Applied Mechanics and Materials Vols. 110-116

Abstract: This paper presents an algorithm for protection of series capacitor compensated line, which is based on the behavior (oscillating and decaying waveform) of DC component of line current. Along with this, it supports the idea of installing the series capacitor at the far end substation from current relaying point. It reduces the complexity of algorithm without affecting the performance of the line. The presented algorithm has been extensively tested on a PSCAD model of a 230kV, 340km long transmission line.

Abstract: The Combined Cycle Power Plants (CCPPs) are attractive in power generation field due to their higher thermal efficiency than individual steam or gas turbine cycles. Therefore thermo optimal design of Heat Recovery Steam Generator (HRSG) in CCPPs is an important subject due to the increasing the fuel prices and decreasing the fossil fuel resources. In this paper the heat recovery steam generator (HRSG) with typical geometry and number of pressure levels used at CCPPs in Iran is modeled. Then the optimal design of HRSG operating parameters was performed by defining an objective function and applying Generic algorithm optimization method. The total cost per unit of produced steam exergy was defined as the objective function. The objective function included capital or investment cost, operational cost, and the corresponding cost of the exergy destruction was minimized while satisfying a group of constraints.

Abstract: This paper aims, to investigate the shunts in multi-crystalline (m-c) Si solar cells by lock-in infrared thermography (LIT) technique and to study their effect on the cell performance by PSpice simulations. LIT provided useful information about the location and nature of shunts which was used in the simulation. Based on the shunt location and shunt resistance of the cell obtained experimentally from the I-V characteristic of the cell, shunt resistance at the shunted region have been estimated by simulation using the distributed diode model approach of solar cell by fitting. Based on these values of shunts, simulation has been performed to obtain the information about the deterioration in cells performance caused by the shunts. This type of simulation is useful to study different types and severity of shunts at different locations of cells. Solar cells which have been used in this study show a power reduction in the range of 3% to 15% due the shunts. This reduction was more severe for the shunt which was on the bus-bar compared to the edges.

Abstract: This paper presents the analysis on flux and electromotive force (EMF) developed by moving coil and moving iron linear generators using finite element method (FEM). A 6 pole moving coil and 6/4 moving iron linear generator are used to analyze and compare the flux distribution in the air gap. These generators will be used for free piston linear engine. A moving permanent-magnet linear generator has drawbacks of thermal and impact force demagnetization, in addition to requiring complex control strategies. To overcome these limitations, one of the solutions is to place magnets on the stator instead on the translator. Based on the analysis it is proposed to replace the moving permanent-magnet by a moving-coil for a linear generator whose prime mover is a free-piston linear combustion engine.

Abstract: Moving permanent magnet linear generator has some limitations such as thermal and impact force demagnetization, and complex control strategies. To overcome these limitations one of the solution is moving iron linear generators. This paper presents the analysis of flux using FEM for moving iron linear generator. The flux density varies with peak value of 0.85 for 6/1, 0.98 for 6/2 and 1.27 for 6/4 MILGs with the movement of translator. The effect of air gap on different MILGs is studied. The FEM analysis indicates that air gap have direct impact on output of the generator. The analysis is performed to replace the moving permanent magnet by moving iron in a different applications.

Abstract: The main objective of this PIC-based excitation control system is to control the terminal voltage by adjusting the generator exciter voltage. Unlike the conventional control system, the PIC-based excitation control system is constructed to reduce the number of components and thus the amount of design work and wiring required for the system. As a consequence, this is constructed to be low cost and high performance. In this work, this design is based on the construction of switched mode power supply (SMPS). MOSFET IRF840 is used as switching element to control the field excitation through the field coil. PIC16F628 microcontroller is used as excitation controller and performs the modulator function in firmware. In this modulator function, Pulse Skipping Modulation (PSM) which generates train of pulses to turn IRF840 (switching device) on/off in order to reach the desired output voltage of the generator is used. In the PIC-based excitation control system, PIC microcontroller senses the feedback voltage and compares this voltage with reference voltage by using onboard reference and two comparators. In this control system, PIC microcontroller generates a train of pulses to turn MOSFET (IRF840) on/off to control the field excitation of the generator. This excitation control system provides 10% voltage regulation from no load and provides the continuous maximum current up to 8A at maximum rating of 32, 63, 125 and 250 V_dc.

Abstract: This paper is aimed to calculate neutron induced fission cross section using TALYS nuclear reaction code by utilizing new fission barrier model parameter. The new fission barrier model is based on minimization method of action functional of deformed nucleus fission trajectory in configuration of space from ground state to the exit barrier. New fission barrier parameter that obtained from this new model will be fed into the TALYS code to calculate the fission cross section of Th-232 and U-238 through statistical method. The result shows a better agreement with ENDF data compared to that of ETFSI (Extended Thomas-Fermi and Strutinsky Integral) or Mamdouh model of fission barrier for energy between 2 and 10 MeV.

Abstract: The future trend of wind energy conversion systems is to draw the maximum power from the available wind. Unfortunately this is not possible with high capacity wind turbine, as they can be rotated only for a particular speed. The wind turbine system stated here is a 3.2 KW wind turbine which is allowed to rotate at any speed to grab the maximum power from the available wind. The size of the wind turbine system is small, as a result they can be placed on the roof tops and de-regulation of power can be done. This wind turbine system provides a three phase variable frequency AC voltage and this variable frequency AC is converted into constant three phase 230V AC by using the converter and inverter systems.

Abstract: Through CFD, Computational Fluid Dynamics application to calculate the numerical simulation, this paper is to study natural wind velocity and temperature distribution of the internal and external room of BIPV with solar skin. The research provides the evidence of more effieicent ventilation mode for sloar energy-saving build skin.

Abstract: Rarefied flows cannot be accurately simulated using Navier-Stokes (N-S) equations. The Direct Simulation Monte-Carlo (DSMC) technique is a particle based method for accurate simulation of flows under such conditions. A DSMC code is developed using an object-oriented (OO) approach which can simulate flows around arbitrary shapes. Hence, the flux from such boundaries can be correctly predicted. The object-oriented approach enables for easy modification of the code. For example, it is easy to use different collision models to implement different relaxation algorithm. The code is validated for the one-dimensional Fourier heat conduction problem. Results for the development of a shock due to supersonic flow over a 15 degree wedge are also presented. Inclined boundary of the wedge is correctly captured as the particles interact with the the exact shape of the boundary. Shock angle is found more than expected due to rarefaction effects.