents the experimental analysis of the transient flow in a horizontal pipe containing an air pocket, which allows the ventilation of the air after the pressurization of the hydraulic system, through an orifice placed at the downstream end. The measurements are made on a laboratory set-up, for different supply pressures and various geometries of water column length, air pocket and expulsion orifice diameter. Dimensional analysis is carried out in order to determine a relation between the parameters influencing the maximum pressure value. A two equations model is obtained and a criterion is established for their use. The equations are validated with experimental data from the present laboratory set-up and with other data available in the literature. The results presented as nondimensional quantities variations show a good agreement with the previous experimental and analytical researches.

  • 117.
    Burman, Anton
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    INHERENT DAMPING IN A PARTIALLY DRY RIVER2019Ingår i: Proceedings of the 38th IAHR World Congress / [ed] Lucas Calvo, 2019, s. 5091-5100Konferensbidrag (Refereegranskat)
    Abstract [en]

    As intermittent power sources such as solar power and wind power gains traction in Scandinavia it is likelythat the electricity production will become increasingly dependent on hydro power as a buffer in times ofpower deficit from intermittent power sources due to weather conditions. Rapid changes in hydro powerdemand can rapidly change the flow conditions in proximity to the power plant. This paper aims to model thetransient behavior and quantify the inherent damping in a dry reach in proximity to the largest hydro powerplant in Sweden, with respect to production. A two-dimensional model solving the Navier-Stokes equationswith shallow water approximations was set up using the open-source solver Delft3D. The Manning numbers inthe reach was calibrated with measured steady state water surface elevation data. The simulation data wasthen validated with transient water level measurements. The results show that it's possible to calibrate theManning numbers using steady state water level measurements. The model also shows that it's possible tocapture the inherent damping and more transient behavior using Delft3D. The results can be used to bettermodel rivers without the need for resolving the upstream reach. The results can also be used forecohydraulical applications where the transient behavior is important

  • 118.
    Burström, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Computational Fluid Dynamics of Processes in Iron Ore Grate-Kiln Plants2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Computational Fluid Dynamics (CFD) approaches have been developed to studypollution reduction in the manufacturing phase and heat transfer in the packed beds of iron ore pellets. CFD is a versatile tool that can be applied to study numerous problems in fluid mechanics. In the present thesis it is used, verified and validated to reveal the fluid mechanics of a couple of processes taking place during the drying and sintering of iron ore pellets. This is interesting in itself and can facilitate the optimization of the production as to product quality of the pellets, reduced energy consumption and reduction of emissions such as NOx and CO2. The practical aim with the pollution reduction research project is to numerically study the use of Selective Non-Catalytic Reduction (SNCR) technologies in gratekiln pelletizing plants for NOx reduction which had, to the best knowledge of the author, never been used in this context before despite that it is commonly used in cement and waste incineration plants. The investigation is done in several stages: 1)Reveal if it is possible to use the technique with the two most commonly reagents, ammonia and urea. 2) Derive a chemistry model for cyanuric acid (CA) so that this reagent also can be scrutinized. 3) Compare the reagents urea and CA in the gratekiln pelletizing process.A CFD model was developed and numerical simulations were carried out solving the flow field. A model for spray injection into the grate was then included in the model enabling a study of the overall mixing between the injected reagent droplets and the NOx polluted air. The results show that the SNCR technique with urea and CA may reduce the amount of NOx in the grate-kiln process under certain conditions while ammonia fails under the conditions investigated. The work also lays grounds for continued development of the proposed chemistry model by the adding of reactions to the RAPRENOx-process for CA as reagent, facilitating an extension to ammonia and urea as reagents.The grate-kiln plant consists of a grate, a rotating kiln and an annular cooler. The pellets are loaded onto the grate to shape a bed with a mean height of about 0.2 m. The pellets in LKABs processes consist mainly of magnetite and different additives chosen to fit the demand from the customer. Throughout the grate a temperature gradient is formed in the bed. This gradient should be as even as possible throughout the grate to ensure an even quality of the pellets. Method to study this numerically is the second main task in this thesis. The aim is to find out how temperature distributions in the bed can be modeled and adjusted. Of special interest is how the incoming process gas, leakage, and the detailed composition of the pellet bed influence the heat transfer through the bed. To achieve the goals and create a trustful model for the heat transfer through the packed bed the model must be build up in steps. Heat transfer to a bed of iron ore pellets is therefore examined numerically on several scales and with three methods: a one-dimensional continuous model, a discrete three-dimensional model and traditional computational fluid dynamics.In a first study the convective heat transport in a relatively thin porous layer ofmonosized particles is set-up and computed with the one-dimensional continuous model and the discrete three-dimensional model. The size of the particles is only one order of magnitude smaller than the thickness of the layer. For the three-dimensional model the methodology applied is Voronoi discretization with minimization of dissipation rate of energy. The discrete model captures local effects, including low heat transfer in sections with low speed of the penetrating fluid and large velocity and temperature variations in a cross section of the bed. The discrete and continuousmodel compares well for low velocities for the studied uniform boundary conditions. When increasing the speed or for a thin porous layer however, the continuous model diverge from the discrete approach if a constant dispersion is used in the continuous approach. The influence is larger from an increase in pellet diameter to bed height ratio than from increased velocity. In a second study the discrete model is compared to simulations performed with CFD. If local values are of importance the discrete model should always be used but if mean predictions are sufficient the CFD model isan attractive alternative that is easy to couple to the physics up- and downstream the packed bed. The good agreement between the discrete and continuous model furthermore indicates that the discrete model may be used also for non-Stokian flow in the transitional region between laminar and turbulent flow, as turbulent effects show little influence of the overall heat transfer rates in the continuous model.

