Mechanical Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10679/9145

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Browsing by By Publication Category "International Refereed Journal"

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    Automated flow rate control of extrusion for 3D concrete printing incorporating rheological parameters
    (Elsevier, 2024-04) Ahi, Oğulcan; Ertunç, Özgür; Bundur, Zeynep Başaran; Bebek, Özkan; Civil Engineering; Mechanical Engineering; ERTUNÇ, Özgür; BUNDUR, Zeynep Başaran; BEBEK, Özkan; Ahi, Oğulcan
    The use of inline quality assessment technologies is of great importance in meeting the consistent extrusion requirements of 3D concrete printing (3DCP) applications. This paper presents a system to regulate extrusion speed and maintain the flow rate at a target value during 3DCP processes. The system is based on a new equation that combines printing parameters and the material's rheological properties in the printing process. The proposed control strategy is designed to effectively function with various cement-based mixtures. Validation tests demonstrate that the proposed system can maintain an instantaneous flow rate within a certain range and eventually achieve a constant flow rate. During operation, the flow rate is consistently maintained around the targeted value with an average error rate of 6.7 percent. The flow rate control mechanism shows promise as a reliable and efficient solution for achieving precise and constant flow rates, regardless of the cement mix design used.
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    Development and 3D spatial calibration of a parallel robot for percutaneous needle procedures with 2D ultrasound guidance
    (World Scientific, 2017-12-01) Ahmad, Mirza Awais; Orhan, Sabri Orçun; Yıldırım, Mehmet Can; Bebek, Özkan; Mechanical Engineering; BEBEK, Özkan; Ahmad, Mirza Awais; Orhan, Sabri Orçun; Yıldırım, Mehmet Can
    Robotic systems are being applied to medical interventions as they increase the operational accuracy. The proposed autonomous and ultrasound guided 5-DOF parallel robot can achieve such accuracy for needle biopsies, which particularly demand precise needle positioning and insertion. In this paper, the robot's mechanical design, system identifications, and the design of its controller are explained. A torque computed controller with gravity compensation and friction models, yielding a 0.678mm RMS position error for the needle tip, was used. A novel method was used for 3D space calibration of the images for detecting the volume of interest in the biopsy procedure by a multipoint crosswire phantom with parallel threads. The calibration technique had a validation RMS error of 0.03mm.
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    ArticlePublicationOpen Access
    Numerical analysis and diffuser vane shape optimization of a radial compressor with the open-source software su2
    (Turk Isi Bilimi ve Teknigi Dernegi, 2023) Uzuner, Mustafa Kürşat; Başol, Altuğ Melik; Mischo, B.; Jenny, P.; Mechanical Engineering; BAŞOL, Altuğ Melik; Uzuner, Mustafa Kürşat
    In recent years, the usage of open-source computational fluid dynamics tools is on a rise both in industry and academia. SU2 is one of these open-source tools. Unlike other open-source alternatives, SU2 is equipped with boundary condition types, solvers and methods that are especially developed for the analysis and design of turbomachinery. The aim of this work is to explore and investigate the capabilities of SU2 in the prediction of performance parameters of radial compressors. Two different single stage shrouded compressor geometries, one with a vaneless diffuser and the other with a vaned diffuser have been investigated with steady state CFD. The compressors were designed by MAN Energy Solutions Schweiz AG. Computational results with SU2 showed a satisfactory agreement with both the experimental data and reference CFD solutions obtained with Fidelity Flow, which is formerly known as Numeca Fine TURBO. Only at the relatively higher mass flow rates the difference between references and SU2 were higher compared to other operating points. After performance parameters were successfully calculated with SU2, the optimization tools that come with SU2 were also used. A 2D adjoint optimization study on the vane of the vaned diffuser was carried out. The study was carried out at a single operating point that is close to choke conditions. The loss generated by the large separated flow region at the suction side of the diffuser vane was reduced by 0.55 % in the optimized geometry using minimal modifications on the existing vane geometry to keep the performance of the compressor intact at other operating points. However, the resulting modification increased the total pressure loss by 0.86 % at one of the design operating points. This performance penalty could be due to the discontinuity in the vane geometry generated by the optimizer. Overall, the study shows that SU2 has the basic numerical schemes and models that are required for the analysis of radial turbomachinery flows and geometry optimization.