Sharif Digital Repository

In this research, a novel quasi-3D design method is developed for the centrifugal compressor impeller on the blade-to-blade plane. In this method, an iterative inverse design method called Ball-Spine Algorithm (BSA) is incorporated into the quasi-3D analysis code solving the Euler equations on the blade-to-blade and meridional planes at each shape modification step. In design procedure, the difference between the target and current pressure distribution along the suction or pressure sides of the impeller causes the blade-to-blade profile to be changed and the target pressure distribution to be satisfied. In order to validate the quasi-3D analysis code, the centrifugal compressor of a gas... 

In recent years, the use of fibers has found considerable attention in concrete structures as in spillways, basins of dams, shell structure, industrial floors, and bridge pedestrians. Fibers modify the brittle nature of concrete and make the composite behave ductile under various types of loading. Fibers have numerous advantages such as higher impact resistance, less shrinkage, smaller crack width, higher durability and low expense for repair and maintenance.
Till now, no adequate data has been reported on concrete beams reinforced with high volume fiber. In this study, flexural behavior of concrete beams reinforced with high volume steel fibers is experimentally investigated. Concrete... 

In recent years, autonomous underwater vehicles have had an increasing role in underwater investigations. These vehicles are used in various fields, including military applications, commercial uses or scientific investigates and also mapping purposes. The test and the fabrication of these kind of vehicles are very costly and time-consuming because of not only the risk of losing the vehicle due to the various computerized errors, but also as a result of the costs of supporting staff, equipment and the structure of a process. As a result of the environment where these vehicles do their missions, there is a crucial need of control methods which have enough accuracy as well as robustness against... 

This study aims to evaluate aerodynamic coefficients of an airplane with air breathing engine experimentally. In these experiments, an ejector is used to better simulate flying conditions and aerodynamic interferences generated in inlet and exhaust engine. Therefore, at first, an ejector was designed for simultaneous simulation of exit cold flow and inlet flow of engine. All tests were conducted at QRC Trisonic wind tunnel and at Mach number of 0.5 to 0.85, angles of -4 to 6 deg. and for various amounts of pressure ejector and control surfaces angles. Finally, for the Mach number of 0.5, effect of roughness on the aerodynamic coefficients was examined. The results showed that, drag... 

In the study of supersonic air intakes, two important issues including performance and stability are considered. In these types of intakes, when inlet mass flow rate is reduced to a specified amount, a self-sustained instability called Buzz phenomenon occurs. During this phenomenon, shocks and expansion waves oscillate ahead of the intake that will degrade the performance considerably due to the periodic pressure fluctuations inside the intake. In the current study, a supersonic axisymmetric air intake with mixed compression which has designed for a free stream Mach number of 2.0 has been tested were conducted for free stream Mach numbers of 1.8, 2.0, and 2.2, and the results were analyzed... 

Turbojet engines are used widely in the aviation industry due to very high specific thrust. The design and manufacture of turbojet components are complex procedures and needs high technology. In this M. S.c Thesis, the structur and function of a turbojet engine are described. then all stages of design,manufacture ,test and control of a small turbojet engine which is developed by use of a turbocharger are specified. the design and construction of combustion chamber, exhaust nozzle, lubrication system, thrust measurement system, data acquisition system, fuel and ignition system ,control system and etc are carried out at Sharif University of Technology gas turbine laboratory. The one... 

A Loop heat pipe (LHP) is an efficient two phase heat transfer device that is widely used in cooling applications. In this research a novel LHP was designed, fabricated and its performance was investigated through various experiments. The novel LHP has a new arrangement in evaporator and reservoir configuration in comparison with conventional LHPs, which results in a different energy and fluid flow. In addition, the novel LHP has a new mechanism for active control of working temperature which was not already used. Aside from its good performance, this LHP has easier and lower cost manufacturing process compared with the conventional ones. Also the proposed temperature control method is... 

The propulsion system plays a significant role in determining of mission and flight regime of an air craft. This system, provides the propulsion force for an air craft. A comprehensive model based on the specifications of gas turbine cycle, with acceptable accuracy, is necessary for quick estimating of the engine performance in different phases of design and development of a propulsion system. The structure and performance of the turbojet engine is elaborated in this project and the previous researches and their simulating methods of the turbojet engine are reviewed. The research plan is justified by explanation of the project’s objects and its assumptions. Then, the zero-dimensional... 

Design optimization of ships by taking maneuverability in account has great influence on the performance of the vessels. Thus providing a method to predict the behavior of vessel in the design process is very important. Ship maneuverability is remarkable from different aspects of view. Especially in high speed vessels of various applications and missions’ good maneuverability would be a positive rating for it. For example, military vessels in specific situations need to change the speed and direction and this is a crucial capability of them. Also in accordance to the rules of IMO all of the vessels should perform maneuvering trials and fulfil the minimum requirements. Accordingly, this issue... 

Vibration based energy harvesting is the process of trapping and collecting vibrational energy from ambient sources which seem unusable at first sight. The smart materials with the capability of coupling two different fields can be used in converting vibrational energy to electrical one. One of this smart material which has been taken into account recently is the Magnetic Shape Memory Alloy (MSMA) and it can couple the magnetic and mechanical fields. In MSMAs the total magnetization vector changes with the application of stress and make it possible to harvest energy from Faraday law’s of induction. An important phenomena that exist in MSMA is the dependency of magnetization-strain behavior... 