  • 119.
    Burström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Antos, Dorota
    Rzeszów University of Technology.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Marjavaara, Daniel
    LKAB.
    A CFD-based evaluation of Selective Non-Catalytic Reduction of Nitric Oxide in iron ore grate-kiln plants2015Ingår i: Progress in Computational Fluid Dynamics, An International Journal, ISSN 1468-4349, E-ISSN 1741-5233, Vol. 15, nr 1, s. 32-46Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The overall goal of this study is to explore the function of selective non-catalytic reduction of nitric oxide (NO) in iron ore grate-kiln plants. Computational fluid dynamics is used to model the flow and the injection of urea and cyanuric acid reagents. Temperature, residence time and inlet NO content are varied, and the effects on the reduction of NO are studied. The simulations show that the use of urea results in a higher reduction of NO within the temperature window investigated as compared to cyanuric acid; however, urea cannot be used for NO reduction over the entire range of applicable temperatures. Cyanuric acid is usable within the entire temperature range for high NO content (i.e., 300 ppm) in the flue gas, but it is not effective for low NO concentration (i.e., 150 ppm). Moreover, the simulations indicate that temperature has a larger influence on the NO reduction than the residence time.

  • 120.
    Burström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Antos, Dorota
    Rzeszów University of Technology.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Marjavaara, Daniel
    LKAB.
    A validated CFD model for prediction of selective non-catalytic reduction of nitric oxide by cyanuric acid2016Ingår i: Progress in Computational Fluid Dynamics, An International Journal, ISSN 1468-4349, E-ISSN 1741-5233, Vol. 16, nr 2, s. 108-117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A CFD model for selective non-catalytic reduction of nitric oxide by cyanuric acid (RAPid REduction of Nitrogen Oxides, RAPRENOx process) is compared against reactor experiments. The numerical simulations were carried out solving the flow field. A model for the RAPRENOx chemistry was then included in the model enabling a study of the chemistry in the reactor. The simulations showed that the proposed chemistry model is valid under certain conditions. There is an especially good agreement for high O2 concentrations while the model failed in reproducing the experimental data for 0% H2O

  • 121.
    Burström, Per E.C.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    CFD-modelling of the SNCR process in iron ore grate-kiln plants2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    LKAB (Luossavaara-Kiirunavaara AB) is an international company that producesiron ore products for the steel industry; their main product is iron ore pellets.The aim with this research project is to numerically investigate if it is possible to use selective non-catalytic reduction (SNCR) technologies in grate-kiln pelletizingplants for NOx reduction. The technique had, to the best knowledge of the author, never been used in this context before despite that it is commonly used in cement and waste incineration plants. The investigation is done in several stages: 1) Reveal if the technique is possible to use with the two most commonly reagents ammonia and urea. 2) Derive a chemistry model for cyanuric acid so that this reagent also can be scrutinized. 3) Compare the reagents urea and cyanuric acid in the grate-kiln pelletizing process.A CFD model of parts of the real grate was created and numerical simulations with the commercial code ANSYS CFX was carried out solving the flow field. A model for spray injection into the grate was then included in the model enabling a study of the overall mixing between the injected reagent droplets and the NOx polluted air. It is shown that the SNCR technique with ammonia does not work in the grate-kiln process. Urea on the other hand can be used under some conditions and also cyanuric acid. The results lay grounds for a continued development of the proposed chemistry model.

