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    Development of a variable-profile cam to enhance the volumetric efficiency of IC engines
    (INDERSCIENCE ENTERPRISES LTD, 2017) Sürmen, Ali; Arslan, Ridvan; Kopmaz, Osman; Avci, Atakan; Karagoz, Irfan; Karamangil, M. Ihsan
    In this study, it is aimed to develop a new concept camshaft for continuously variable valve timing (CVVT). The concept is based on obtaining a curvilinear cam surface by integrating a number of conventional cam contours. Thirteen unworked camshafts, with arbitrary different contours, i. e., valve opening and closing times, were machined and tested on a fourstroke single-cylinder diesel engine to determine their volumetric efficiency at varied engine speeds. Then with suitable axial arrangement of these individual contours on a camshaft and integration of them, a single curvilinear cam surface was obtained. It is expected to get the same volumetric efficiency, with a ball contact follower when it follows a specific contour, as obtained when the specific cam of the same contour individually yielded. By giving an axial motion to the camshaft, allowing the follower to follow different contours, continuous variation of valve timing will be achieved.
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    The thermal analysis of paraffin wax in a box-type solar cooker
    (Amer Inst Physics, 2012) Yüksel, Numan; Arabacigil, Bihter; Avci, Atakan
    In this study, the potential use and effectiveness of paraffin wax in solar cooker during the daylight and/or late evening hours is experimentally investigated. For these experiments, a box-type solar cooker was constructed by filling paraffin wax with metal shavings. The side-and sub-surface temperatures of the paraffin wax in the cooker are continuously measured during June and July 2011. The effect of the reflector angle on the thermal efficiency of the cooker is tested with different isolation conditions on different days. In conclusion, the designed cooker can be effectively used at an angle of 30 degrees. The thermal efficiency is increased to around 18.35% with the reflector. The maximum temperature of the paraffin achieved during the experiments is in the range of 75.1 degrees C to 80.5 degrees C. The reflected radiation makes a maximum contribution of 13.29% to the temperature of the paraffin wax. In addition, the heating time is decreased to approximately 1 h. So, the paraffin wax could be used as a phase change material integrated with the solar system. The rectangular solar cooker filled with the paraffin wax has a high thermal performance, which is indicated by high temperatures and decreased cooking times, for the given design conditions. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768547]
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    THE USE OF PARAFFIN WAX IN A NEW SOLAR COOKER WITH INNER AND OUTER REFLECTORS
    (Vinca Inst Nuclear Sci, 2015) Arabacigil, Bihter; Yüksel, Numan; Avci, Atakan
    The potential use and effectiveness of paraffin wax in a new solar cooker was experimentally investigated during daylight and late evening hours. For these experiments, a cooker having an inner reflecting surface was designed, constructed by filling paraffin wax and metal shavings. The side- and sub-surface temperatures of the paraffin wax in the cooker were measured in the summer months of June and July. The thermal efficiency of the cooker was tested on different conditions. The results show that the optimum angle of the outer reflector is 30 degrees. Here, the peak temperature of the paraffin wax in the solar cooker was 83.4 degrees C. The average solar radiation reflected makes a contribution of 9.26% to the temperature of paraffin wax with the outer reflector. The solar cooker with the outer reflector angle of 30 degrees receives also reflected radiation from the inner reflectors. Besides, the heating time decreased to approximately one hour. The designed solar cooker can be effectively used with 30.3% daily thermal efficiency and paraffin wax due to the amount of energy stored.