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  • 1.
    Jahedi, Mohammad
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Berntsson, Fredrik
    Department of Mathematics, Linköping University, Linköping, Sweden.
    Wren, Joakim
    Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Transient inverse heat conduction problem of quenching a hollow cylinder by one row of water jets2018In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 117, p. 748-756Article in journal (Refereed)
    Abstract [en]

    In this study, a two-dimensional linear transition inverse heat conduction problem (IHCP) was solved using the Generalized Minimal Residual Method (GMRES) in quenching process by water jets. The inverse solution method was validated by set of artificial data and solution sensitivity analysis was done on data noise level, regularization parameter, cell size, etc. An experimental study has been carried out on quenching a rotary hollow cylinder by one row of subcooled water jets. The inverse solution approach enabled prediction of surface temperature and heat flux distribution of test specimen in the quenching experiments by using measured internal specimen temperature. Three different boiling curves were defined in the quenching process of a rotary cylinder. Result obtained by the inverse solution showed clear footprint of rotation in surface temperature and heat flux on each revolution of cylinder and temperature variation damping from quenching surface toward interior of specimen.

  • 2.
    Jahedi, Mohammad
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system. Division of Energy Systems, Department of Management and Engineering, Linköping University.
    Experimental study of quenching process on a rotating hollow cylinder by one row of impinging jets2017In: 9th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, 12-15 June, 2017, Iguazu Falls, Brazil, 2017Conference paper (Refereed)
    Abstract [en]

    Quenching cooling rate of rotary hollow cylinder by one row of water impinging jets has been experimentallystudied. Water jets (d = 8 mm) with sub-cooling 55 to 85°C and Reynolds number 8,006 to 36,738 impinged over rotaryhot hollow cylinder (rotation speed 10 to 70 rpm) with initial temperature 250 to 600°C. Impingement impact angle of row of jets varied between 0 to 135° and jet-to-jet spacing in row patten was 2 to 8d. The results revealed more uniformityon cooling rate of quenching in smaller jet-to-jet spacing (2 and 4d) where wetting front regions are located closer toneighbor jet’s region. By increasing spacing, footprint of annular transition region was highlighted in quenching coolingrate contour. A distinct quenching characteristic was obtained for impingement impact angle of 0° compare to otherangles. With initial temperature above the Leidenfrost temperature, low cooling rate was achieved in film and transitionboiling compare to a steep increase of cooling rate at start of quenching with higher maximum heat transfer for experimentswith initial temperatures less than Leidenfrost temperature. The effect of other parameters on quenching coolingrate was highlighted in film and transition boiling while no significant differences were observed in nucleate boiling.

  • 3.
    Jahedi, Mohammad
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Moshfegh, Bahram
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. Department of Management and Engineering, Linköping University.
    Quenching a rotary hollow cylinder by multiple configurations of water-impinging jets2019In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 137, p. 124-137Article in journal (Refereed)
    Abstract [en]

    Experiments have been conducted to analyze quenching of a hot rotary hollow cylinder by one and two rows of water-impinging jets. Sub-cooled water jets (ΔTsub = 45–85 K) with flow rate 8006 to 36,738 impinged on hollow cylinder with rotation speed 10 to 70 rpm at various initial wall superheat temperatures from 250 to 600ºC. Jet-to-jet and jet-to-surface spacing varied between 4 to 10d and 1.5 to 7d respectively and angular position of impinging jets were tested from 0 to 135º. Effectiveness of the defined parameters on stagnation point’s local average heat flux was found lower in the film and nucleate boiling compare to transition boiling regime where rotation speed had the highest impact. Characteristic of maximum heat flux (MHF) at stagnation point and upwash flow point were analyzed based on surface heat flux, time and temperature corresponding to MHF. Same maximum heat flux levels were captured in the both points which reveals importance of the flow behavior at the upwash flow point. The effectiveness of the parameters to improve average heat transfer was studied based on cooling area of each water impingingjet in the multiple configurations. Higher average heat transfer was obtained by increasing flow rate and subcooling temperature and lower initial wall superheat temperature corresponding to onset of transition boiling regime.

