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Title          
 Decline of the Tip-Jet 
 
Abstract
 One way to power a helicopter rotor is to blow air through the rotor tip. Such helicopters are known as tip-jets and have the potential to be lighter and simpler than conventional helicopters. Tip-jets were widely studied in the 1950s but have not seen production due to low efficiency and very high noise levels. However, based on historical data, a compound configuration which uses tip-jet power only during vertical take-off and landing, and then transitions to an autogiro mode using a propeller for forward thrust has the potential to provide fast, efficient, and reliable flight characteristics, while minimizing noise levels to those encountered in conventional rotorcraft.
 
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Added By - daanish
Subject - Aeronautics and Astronautics
Document Type - Assignment
 
 
   
   

 

Title          
 Modeling and Simulation of Mixing Layer Flows... 
 
Abstract
 Film cooling has been selected for the thermal protection of the composite nozzle extension of the J-2X engine which is currently being developed for the second stage of NASA’s next generation launch vehicle, the Ares I rocket. However,several challenges remain in order to achieve effective film cooling of the nozzle extension and to ensure its safe operation. The extreme complexity of the flow (three-dimensionalwakes, lateral flows, vorticity, and flow separation) makes predicting film cooling performance difficult. There is also a dearth of useful supersonic film cooling data available for engineers to use in engine design and a lack of maturity of CFD tools to quantitatively match supersonic film cooling data. This dissertation advances the state of the art in film cooling by presenting semi-empirical analytical models which improve the basic physical understanding and prediction of the effects of pressure gradients, compressibility and density gradients on film cooling effectiveness. These models are shown to correlate most experimental data well and to resolve several conflicts in the open literature. The core-to-coolant stream velocity ratio, R, and the Kays acceleration parameter, KP, are identified as the critical paramete...
 
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Added By - kdellimo
Subject - Aeronautics and Astronautics
Document Type - PhD Thesis
 
 
   
   

 

Title          
 The Combustion of Aluminum in Solid Rocket Pr... 
 
Abstract
 The trophy piece of technology in any modern rocket system is without question the liquid bi-propellant engine. Despite their sophistication, power, and precision the workhorse responsible for launching men and machines into space is based on solid rocket technology more than 700 years old. The earliest historical use of gunpowder dates back to the 300 B.C where in modern day China bamboo tubes filed with gunpowder were thrown into fires during celebrations, the noise warding away evil spirits. 500 years later in 1232 A.D at the battle of Kai-fung-fu the Chinese military used the first recorded rockets against the invading Mongol Horde. As the Mongols moved through china, they took emerging technologies with them and by 1241 A.D, the rocket had made it to the battlefields of Europe. By 1300 A.D, arsenals around Europe had some rocket technology, based entirely on the use of gunpowder for propulsive motive. A lack of control over rocket trajectories hindered much development by western militaries, who also found the tendency of a misguided missile to start a fire counterproductive. In the Eighteenth century, work had begun on developing a more powerful propellant, and although some progress had been made the independent work of Rob...
 
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Added By - ajayvs
Subject - Aeronautics and Astronautics
Document Type - Term Paper
 
 
   
   

 

Title          
 The Role of Density Gradient in Liquid Rocket... 
 
Abstract
 Experimental and analytical studies were conducted to investigate key physical mechanisms responsible for flame-acoustic coupling during the onset of acoustically driven combustion instabilities in liquid rocket engines (LREs). Controlled experiments were conducted in which a turbulent hydrogen-oxygen (GH2-GO2) diffusion flame, established downstream of a two-dimensional model shear coaxial injector was acoustically forced by a compression driver unit mounted in a transverse direction and excited through a broad range of frequencies (200Hz-2000Hz) and amplitudes. Characteristic interactions between flame and acoustics visualized through OH* and CH* chemiluminescence imaging and dynamic pressure measurements obtained using high frequency dynamic pressure transducers indicated that small acoustic disturbances could be amplified by flame-acoustic coupling under certain conditions leading to substantial modulation in spatial heat release fluctuations. Density gradient between fuel and oxidizer was found to significantly affect the way acoustic waves interacted with density stratified flame fronts. The particular case of an asymmetric flame front oscillation under transverse acoustic forcing indicated that baroclinic vorticity, generat...
 
