Sharif Digital Repository

An important issue in aerospace propulsion systems is the reacting flow analyses, which involve many different concepts and physics including various chemical reactions mechanisms and radiation and convection heat transfer physics. As known, the computer simulation is a powerful tool to analyze the reacting flow physics in various combusting environments. It can suitably provide details of both chemical reaction occurrences and heat transfer physics. In combustion environments, the temperature gradient is noticeably affected by the density gradient. On the other hand, the accurate modeling of density gradients highly affects the computational results. In practice, the density-based methods... 

Combustion procedure in porous media is of great importance and also has numerous technical applications. Currently several usages of porous burners in thermodynamic engineering and thermal industries have been identified, in which they perform based on stabilized combustion in porous media. Among the advantages that porous burners have over conventional burners are pollution reduction, decrease in burner dimension, enhanced flame stabilization and also noise reduction.
According to physical and chemical attributes of porous material, combustion can occur in one of the three main types of media including: inert, catalytic, combustible. The concepts mentioned in this proposal are... 

Heat transfer to combustion chamber walls is an unwanted phenomenon. Reduction of this heat transfer by using bidirectional swirl flow, as proved in past studies, can result in time and cost saving methods in design and fabrication of combustion chambers. Bidirectional Swirl flow, existing in vortex engine, maintains the chamber wall cool. This characteristic of such flow field, among with many other advantages for it, makes researchers more interested in studying the propulsion of it as well as its other applications. Bidirectional swirl flow in liquid fuel ramjet engines has the proven advantage of keeping the combustion chamber walls cool and in solid fuel ramjet engines in increasing the... 

A new experimental setup was fabricated; equipped with an adjustable chamber’s length, with air tangentially flowing through the wall of vortex engine. In a vortex combustion chamber, the tangential inlet fuel or oxidizer creates both inner and outer vortices which are rotating in the same angular direction. Indeed, inner vortex moves from head to the end of engine in the axial direction; however, outer vortex moves in the opposite direction. This setup was fabricated to see the effect of fuel nozzle characteristics on the wall temperature of the chamber. In a vortex engine, vortices affect spray droplets and force them to have a spiral path. Moreover, relative velocity of droplets and flow... 

Vortex engine has shown to be a credible substitute in thermal power and aerospace industries mainly due to their advantages such as better mixing, improved combustion, and considerable cooled walls of combustion chamber. The engine geometry and tangential inlet oxidizer create inner and outer vortices rotating in the same angular direction. The inner vortex moves from head to the end of engine in the axial direction and outer vortex moves in the opposite direction. In the vortex engine, vortices affect spray droplets and force them to have a spiral path and apply a centrifugal force on the droplets to push them towards sidewall. Also axial relative velocity of droplets and flow filed act as... 

Vortex flow is one of the most sophisticated fluid movements in nature which has great industrial and scientific importance. In this dissertation, in order to study the combustion process due to a vortex flow, a new experimental model of a cold wall vortex engine, was designed, fabricated and tested with oxidizer issuing tangentially toward the end of the chamber. The cold wall effect in these chambers is a result of the cool layer of oxidizer which significantly reduces the amount of heat transfer to the chamber’s wall. This experimental model was designed to withstand the massive temperature rise resulting from the usage of Polyethylene as fuel and Nitrous oxide as oxidizer. In a series of... 

Conversation modeling is one of the most important goals in the field of understanding natural language and machine intelligence. Recently, with the enormous growth of the Internet and social networks, the amount of available data on the Web has increased significantly.This makes it possible to use data-driven approaches to solve the modeling problem of conversation.One of the most recent data-driven methods is the sequence to sequence modeling. In this document, after providing the necessary prerequisites, we examined the various models that have used the sequence to sequence approach for conversation modeling. We further examined the ways of improving the efficiency of this modeling... 

Crop classification is one of the most important applications of remote sensing in agriculture. Knowing what crops are on the farm is invaluable both on a micro and macro scale. For example, this information can be used to design and imple- ment agricultural policies, product management and ensure food security. Also, this information can be used as a prerequisite for implementing other programs at the farm scale, such as monitoring and detecting anomalies during the crop growth cycle. Most of the studies in this field are focused on the optical data of the Sentinel-2 satel- lite, but the optical data are vulnerable to atmospheric conditions, and on the other hand, there is valuable...