  • 122.
    Burström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Frishfelds, Vilnis
    Liepaja University .
    Ljung, Anna-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Marjavaara, B. Daniel
    LKAB, Kiruna.
    Modelling heat transfer during flow through a random packed bed of spheres2018Ingår i: Heat and Mass Transfer, ISSN 0947-7411, E-ISSN 1432-1181, Vol. 54, nr 4, s. 1225-1245Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Heat transfer in a random packed bed of monosized iron ore pellets is modelled with both a discrete three-dimensional system of spheres and a continuous Computational Fluid Dynamics (CFD) model. Results show a good agreement between the two models for average values over a cross section of the bed for an even temperature profiles at the inlet. The advantage with the discrete model is that it captures local effects such as decreased heat transfer in sections with low speed. The disadvantage is that it is computationally heavy for larger systems of pellets. If averaged values are sufficient, the CFD model is an attractive alternative that is easy to couple to the physics up- and downstream the packed bed. The good agreement between the discrete and continuous model furthermore indicates that the discrete model may be used also on non-Stokian flow in the transitional region between laminar and turbulent flow, as turbulent effects show little influence of the overall heat transfer rates in the continuous model.

  • 123.
    Burström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Frishfelds, Vilnis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Ljung, Anna-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Marjavaara, Daniel
    LKAB.
    Discrete and continuous modelling of convective heat transport in a thin porous layer of mono sized spheres2017Ingår i: Heat and Mass Transfer, ISSN 0947-7411, E-ISSN 1432-1181, Vol. 53, nr 1, s. 151-160Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Convective heat transport in a relatively thin porous layer of monosized particles is here modeled. The size of the particles is only one order of magnitude smaller than the thickness of the layer. Both a discrete three-dimensional system of particles and a continuous one-dimensional model are considered. The methodology applied for the discrete system is Voronoi discretization with minimization of dissipation rate of energy. The discrete and continuous model compares well for low velocities for the studied uniform inlet boundary conditions. When increasing the speed or for a thin porous layer however, the continuous model diverge from the discrete approach if a constant dispersion is used in the continuous approach. The new result is thus that a special correlation must be used when using a continuous model for flow perpendicular to a thin porous media in order to predict the dispersion in proper manner, especially in combination with higher velocities.

  • 124.
    Burström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Frishfelds, Vilnis
    Liepaja University.
    Ljung, Anna-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Marjavaara, Daniel
    LKAB Research and Development.
    Grate aerodynamic: Model strategies for gas flow through a 2D iron ore pellet bed2014Konferensbidrag (Refereegranskat)
  • 125.
    Burström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, Staffan
    Marjavaara, B. Daniel
    LKAB.
    Töyrä, Simon
    LKAB.
    CFD-modelling of selective non-catalytic reduction of NOx in grate-kiln plants2009Ingår i: Seventh International Conference on CFD in the Minerals and Process Industries: CSIRO, Melbourne, Australia 9-11 December 2009, CSIRO Publishing, 2009, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    The overall goal of this project is to find out if selective non-catalytic reduction (SNCR) technologies can be used in grate-kiln plants for NOx reduction. The technique has, to the best knowledge of the authors, never been used in this context before despite that it is commonly used in cement and waste incineration plants.   A Computational Fluid Dynamic model of parts of a real grate was created and numerical simulations with a commercial code was carried out solving the flow field. A model for spray injection into the grate was then included in the model enabling a study of the overall mixing between the injected reagent droplets and the NOx polluted air. The simulations show promising results for SNCR with urea but not with ammonia.

  • 126.
    Burström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, Staffan
    Marjavaara, Daniel
    LKAB.
    Töyrä, Simon
    LKAB.
    CFD-modelling of selective non-catalytic reduction of NOx in grate-kiln plants2010Ingår i: Progress in Computational Fluid Dynamics, An International Journal, ISSN 1468-4349, E-ISSN 1741-5233, Vol. 10, nr 5/6, s. 284-291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The overall goal of this project is to find out if Selective Non-Catalytic Reduction (SNCR) technologies can be used in grate-kiln plants for NOx reduction. The technique has, to the best knowledge of the authors, never been used in this context before, despite that it is commonly used in cement and waste incineration plants. A model for spray injection into the grate was included in the model enabling a study of the overall mixing between the injected reagent droplets and the NOx polluted air. The simulations indicate that the SNCR-technique works with urea, but not with ammonia.

