-
دسترسی آزاد مقاله
1 - استخراج عوارض سطح زمین از تصاویر سنجنده OLI
محمد ملکی سید محمد توکلی صبوراشکال ژئومورفولوژی و فرآیند‌های حاکم بر آن منشاء بسیاری از مخاطرات و منابع محیطی هستند، همچنین با توجه به شکل-گیری صنعت و علم ژئومورفوتوریسم و در نهایت پایه‌ای بودن مطالعه این اشکال برای طرح‌های عمرانی، ضرورت تهیه چنین نقشه‌ها بیشتر می‌شود. با گسترش استفاده از علوم مکان چکیده کاملاشکال ژئومورفولوژی و فرآیند‌های حاکم بر آن منشاء بسیاری از مخاطرات و منابع محیطی هستند، همچنین با توجه به شکل-گیری صنعت و علم ژئومورفوتوریسم و در نهایت پایه‌ای بودن مطالعه این اشکال برای طرح‌های عمرانی، ضرورت تهیه چنین نقشه‌ها بیشتر می‌شود. با گسترش استفاده از علوم مکانی همانند سنجش از دور و سیستم اطلاعات جغرافیایی، و کاربرد آن در مطالعات علوم زمین در این تحقیق از تصاویر سنجنده OLI برای تهیه نقشه دره، تیغه، مخروط‌افکنه و واریزه استفاده شد. و با استفاده از روش تفسیر بصری اشکال موردنظر استخراج شدند. نتایج با تصاویر لایه World Imagery ازArc GIS Online مقایسه شد و چهار پارامتر صحت، دقت، کیفت و کاپا برای آن محاسبه شد. و نتایج بدین صورت بدست آمد، صحت‌کل 80 درصد، دقت‌کل 01/62 درصد، کیفیت 87/53 درصد و ضریب کاپا 74/49 درصد بود. از نتایج بدست آمده مشخص گردید که موفقیت تشخیص تمامی عواض بجز واریزه درحد قابل قبولی بوده است. با توجه به ضریب کاپا مشخص می‌شود که قطعه‌بندی انجام شده برای استخراج عوارض در حد متناسبی است. پرونده مقاله -
دسترسی آزاد مقاله
2 - Evaluation of the Application of Non-Destructive Tests in Investigating the Defects of Gas Turbine Blades and Using Thermography Method as an Alternative Method
R Hedayatnejad S FarhadiBlades of a gas turbine are the main and most important parts of turbine machines that work in very difficult and complex conditions. Existence of discontinuities and defects in the structure of these parts cause sudden and irreparable damage. It can completely take a t چکیده کاملBlades of a gas turbine are the main and most important parts of turbine machines that work in very difficult and complex conditions. Existence of discontinuities and defects in the structure of these parts cause sudden and irreparable damage. It can completely take a turbine out of operation and impose huge costs on a power plant. Therefore, pre-installation controls and inspections for these parts are of great importance. One of the safest and most reliable methods of control and inspection is the use of non-destructive tests. One of the methods that has been considered in recent years is the use of infrared waves, which in this method; Surface defects and sometimes even internal defects can be detected by using infrared cameras that operate within a certain range of the electromagnetic wave spectrum (0.8-14 nm). In this paper, we try to review the conventional methods of non-destructive testing that are used in troubleshooting blades of gas turbines, and the method of using infrared waves as an alternative method to conventional methods to be discussed. پرونده مقاله -
دسترسی آزاد مقاله
3 - Application of Fully Green Bio-Composites in Manufacturing of Wind Turbine Blades: A Strategic Review
N Desai P Bhatt M SolankiEnergy crisis has been posing a great concern on the exploitation of limited resources and causing dramatic impact on the global economy. With the growing shortage of electricity, a rapid evolution has been observed in the wind power technology as a clean source of rene چکیده کاملEnergy crisis has been posing a great concern on the exploitation of limited resources and causing dramatic impact on the global economy. With the growing shortage of electricity, a rapid evolution has been observed in the wind power technology as a clean source of renewable energy. Along with considering the strength requirements and considerable forces acting on the blades of wind turbines throughout its operating lifetime, the continued growth of the industry also strengthens the need for gaining critical material knowledge for the wind turbine blades. This gives direct rise to challenges in material selection process, a major area of potential improvement. The focus of this review paper is the need for improved material knowledge, advanced, economic, and environmentally friendly materials for wind turbine blades. Present piece of research attempts to conclude various potential green bio-composites which have an edge over the existing conventional materials for the application of wind turbine blades and could prove to be a remarkable advancement in the field of wind energy. Along with the material selection, detailed insights about property requirements for wind turbine blades, problems encountered in the present-day materials, characteristics for selecting reinforced fibres, material testing, and manufacturing process of wind turbine blades have also been studied پرونده مقاله -
دسترسی آزاد مقاله
