جستجوی مقالات مرتبط با کلیدواژه « طراحی و ساخت » در نشریات گروه « مکانیک »

These days, societies' need for energy increased due to the expansion of societies, industries, and technology. The production of electricity from renewable energy sources such as solar energy, which does not harm the environment and has little pollution, has attracted the attention of many researchers and engineers. This article will present a new plan for the dual polar axis solar tracker, its design and construction in laboratory dimensions, and the experimental evaluation of its performance using the open-loop control method. For this purpose, after examining the advantages and disadvantages of the previous designs, a new and different conceptual design for the tracker is proposed. Among the features of the proposed tracker, we can point out the ability to combine, install and operate quickly and easily, the self-locking feature, and the ability to rotate 360 ​​degrees around both axes. This tracker has no restrictions for use in different geographical areas, including areas near the North or South Pole and in the early and late hours of the day when the direction of the sun's radiation is strongly inclined. In the following, the detailed design of the proposed detector and the presentation of the open-loop control method will be discussed. Finally, by conducting experimental tests, the production power of the proposed detector is evaluated in comparison with a fixed solar panel. Based on the results, the electricity energy produced from the proposed solar tracker is 49% more than the fixed solar panel.

In this research, a transparent PEM fuel cell is designed and manufactured to visualize the anode and cathode side flow channels and study flooding phenomenon in them. Manufacturing challenges are found, and cell design is simulated prior to manufacturing. Restrictions are expressed in the first place and then practical solutions are presented to cope with them; materials and dimensions are then determined accordingly. As the second step, the cell’s operation is simulated and the polarization curve is extracted using a steady-state two-phase computation fluid dynamics model. After the manufacturing of all components, due to the high influence of the torque of the bolts on the leakage, lifetime and operation of the cell, this parameter is optimized using polarization curves. A torque of 1N.m for the bolts is found to be optimum. In order to validate the numerical model, the polarization curve of the model is compared with that of the experiment. An error of 6.76% demonstrates the suitable accuracy of the numerical model. Finally, the accumulated water on the cathode side is detected using direct visualization and image processing technique.

In this research, the design, fabrication, and aerodynamic analysis of a small remote-controlled airship are investigated. The airship must be capable of carrying a 2kg payload. In this research, the design of various parts of an airship such as envelope, gondola and tail has been investigated by using theoretical and empirical formulas. To check the accuracy of the design, digital datcom software was used to perform an analytical analysis as well as the fluent software to numerically evaluate the flow around the airship and calculate the forces and moments applied to it. The investigations were carried out at a free stream speed 15m / s and in the various angles of attack from -10 ° to 10 °. In the numerical study with fluent software, the unstructured grid and the   turbulence model were used. The results showed that the airship was well modeled in digital Datcom software. Also, at low angles of attack, the good agreement between fluent's data and digital Datcom's data is observed. Digital Datcom's data can be used to obtain aerodynamic coefficients during the design phase. At all angles of attack, the airship has static stability and at low angles of attack, it has the least stability and maximum maneuverability. The drag coefficient obtained from Digital Datcom has a significant difference with the Fluent and other references data. therefore, Digital Datcom cannot be predicted at design phases for the drag coefficient.

in this paper, design, implementation and test of 24 bit acoustic DAQ subsystem for bio-capsule of Pajohesh explorer is presented. the proposed structure has been used B&K 4942 microphone as input sensing element. the proposed DAQ, has 48Ksps speed, 24 bit resolution, 113dB dynamic range and 23 KHz BW. we used a ARM Cortex M3 for signal handling and processing. the acquiescing data have been sending to Bio- capsule FC and also recorded in a Micro-SD card. power consumption of the proposed DAQ is obtained 2.8W. the proposed DAQ take a place with dimentions of 40*40*100 mm3 inside of bio-capsule stand.

The bobbin tool is a new design of the friction stir welding tool that provides the opportunity of the simultaneous double sided welding. The present research aims to design and manufacture a floating bobbin tool; the capability of which is examined through welding aluminum alloy 6061. The results indicated that the high quality and defect-free butt welds can be produced via this tool. Moreover, the strength of the welds is similar to the strength of welded samples done by the conventional friction stir welding method. Regarding the quality and strength, the obtained samples were investigated by mechanical tests including tensile strength test and hardness test. Obtaining 60.7% joint efficiency is indicative of success in the friction stir welding process; and, thus the efficiency of the designed tool. Besides, the second major characteristic of welding is the hardness, which is due to the dissolution of sediments, is decreased in the stirred area. This finding is confirmed by the behavior reported by the other investigators in the literature.

The present study is a numerical and experimental study that investigates the effect of using exhaust smoke extractors as an alternative to traditional manifolds in a spark ignition engine designed to maximize engine power. For this purpose, a specific engine is considered as the base engine and to investigate the effect of the extractors on the engine performance and selection of superior design, the proposed geometric model of proposed manifolds in a numerical simulation process has been investigated and after optimization, the model is simulated by numerical simulation softwares and after verifying the performance improvement, the model has been constructed and installed on the engine. At the next step, the engine was experimentally tested in the test cell. Results were compared with the base engine. It was observed that the designed exhaust extractors would increase the maximum engine power up to 15% That this amount of increasiaton in engine efficiency relative to the required costs, is very significant.

Explosion is fast chemical reaction that alters primary explosive material to gas. Explosion process include two general part of starting explosion and interaction between environment and explosion products. Study of plate performance and investigation elastic – plastic behavior and plate rupture is essential to determine relation of those with plate geometric parameter. Shock tube is used for modeling and simulation of loading explosion. In this paper, Experimental and FEM modeling are used to Investigation of Explosive Wave blasting on the Aluminum Plate. Simulation is done by ANSIS Autodyn software. Shock tube was designed and fabricated in order to experimental study.