  • 127.
    Burström, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    CFD-modellering av selektiv icke-katalytisk reduktion av NOX under tillverkning av järnmalmspellets2011Konferensbidrag (Refereegranskat)
    Abstract [sv]

    Syftet med projektet är att utreda om rökgasreningstekniken selektiv icke-katalytiskreduktion (SNCR) kan användas till NOX-reduktion under tillverkning av järnmalmspellets.Tekniken har till vår vetskap aldrig använts i detta sammanhang. SNCR-tekniken innebäratt man vid hög temperatur injicerar ett reduktionsmedel i rökgaserna vilket reagerar medkväveoxiderna och bildar kvävgas och vattenånga.En strömningsmekanisk beräkningsmodell av processen har tagits fram och numeriskasimuleringar har genomförts med en kommersiell kod för att lösa flödesfältet. Sedaninkluderades en modell för sprayinjektion i processen vilket möjliggjorde en undersökningav den övergripande mixningen mellan de injicerade dropparna och den NOX-förorenaderökgasen. Det övergripande resultatet är att SNCR-tekniken fungerar med urea somreduktionsmedel men inte med ammoniak.

  • 128.
    Carlsson, Per
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lycksam, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wiinikka, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Iisa, Kristiina
    National Renewable Energy Laboratory, Golden, Colorado.
    High-speed imaging of biomass particles heated with a laser2013Ingår i: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 103, s. 278-286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work two types of lignocellulosic biomass particles, European spruce and American hardwood (particle sizes from 100 μm to 500 μm) were pyrolysed with a continuous wave 2 W Nd:YAG laser. Simultaneously a high-speed camera was used to capture the behavior of the biomass particle as it was heated for about 0.1 s. Cover glasses were used as a sample holder which allowed for light microscope studies after the heating. Since the cover glasses are not initially heated by the laser, vapors from the biomass particle are quenched on the glass within about 1 particle diameter from the initial particle. Image processing was used to track the contour of the biomass particle and the enclosed area of the contour was calculated for each frame.The main observations are: There is a significant difference between how much surface energy is needed to pyrolyses the spruce (about 75% more) compared to the hardwood. The oil-like substance which appeared on the glass during the experiment is solid at room temperature and shows different levels of transparency. A fraction of this substance is water soluble. A brownish coat is seen on the unreacted biomass. The biomass showed insignificant swelling as it was heated. The biomass particle appears to melt and boil at the front that is formed between the laser beam and the biomass particle. The part of the particle that is not subjected to the laser beam seems to be unaffected.

  • 129.
    Carlsson, Torgny E.
    et al.
    Swedish Defence Research Agency, FOI.
    Mattsson, Roger
    Luleå tekniska universitet.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Elfsberg, Mattias
    Swedish Defence Research Agency, FOI.
    Tegner, Jon
    Swedish Defence Research Agency, FOI.
    Combination of schlieren and pulsed TV holography in the study of a high-speed flame jet2006Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 44, nr 6, s. 535-554Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents studies of the propagation of a high-speed turbulent flame jet of an air/hydrogen gas mixture. The experimental results are recorded with the schlieren and the pulsed TV holography method. These methods are compared and combined to benefit from the advantages of each of them. Abel inversion has been used to achieve three-dimensional information i.e. refractive index distributions. Evaluation, calibration and Abel inversion algorithms are described together with experimental results. The results obtained from the different techniques show remarkable similarities concerning both qualitative and quantitative aspects.

  • 130.
    Casselgren, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Road surface characterization using near infrared spectroscopy2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Denna avhandling presenterar en teknik och metod för att klassificera och beskriva olika vägförhållanden som torr asfalt och asfalt täckt med vatten, is och snö. Metoden använder ljuskällor av olika våglängder för att belysa vägbanan och en detektor för att mäta det reflekterade ljuset från vägbanan, beroende på hur ytan har absorberats, spritt och polariserat ljuset är det möjligt att klassificera de olika vägförhållanden. Men att veta vad för beläggning som är på asfalt är inte tillräckligt för att göra en bra uppskattning av väggreppet. Därför, genom att tillämpa en ljuspropageringsmodell och skatta parametrar såsom porositet, ojämnhet och djup i beläggningen är det möjligt att få mer information som kan förbättra en uppskattning av väggreppet. Dessa undersökningar genomfördes både i laboratoriemiljö och på verkliga vägar.Tekniken som presenteras i denna avhandling visar potential för att klassificera och beskriva olika väglag. Statistiken visar att många trafikolyckor med dödlig utgång kan relateras till halt väglag. De mest riskfyllda väglagen är de som är svåra för föraren att upptäcka och som uppkommer plötsligt på vägen. En sensor som kan klassificera vägförhållanden, skulle kunna förbättra trafiksäkerheten avsevärt. Information om rådande vägförhållanden skulle kunna användas i flera tillämpningar, exempelvis i det egna fordonet både för att informera föraren och till olika system i fordonet som t ex elektroniska stabilitetsprogrammet (ESP), låsningsfria bromsar (ABS) eller antispinnsystem (TCS). Sådan information kan även överföras till andra förare och till infrastrukturen, vilket gör det möjligt att planera en resväg beroende på rådande vägförhållanden. Men även för vägunderhåll och då på en lokal nivå på de vägsträckor där det verkligen behövs.Eftersom det finns ett antal prototyper och idéer hur man kan uppskatta väggrepp, är det viktigt att olika metoder utvärderas och testas på samma sätt. Därför innehåller denna avhandling en testmetod och ett antal mått för att kontrollera de olika systemen och undersöka svagheter och styrkor hos olika tekniker. Den teknik som har undersökts i denna avhandling har även utvärderats enligt denna metod.