4 - Optimization of the Forging Process of a Gas Turbine Blade using the Finite Element Analysis and Response Surface Method
V. Alimirzaloo F. R. BiglariForging of gas turbine blades needs a close control of the process parameters. These parameters require a suitable optimization method to achieve the best process conditions. This paper presents a hybrid method for the optimization of the forging process of an aerofoil چکیده کاملForging of gas turbine blades needs a close control of the process parameters. These parameters require a suitable optimization method to achieve the best process conditions. This paper presents a hybrid method for the optimization of the forging process of an aerofoil blade. Forging process of the aerofoil blade was simulated using 3-dimentional finite element method. Preform shape and die parting-line angle are optimized in order to minimize the volume of the unfilled die cavity, material waste, and forging forces. The overall optimization scheme used in this research work includes a multi-objective approach that is a combination of response surface and finite element methods. The results show that the proposed optimization approach accrued to decrease the flash volume and the forging force of the aerofoil forging process. Therefore the proposed algorithm is a suitable method for the optimization of the gas turbine blade forging processes. پرونده مقاله -
دسترسی آزاد مقاله
5 - Preform and Process Design of Ti-6Al-4V Compressor Blade using Equipotential Lines and 3D FE Simulation
M. Soleimanzadeh M.M. FallahForging is one of the most important processes for production of titanium parts. Selection and evolution of forging parameters such as the forging preforms, part and die temperatures and strain rate are of great importance to achieve optimal process. In this work, a com چکیده کاملForging is one of the most important processes for production of titanium parts. Selection and evolution of forging parameters such as the forging preforms, part and die temperatures and strain rate are of great importance to achieve optimal process. In this work, a comprehensive study on the near net hot forging of a Ti-6Al-4V compressor blade is performed through designing several preforms and simulating the process in several die and preform temperatures. The Equipotential lines method is used for the optimal design of preforms and Johnson-Cook constitutive model is used for 3D FE simulations and the criteria for selecting the parameters was the material temperature during the process that is necessary for achieving desired properties of Ti-6Al-4V parts. According to the results, performing the isothermal forging process in increased speeds could lead to increasing the temperature over the β-transus and improper mechanical properties development. So, finding a proper die and preform temperature is necessarily accomplished in this work. According to results the appropriate temperatures for performing the process using modified 0.1v preform and ram speed of 1mm/s were 1050˚C and 450˚C for the preform and die respectively. پرونده مقاله -
دسترسی آزاد مقاله
6 - Time-Dependent Reliability Analysis of Mechanical Structures using an Analytical Approach
Mohammad Reza MoarefzadehTime-dependent reliability analysis of mechanical structures is concerned by the use of an outcrossing approach. In this approach the so-called outcrossing rate plays a critical role and thus it is important to estimate it as straight ward as possible. Despite the avail چکیده کاملTime-dependent reliability analysis of mechanical structures is concerned by the use of an outcrossing approach. In this approach the so-called outcrossing rate plays a critical role and thus it is important to estimate it as straight ward as possible. Despite the availability of a variety of methods to estimate this rate in the literature, still more general and at the same time less sophisticated approaches are desired. In this paper, an analytical method is proposed to evaluate the required outcrossing rate in which the basics of "Parallel System Reliability Formulation" in the framework of directional simulation are used. To indicate the accuracy and efficiency of the method, it is applied to carry out the reliability analysis of a hydrokinetic turbine blade. Since the random variables/processes involved in this analysis possess a set of extremely different variances (and thus make a so-called "non-proportional space); it is shown that the proposed method is also capable to satisfactorily employ a technique of directional importance sampling in order to prohibit massive computations, normally required in such spaces. The results of the analysis show that the proposed method could be successfully applied for the circumstances whose involving processes may be non-stationary and whose space of random variables/processes is extremely non-proportional. پرونده مقاله -
