Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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COAR Access Rights: search.filters.coarAccessRights.open accessSubject: search.filters.subject.Valve

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  • Master Thesis
    Numerical Detection of Cavitation in Plunger Valves
    (01. Izmir Institute of Technology, 2020) Akbulut, Bedia; Özkol, Ünver
    Cavitation is a very serious problem for control valves. Besides noise and vibration, cavitation can seriously damage mechanical parts. Experimental costs for cavitation tests are high, especially when the difficulty of testing large sized valves is considered. For these reasons, developing a Computational Fluid Dynamics (CFD) model can be an attractive solution for predicting cavitation. Cavitation; is a phase change event where the bubbles that occur when the fluid pressure drops below the vapor pressure seriously damage the parts of the machines such as pumps, impellers, and valves. The first aim of this research is to determine the onset of cavitation by performing two-phase CFD simulations in plunger valves. Then, several cavitation cages are connected to observe the change at the beginning of cavitation. A cavitation cage is used to protect the valve and valve disc when downstream pressure is too low. As a result of the analysis, it was observed that the cavitation delayed using the cavitation cage. The second purpose of this research is to design an interface program that will present the Loss and Flow Coefficient diagrams obtained from tests and CFD analysis to the user. Each valve has its own flow coefficient. This depends on how the valve is designed to allow flow through the valve. Therefore, the main differences between the different flow coefficients are due to the valve type and of course the valve opening position. The flow coefficient is important to choose the best valve to use in a particular application.
  • Master Thesis
    Microscale Precise Position Measurement and Monitoring of Sliding Valves
    (Izmir Institute of Technology, 2019) Tanrıyapısı, Önder Mahir; Özdemir, Serhan; Özdemir, Serhan
    In present study, a sensor, Accuciser, is presented to know the position of sliding valves which have ferromagnetic or diamagnetic guide. The main objective is to develop a sensor, which has low cost and high resolution, that measures the displacement of engine valves or SCR injectors which are used in especially in the automotive industry. For now, the position of the valves, which are using in propulsion systems, or SCR injector cannot be known with a signal from an analog sensor. Instead of analog sensor, the mapping is used from experimental data. However, this mapping gives inaccurate results due to driving style or usage of the system. After seeing the gap in these systems, the sensor was developed, and it fulfils this gap. The sensor is developed based on Faraday’s Law of Induction which was discovered by Michael Faraday in 1830. The sensor consists of two coils and one coil located on top of the other. The most important property of the proposed sensor is working with a direct current. In fact, if the valve is actuated by an electromagnetic force, there is no power consumption on the sensor. The experimental results, for the latter property, are corroborated by theoretical calculations. The output of the sensor is directly proportional to the displacement of the core and it has high signal-to-noise ratio because of the nature of magnetism. The results show that using Accuciser, the proposed sensor, to monitor valve displacement gives more reliable results than current technology.