  • 131.
    Casselgren, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Road surface classification using near infrared spectroscopy2007Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Statistics shows that most traffic accidents with fatal outcome can be related to slippery road conditions. The most hazardous road conditions are the ones that are hard for the driver to detect and that appears sudden on the road. A sensor that classify the road condition in front of the vehicle, warning both the driver and the systems in the vehicle that are incorporated to help the driver, like the electronic stability program (ESP), anti-lock brake system (ABS) or the traction control system (TCS), could help to reduce these accidents. There are several prototypes for classification of road conditions available but they are not yet fully functional. In this thesis a method that makes it possible to classify the four distinct road conditions dry asphalt and asphalt covered with water, ice and snow, respectively, with a low probability of wrong classification using three wavelengths is presented. A prototype sensor built on the a technique using two laser diodes and a photo detector is tested in a real environment and compared with laboratory measurements which shows a promising result characterizing dry asphalt and asphalt covered with ice and snow. Both theory and experiments are presented. The most difficult road conditions to classify from each other are water and clear ice for which a method using polarized light is investigated. The investigation shows that using polarized light for illumination and a polarizer as an analyzer for classification of water and ice on asphalt is a more reliable method than using unpolarized light. All three investigations show promising results in developing an actual sensor to reduce fatal accidents in traffic.

  • 132.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Bodin, Ulf
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Reusable road condition information system for traffic safety and targeted maintenance2017Ingår i: IET Intelligent Transport Systems, ISSN 1751-956X, E-ISSN 1751-9578, Vol. 11, nr 4, s. 230-238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Driver awareness of current winter road conditions (RCs) is known to affect the frequency of accidents due to sudden changes in these conditions. For example, partially icy roads that appear during autumn in northern areas typically result in collisions and ditch runs unless the drivers are generally aware of the situation. Availing motorists who drive under winter RCs of enhanced information is therefore highly desirable to increase their awareness of hazardous driving conditions. Such conditions need to be predicted ahead of time and presented to drivers before they attempt slippery road sections. Moreover, the identification of slippery RCs should quickly trigger targeted road maintenance to reduce the risk of accidents. This study presents a scalable and reusable collaborative intelligent transport system, herein referred to as an RC information system (RCIS). RCIS provides accurate RC predictions and forecasts based on RC measurements, road weather observations, and short-term weather forecasts. The prediction methods in the context of the distributed RCIS have been tested using a prototype implementation. These tests confirmed that these inputs could be combined into useful and accurate information about winter RCs that can be adapted for different types of users.

  • 133.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Engström, Niclas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Fransson, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Investigation of ice surface change during vehicle testing2014Ingår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 9, nr 2, s. 137-150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Today, there are a lot of vehicles and tyre testing carried out on lake ice surfaces. Thus, it is important to have knowledge about parameters that affect roadgrip. The thesis within this paper is that the liquid like layer which appears due to increasing temperature can be reduced by manipulating the ice roughness. This in turn should decrease the temperature dependence of the roadgrip in temperatures around 0°C. In order to investigate this, measurements of temperature, surface roughness and hardness and roadgrip were performed on three outdoor ice surfaces using an IR thermometer, an optical sensor with three IR-diodes, a steel ball drop indentation test and an RT3 curve, respectively. Additional ice roughness measurements were also made on two tempered ice surfaces in an ice hall. Results show a clear connection between ice temperature and roadgrip, unfortunately the created ice roughness was too small to influence the change in roadgrip

  • 134.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Kutila, Matti
    VTT Technical Research Centre of Finland, Espoo.
    Jokela, Maria
    VTT Technical Research Centre of Finland, Espoo.
    Slippery road detection by using different methods of polarised light2012Ingår i: Advanced Microsystems for Automotive Applications 2012: Smart Systems for Safe, Sustainable and Networked Vehicles / [ed] Meyer Gereon, Berlin: Springer Science+Business Media B.V., 2012, s. 207-220Konferensbidrag (Refereegranskat)
    Abstract [en]