دسترسی آزاد مقاله
7 - Effect of Aerodynamic Blade Change of Two-Stage Axial Subsonic Turbine on Design Point
Mahmood Adami Behrooz Shahriari Ali Zamani GharaghoushiIn this research for reducing the effect of losses and increasing the efficiency, the bowing in the rotor and stator blades is used. In one mode rotor blades are curved and in other one, stator blades are curved. The amount of rotor loss, due to changes in the thickness چکیده کاملIn this research for reducing the effect of losses and increasing the efficiency, the bowing in the rotor and stator blades is used. In one mode rotor blades are curved and in other one, stator blades are curved. The amount of rotor loss, due to changes in the thickness of the trailing edge and operating rotational speed, have been investigated. To confirm the accuracy of the results, a turbine stage whose experimental results are available is modeled and numerical results have been compared with experimental results that indicate acceptable compliance. The turbulence model k-w-SST is used to solve turbulent flow. The positive bowing, creates a pressure gradient from the two ends of the blade towards the center of the blade, which leads to the directing of the secondary flows toward the center of the blade. This reduces the losses in the two ends of the blade and increases the loss in the middle part of the blade. Increasing the thickness of the trailing edge, as well as increasing the turbine’s operating rotational speed, will increase the loss. The curved rotor increases the efficiency and mass flow and power by 0.4% and 0.5% and 0.8% respectively and the curved nozzle reduces the efficiency and power by 0.3% and 4.9% but increases the mass flow by 0.2%. It also increases the thickness of the trailing edge of the first rotor from 0.2mm to 0.9mm at 24000 rotational speed and increases the total loss by about 35%. پرونده مقاله -
دسترسی آزاد مقاله
8 - Increasing the Fundamental Frequency of the Cantilever Rotating Beam by Placing the Intermediate Elastic Support with Minimum Stiffness at the Optimum Point Based on the Courant’s Maximum–Minimum Theorem using Finite-Element Analysis Software
Mehdi Asgarikia Farshad Kakavand Hasan Seidi: In this paper, the effect of the optimal position and minimum stiffness of the elastic middle support on increasing the fundamental frequency of a rotating cantilever beam is investigated based on the Courant’s maximum–minimum theorem using ABAQUS finite e چکیده کامل: In this paper, the effect of the optimal position and minimum stiffness of the elastic middle support on increasing the fundamental frequency of a rotating cantilever beam is investigated based on the Courant’s maximum–minimum theorem using ABAQUS finite element software. First, the software analysis results are compared with the numerical analysis results for a non-rotating cantilever beam to confirm the accuracy of the software model. Next, by placing the middle elastic support at the optimal point selected based on the Courant theorem, the minimum stiffness of the elastic intermediate support for the maximum fundamental frequency of the rotating console beam was obtained. The results of this study prove that the Courant’s maximum–minimum theorem is completely valid for rotating cantilever beams and can be used to improve the vibrational behavior of rotating engineering components. Finally, the minimum diameter of damping wire for the turbomachine blade is calculated as a practical application of the minimum stiffness of the intermediate elastic support for the rotating beam. پرونده مقاله -
دسترسی آزاد مقاله
9 - Analysis of the Fracture of a Turbine Blade
A.R Shourangiz Haghighi S Rahmanian A Shamsabadi A zare I ZareThe cause of crack initiation turbine blade had initially cracked by a fatigue mechanism over a period of time and then fractured by the overload at the last moment. Experimental procedure consists of macroscopic inspection, material verification, microscopic examination چکیده کاملThe cause of crack initiation turbine blade had initially cracked by a fatigue mechanism over a period of time and then fractured by the overload at the last moment. Experimental procedure consists of macroscopic inspection, material verification, microscopic examination, and metallographic analysis and finally FE. And for these procedures, some specimens were prepared from a fractured blade. Using ICP and energy dispersive X-ray fluorescence, the chemical composition of the blade was carefully analyzed. The segregated area of Ti and Mo, caused generally by inappropriate manufacturing process, is found by the microstructure and EDX analysis of the blade. The fracture blade which installed on the third stage rotor of the turbojet was fractured at about 6 cm distance from the hub of proposed blade. The non-linear finite element method (FEM) was utilized in order to define the stress state of the disc or blade segment under operating conditions. High stress zones were found at the region of the lower fir-tree slot, where the failure occurred. A computation were also achieved with excessive rotational speed. The aim of this study is devoted to the mechanisms of damage of the turbine disc, and furthermore the critical high stress areas. پرونده مقاله -
