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Hossein Hooshmandi Safa,Mohammad Ebrahimi,Hossein Abootorabi Zarchi,Mohammad Abshari 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.12
In this paper, an index is proposed for the detection of static eccentricity (SE), dynamic eccentricity (DE), and mixed eccentricity (ME) in a three-phase permanent magnet synchronous generator (PMSG). The proposed index is the amplitude of the sideband components with a particular frequency pattern which is extracted from the spectrum of the stator voltage. This index can be used in no load state prior to the loading of the generator which can cause damage in eccentricity conditions. Moreover, the proposed index works properly in loaded condition. Extraction of the proper indexes highly depends on precise computation of the necessary signals. Therefore, in order to fulfil the required precision, the time-stepping finite element method (TSFEM) is used to model the PMSG under eccentricity fault and to calculate the stator voltage as an appropriate signal for processing.
Numerical simulation of the flow in pipes with numerical models
Hongjie Gao,Xinyu Li,Abdolreza Hooshmandi Nezhad,Amir Behshad 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.4
The objective of this study is to simulate the flow in pipes with various boundary conditions. Free-pressure fluid model, is used in the pipe based on Navier-Stokes equation. The models are solved by using the numerical method. A problem called “stability of pipes” is used in order to compare frequency and critical fluid velocity. When the initial conditions of problem satisfied the instability conditions, the free-pressure model could accurately predict discontinuities in the solution field. Employing nonlinear strains-displacements, stress-strain energy method the governing equations were derived using Hamilton's principal. Differential quadrature method (DQM) is used for obtaining the frequency and critical fluid velocity. The results of this paper are analyzed by hyperbolic numerical method. Results show that the level of numerical diffusion in the solution field and the range of well-posedness are two important criteria for selecting the two-fluid models. The solutions for predicting the flow variables is approximately equal to the two-pressure model 2. Therefore, the predicted pressure changes profile in the twopressure model is more consistent with actual physics. Therefore, in numerical modeling of gas-liquid two-phase flows in the vertical pipe, the present model can be applied.