Sharif Digital Repository

In this paper, the problem of designing optimal conflict-free maneuvers for multiple aircraft encounters is studied. The proposed maneuvers are based on changes of heading, speed and maneuvering time. The optimality of maneuvers among the conflict-free constraint is based on minimization of a certain cost function based on kinetic energy of either aircraft involved. Some suitable priority weight factors are incorporated into the cost function so that optimal resolution maneuvers are such that aircraft with lower priorities assume more responsibility in resolving the conflicts. As for considering aircraft turning dynamics, the circular 3-arced path with constant speed are proposed for each... 

The feasibility of using fluidic thrust-vectoring system, as a control technique for the longitudinal and lateral trim purpose was investigated in this study. For this purpose, integration of a Co-flow method into the propulsion unit of a conceptual aerial vehicle was assumed. The focus of the research presented was to estimate the required thrust vector angle in order to trim the aerial vehicle in different flight phases. Since the fluidic thrust vectoring requires secondary air flow to deflect the engine exhaust gas, this research also provides an analytical toolset for preliminary sizing of a suitable secondary air supply. It was found that thrust vectoring could be an effective mean of... 

In this study, we numerically investigate the size effect of a bluff body, embedded inside a combustor, on the formation of carbonaceous nano-particulate matter (PM). The combustor is fed with a jet propulsion fuel. We first evaluate our extended numerical tool by simulating a turbulent kerosene/air nonpremixed flame in a combustor. The achieved results are then compared with those of experiment. The comparisons show that there are good agreements between them. Next, we embed an O-ring type flame holder inside the combustor to change its configuration, i.e., to extend it to a bluff-body burner. Assuming a constant air mass flow rate, we investigate the blockage ratio effects of the burner... 

The use of advanced cycles to take advantage of the gas turbine's thermodynamic characteristics has received increasing attention in recent years. These cycles have been developed for large scale power generation. Due to the powerful abilities of bio-inspired computing techniques such as Genetic Algorithm in locating the optimal (or near optimal) solutions to a given optimization problem, they are widely utilized for determining the parameters of different engineering systems in order to meet the specified performance objectives for a given problem. In order to illustrate the performance of one of these techniques, development and application of it for an engineering problem is presented. In... 

As is known, jet propulsion fuels are rather complex with combustion resulting in a vast range of chemical compounds. So, their real modeling is rather hard and the application of final constructed models is restricted to a narrow band of real propulsion jet fuels. The main objective of this study is to extend suitable surrogate fuel models to reliably predict the combustion and soot characteristics of the equivalent jet propulsion fuel. In this regard, the combustion of proposed surrogate fuels is numerically studied in the above chosen combustion chamber. Of importance, the surrogate fuels should be proposed suitably to represent the correct physical characteristics and the real chemical... 

In this article, an attempt is made to utilize the exhaust gases of a small gas turbine to augment power output through the employment of a thermoacoustic system. A simple gas turbine cycle is selected as the base cycle and it is assumed that the thermoacoustic system is powered only by the waste heat of the base gas turbine. A comprehensive cycle analysis of the integrated gas turbine thermoacoustic engine (IGTTE) is carried out from an energy and exergy point of view. Exergy efficiency and internal exergy efficiency are calculated for the different components of the base gas turbine engine as well as the IGTTE. Value and exergy flow diagrams are used to investigate the possible... 

This paper presents the fuzzy logic computing for the design and implementation of fuel controller for gas turbine engines. For this purpose, a fuzz controller is designed in order to be implemented on an electronic control unit where it is used to drive a servo operated fuel control valve. The fuzzy logic computing approach for different parts of the controller including fuzzification, rule base, inference engine and defuzzification are then described. Finally, computer simulation of the fuzzy controllers integrated with the engine model is performed to investigate the effectiveness of the proposed fuzzy controller on the performance of a turbojet engine. The results are provided to show... 

This work numerically studies the effects of inlet air and fuel turbulators on the thermal behavior of a combustor burning the jet propulsion (JP) (kerosene-surrogate) fuel and its resulting pollutants emission including the nanoparticulate soot aerosols and aromatic compounds. To model the soot formation, the method employs a semi-empirical two-equation model, in which the transport equations for soot mass fraction and soot number density are solved considering soot nanoparticles evolutionary process. The soot nucleation is described using the phenyl route in which the soot is formed from the polycyclic aromatic hydrocarbons. Incorporating a detailed chemical mechanism described by 200...