دسترسی آزاد مقاله
10 - Modal Testing and Finite Element Analysis of Crack Effects on Turbine Blades
K.R.P Babu B.R Kumar K.M RaoThe study of vibration response of a turbine blade helps to detect the crack presence in the blade which alters its dynamic characteristics. The change is characterized by changes in the modal parameters associated with natural frequencies. In this paper, study of vibra چکیده کاملThe study of vibration response of a turbine blade helps to detect the crack presence in the blade which alters its dynamic characteristics. The change is characterized by changes in the modal parameters associated with natural frequencies. In this paper, study of vibration response is made for turbine blade in the presence of a crack like defect. Turbine blade is initially assumed as a cantilever beam. Modal testing has been carried out for both the beams with different crack depth and crack location ratios using FFT spectrum analyzer and ANSYS software. From the analysis, it has been observed that the crack depth and its location have noticeable effect on the natural frequencies. Later the same cantilever beam was twisted with different angle of twists to validate the cantilever beam model to turbine blade. پرونده مقاله -
دسترسی آزاد مقاله
11 - تاثیر تغییر پارامترهای عمق بار، قطر ابزار و نرخ پیشروی در فرآیند فرزکاری 4 محورۀ پره توربین بر روی زبری و شکل بافت سطح
امیر علی نقی زاده بهروز نوروزی علی فرهمندیهمواره در فرآیند تولید پره های توربین سعی شده از عملیات ثانویه ای همچون پرداختکاری که در قبال افزایش کیفیت سطح از درستی هندسی سطح می کاهد کمتر استفاده شود. بر این اساس در مقاله حاضر، بهبود زبری و شکل بافت سطح پره توربین مستقیما با استفاده از بهینه سازی پارامترهای ماشینک چکیده کاملهمواره در فرآیند تولید پره های توربین سعی شده از عملیات ثانویه ای همچون پرداختکاری که در قبال افزایش کیفیت سطح از درستی هندسی سطح می کاهد کمتر استفاده شود. بر این اساس در مقاله حاضر، بهبود زبری و شکل بافت سطح پره توربین مستقیما با استفاده از بهینه سازی پارامترهای ماشینکاری مورد بررسی قرار گرفته است. پارامترهای متغیر این تحقیق قطر ابزار، عمق بار ونرخ پیشروی بوده اند. کار آزمایشی با استفاده از ماشین فرز CNC4 محور بر روی پره توربین آلومینیومی انجام گرفته است.طراحی آزمایشات به صورت فول فاکتوریل بوده وتمامی جایگشت های سطح های پارامترهای متغیر به اجرا در آمده است.زیری سطح مناطق ماشینکاری شده با استفاده از زبری سنج وشکل بافت سطح آنها با بهره گیری از میکروسکوپ استریو مورد بررسی قرار گرفته است و در نهایت با مقایسه داده های بدست آمده بهترین حالت معرفی شده است. پرونده مقاله -
دسترسی آزاد مقاله
12 - Vortex-induced energy harvesting of an elliptic blade in high-Reynolds lid-driven cavity flow
Ali Akbar Hosseinjani Ghasem AkbariLid-driven cavity flow is characterized by large-scale energetic eddies which are potential for energy harvesting purposes. The present article deals with numerical study of vortex-induced autorotation of an elliptic blade hinged at the center of a lid-driven cavity.Imm چکیده کاملLid-driven cavity flow is characterized by large-scale energetic eddies which are potential for energy harvesting purposes. The present article deals with numerical study of vortex-induced autorotation of an elliptic blade hinged at the center of a lid-driven cavity.Immersed boundary method is utilized to solve the governing equations for this moving boundary problem. Four different blade dimensions are considered at a fairly high-Reynolds number to evaluate the impact of various vortex types and flow unsteadiness on the blade dynamics. Small-amplitude fluttering, clockwise autorotation and counter-clockwise autorotation are three dominant modes observed at various configurations and different temporal stages. The average-length blade is equally characterized by vortices at both directions, and consequently experiences a fluttering mode. In contrast, short (long) bladeis mainly affected by one dominant vortex type, leading to steady autorotation in counter-clockwise (clockwise) direction. At stable autorotation of blade in both directions, regular cyclic temporal oscillations are observed in the rotational speed, which are due to cyclic evolution of the near-blade vortices and their alternating moment applied to the blade. پرونده مقاله -
