Matching Items (30)

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Design of Rocket Engine Nozzle Ejectors

Description

This work describes the numerical process developed for use of rocket engine nozzle ejectors. Ejector nozzles, while applied to jet engines extensively, have not been applied to rockets, and have

This work describes the numerical process developed for use of rocket engine nozzle ejectors. Ejector nozzles, while applied to jet engines extensively, have not been applied to rockets, and have great potential to improve the performance of endoatmospheric rocket propulsion systems. Utilizing the low pressure, high velocity flow in the plume, this secondary structure entrains a secondary mass flow to increase the mass flow of the propulsion system. Rocket engine nozzle ejectors must be designed with the high supersonic conditions associated with rocket engines. These designs rely on the numerical process described in this paper.

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  • 2014-05

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Design of a Gravity-Fed Hydrodynamic Testing Tunnel

Description

The purpose of this project is to determine the feasibility of a water tunnel designed to meet certain constraints. The project goals are to tailor a design for a given

The purpose of this project is to determine the feasibility of a water tunnel designed to meet certain constraints. The project goals are to tailor a design for a given location, and to produce a repeatable design sizing and shape process for specified constraints. The primary design goals include a 1 m/s flow velocity in a 30cm x 30cm test section for 300 seconds. Secondary parameters, such as system height, tank height, area contraction ratio, and roof loading limits, may change depending on preference, location, or environment. The final chosen configuration is a gravity fed design with six major components: the reservoir tank, the initial duct, the contraction nozzle, the test section, the exit duct, and the variable control exit nozzle. Important sizing results include a minimum water weight of 60,000 pounds, a system height of 7.65 meters, a system length of 6 meters (not including the reservoir tank), a large shallow reservoir tank width of 12.2 meters, and height of 0.22 meters, and a control nozzle exit radius range of 5.25 cm to 5.3 cm. Computational fluid dynamic simulation further supports adherence to the design constraints but points out some potential areas for improvement in dealing with flow irregularities. These areas include the bends in the ducts, and the contraction nozzle. Despite those areas recommended for improvement, it is reasonable to conclude that the design and process fulfill the project goals.

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Date Created
  • 2014-05

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Validation and Refinement of a Drag Build Up Method for Unmanned Aerial Vehicles

Description

The emerging market for unmanned aerial vehicles, or UAV's, demands the development of effective design tools for small-scale aircraft. This research seeks to validate a previously developed drag build-up method

The emerging market for unmanned aerial vehicles, or UAV's, demands the development of effective design tools for small-scale aircraft. This research seeks to validate a previously developed drag build-up method for small air vehicles. Using the method, a drag prediction was made for an off-the-shelf, remotely controlled aircraft. The Oswald efficiency was predicted to be 0.852. Flight tests were then conducted using the RC plane, and the aircraft performance data was compared with the predicted performance data. Although there were variations in the data due to flight conditions and equipment, the drag build up method was capable of predicting the aircraft's drag. The experimental Oswald efficiency was found to be 0.863 with an error of 1.27%. As for the CDp the prediction of 0.0477 was comparable to the experimental value of 0.0424. Moving forward this method can be used to create conceptual designs of UAV's to explore the most efficient designs, without the need to build a model.

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Date Created
  • 2014-05

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Characterization of Helicopter Blade Wake Phenomena

Description

The purpose of this investigation is to computationally investigate instabilities appearing in the wake of a simulated helicopter rotor. Existing data suggests further understanding of these instabilities may yield design

The purpose of this investigation is to computationally investigate instabilities appearing in the wake of a simulated helicopter rotor. Existing data suggests further understanding of these instabilities may yield design changes to the rotor blades to reduce the acoustic signature and improve the aerodynamic efficiencies of the aircraft. Test cases of a double-bladed and single-bladed rotor have been run to investigate the causes and types of wake instabilities, as well as compare them to the short wave, long wave, and mutual inductance modes proposed by Widnall[2]. Evaluation of results revealed several perturbations appearing in both single and double-bladed wakes, the origin of which was unknown and difficult to trace. This made the computations not directly comparable to theoretical results, and drawing into question the physical flight conditions being modeled. Nonetheless, they displayed a wake structure highly sensitive to both computational and physical disturbances; thus extreme care must be taken in constructing grids and applying boundary conditions when doing wake computations to ensure results relevant to the complex and dynamic flight conditions of physical aircraft are generated.