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Added By - A Ghosh
Subject - Aeronautics and Astronautics
Document Type - PhD Thesis
 
 
   
   

 

Title          
 Plasma Physics 
 
Abstract
 

A whitepaper on plasma physics by Prof. Kalevi Mursula from the university of Oulu, department of physical sciences. Contains a great introduction to this exciting area and a useful list of references. In physics and chemistry, plasma is a gas in which a certain portion of the particles are ionized. The presence of a non-negligible number of charge carriers makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma, therefore, has properties quite unlike those of solids, liquids, or  

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Added By - A Ghosh
Subject - Aeronautics and Astronautics
Document Type - White Paper
 
 
   
   

 

Title          
 Combustion Instability in Liquid Rocket Engin... 
 
Abstract
 Work on liquid rocket engine combustion instabilities began in the early 1940s (Culick and Yang 1995). One of the most critical concepts in liquid rocket combustion instability, that of time lag (as a coordinating factor in influencing organized oscillations in liquid rocket combustion chambers) originated around this time in von Kármán‟s group at the Jet Propulsion Laboratory around 1941 (cf. Summerfield 1951) shortly after oscillations were observed in early tests in liquid rocket engines in the United States. The essential idea was that there existed a finite time delay when an element of propellant entered the combustor and when heat was released from it. This delay controlled the phasing between heat release and pressure oscillations thereby making the system stable or unstable as per Rayleigh‟s criteria. In the years that followed, this model was applied to various studies involving combustion instability in liquid rocket engines. Gunder and Friant (1950), Yachter (1951) and Summerfield (1951) analyzed low frequency chugging instability arising from the interaction between feed system and combustion process using a constant time lag model. Crocco (1951;1952) introduced the time varying combustion time lag and use...
 
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Added By - A Ghosh
Subject - Aeronautics and Astronautics
Document Type - Literature Review
 
 
   
   

 

Title          
 Rayleigh criteria and Combustion Instability 
 
Abstract
 A short literature review on Rayleigh's Criteria is provided. This criteria is widely used in mechanical and aerospace engineering areas to understand the phenomena of combustion instability. In continuously running combustion systems where combustion occurs inside a volume of relatively low losses, small amplitude pressure disturbance and small amplitude heat release fluctuations can couple with each other in a positive feedback loop leading to very large amplitude pressure oscillations often ending up in limit cycle oscillations. Such oscillations are detrimental to the combustion system (power or propulsion) for it exposes the system to large mechanical fatigue, thermal loads and can lead to catastrophic failures.
 
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Added By - A Ghosh
Subject - Aeronautics and Astronautics
Document Type - Literature Review
 
 
   
   

 

Title          
 NOTAR Helicopter 
 
Abstract
 The NOTAR (no tail rotor) patent is an anti-torque system replacement for helicopter tail rotors with a standard configuration. Production models that are currently available with the NOTAR system are the MD Explorer, MD 600N, and the MD 520/530N. This unconventional system implements circulation control around the tail boom (Coanda effect) that allows the tail boom to act as a wing that produces lateral lift allowing the helicopter to hover. Circulation control is being used extensively for improving the aerodynamic characteristics of rotorcraft airfoils. Some benefits of circulation control have increased the lift to drag ratio and lowered the drag coefficient. The absence of a tail rotor is very beneficial for many reasons. While on the ground, there is no invisible tail rotor disk that ground personnel or (de)boarding passengers can walk into. While in hover, trees are of no concern for the rotor-less tail boom. The NOTAR system is not as susceptible as a tail rotor to foreign object interference, such as rocks or other thrown projectiles. NOTAR helicopters have decreased decibel (db) output, and have reasonable maintenance requirements. This paper will give a brief overview of the circulation control technology used on the NO...
 
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Added By - hareen
Subject - Aeronautics and Astronautics
Document Type - Assignment
 
 
   
   

 

Title          
 Hummingbird Flight 
 
Abstract
 This paper will give a brief explanation about the kinematics and the aerodynamics of the hovering flight achieved by hummingbirds and other hovering insects. The paper will be presented in two parts. The first part will deal with the kinematics of hovering bird/insects. The second part will discuss the aerodynamics of hovering flight.
 
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Added By - hareen
Subject - Aeronautics and Astronautics
Document Type - Assignment
 
 
   
   

 

Title          
 Coefficient of Thermal Expansion and Thermal ... 
 
Abstract
 The surface temperature and heat flux measurements from the arc jet testing are used to determine the TPS material’s thermal conductivity. To further validate a TPS material a second thermal property is measured.That is the coefficient of thermal expansion (CTE).These two properties are combined with the mechanical properties of the material into a metric for the relative robustness of the material called the Thermal Shock Parameter (RT)
 
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Added By - sidpatel
Subject - Aeronautics and Astronautics
Document Type - White Paper
 
 
   
   

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