    Road friction measurement is an important issue for active safety systems on vehicles; hence knowledge of this key parameter can significantly improve the interventions on vehicle dynamics. This study compares two different on-board sensors for the classification of road conditions with polarised infrared light. Several tests are performed on a dedicated track, with focus on detection of dry or wet surfaces, and the presence of ice or snow. The work shows the capability of both sensors to provide a correct classification. In particular, results indicate how the monitored area, the presence of active illumination and the mounting position influence measurements and response times. It is concluded that both systems classify different road conditions in all cases. Performance of the RoadEye system varied from 80 to 90 % whereas the camera based IcOR achieved 70-80 % accuracy level. Since these are being prototype sensors more development is needed before implemented into advanced safety applications.

  • 135.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Olofsson, Ulf
    Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
    Zhu, Yi
    Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
    Löfving, Sten
    Optical sensors.
    Mayer, Laura
    Stockholm Public Transport.
    Nilsson, Rickard
    Stockholm Public Transport.
    An optical sensor for the identification of low adhesion in the wheel–rail contact2012Ingår i: The international Journal of railway technology, ISSN 2049-5358, E-ISSN 2053-602X, Vol. 1, nr 3, s. 97-110Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low adhesion between railway wheel and rail, usually induced by contaminants such as water, oil, and leaves, affects railway performance and safety. This study uses an optical sensor to identify various surface layers that cause low adhesion. In both a laboratory set-up and field tests under various conditions, the surface layers were identified by the optical sensor; in addition, the friction coefficients for the same surface layers were measured. The results indicate that the sensor can distinguish between different surface layers. This information, together with friction coefficient data, can be used in a prediction system for use by railway operators.

  • 136.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Eliasson, Jens
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Road surface information system2013Ingår i: Proceedings of the 16th SIRWEC conference: Helsinki, FInland (23-25th May 2012), Standing International Road Weather Commission , 2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In order to classify the road condition, dry asphalt and asphalt covered with water, ice and snow a technique using a sensor called Road eye is presented. The Road eye sensor uses three wavelengths and one photo detector to determine the intensities that are reflected from the road surface and is then able to estimate the road condition. By linking the Road eye sensor to a GPS and a Mulle, a miniature wireless Embedded Internet System, the road conditions can be associated with the correct road position, making it possible to use the information in many different applications.

  • 137.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Engström, Niclas
    LKAB, SE-981-86 Kiruna, Sweden.
    Grönlund, Ulrika
    Autoliv Sverige AB, Active Saftey Tech Center, Linköping, Sweden.
    Evaluation of velocity and curvature dependence for roadgrip measured by low lateral slip2017Ingår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 12, nr 1/2, s. 1-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Roadgrip is an important parameter for vehicle testing and road maintenance. Therefore, an evaluation of the velocity and curvature effects on roadgrip measurement was performed on asphalt roads and on two ice tracks using the continuous roadgrip apparatus RT3 Curve. The aim was to find suitable driving patterns for measurements on public roads and test tracks to ensure the repeatability of roadgrip measurements. During the evaluation, it was concluded that in order to achieve a reliable roadgrip value, regardless of road conditions, the radius of curvature should not be less than 20 m. The velocity dependency of the RT3 Curve is different for the two road conditions, with the measurements on ice being much more sensitive to velocity changes than the measurements on the dry asphalt.

  • 138.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Rosendahl, Sara
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Jonsson, Patrik
    Combitech AB, Mittuniversitetet, Department of Information Technology and Media, Mid-Sweden University.
    Road condition analysis using NIR illumination and compensating for surrounding light2016Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 77, s. 175-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An investigation of a NIR camera system for road surface classification has been conducted for several road conditions. The surfaces were illuminated with three wavelengths, 980 nm, 1310 nm and 1550 nm and a halogen lamp, to simulate a real environment application with surrounding light. A measuring scheme to deal with surrounding light has been implemented enabling road condition classification from NIR images in a real environment. The retrieved camera images have been analyzed and an RGB representation of the different surfaces has been created to classify the different road conditions. The investigation shows that it is possible to distinguish between dry, moist, wet, frosty, icy and snowy road surfaces using a NIR camera system in a disturbed environment.

