Department of Mechanical Engineering
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Browsing Department of Mechanical Engineering by Author "JAFARI, Rahim"
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Item DESIGN, FABRICATION, INSTRUMENTATION AND TESTING OF AN EDUCATIONAL WIND TUNNEL(2022-05-22) KILIÇKAYA, Murat Çığıl; AKAY, Hasan Umur; JAFARI, Rahim; TÜRKAKAR, GökerAn educational wind tunnel with a test section of 350x350 mm dimensions and 650 mm length, in which the maximum air velocity reaches up to 11.3 m/s with Reynold’s number of 267,000, was designed and built in 2019 by the author of this thesis with the help of a team of students in the Automotive Engineering Laboratory in Atılım University. In the scope of instrumentation studies, three force balance systems for drag/lift force measurements were designed, produced and tested. First balance sys tem was capable of measuring drag and lift force at only 90 degree angle of attack. Using it, a circular disc and rectangular plate the drag coefficient values of which are available on textbooks were tested and two velocity data were obtained. These two velocity data matched with a relative to each other percentage error with a maximum value of 2 in percent. Having obtained a velocity data and verified the reliability of drag load cell with first balance system, a second force balance system with angle adjusting capability was manufactured but lift load cell’s reliability could not verified due to high noise occurred during wind tunnel measurements and to the suspect that some components of second force balance may have interfered to the aerodynamics of test specimens. So, a third force system all components of which are outside the wind tunnel test section and that is still in use, was designed, manufactured and tested using the same test specimens that had been used during testing second force balance. They are/were NACA 2418 (Chord=80 mm and Span=80 mm) in 2D air flow, 81×81×2 mm Square Plate in 2D flow, and 81×81×2 mm Square Plate in 3D flow. All these wind tunnel measurements were compared using CFD analyses results (with ANSYS and COMSOL), 2D Thin Airfoil Theory, and a similar study presented with a paper. The outcomes were promising because in the case of no or low noise, wind tunnel measurements were close enough to the compared studies. Especially, some impor tant results were obtained about 2D Thin Airfoil Theory. All these studies show that wind tunnel setup can create a reliable flow in wind tunnel test section and in the case of no or low noise, a force balance system with strain gauge load cells can work well. The common solution to noise problem that is a Faraday Cage should be integrated to the upcoming force balance system(s). Furthermore, a moment balance system to be integrated to wind tunnel test setup can be a useful tool for producing scientific knowledge using this educational wind tunnel.Item EVALUATION OF THE THERMAL PERFORMANCE OF AUTOMOTIVE BRAKE DISC(2023-01-27) ERKILIÇ, Kaan Tamer; JAFARI, RahimAcceleration is a crucial dynamic for a vehicle, although deceleration is the key element for vehicle safety. A vehicle's braking system is the sole piece of equipment that can bring it to a slowdown or halt. The function of a brake system is performed with the friction between disc and the pad. The thermal performance of the components it contains must be measured precisely in the design and test steps, and the component must show the required performance under operating conditions. In this study, an experimental setup was designed and produced to observe both aerodynamic and thermal characteristics of brake discs. Parts such as disc, pad, rim and tire on the experimental setup are exactly the same as those used in a typical passenger car. The quarter weight of a passenger car was adapted to the experimental setup on the shaft with cylindrical weights. In addition, a repetitive braking scenario was used in the experimental setup and simulations of the aerodynamic and thermal outputs of braking were carried out using detailed numerical models. In the experiments and simulations, it was observed that the air flow caused by the acceleration of the vehicle reduced significantly inside the rim, despites there was a turbulent air flow that takes place with the form of eddies inside the rim. As a result of thermal simulations and experiments, the temperature distribution on the brake disc has been observed, and it has been predicted that the area where the brake disc contact with the brake pad is higher than the temperature of the area directly opposite the contact area and the temperature is not uniformly distributed across the brake disc.