Rolling element bearings are the most widely used components in rotating machinery and so, estimation of their remaining useful lifetime in order to increase the reliability and availability of them is a critical issue in the field of condition monitoring of these machinery. Despite numerous researches which have tried to develop a model for precise prediction of rolling element bearings’ lifetime, there is no method which can predict their remaining lifetime exactly. The failure criterion in these components is the area of defect in their races and rolling elements. Consequently, an approach which can predict the defect area of these components is susceptible to prediction of their... 

Suspension system is one of the most influential components of vehicle in the area of stability and comfort. The suspension system is designed based on the use of the vehicle and stable characteristics. Obviously, being distant from the designed spots and applying various gates, its optimized performance is lost. Semi-active suspensions by changing their features get floating designed spots to be created and suspension system is always in optimum conditions through a suitable control. This research covers the efficacy of using damper Magneto Rheological which is called damper (MR) on the performance of seat suspension system in reducing vibrations. This damper is considered as a device in... 

The aim of this study is numerical simulation of progerasive failure in conical structures that manufactured by tape-winding proceses in various temperatures. For this purpose, flat laminates by tape-winding proceses firstly manufactured using carbon/phenolic prepreg tape. Then tensile, compression, shear and thermal expansion coefficient specimens are cut from these laminates. Tensile and compression test are done on these specemens in fiber and matrix directions in temperature range 23-200℃ and stress-strain and stress-time curves are achavied. Using these curves tensile elastic modulus in fiber and matrix directions and Poisson's ratio are obtained in room temperature. Also tensile and... 

According to the increasing need of the world to increase the speed of existing technologies such as computers, cars, urban transport, etc. The need to carry goods at higher speeds is also a concern that due to its cost It can make a significant contribution to the economy. In the maritime industries, in addition to the commercial and economic orientation, there is also military capability the speed factor and the ability to navigate is very important for military vessels. The power in the sea is inevitably dependent to speed, so for Increasing the speed of vessels with regard to military and economic objectives needs optimized Propulsion systems which There are also limitations for them.... 

In recent years, unmanned vehicles have intensively been developed to reduce human dangers for marine applications. Predicting the dynamic behaviour of an autonomous underwater vehicle is important during the vehicle’s design phase. In other words to design an AUV, one must clarify its maneuverability and controllability based on a mathematical model. The mathematical model contains various hydrodynamic forces and moments expressed collectively in terms of dynamic equations. Therefore, to optimizing the AUV design it is necessary to predict maneuvering abillity and dynamic behaviour of AUV. This can be able by computational simulation. SUT-2 is an AUV, being developed by Marine Engineering... 

This research evaluates the effect of external corrosion geometry and bending moment on the burst pressure of pipes. In recent decades, the use of natural resources of offshore oil and gas has increased, as a result, the use of offshore pipelines for transferring products has grown dramatically. At the same time, numerous accidents and explosions in offshore pipelines and its economic and environmental consequences indicates the importance of ensuring safe operation. Pipeline Integrity Management has been developed to ensure safe and efficient operation of pipelines. Integrity management includes planning, inspection, evaluation and repair. This cycle is checked continuously. The importance... 

The lateral force & its control has always been a great concern to structural designers. Based on the project’s location, this force can be either earthquake or wind force. In our country, Iran, the earthquake force is usually the dominant one. Of the most important differences between these two kinds of forces, we may point out the cyclic characteristics and nature of earthquake forces. One can choose different strategies to face the earthquake force including the use of dampers. Dampers exist in vast varieties of different categories which we will briefly explain in this thesis. Dampers can be used on their own or in combination with other lateral force resistance systems like bracings or... 

Cancer is one of the deadliest diseases of the modern era and accounts for 13% of all deaths in humans. Most cancers and lesions in the human body are related to soft tissue. Many soft-tissue cancers and lesions occur in sensitive areas of the body, such as the brain, pituitary, and intestine. The pituitary gland is located in the human head and near the optic nerves. Surgery in a typical way can result in risks such as heat loss of the optic nerve or injuries to healthy tissues due to the sharpness of the surgery tool. One of the alternatives to conventional surgery is water jet surgery. This method minimizes the risks of human error. In the present study, a water jet machine was designed... 

This thesis aims to introduce a numerical method for investigating the appropriate arrangement of visco-pseudo-elastic dampers applicable to shell and plate structures under large deformation. These passive dampers are considered as viscoelastic layers and discrete shape memory alloy (SMA) wires in which this combination improves their overall efficiency and reduces their drawbacks. Also, the main advantages of these dampers are discussed during some illustrative problems. The current finite element formulation is based on an incremental updated Lagrangian (UL) approach along with the Newmark's integration technique. In the layerwise shell element, the Mindlin-Reissner theory is adopted in... 

Today, the cleaning and moss removal of the hulls of ships is very important due to the strict and international laws of reducing pollutants and the exorbitant cost of fuel of the country's navy. The advantages of cleaning the hull of vessels are reduced fuel consumption, increased ship speed and longer hull life. Traditionally, the hulls are cleaned by divers, and in recent years the use of crawling robots has been welcomed by the industry because of its benefits. This important thing in Iran is still done by divers and therefore the need for indigenous development of such robots in the country is felt.In the present study, the aim is to design and build a reliance system for the ship's...