Majlesi Journal of Energy Management
Volume:3 Issue: 2, Jun 2014

Supersonic wind tunnels are widely used in the survey of fluid flow behavior around flying vehicles. In the start stage which is occurring in a very short time interval in an unsteady and transient mode, some strong shock waves are formed who should rapidly pass the test section to be swallowed by the second throat of the supersonic diffuser. In otherwise, the normal shocks formed in the test section will remain and in addition to causing severe pressure drop, will hinder the flow in the tunnel. Such a phenomenon will practically make the tunnel unusable. In this paper, the starting stage of a blowdown supersonic wind tunnel with a target Mach number 3 is investigated. The design of nozzle geometry is carried out by the method of characteristics. The propagation of shock waves in the tunnel is presented by Mach number contours and diagrams. y+ diagram was used to cross examine the modeling of the flow turbulence done in Spalart – Allmaras method. The results obtained in this work are in agreement with the expected physical behavior of the flow field and can be exploited as the design criterion of the blowdown supersonic wind tunnels.

In this paper, a new method based on branch placement for the optimal placement of Phasor measurement units (PMUs) in power systems isproposed. In this method, the PMUs may be installed on branches. The PMUs are in type of single-channel and are installed at the beginning of the branches. So, they are able to measure the bus voltages. By installing the PMUs on the branches, in the probable conditions such as line or PMU outages,the security of observablilitymay be increased in comparison to the bus placement method. In this paperinvestigates the application of harmony search algorithm (HAS) for the problem of optimal placement of phasor measurement units (PMUs) in an electric power network.The proposed method is applied to IEEE 39-bus,30-bus and 24-bus case studynetworks.

In this paper we deal with the problem of stabilizing time delay systems using proportional-integral-derivative (PID) controller. We describe a simple approach which can be used for stabilizing time delay system with transfer function of different order. Based on this approach, transfer function is decomposed into real and imaginary parts and then the set of controllers which will ensure stability for a constant value of proportional controller is determined. All stabilizing PID controllers are also determined. Padé approximation is used here which simplifies the analysis and design of time delay system and it is avoided from direct computation of the roots of transfer function. Closed-loop step response is also used to show the correctness of the approach. Two examples are given to illustrate the approach which will be described in detail in continuation.

Static var compensator (SVC) as the shunt reactive power compensator plays a major role in enhancing the transient stability, minimizing low frequency oscillations, etc. The present paper investigate and improves the damping of oscillations of a single machine connected to infinite bus by the presence of SVC in line. By simulating the suggested system with using simulink Matlab and applying an fault to the system, First, we are going to examine the simulated power system by using proportional, integral and derivative (PID) controllers, then instead of PID, fuzzy logic controller (FLC) is used which is designed for SVC, and consequently the results of computer simulation will extract. The study of results is observed that the fuzzy controller has a better performance on improving the oscillations damping than PID controller.

Gaza Strip gets its power supplies from three sources where two of them are controlled by Israel. Over the last seven years, Gaza has been under unjust and strict siege where fuel and electricity have been limited. Gaza Strip suffers from daily scheduled electric power outages. Many of the 1.6 million Palestinians residing in the Gaza Strip must cope with scheduled electricity cuts of 6-8 hours daily; thus, a need for standby generator. Switching between utilities power supply and the standby generator is mostly done manually. This paper designs and implements a low cost automatic changeover system that can be used mainly in residential places.

Limitation of fossil energy reserves, threats posed by environmental destruction, harmful effects of greenhouse gas emissions and problems arising from disposal and recycling of human excreta, livestock and municipal waste have caused to increasing public interest to utilization of renewable energy especially from waste and biogas production. The biogas production from wastewater treatment is a permanent process, so it proposes a new source of energy in every city and state. But obtaining permanent and stable energy of this source is possible which a robust automatic control system governs on process and works based on wastewater treatment process, biogas production and refining and electrical power production. In this article we propose a summary of possible actions to mechanize energy generation system of municipal wastewater biogas to increase efficiency and make the power generation system more viable and sustainable. Therefore, according to the wastewater treatment process and its factors that influence biogas production and refining and electric energy generation processes, suitable feedbacks will be used to appropriate decisions. Then we try to keep situation of the process near ideal case by locating operators in appropriate points and designing a logical system. In addition to improve efficiency of system we use some auxiliary units like secondary tank beside main digesters, gas storage tanks near the biogas refining system and heating system to help digesters in emergency times.