دسترسی آزاد مقاله
13 - Investigation of Mass Magnetic Abrasive Finishing Process on Compressor Blades
Seyed Alireza Rasouli Davood NoriAttempts at research across various industries to achieve high-quality surfaces have led to the development of new finishing processes. Magnetic Abrasive Finishing is a novel technique where a magnetic field is employed to control an abrasive tool. Gas turbine compresso چکیده کاملAttempts at research across various industries to achieve high-quality surfaces have led to the development of new finishing processes. Magnetic Abrasive Finishing is a novel technique where a magnetic field is employed to control an abrasive tool. Gas turbine compressor blades are among the industrial components requiring high surface quality due to their exposed surfaces. The reduction in surface roughness on these components has a significant impact on the efficiency of motor turbines. This paper focuses on studying the Magnetic Abrasive Finishing process parameters for the free surfaces of Titanium blades. Using a mass Magnetic Abrasive Finishing machine, the influence of powder weight, type of abrasive particles, and gap on the variation of surface roughness is investigated through statistical methods such as the response surface. The fabrication of the machine and determination of magnet polarity are carried out using Maxwell simulation software. The Factorial method is employed for experiment configuration. Mechanically alloyed powders produced by ball mills are used in this study. Results demonstrate that employing the magnetic abrasive method can reduce the surface roughness of the blade by up to 33%. The empirical model derived from regression analysis is utilized to predict the variation in surface roughness. Variance analysis of the experimental results indicates the significance of all studied parameters. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) are employed for a qualitative evaluation of the results. پرونده مقاله -
دسترسی آزاد مقاله
14 - بررسی تاثیر ارتفاع و زاویه ی قرارگیری پره های‌هادی جریان بر ضریب دبی سرریز چند وجهی زیگزاگی ذوزنقه ای
محمود منتظمیان ابراهیم نوحانی محمد حیدرنژادسرریزهای زیگزاگی سازه های هیدرولیکی مهم جهت تنظیم سطح آب و کنترل جریان در کانال ها، رودخانه ها و مخازن سدها بشمار می آیند. سرریزهای زیگزاگی از طریق افزایش طول تاج سرریز در یک محدوده معین عرضی ظرفیت انتقال جریان بر روی سرریز را افزایش می دهند. هدف اصلی در تحقیق حاضر، برر چکیده کاملسرریزهای زیگزاگی سازه های هیدرولیکی مهم جهت تنظیم سطح آب و کنترل جریان در کانال ها، رودخانه ها و مخازن سدها بشمار می آیند. سرریزهای زیگزاگی از طریق افزایش طول تاج سرریز در یک محدوده معین عرضی ظرفیت انتقال جریان بر روی سرریز را افزایش می دهند. هدف اصلی در تحقیق حاضر، بررسی تاثیر زاویه و ارتفاع مختلف پره های هادی جریان بر ضریب دبی سرریز زیگزاگی ذوزنقه ای است. به همین منظور پس از انجام آنالیز ابعادی به روش باکینگهام، رابطه ای بدست آمد که در آن ضریب دبی (Cd) تابع پارامترهایی همچون زاویه پره (θ)، ارتفاع پره (hb) و نسبت بارهیدرولیکی به ارتفاع سرریز (H0/P) شد. آزمایش های تحقیق حاضر بر روی یک فلوم به طول 12 متر، عرض 30 سانتی متر و ارتفاع 50 سانتی متر انجام شد. نتایج حاصل از تحقیق نشان داد که روند افزایش زاویه قرارگیری پره هادی به ازای یک ارتفاع ثابت و مشخص (5/7، 15 و 5/22 سانتی متر) موجب شد تا ضریب دبی به ازای تمامی نسبت های بارهیدرولیکی کاهش یابد دلیل این امر افزایش اغتشاش و تلاطم در خطوط جریان عبوری از روی سرریز و به تبع آن ایجاد اختلال در روند هواگیری به ازای نسبت های بارهیدرولیکی مختلف است، سرریزی که دارای بیشترین ضریب دبی است، سرریز با زاویه 30 درجه پره بود. همچنین نتایج نشان داد که سیر صعودی ضریب دبی به ترتیب از سرریز شاهد تا سرریز با ارتفاع 5/7 و 15 سانتی متر پره بوده است. به عبارت دیگر حد نهایی پرونده مقاله -
دسترسی آزاد مقاله
15 - Investigation of water head variation& relation to empirical Coefficient n of Stepped short Shaft Spill way
روزبه آقا مجیدی محمد نصر اصفهانیThese spillways (Stepped shaft spillways) pass more flow discharges through themselves in comparison to smooth spillways theoretically. Therefore knowing of flow behavior of these Spillways, help using better and more efficiently. Moreover, using vortex breaker has grea چکیده کاملThese spillways (Stepped shaft spillways) pass more flow discharges through themselves in comparison to smooth spillways theoretically. Therefore knowing of flow behavior of these Spillways, help using better and more efficiently. Moreover, using vortex breaker has great effect on passing Flow through Shaft Spillway. For using more efficiently, the risk of flow water head on the crest decreases to less than fluid vapor water head on the crest , called cavitation’s, should be prevented as far as possible. At this research, it has been tried to study different behavior of Stepped chamber and different vortex breaker shapes on spillway flow. From the viewpoint of the effects of flow regime changes on spillway, changes of step dimensions, and the change of type of flow range will Studied Effectively. And finally the best the relation between water head on the crest and Discharge Coefficient are determined. پرونده مقاله -
