Sharif Digital Repository

Valve leak detection is very important due to bad direct effects on parts life and engine power. Acoustic emission (AE) has a good known ability on leak detection between fault detection methods. The aim of this thesis is presenting the ability of AE method for valve leak detection in internal combustion engines. The research method in a general framework based on the idea that firstly some evaluations were done in static tests for leakage due to three faults including clearance, quasi-crack and notch. Then, the evaluations were continued with dynamic analysis of rotational speeds and different loads on the engine. Finally, the neural network approach was used to automatically detect all... 

MPD technique manages drilling pressure to keep bottom hole Pressure balanced in the well. The objective to this studs, is to approximate the well pressure to formation pressure to prevent entry of fluid into the well. MPD is a new method drilling in which, driller controls the annulus pressure in order prevent drilling problems. the circulating fluids system employed by MPD technology is more akin to that of a pressure vessel. In this thesis, using in laboratory-made machine, reacts with sudden changes in pressure at the bottom hole in the shortest possible time. Basically, this system is a system where well bore pressure management is obtained by adjusting the pressures along the well bore... 

Anti-lock brakes car as one of the most fundamental and vehicle stability control system is considered. Solenoid valves, one-way valves, Accumulator, damper orifices and other components is a crucial role in the anti-lock system performance, so that the performance of the system and thus affect the dynamic performance of the vehicle. This is the most important part of the anti-lock brake System and These components are all new brake system.In this study a complete modeling of hydraulic control unit and obtain sufficient data to model the dynamic behavior of the hydraulic control unit to be seen. operators working in higher frequencies are weak and virtually reached saturation and efficient... 

Servo control valves including pressure control valves and flow control valves are the main components of the hydraulic system. Since these valves are responsible for controlling the flow or pressure in hydraulic systems, are important. In the present study, we focus on modeling and sensitivity analysis of an electro-servo-hydraulic valve with two stages. The first stage mechanism is the seating type (flapper-nozzle) and the second stage mechanism is the sliding type (spool type). For simulation main components of the servo valve include torque motor, flapper, flow through the nozzle-flapper, flow through the orifice and flow through the valve spool and body separately have been modeled.... 

Servo hydraulic pumps are being utilized in hydraulic circuits to prevent hydraulic oil reaching high temperatures in result of relief valve’s functions. In this study, we focus on modeling and sensitivity analysis of a pump of this kind. At first the importance of the current study and some of related studies has been discussed and some of the appropriate results has been represented. Then by employing CFD and Fluent code, the flow around servo valve of pump has been simulated, and operational curve of the valve has been calculated. This curve has been verified by results of the experimental set. At the next stage of the study, by modeling Dynamic parts of the pump in SIMULINK software and... 

Problems with the mitral valve can make the heart less efficient at pumping blood around the body. Severe problems can lead to heart failure if the valve is not surgically repaired or replaced. A simple approximation of the heart geometry is used and the valve dimensions are based on reported measurements. The primary objective for this study is to design and simulate the opening and closing behavior of the mitral valve using 2D fluid-structure interaction (FSI) model using ADINA software in order to evaluate and investigate the hemodynamic performance and problems of mitral valve, in which the blood is described as a viscous incompressible fluid, and the mitral valve is described as an... 

Due to inherent dangerous on human and environment safety in the nuclear power plant has significant importance. In order to ensure the safety of the plant and proper functioning ofits various components,before its operational exploitation, a series of commissioning tests should be conducted according to international standards for nuclear power plants. In addition, safety of the plant can be guaranteed bymodeling of transient states and possible scenarios of accident in different situations.In this research,by gathering geometric data and information about the facilities installed in the plant, modeling of Commissioning test of Bushehr Nuclear Power Plant (BNPP) and its associated accident... 

Designing a part of an on site repair system for refurbishing steam turbine high pressure control valve has been done in this project. The main role of this control valve is to control the input flow to the turbine in different working condition . However, due to high temperature and pressure, the seat is exposed to erosion. R epairing this part in workshop requires great amount of time and cost, because the valve is a part of the turbine body and must be cut and rewelded to the turbine body. S o using an on-site repair method is highly needed. In addition, due to the limited visibility and access to the valve seat, and accurate... 

Control valves of steam turbine of steam powerplant or the combined cycle are conected to the turbine's body and if there is any malfunction, it must be separated from turbine and after repairing, should be welded again to the body.This process needs enough time and high cost that’s why some well-known companies are repairing in the powerplant by design and making robots.Also using robots are made by well-known companies has high cost fees which can't justify it according to repair times.Thats why on the strangth of powerplant's authorities discussion (negotiation) design and making valve repaired robots which consists measurement, machining and welding is known as a project that repairs on... 

The focus of this project was on gaining the knowledge of design characteristics and manufacturing of a hydraulic servo valve. Hence, in the first stage, the model of the valve was considered. After investigating the important parameters which influence the performance of the valve, the effect of each parameter on the valve's efficiency was examined. One of the most important characteristics of the valve is the amount of lapping between the spool and sleeve. Numerical analysis was done and all the characteristic curves were elicited. Equations governing the dynamics of the plant including a servo valve, servo actuator and dynamic model of the turbine and waterway were presented. Then the... 