  • 139.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Polarization resolved classification of winter road condition in the near-infrared region2012Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 51, nr 15, s. 3036-3045Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three different configurations utilizing polarized short-wave infrared light to classify winter road conditions have been investigated. In the first configuration, polarized broadband light was detected in the specular and backward directions, and the quotient between the detected intensities was used as the classification parameter. Best results were obtained for the SS-configuration. This sensor was shown to be able to distinguish between the smooth road conditions of water and ice from the diffuse road conditions of snow and dry asphalt with a probability of wrong classification as low as 7%. The second sensor configuration was a pure backward architecture utilizing polarized light with two distinct wavelengths. This configuration was shown to be effective for the important problem of distinguishing water from ice with a probability of wrong classification of only 1.5%. The third configuration was a combination of the two previous ones. This combined sensor utilizing bispectral illumination and bidirectional detection resulted in a probability of wrong classification as low as 2% among all four surfaces.

  • 140.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Angular spectral response from covered asphalt2007Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, nr 20, s. 4277-4288Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By measuring the spectral reflection from the four different road conditions dry, wet, icy, and snowy asphalt, a method of classification for the different surfaces -- using two and three wavelengths -- is developed. The method is tested against measurements to ascertain the probability of wrong classification between the surfaces. From the angular spectral response, the fact that asphalt and snow are diffuse reflectors and water and ice are reflective are confirmed.

  • 141.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Model-based winter road classification2012Ingår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 7, nr 3, s. 268-284Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An investigation of different road conditions has been conducted using a short-wave infrared (SWIR) light online sensor to examine the possibility of estimating road condition parameters such as porosity, depth and roughness. These parameters are essential for non-contact road friction estimation. The investigation show that it is possible to detect changes of depths of water and ice as well as classify different types of ice, by utilising polarised short-wave infrared (SWIR) light and a modified Hapke directional reflectance model

  • 142. Casselgren, Johan
    et al.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sanfridsson, M
    Volvo Technology.
    Woxneryd, S
    Volvo Technology.
    Classification of road conditions - to improve safety2007Ingår i: Advanced microsystems for automotive applications 2007 / [ed] Jürgen Valldorf; Wolfgang Gessner, 2007, s. 47-59Konferensbidrag (Refereegranskat)
    Abstract [en]

    Measuring the road condition in front of a vehicle could prevent accidents and make technologies like electronic stability control (ESP) more efficient. By making three investigations of the classifications of the four road conditions dry asphalt, asphalt covered with water, ice and snow the possibility of a preview sensor is exploited. By measuring the reflectance from the different surfaces with a halogen light and an actual sensor (Road eye) in a laboratory surroundings the advantage and disadvantage are revealed. The sensor is also mounted in a Volvo truck for real-life condition measurements.

  • 143.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    A reaction probe for flow measurements in liquid steel1998Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 144.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Counter rotating runner cone in a Kaplan elbow draft tube for increased efficiency2009Ingår i: Proceedings of the 3rd IAHR International Meeting of the WorkGroup on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems / [ed] Pavel Rudolf, Brno: Brno University of Technology , 2009, s. 133-142Konferensbidrag (Refereegranskat)
  • 145.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Effect of surface roughness on a counter rotating runner cone2010Konferensbidrag (Refereegranskat)
  • 146.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Effects of boundary conditions and unsteadiness on draft tube flow2003Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The present research focuses on flow properties of the elbow draft tube. This element has a major function in low head turbines, since up to half of the losses may arise there at part load. The use of computational fluid dynamic (CFD) to redisign a draft tube necessitates detailed knowledged of the boundary conditions. They are generally not available and qualified guesses must be made. This applies in particular to the radial velocity at the inlet. A method to estimate this component in swirling flow from experimental values of the axial and tangential velocities is derived. The method uses a two dimensional non- viscous description of the flow, the Squire-Long formulation. It is tested against swirling flow in a diffuser and applied to the Turbine-99 draft tube flow. As several other boundary conditions are difficult to estimate and many input parameters are available to perform a simulation, the use of factorial design is proposed as an alternative to design simulations in a systematic, objective and quantitative way. The method allows the deternmination of the main and joint effects of input parameters on the numerical simulation. The input parameters may be experimental uncertainty on boundary conditions, unknown boundary conditions, grid and turbulence models. The method is applied to the Turbine-99 test case, where the radial velocity, the surface roughness, the turbulence length scale and the grid were the factors investigated. The inlet radial velocity is found to have a major effect on the pressure recovery. The flow in water turbines is highly unsteady due to the runner blade rotation, guide vanes and stay vanes. Unsteady pressure measurements on a Kaplan prototype point out unsteadiness in the high and low pressure regions of the turbine. Since model and prototype are not running in dynamically similar conditions, the influence of unsteadiness on the losses is of interest. The derivation of the variation of the mechanical energy for the mean, oscillating and turbulent fields point out the contribution of unsteadiness to the losses and the turbulent production. Application to turbulent channel flow reveals that the contribution is a function of the amplitude of the oscillation, the frequency and the friction velocity. Turbulent pulsating flow in a generic model of the rectangular diffuser found at the end of elbow draft tube is studied in detail with laser Doppler anemometry (LDA). Three frequencies, corresponding to the quasi-steady, relaxation and quasi-laminar regimes with an amplitude of about 10% are investigated. The results indicate no alteration of the mean flow by the excitation of a single frequency. Furthermore. the existence of the different regimes, as found in turbulent pulsating turbulent pipe and channel flows, is confirmed.