دسترسی آزاد مقاله
16 - Different methods of forging; applications and obstacles
امیرحسین زمانپور نیاوران مصیب جعفرنودForging is a manufacturing process that consists of shaping the metal using localized compression forces. The blows are delivered with a hammer (often an electric hammer) or a die. In this paper, different methods of forging (multi-directional forging, hot forging, near چکیده کاملForging is a manufacturing process that consists of shaping the metal using localized compression forces. The blows are delivered with a hammer (often an electric hammer) or a die. In this paper, different methods of forging (multi-directional forging, hot forging, near-beta forging, multi-axial forging, direct powder forging, warm forging and ring forging) are discussed. The main problems that may be encountered by users are investigated. In some cases, the problems are being solved by researchers in which the process is presented. Afterwards, one of the main applications of forging process, blade forging, is discussed. Furthermore, forging process’s effect on mechanical properties of components has been investigated. In this review paper, readers could find important information about forging process and get familiar with some forging methods and their impact on the properties of the components. And readers also can develop some ideas about how to solve the main obstacles of forging process. پرونده مقاله -
دسترسی آزاد مقاله
17 - One Sixth Wavelength Printed Monopole Blade Antenna
امیرمجمد چیت ساز نسرین امیریA Printed Monopole, One Sixth Wavelength Blade Antenna using printing micro strip on substrate that reduces the cost & increases the ease & precision in manufacturing. In this paper, the process of combining conventional blade antenna that cut a desired piece of metal, چکیده کاملA Printed Monopole, One Sixth Wavelength Blade Antenna using printing micro strip on substrate that reduces the cost & increases the ease & precision in manufacturing. In this paper, the process of combining conventional blade antenna that cut a desired piece of metal, & alternative the printed version is represented. Due to increase mechanical strength of parasitic element, it has substrate in common with main antenna. A sample of the proposed antenna has been designed & manufactured that measurement and simulation results are in good agreement with each other. پرونده مقاله -
دسترسی آزاد مقاله
18 - Design, Development and Testing of Low Capital and Operational Cost Shrub Cutting Machine
R. K. Mandloi Rajesh Gupta A. RehmanThe machine to be designed and developed with a view to resolve one ofthe irksome problems of this institute has been facing every year. This institute issurrounded by vast non- fertile land area of about 200 acres, which becomes widelyoccupied by numerous breads of bus چکیده کاملThe machine to be designed and developed with a view to resolve one ofthe irksome problems of this institute has been facing every year. This institute issurrounded by vast non- fertile land area of about 200 acres, which becomes widelyoccupied by numerous breads of bushes and shrubs during post-rainy season. Due tothis unwanted proliferation of such verdant institute gets abysmal look and thatdumps off massive fund every year to get rid off it. The shrubs cutting machinescomprises a main body (chassis) with two wheels and handle to provide movementin the field. One power unit (small S.I. engine) is mounted on this to give power forthe cutting blades through small transmission mechanism. The cutting blades aremounted on a small shaft. Which actually perform the cutting operation? We intendto develop a machine which would provide better cutting action of bushes with lowcapital and operational cost.With reference to literature available there are many types of lawn mowers, bushcutters and lawn tractors are exist in the market, which may not fulfill the capital andoperational cost criteria. The main concentration of our design is the cost andoperational ease. During design, development and fabrication the machine wasundergone several laboratory. Field tests like; determination of torque and forceanalysis, load and speed test on design specifications (for shaft, gear and bearings),impact test, balance test and finally cutting output test. After testing we succeed tohave a satisfactory performance, though it requires further more improvementswhich can be done in due course of time in stage II of the project. پرونده مقاله -
دسترسی آزاد مقاله