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  • 2014-12

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Modeling of Autonomous Quadcopter Flight

Description

The purpose of this honors thesis was to create a quadcopter equation of motion software model in order to develop a control system to make the quadcopter autonomous. This control

The purpose of this honors thesis was to create a quadcopter equation of motion software model in order to develop a control system to make the quadcopter autonomous. This control system was developed using Matlab and Simulink, and the aspects of the quadcopter's flight that were chosen to be controlled were the roll angle, pitch angle, and height of the quadcopter. Upon the completion of this control system model, the actual quadcopter was to be constructed, flown, and used to collect experimental data for comparison to the model. However, the hardware was never made available due to back order problems, and so unfortunately no experimental data from actual test flights was able to be gathered and compared to the Simulink control system model. None the less, the final Simulink model is still accurate because the actual geometry of the chosen quadcopter was used during simulation (including the moments of inertia and moment arm lengths). To begin, background research into quadcopter design is presented to give insight into the progress that has been made in the design of this type of aircraft. The equations of motion for the quadcopter considered in the control system are then derived through the use of twelve state variables. The Simulink model for the open loop system was then constructed in a fashion that converts the change in rotor thrust to the associated orientation angles of the quadcopter. Linear approximations were then used to distinguish the open loop transfer functions for each controlled variable (roll angle, pitch angle, and height), and compensators were designed for the control system in order to produce a natural frequency and damping that allowed for a 5% settling time of approximately two seconds.

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  • 2013-05

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Identification of the Origins of Blade-Vortex Interaction (BVI) Noise in Helicopters

Description

One of the leading concerns regarding the commercial and military applications of rotary wing powered vehicles is the issue of blade-vortex interaction (BVI) noise occurring during forward descent. This impulsive

One of the leading concerns regarding the commercial and military applications of rotary wing powered vehicles is the issue of blade-vortex interaction (BVI) noise occurring during forward descent. This impulsive noise-generating phenomenon occurs due to the close proximity and interference between the main rotor blades and the wake vortices generated by the rotor blades from previous revolutions. Throughout the descent phase of a helicopter in forward flight, the rotating blades pass through these induced vortices, thus generating an impulsive "slap" noise that is characteristic of the common sound associated with helicopter flight among the general population. Therefore, parameterization of the variables of interest that affect BVI noise generation will allow for thorough analysis of the origins of the noise and open pathways for innovation that may offer significant improvements in acoustic performance. Gaining an understanding of the factors that govern the intensity of the BVI acoustic signature provides a strong analytical and experimental basis for enhanced rotor blade design.

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  • 2016-05

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Effect of Winglet Morphology on Variable Range Commercial Aircraft

Description

Winglets and wingtip structures have been prominent in commercial aircraft design in the past few decades. These designs are known to reduce the induced drag on an aircraft wing, thus

Winglets and wingtip structures have been prominent in commercial aircraft design in the past few decades. These designs are known to reduce the induced drag on an aircraft wing, thus increasing its overall fuel efficiency. Several different winglet designs exist, and little reason is offered as to why different winglet designs are used in practice on different aircraft, especially those of variable range. This research tests existing winglets (no winglet, raked winglet, flat plate winglet, blended winglet, and wingtip fence) on a span-constrained wing planform design both computationally and in the wind tunnel. While computational tests using a vortex lattice code indicate that the wingtip fence minimizes induced drag and maximizes lift to drag ratio in most cases, wind tunnel tests show that at different lift coefficients and angles of attack, the raked winglet and blended winglet optimize the aerodynamic efficiency at incompressible flow velocities. Applying the wing aerodynamic data to existing variable range commercial aircraft, mission performance analysis is run on a Bombardier CRJ200, Airbus A320, and Airbus A340-300. By comparing flight lift coefficients in cruise for these aircraft to the lift coefficients at which winglets minimize drag in compressible flows, optimal winglet designs are chosen. It is found that the short range CRJ200 is best equipped with a flat plate or blended winglet, the medium range A320 can reduce drag with either a wingtip fence, raked winglet, or blended winglet, and the long range A340 performs best with a flat plate, blended, or raked winglet. Overall, despite the discrepancy in winglet selection depending on which experimental results are used, it is clear that addition of a winglet to a span-constrained wing is beneficial in that it reduces induced drag and therefore increases overall fuel efficiency.

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  • 2017-05

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Monatomic Gas Effects on Brayton Cycle Propulsion and Power Systems

Description

Monatomic gases are ideal working mediums for Brayton cycle systems due to their favorable thermodynamic properties. Closed Brayton cycle systems make use of these monatomic gases to increase system performance

