Sharif Digital Repository

Nowadays, reaching higher speed in marine crafts and underwater vehicles mostly requires a modern propulsor with high efficiency and enhanced cavitation performance. Because of these requirements, numerous researches for developing the existing propulsion systems and invention of new systems have been conducted in recent years. One of the most sophisticated and developed propulsion systems that have high hydrodynamic efficiency and high cavitation performance and low acoustic signature is pumpjet. This propulsor contains a rotor, stator and a duct that surrounds two other parts. Stator reduces the swirl of flow coming from rotor and thereby reduces the loss of energy. High cavitation... 

Underwater robots are broadly used in oceanography to explore ocean environments,inside inspection of pipes, and also to provide security at maritime boundaries. To design an underwater autonomous robot, it is compulsive to take advantage of a high efficient propulsion mechanism to lengthen the tour time span. Since fish-like propulsion mechanisms have presented higher efficiency comparing other mechanisms, they have been paid a lot of attention.In the present research, the hydrodynamic of a thunniform fish robot is analyzed under some reasonable simplifications. Based on the results achieved from this study, closed expressions are developed to predict the steady mean velocity and the... 

Measurements of magnitude and direction of thrust generated by a propulsion engine is important for verification of design, fabrication, assembely and or repare procedure used for a engine. Due to possible simplification in design calculations, human and machine errors in manufacturing process, the resulted thrust generated may be different from those values expected. Also, It is important to determine the dependency of magnitude and direction of thrust forces relative to tolerances and manufacturing processes. It is necessary to have thrust measuring stand with high accuracy with capability to measure the forces in different directions. A new digital engine test stand has been designed,... 

Over the past two decades, the production of ultra-light drones has increased dramatically. These aircraft are used in applications such as filming, surveying, etc. One of the most important goals is to fly them for a long time. From time immemorial, a lot of work has been done to get such birds to fly, but nothing has ever been done on their engines and propellers, and they have always been considered ideal models (in other words, their efficiency is a bit ideal). In this dissertation, the main purpose is to study some of these sets and to obtain the flight time of a particular drone. First, a low-velocity wind tunnel was built to examine these complexes, then we tested these complexes... 

Monopropellant thrusters are one of the most common types of propulsion systems that are used extensively in space applications. Especially thrusters with a capacity of less than 50N, they are used on space satellites and are developing rapidly. Problems such as contamination, toxicity of the propellant, difficulty in storing and custody, as well as price, led to the removal of the hydrazine from the focus of attention and focus on green propulsion. One of these, is the green propellant of hydrogen peroxide, which is decomposed in the proper catalytic vicinity, and the only chemical decomposition products are oxygen and water vapour. The present study aims to design and construct mono... 

Drawing inspiration from natural phenomena can provide simple solutions for creating new inventions. The graceful spinning and aerodynamic properties of maple leaves motivated a study on their rotation mechanics and physics, ultimately leading to the design of a propeller blade inspired by their shape and properties. Given that each maple tree produces thousands of leaves varying in dimensions, an average shape was calculated using digitizer software and Excel. Due to the small size of the leaves, one leaf was selected for 3D scanning. From various sections of the scanned leaf, airfoils were extracted and propellers were designed using SolidWorks software. Observing that these leaves...