  • 4.
    Levin, Sebastian
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Implementering av centraldifferential i pansarbandvagn BvS10s fördelningsväxeln samt teoretisk utredning av ljudnivån i kuggväxlar2015Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    This thesis was made on behalf of BAE Systems Hägglunds AB a company that is designing and manufacturing military vehicles. The thesis was made on one of the products called BvS10 an armored personnel carrier. The purpose of this vehicle is to be able to transport soldiers in hard terrain and work as a shrapnel cover. This vehicle have a transfer gear box that is what this thesis is focusing on. This gear have the purpose to split the torque from the engine to back unit and to the front. The transfer gear box contains of three spur gears. In the gear box the noise level is high and BAE systems want to investigate what can be changed to reduce noise from the gearbox. They also want to integrate a differential gear. This is to reduce tensions in the gear and the shaft when the vehicle is traveling in harsh terrain. The purpose of this thesis is to theoretically examine what different parameters have an impact on the noise level of the gearbox and also to develop a concept model to integrate the differential gear. The method that’s been used to determine the different parameters for the noise in gears is to conduct a literature revue about noise in sprue gears and the results from a noise level test done by BAE systems ben included to get an idea of the noise level. The design work is based on specifications and framework that can’t be changed and has agreed upon with Bea Systems. After that different sketches was made on possible solutions the best of these solutions was chosen and modeled in Autodesk Inventor Professional. After that calculations was conducted on the spur gears regarding teeth strength. The calculations is based of Swedish standards recommendations. In the literature revue it was found that a big part of noise reduction in spur gears could be to use tighter tolerances witch also increases the manufacturing costs. Another factor to the noise is the helix angle in the spur gear that is also a good thing because it increases the teeth strength with regards for bending stresses. Another method that could be used is to use threaded wheel grinding as finishing method witch have been proven to decrees the noise level.  The result of the sound measurement resulted in that you could see an increase of the noise level with an increase of the RPM but it is hard to draw any more conclusions regarding this because it is hard to judge if this is caused by the hydraulic engine who are running the gearbox.  The result of the engineering work was to use fore different sprue gears. That solution was created because of the axle distance and the gear ratio that needs to stay the same and that the differential gear have a set dimension. The gears was calculated with regards on bending stress and edge stressThe conclusion is that it is possible to implement a differential in the transfer gearbox. The gear housings outer dimensions was kept intact but on one spot a part of the cooling flanges was used to fit the middle shaft. The bearings that was used was the same as in the old gearbox except for two spherical bearings that was used to set the differential in place.  The conclusion is that it is possible to implement a differential in the gearbox but if possible in the future a bigger gearbox should be developed or to change the ratio on the final drive the solution is safe because there is no rotating parts in the open and there is no environmental impact. For the noise reducing effects in the engineering part is hard to prove and to implement in this solution because of the lack of space the helix angel that was used was put to 20 degrees because this is a standard.  To reduce the noise level in a gearbox you can look at the problem in many ways reduction of transmission error is one big thing. It is a matter of building a stable gearbox and increase the tolerances in the gear. Another aria to look in to is to optimise the gear housing chap how is the cheapest solution. This things is possible to do.  Further studies may be to implement a differential lock as well as further studies can be conducted on the old transfer gear to find out where the noise is coming from with a detailed sound and vibration analysis.

  • 5.
    Nordkvist, Erika
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Konstruktion av hydraulben till mobilt siktverk tillhörande Aktiebolaget Arbrå Sikt & Matare2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
  • 6.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Is building ventilation a process of diluting contaminants or delivering clean air?2019In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to discuss the performance of air distribution systems intended for dilution of contaminants (e.g. mixing ventilation) and those intended for delivery of clean air to local regions within rooms (e.g. personalized ventilation). We first start by distinguishing the systems by their visiting frequency behaviour. Then, the performance of the systems with respect to their possibility to influence contaminant concentration in the room or regions within the room is dealt with. Dilution capacity concept for mixing systems is discussed, and delivery capacity concept for systems intended to deliver clean air locally is introduced. Various ways for supply of clean air to regions within the room are presented and their pros and cons are discussed. In delivery capacity systems, the most important single parameter is the entrainment of ambient air into the primary supply flow. Therefore, methods of determining entrainment in these systems need to be defined and the results should be included when describing the performance of the air terminal devices.

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