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Showing 3 results for Jafargholi
Ali Jafargholi, Hassan Karimi, Seyed Reza Mousavi Firdeh,
Volume 15, Issue 7 (9-2015)
Abstract
In this paper, the algorithms for low frequency non-linear dynamic modeling and frequency model determining of LPRE is presented. Considerations that facilitate modeling and debugging processes is also investigated. Using of defined algorithms and also presented considerations is considered for a liquid propellant engine with oxidizer and fuel tanks. Describing equations of LPE is classified as many subsystems. Simulation is done in the SIMULINK environment of MATLAB software. Each simulated subsystem show one or more physical subsystem that their interaction is determined in LPE configuration modeling results demonstrate excellent dynamic behavior of LPE. Then SISO engine model in frequency domain is outcome based on resulted non-linear model of LPE using describing function. Frequency response code is developed for derivation of engine frequency model. Adequate frequency interval and input or excited signal amplitude are selected regarding LPE operating modes. In next step, frequency model is derived by stimulation of non-linear dynamic model with sinusoidal inputs includes considered amplitudes and frequencies. This subject is done by integration and engine output obtaining and Furrier integrals calculation at time that output get to steady state. Then system gains and phases calculation is done at the various amplitudes and frequencies for obtaining describing functions models. Frequency model evaluation characterized that can provide more efficient, simple and adequate conditions for analysis of LPE dynamics.
Mohammad PourJafargholi, Ghanbarali Sheikhzadeh, Reza Maddahian,
Volume 17, Issue 8 (10-2017)
Abstract
In the present work, numerical simulation of steady, compressible and supersonic airflow in a magneto-hydrodynamic (MHD) generator has been studied. This flow considered to be ideal with low magnetic Reynolds number. A two-dimensional channel with four-pair electrodes and with various geometries and boundary conditions were utilized as a MHD Faraday generator model. The computational model consists of the Navier-Stokes equations coupled with electromagnetic source terms, Maxwell's equations and Ohm's law. Implicit based on density solver is used to solve the Navier-Stokes and the electric potential method is used to solve the Poisson's equation. First, the boundary conditions of constant temperature and constant heat flux were compared. Due to the less Joule heating and generation of higher electrical power, constant heat flux boundary condition was selected to continue working.
F.s. Moghanlou , E. Ghazanfari Jajin, M. Vajdy Hokmabad , Sh. Jafargholinejad ,
Volume 20, Issue 9 (September 2020)
Abstract
The study of micro-scale fluid behavior is known as microfluidics, which has received much attention in many scientific fields. In the current research, the droplet generation in the micro channel has been studied numerically and experimentally. Two micro channels were fabricated by soft lithography method and the results of generated droplets were compared. The process of droplet formation was investigated using two fluids including water (dispersed fluid phase), and oil (continuous fluid phase) at different flow ratios. The images of the droplet formation and crossing steps in the micro channels were analyzed using image processing. The results showed that by increasing the ratio of dispersed to continuous flow, the size of droplets was increased, the droplet formation distance (the distance of the produced droplets) was increased, and the frequency of droplets generation was decreased. Also, the proposed new geometry leads to the production of smaller droplets with higher production frequencies. In the basic geometry, the droplet diameter was observed to be between 117 and 700 micrometers while in the proposed geometry, the diameter of droplets is between 46 and 466 micrometers. In the proposed geometry, the size of the produced droplets decreases, and the production frequency increases.