  • 147.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hydropower engineering2005Ingår i: Proceedings of the International Green Energy Conference: IGEC-1, Waterloo, Ontario: University of Waterloo , Dept. of Mechnical Engineering , 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    Hydropower, one of the corner stones of sustainable energy development, is the largest renewable source of energy. There is a large demand worldwide for people trained to design, operate, maintain and optimise hydropower systems. Hydro Power University, a name which encompasses both education, research and development within hydropower in Sweden, offers a unique and broad international masters programme within hydropower engineering including civil, mechanical and electrical engineering. The programme is the result of a close collaboration between Lulea University of Technology and Uppsala University, at the research and education level. This master programme, Hydropower Engineering, is open to both Swedish and foreign students free of charge. It aims to provide students with state of the art knowledge and experience on parts of the hydropower system such as turbine technology, generator design, rotor dynamics, tribology, dams/dam safety, maintenance and operation and environmental aspects. World unique laboratory experiments are offered to the students at Porjus and Alvkarleby, Sweden. The Porjus Hydropower Centre offers world unique facilities: two full scale turbines of 10 MW each, one with the latest generator technology - Powerformer. The turbines are exclusively dedicated for use in education, research and development. State of the art in measurement technology is available. Both units are at the centre of each education programme offered by the Hydro Power University. In Alvkarleby, spillways, discharge capacity and turbines model testing can be undertaken at the Vattenfall laboratory also with state of the art experimental material and highly qualified staff. The large number of applications from developing countries indicates a need of scholarships, which needs to be resolved for the development of hydropower

  • 148.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Hydropower Engineering: an International Master Programme at Luleå University of Technology2005Ingår i: International Water Power and Dam Construction, ISSN 0306-400X, E-ISSN 1538-6414, Vol. 57, nr 8, s. 42-44Artikel i tidskrift (Övrigt vetenskapligt)
  • 149.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Runner cone boundary layer control2007Ingår i: Proceedings of the 2nd IAHR International Meeting of the Workgroup on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems, Timisoara,Romania, October 24-26, 2007 / [ed] R. Susan-Resiga; S. Bernad; S. Muntean, Timişoara, 2007, s. 153-158Konferensbidrag (Refereegranskat)
    Abstract [en]

    The runner cone plays an essential role in the performance of elbow draft tube and de facto of low head machines. An earlier separation on the runner cone deteriorates the pressure recovery and thus the overall efficiency of the machine. Control of the separation point on the runner cone is therefore of interest to improve efficiency at any regime. Onealternative to control the separation on the runner cone may be to rotate the runner cone with a different angular velocity than the runner blades. In the present work, the effect of runner cone angular rotation on elbow draft tube, typical in Kaplan turbine, is investigated using numerical simulations. The Turbine-99 test case (T-99) is used as benchmark at the top of the propeller curve. Simulations are performed for 4 different angular rotations: -595(stipulated in T-99), 0, +600 and +1200 rpm. The results indicate a delay of the separation on the cone at 0, +600 and +1200 rpm. The mean pressure recovery increases in all cases. The improvement reaches 6.6 % for the mean pressure recovery for an angular velocity of +600 rpm where separation disappear, while the loss factor decreases with 23.6 %.

  • 150.
    Cervantes, Michel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    To a higher degree: power engineering education2005Ingår i: International Water Power and Dam Construction, ISSN 0306-400X, E-ISSN 1538-6414, Vol. 57, nr 8, s. 42-44Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This paper describes how the need for more skilled professionals in the hydroelectric sector led to the formation of the Hydro Power Engineering Masters Programme at Lulea University of Technology, Sweden. The goal of the Masters program is to allow students to obtain an overall picture of the field, to answer the need of the industry without neglecting the content. Such a program aims to give the student a choice between a position as a specialist within a specific area and a management position where discussions with specialists are required

1234567 101 - 150 av 1078
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf