Vibration Modeling of Gas Turbine with Possible Faults

, M.Sc. Thesis Sharif University of Technology Tamaddon, Ali (Author) ; Zohoor, Hassan (Supervisor)

Abstract

Vibrational modeling of a gas turbine considering simultaneous faults is considered. Faults including: unbalance, misalignment, and rotor crack are selected to be modeled. Oil film forces of hydrodynamic bearings are chosen as the supports of the rotor. Modeling starts with choosing an appropriate finite element model for the rotor which includes the effects of shear deflection, rotary inertia, gyroscopic moment, and rotor cross section variation. Modeling of unbalance is in fact a part of rotor finite element modeling. The forces that origniate form misalignment are computed using the static relations of a rigid coupling. Modeling of bearing faults along with bearing forces is performed...

Designing a Mechanism for Fault Diagnosis of Space Reaction Wheel by Piezoelectric Sensors and Neglecting the Rotor Inertia

, M.Sc. Thesis Sharif University of Technology Abbasi, Meisam (Author) ; Salarieh, Hassan (Supervisor) ; Zabihollah, Abolghasem (Supervisor)

Abstract

A Reaction Wheel (RW) is a torque actuator which is used for attitude control of a satellite. Reaction Wheels usually consist of a brushless DC motor which rotates a flywheel. When the flywheel is accelerated by the motor, the reaction torque of the motor applies to the base of the RW and therefore the satellite can rotate along the RW spin axis. Due to frictionless surrounding of a satellite in space, a very small disturbance in a reaction wheel structure during its function may lead to instability of satellite and decrease the satellite precision and performance. There are some important sources of disturbance in an RW. Some of them are: 1- Unbalances in wheel (offset of center of gravity...

Design and lmplementation of Wireless Electric Vehicle Charger using Multilevel Converters with Misalignment Compensation

, M.Sc. Thesis Sharif University of Technology Poorfakhraei, Amir Reza (Author) ; Tahami, Farzad (Supervisor)

Abstract

Wireless power transfer has been found to be a practical replacement for cable power transfer in a wide range of applications. For instance, this technology offers significant solutions for medical and industrial applications as well as electrical home appliances and electric vehicle chargers. All over the world, researchers are investigating and implementing experimental prototypes to simplify power transfer in applications in which the use of cables is impossible, troublesome, or hazardous. There are different issues in each of the mentioned applications which should be solved in order to use wireless power transfer systems more beneficially. These issues include power transfer efficiency,...

Simulation of Three Dimensional Crack in Spur Gears due to Misalignment

, Ph.D. Dissertation Sharif University of Technology Ghassabzadeh Saryazdi, Maryam (Author) ; Durali, Mohammad (Supervisor)

Abstract

Fatigue crack is one of the most important causes of defect for gear systems. This effect results tooth fracture and failure of other elements of the power transmission systems. As a result, much effort has been devoted to the modeling of fatigue crack and improving the methods of crack detection. Simulations of three dimensional crack growth in spur gears due to misalignment and examination of this effect on vibration response of gear system are the main goals of this research. To model the crack growth, a new method of gear meshing modeling was proposed. In this method, the effects of pinion on the gear and vice-versa are modeled by a finite set of virtual interconnected springs. The...

Investigating Nonlinear Vibration of a Turbine-Shaft in the Start-up Process Using Timoshenko Beam Theory

, M.Sc. Thesis Sharif University of Technology Arefikhah, Mohammad Reza (Author) ; Dehghani Firouzabadi, Rohollah (Supervisor)

Abstract

In this study, the nonlinear vibrations of an elastic rotor that is under the elastic support and under the follower force caused by the airflow passing through the rotating plane are investigated. The elastic shaft is modeled by the Timoshenko beam theory, which is connected to a motor through a flexible coupling and the motor increases the rotational speed of the rotor by applying torque. Gibbons’ equations have been used to model the misalignment forces. First, the kinetic energy of the rotating system is calculated nonlinearly to take into account the effect of nonlinear terms due to the rotational inertia of the system, and then the potential energy and The work of external forces on...

Auv Parameter Estimation Using Sensor Data Fusion Methods Based on Nonlinear Filters

, M.Sc. Thesis Sharif University of Technology Ghanipoor, Farhad (Author) ; Alasty, Aria (Supervisor) ; Salarieh, Hassan (Co-Supervisor)

Abstract

Nowadays, application of AUVs in marine missions is a crucial research field. To reach a fully automated underwater vehicle, it should suitably be designed, controlled, navigated and its fault is detected immediately. An Identified model of AUV is usable for all of these goals. Thus, in this project, parameters of an appropriate dynamic model of AUV is estimated using augmented state space method and TUKF.By investigating possibility of parameter estimation of 6-DOF model and sub models in different cases, a scenario for estimation of cruise, steering and diving sub model parameters of AUV, using output of DVL and Gyroscope is proposed. Furthermore, planar misalignment between DVL and IMU,...