Monatomic gases are ideal working mediums for Brayton cycle systems due to their favorable thermodynamic properties. Closed Brayton cycle systems make use of these monatomic gases to increase system performance and thermal efficiency. Open Brayton cycles, on the other hand, operate with primarily diatomic and polyatomic gases from air and combustion products, which have less favorable properties. The focus of this study is to determine if monatomic gases can be utilized in an open Brayton cycle system, in a way that increases the overall performance, but is still cost effective.
Two variations on open cycle Brayton systems were analyzed, consisting of an “airborne” thrust producing propulsion system, and a “ground-based” power generation system. Both of these systems have some mole fraction of He, Ne, or Ar injected into the flow path at the inlet, and some fraction of monatomic gas recuperated and at the nozzle exit to be re-circulated through the system. This creates a working medium of an air-monatomic gas mixture before the combustor, and a combustion products-monatomic gas mixture after combustor. The system’s specific compressor work, specific turbine work, specific net power output, and thermal efficiency were analyzed for each case. The most dominant metric for performance is the thermal efficiency (η_sys), which showed a significant increase as the mole fraction of monatomic gas increased for all three gas types. With a mole fraction of 0.15, there was a 2-2.5% increase in the airborne system, and a 1.75% increase of the ground-based system. This confirms that “spiking” any open Brayton system with monatomic gas will lead to an increase in performance. Additionally, both systems showed an increase in compressor and turbine work for a set temperature difference with He and Ne, which can additionally lead to longer component lifecycles with less frequent maintenance checks.
The cost analysis essentially compares the operating cost of a standard system with the operating cost of the monatomic gas “spiked” system, while keeping the internal mass flow rate and total power output the same. This savings is denoted as a percent of the standard system with %NCS. This metric lumps the cost ratio of the monatomic gas and fuel (MGC/FC) with the fraction of recuperated monatomic gas (RF) into an effective cost ratio that represents the cost per second of monatomic gas injected into the system. Without recuperation, the results showed there is no mole fraction of any monatomic gas type that yields a positive %NCS for a reasonable range of current MGC/FC values. Integrating recuperation machinery in an airborne system is hugely impractical, effectively meaning that the use of monatomic gas in this case is not feasible. For a ground-based system on the other hand, recuperation is much more practical. The ground-based system showed that a RF value of at least 50% for He, 89% for Ne, and 94% for Ar is needed for positive savings. This shows that monatomic gas could theoretically be used cost effectively in a ground-based, power-generating open Brayton system. With an injected monatomic gas mole fraction of 0.15, and full 100% recuperation, there is a net cost savings of about 3.75% in this ground-based system.

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  • 2017-05

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A Modeling System to Understand the Design and Performance of a Two Spool Gas Turbine Engine

Description

The purpose of my Honors Thesis was to generate a tool that could be implemented by Aerospace students at Arizona State University. This tool was created using MatLab which is

The purpose of my Honors Thesis was to generate a tool that could be implemented by Aerospace students at Arizona State University. This tool was created using MatLab which is the current program students are using. The modeling system that was generated goes step-by-step through the flow of a two spool gas turbine engine. The code was then compared to an ideal case engine with predictable values. It was found to have less than a 3 percent error for these parameters, which included optimal net work produced, optimal overall pressure ratio, and maximum pressure ratio. The modeling system was then run through a parametric analysis. In the first case, the bypass ratio was set to 0 and the freestream Mach number was set to 0. The second case was with a bypass ratio of 0 and fresstream Mach number of 0.85. The third case was with a bypass ratio of 5 and freestream Mach number of 0. The fourth case was with a bypass ratio of 5 and fresstream Mach number of 0.85. Each of these cases was run at various overall pressure ratios and maximum Temperatures of 1500 K, 1600 K and 1700 K. The results modeled the behavior that was expected. As the freestream Mach number was increased, the thrust decreased and the thrust specific fuel consumption increased, corresponding to an increase in total pressure at the combustor inlet. It was also found that the thrust was increased and the thrust specific fuel consumption decreased as the bypass ratio was increased. These results also make sense as there is less airflow passing through the engine core. Finally the engine was compared to two real engines. Both of which are General Electric G6 series engines. For the 80C2A3 engine, the percent difference between thrust and thrust specific fuel consumption was less than five percent. For the 50B, the thrust was below a two percent difference, but the thrust specific fuel consumption clearly provided inaccurate results. This could be caused by the lack of inputs provided by General Electric. The amount of fuel injected is largely dependent on the maximum temperature which is not available to the public. Overall, the code produces comparable results to real engines and can display how isolating and modifying a certain parameter effects engine performance.

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  • 2015-05

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Analysis of the Reverse Osmosis Process

Description

This paper considers the state of desalination today and explores improvement of the reverse osmosis process via exergy analysis. Various methods of desalination in place today were explored, along with

This paper considers the state of desalination today and explores improvement of the reverse osmosis process via exergy analysis. Various methods of desalination in place today were explored, along with the proportion of each of those methods in use today. From literature reviews, it was found the reverse osmosis (RO) and multi-stage flash (MSF) desalination were the main methods of desalination in use today. Desalination is an energy intensive process and so this paper aimed to address this issue in three ways: by exploring various coupling with renewable energy sources, carrying out an exergy analysis on the MSF and RO processes, and finally exploring conceptual methods of interest. It was found that concentrated solar power was best suited for the MSF process, since the MSF process require direct heat. Wind energy was best suited for the RO process, since RO was less energy intensive and so could account for wind variability. The exergy analysis demonstrated very low second law efficiency for both desalination processes (~4%), with most of the exergy being destroyed in the separation process (~75%). The RO process also demonstrated a higher efficiency and lower exergy destruction, reinforcing the conlcusion that RO is the less energy intensive of the two. Based on the analysis, it was found throttling valves account for the next highest exergy destruction after the separation process. An alternate plant design was proposed to fully utilize wasted pressure, which resulted in less energy consumption. Finally, two conceptual methods, a mobile desalination plant and the Hybrid process, were explored that could potentially make the RO process a more valuable asset to society and more economically viable with a higher yield

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Date Created
  • 2015-05