In this paper, an advisory driver assistance system is designed and implemented in real traffic flow. This system gives environmental information to the drivers by visual and audio signals to avoidance form possible collisions. The performance of this system is based on estimation of instantaneous delay of Driver-Vehicle Unit (DVU). This estimation helps us to specify the consciousness of drivers. To reach this aim, some sensors must be mounted on the vehicle, then information fusion of these sensors obtains conditions of environmental hazards. To investigate the performance of the designed system, the subsystems are implemented on a Peugeot 206 passenger vehicle and some scenarios are tested in real traffic conditions. The results show the high accuracy and good performance of this system to reach control aims and reduction of the tracking errors. This system is useful for safety improvement for vehicles in longitudinal maneuvers and decrease of reaction time of DVU.

Due to the problems in the country (Islamic Republic of Iran) for purchasing aircraft and aircraft old fleet, a solution should be proposedfor this problem. One way to address this need is designing and manufacturing the aircraft in the country.According to the previous investigations carried out, 180-seater passenger planes with a range about 5,000 Km are part of the requirements of the country. In this paper, the costs of design, construction and operation of this type of aircraft has been studied. Also, the inventory costs in the United States of America have been investigated and compared with the costs in the Islamic Republic of Iran. There are three main objectives in this research: the first is to estimate the total expenditures in terms of the different phases of the design, construction and operation; the second concerns reducing design costs to much less than the costs of construction and mining; and finally, the third involves an analogy of the costs of design and production in Iran versus the U.S.

In this paper, a Proton Exchange Membrane (PEM) fuel cell with new symmetrical flow channel pattern was designed and fabricated in-house. The fabricated PEM fuel cell has nominal power of 10 W, with an active area of 25 cm2 and Nafion 117 membrane. Using a fuel cell test station, the effects of temperature and relative humidity on the performance of fabricated PEM fuel cell (i.e. voltage - current density curve) was examined. Laboratory results showed that fabricated PEM fuel cell is able to produce maximum power density of about 0.45 [Wcm-2] or 11W power. A comprehensive three-dimensional, single phase and non-isothermal model is developed for the fabricated PEMFC. The presented model is a nine-layer model that consists of current collectors, flow channels, gas diffusion layers, catalysts layers at the anode and the cathode as well as the membrane. A commercial CFD software (Fluent) was used to solve the governing equation. Comparison of numerical and experimental results shows that there is a good agreement between them. The results indicate that the new flow pattern can produce uniform temperature, current density and concentration distributions over the PEM fuel cell active area.

In order to be sure from true function of satellite’s Attitude determination and Control Subsystem (ADCS) and its parts, some tests are needed to be done in part or subsystem level. One of the useful tools for doing these tests is Helmholtz Coil. This tool is usable in functional tests and calibration of satellite’s magnetic sensors and actuators, in Hardware In the Loop (HIL) tests of ADCS subsystem, and also in related tests to residual magnetic of satellite’s part. In this paper, we study mathematical equations of Helmholtz coil, propose design procedure and requirements, also introduce set of functional and identification tests for evaluating the constructed Helmholtz Coil. By obtaining results and finding the mathematical model of Helmholtz Coil, preparations for designing closed loop control system to eliminate environmental magnetic disturbances and create desired magnetic field by Helmholtz coil are provided.

Parallel manipulators are mechanisms with closed kinematic chains which have been developed in different forms, but these manipulators have several drawbacks such as small workspace, existence of singular points in their workspace, and complex kinematics and dynamics equations that lead to increase of difficulty in their control. In spite of this, this mechanism has been being conventionally used in many different industrial applications such as machining, motion simulators, medical robots, etc. To overcome these drawbacks, design and manufacturing of a manipulator with three translational degrees of freedom are provided. Design of this manipulator was based on the possibility of three translational motions for its end-effector. The manipulator degrees of freedom are obtained via screw theory. Basic features, consisting of forward and inverse kinematics, workspace and singularity analyzes and also velocity analysis, are considered in this paper. A numerical algorithm is implemented to determine the workspace regarding applied joint limitations and the design parameters were extracted based on to achieving to the desired workspace. The robot motion is created by using of pneumatic actuators which receive their command from a pneumatic servo valve. After design steps, the required elements were provided and assembled in a robotic lab. Finally, the simulation results have transparently approved the improved robots.

Although Pulsed Plasma Thruster (PPT) has first been utilized in a space mission in 1964 but after more than four decades, it is still a space rated technology which has performed various propulsion tasks from stationkeeping tasks to three-axis attitude control for a variety of former missions. With respect to the rapid growth in the small satellite community and the growing interest for smaller satellites in recent years, PPT is one of the promising electric propulsion devices for small satellites (e.g. CubeSats) as the following advantages: simplicity, lightweight, robustness, low power consumptions, low production costs and small dimensions. In spite of the fact that the issues relating to 􀈝PPT scaling have been investigated to a certain degree in recent years, it is felt that for an application on CubeSats this topic has to be investigated in greater detail for even smaller dimensions and better performance. Therefore a laboratory benchmark rectangular breech-fed pulsed plasma thruster (PPT) was designed, developed and successfully tested in a bell-type vacuum chamber at 10-6 mbar for the first time in west Asia (Iran). The PPT has been tested while the main capacitor, which is a 35 􀈝F, 2.5 kV oil-filled capacitor, has been charged with a wide range of voltage, ranging from 250 V to 1750 V making the system stored energy range from less than 1 J to 60 J, producing the impulse bit varying from 30 􀈝N-s to 1.3 mN-s. This work initiated a research program in Iran for working on PPTs and miniaturization of PPTs while increasing the performance parameters. The present paper reviews the PPT design and the development briefly.