19 - Analysis of Stresses in Helicopter Composite blade in Hovering Maneuver
علی اصغر نادری محسن نظریThe main purpose of this article is the structural analysis of a composite blade of a selected helicopter. In this study, the stresses on rotors' blades caused by centrifugal forces, lift, drag and torque are analyzed. The governing equations of the structure behavior a چکیده کاملThe main purpose of this article is the structural analysis of a composite blade of a selected helicopter. In this study, the stresses on rotors' blades caused by centrifugal forces, lift, drag and torque are analyzed. The governing equations of the structure behavior and solving processes were carried out by MATLAB software, and simulation is carried out by ABAQUS software, and they are compared with each other. The program written for MATLAB is based on beam element theory and the computation of stress and displacement of considered elements of a blade, is one of the properties of the written code. In ABAQUS, the helicopter blade is simulated in various states such as composite and aluminum blade with/without web and composite blade with laminations in different angles. The results of the mentioned states are compared with each other and with the code and finally, the results are compared with reference article. Comparison between beam element results and ABAQUS simulation shows proper match. In order to optimize a composite blade, attention must be paid to factors such as, displacement and stress reduction and prevention of excess in weight, as by an increase in thickness of 45 and 90 degree laminates to 6.5 mm, maximum displacement would be 12.9 cm, and total weight of the structure would be 8 Kg. پرونده مقاله -
دسترسی آزاد مقاله
20 - Numerical solution of hovering propeller performance at various blade pitch angles and revolutions with different turbulence models
Behrooz Shahriari Mohammad Reza HashemiIn this research the validation of different turbulence models of a hovering propeller at different pitch angles and revolutions has been investigated. For this purpose, the pressure on the propeller surface at different cross sections has been calculated numerically by چکیده کاملIn this research the validation of different turbulence models of a hovering propeller at different pitch angles and revolutions has been investigated. For this purpose, the pressure on the propeller surface at different cross sections has been calculated numerically by six different turbulence models and compared with the experimental data. In the first part, the effects of changing the blade angle have been discussed, in this case, the angles of 0, 2, and 12 degrees have been selected. The results showed that changes in the pitch angle of the propeller have led to an increase in the error rate of numerical calculations. At a high pitch angle and in the same chord section, the highest amount of error is produced in leading edge section of the propeller, among which the best model in terms of production error is the k-e RNG. Also, due to the possibility of the formation of shock waves, the S-A and k-e standard models have very large errors, which shows these models' inability to simulate rotating flow with shock waves. پرونده مقاله -
دسترسی آزاد مقاله
21 - Study of the Effects of Lacing Rods Location on Natural Frequencies in Last Stage Blades of a Steam Turbine
مهدی نوذرپور عباس رهیIn this study, effects of lacing rods location on natural frequencies of last stage of a Steam Turbine Blades (STBs) have been investigated. STBs are critical and important elements in a turbine as well as power plants. One of the most important parameters in turbine bl چکیده کاملIn this study, effects of lacing rods location on natural frequencies of last stage of a Steam Turbine Blades (STBs) have been investigated. STBs are critical and important elements in a turbine as well as power plants. One of the most important parameters in turbine blades is lacing rods location. In this paper, first, a three dimensional (3D) scan was used to produce the geometrical model of the blade. Then, last stage of a low pressure turbine have been produced and simulated by assembling of the one-blade model. There are two rows of lacing rods in the last stage of turbine. In this paper, effecting the lacing rods location on natural frequencies of system has been studied. According to the Campbell diagrams, the results showed there is no resonance in the last stage blades of the steam turbine for different locations of the lacing rods. پرونده مقاله
سکوی نشر دانش
سند یا سکوی نشر دانش ،سامانه ای جهت مدیریت حوزه علمی و پژوهشی نشریات دانشگاه آزاد می باشد
پیوندهای سایت
مراکز مرتبط
پشتیبانی
صفحات رسمی
حقوق این وب‌سایت متعلق به سامانه مدیریت نشریات دانشگاه آزاد اسلامی است.
حق نشر © 1403-1400