An inexpensive microfluidic chip–silicon rubber–based system was fabricated. A triangle–shaped micro canal with a 135 µm width and 234 µm depth was grooved by laser ablation technique. The groove was sealed by a thin glass cover while two pieces of stainless steel tubings were connected to each side of canal. Then, a polyaniline film with a thickness of 17±1 µm was synthesized on the walls of the canal by chemical oxidation using a syringe pump to deliver the relevant reagents. The microfluidic system was eventually connected to gas chromatography-mass spectrometry. To evaluate the capability of the constructed fluidic system, it was implemented to the analysis of sub–mL volumes of... 

In this research Quality Function Deployment (QFD) is used to define a set of improvement project for Kelarpooya company to increase it's market share. For this purpose the following activities were performed: Defining the scope of the research and it's approval by the management. Selecting the QFD team. Finding customer requirements and expectations about company's products and services. Identifying technical descriptors affecting customer requirements and deploying the interrelationship between them. Developing the relationship between customer requirements and technical descriptors. Developing prioritized technical descriptors. And finally defining improvement project for technical... 

In this research, oscillation in control loop caused by control valve stiction, external harmonic disturbance, poor controller tuning or their combination, is recognized and compensated. In control valve stiction based study, flaws in one of the important modeling methods are described and some modifications are proposed. For diagnosis of oscillation source, signal is decomposed to its fundamental modes and oscillation in each mode is investigated. Then, from the existence of harmonics in decomposed modes, stiction is diagnosed. Also, relation between peak differences in autocorrelation functions of other modes, results to external harmonic disturbance or poor controller tuning as... 

With the emergence of a variety of surgical glues in the market and utilizing them in recent years, nowadays, based on the post-surgery studies, it has become transparent that there are additional factors, such as the long-term effect of surgical glues on tissue, to consider beyond the sealants ability to act as a mechanical barrier or a means to buttress friable tissue so that it can hold sutures. Mechanical properties of the surgical glues have especially a significant role in the applications that the tissue undergoes cyclic loading (such as arteries’ tissues). A mismatch between the mechanical properties of the tissue and the sealant can result in the remodeling of the artery that may... 

Regard to high temperature and using dry fuel in engines with CNG (Compressed Natural Gas), wear problems and instability of valve seat insert (VSI) in these types of engines have been increased. Today some of high alloy steel (consist of Cr,Ni,Co,W,Mo, . . .), Ni-base alloy or Co-base alloy are used in manufacturing VSI. It's clear these materials have high price. In powder metallurgy methods high percentage alloy is used for manufacturing VSI. These are the reasons why casting method for VSI manufacturing has been pleasant to be used.
In this project the cast iron has been used for CNG engine VSI, by adding some elements like Mo,V,W, and Nb. The graphite has been used as solid... 

Smart wellsareunconventional wells with down-hole devices installed on their production tubing. Such wells allow us to continuouslymonitor flow rates, pressures, temperature and periodically adjust down-holevalves setting without any production intervention. This makes smart well technology to be considered as one of the most significantbreakthroughs in reservoir management technologies. So, modeling and simulating smart wellsautomated action represents a challenge in forecastingtheir performances.One of the easiest ways to model such wells is to transform theminto a multi-segment well with the ability tocontrol each segment independently. By using the commercial reservoir simulator,... 

In humans, the heart is roughly the size of a large fist and weighs between about 280 to 340 grams in men and 230 to 280 grams in women. Your body has about 5.6 liters of blood. The human heart is an organ that pumps blood throughout the body via the circulatory system, supplying oxygen and nutrients to the tissues and removing carbon dioxide and other wastes. Any damage to the heart, will affect on the other organs. They are four valves within the heart, in which aortic valve is the most important and crucial part of the heart. Calcium sediment on aortic valve leaflets causes reduction in the flexibility of the leaflets, one of the most common heart diseases. In this study, the flexibility... 

Knock is an abnormal phenomena in combustion engines and one the main limiter elements in increasing engine efficiency. From years ago, recognition and elimination of this phenomenon had studied by investigators and various approaches to anticipation had presented. One of the newest methods is using of property variety in air and fuel mixture with using technologies like Variable Valve Timing (VVT) system.
The purpose of this work is development a simple model in basis physics of 3 zone, homogeneous, ignition combustion with a partial kinetics model that this model can predict the knock phenomenon onset with good precision for various qualities of mixture. This study survey effect of... 

Blood vessels are subjected to complex mechanical loads, including internal pressure, external pressure, axial stress due to connection to tissues, and the twist caused by movement of the body. The veins and venous valves, which are responsible for returning blood to the heart, become bent and twisted (tortuosity) for various reasons. This venous tortuosity causes valve insufficiency and changes the hemodynamic pattern of blood flow and varicose veins. Studies show that more than a third of old people suffer from varicose veins. These injuries have made it important to study the physical mechanism of venous tortuosity and the function of venous valves.The purpose of this study is to...