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Propulsion and Power

Air Force Institute of Technology

2009

Articles 1 - 9 of 9

Full-Text Articles in Engineering

Discrete Film Cooling In A Rocket With Curved Walls, Jonathan F. Mccall Dec 2009

Discrete Film Cooling In A Rocket With Curved Walls, Jonathan F. Mccall

Theses and Dissertations

This study quantified the effects of discrete wall-based film cooling in a rocket with curved walls. Simulations and experiments showed decreasing with wall radius of curvature, holding jet diameter constant, improves net heat flux reduction (NHFR) and adiabatic effectiveness (η) for 90˚ compound injected cylindrical jets, though η is reduced at the highest curvature. NHFR and η improved further with a high favorable stream-wise pressure gradient (K=2.1x10-5) at all tested blowing ratios, but were affected little by a high density ratio (DR=1.76) using carbon dioxide as the coolant. Experiments were run at a Reynolds number of 31K and …

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Flow Visualization Study Of Passive Flow Control Features On A Film-Cooled Turbine Blade Leading Edge, Daniel R. Carroll Dec 2009

Flow Visualization Study Of Passive Flow Control Features On A Film-Cooled Turbine Blade Leading Edge, Daniel R. Carroll

Theses and Dissertations

A flow visualization study was conducted on a model of a film-cooled turbine blade leading edge in a closed-loop water channel at ReD = 30k. The model consisted of an 8.89 cm diameter half-cylinder with flat afterbody joined at the ninety degree point. A single radial coolant hole (dc / D = 0.054) drilled 21.5° from the stagnation line, angled 20° to the surface and 90° to the flow direction generated a coolant jet transverse to the freestream. Water channel testing assessed the hydrodynamic effects of 16 passive flow control features, to include a variety of …

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Laser-Induced Fluorescence And Synthetic Jet Fuel Analysis In The Ultra Compact Combustor, Aaron C. Drenth Dec 2009

Laser-Induced Fluorescence And Synthetic Jet Fuel Analysis In The Ultra Compact Combustor, Aaron C. Drenth

Theses and Dissertations

The Ultra-Compact Combustor (UCC) is currently under investigation at the Air Force Institute of Technology (AFIT) and Air Force Research Laboratory’s Propulsion Directorate. The combustor is a small-scale, axi-symmetric, atmospheric pressure, laboratory combustor with an outer circumferential cavity in which the flame is stabilized by a highly accelerated swirled flow. UCCs will enable aero gas turbine reheat cycle engines and significantly shorten conventional aero gas turbine engines. The experiments of this work utilized the AFIT small-scale combustion diagnostics facility, investigating a sector model of the UCC. The research objectives were to perform an addition to the COAL lab laser diagnostic …

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Cavity Coupled Aeroramp Injector Combustion Study, Dell T. Olmstead Jun 2009

Cavity Coupled Aeroramp Injector Combustion Study, Dell T. Olmstead

Theses and Dissertations

The difficulties with fueling of supersonic combustion ramjet engines with hydrocarbon based fuels presents many challenges that are currently being tackled by the Air Force Research Lab Propulsion Directorate Aerospace Propulsion Division. As the scramjet engine designs are scaled up, the need for a better solution to supersonic mixing has led to the development of many different styles of fuel injection. An aerodynamic ramp injector has been shown to have a quantitative improvement over a physical ramp while still achieving desirable mixing characteristics. The objectives for this research was quantifying the performance and operability implications of replacing four 15 degree …

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Fuel Composition And Performance Analysis Of Endothermically Heated Fuels For Pulse Detonation Engines, Christopher A. Stevens Mar 2009

Fuel Composition And Performance Analysis Of Endothermically Heated Fuels For Pulse Detonation Engines, Christopher A. Stevens

Theses and Dissertations

Waste heat from a pulse detonation engine (PDE) was extracted via concentric, counter flow heat exchangers to produce supercritical pyrolytic conditions for JP-7 and JP-8 fuels. A sampling system and method was utilized to collect samples of reacted fuel to be extracted during steady state operation. Samples were collected over a range of heat exchanger exit temperatures from 820 K (1016° F) to 940 K (1232 degrees F) and for two sets of heat exchangers, one set coated with zeolite catalyst and one set left uncoated. Variation in fuel mass flow rate required the calculation of heat addition as an …

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Critical Design Parameters For Pylon-Aided Gaseous Fuel Injection Upstream Of A Flameholding Cavity, Mitchell R. Pohlman Mar 2009

Critical Design Parameters For Pylon-Aided Gaseous Fuel Injection Upstream Of A Flameholding Cavity, Mitchell R. Pohlman

Theses and Dissertations

The Air Force Institute of Technology and the AFRL are investigating means to increase the efficiency of fuel-air mixing into supersonic flow. Previous work has shown much promise in increasing the penetration and mixing of a fuel-air mixture into the freestream by injecting fuel behind small triangular pylons. Pylon-aided fuel injection has also shown to lift the fuel plume off the combustor floor; this floor-gap prevents the ignition of fuel seeded in the boundary layer. In this paper twenty-one pylons of varying widths, heights, and lengths were examined in four specific test matrices within a CFD environment. Pylons in test …

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Ceramic Matrix Composite Characterization Under A Combustion And Loading Environment, Andrew R. Nye Mar 2009

Ceramic Matrix Composite Characterization Under A Combustion And Loading Environment, Andrew R. Nye

Theses and Dissertations

Lightweight materials that can withstand high temperatures and corrosive environments are constantly sought after in the aerospace industry, typically for Gas Turbine Engine (GTE) application. These materials need to retain their strength throughout the long service period they would see in the combustor and turbine components of a GTE. One material that is ideal for these types of applications is an oxide/oxide Ceramic Matrix Composite (CMC). The fatigue behavior of the oxide/oxide CMC NextelTM 720/Alumina (N720/A) was investigated in a unique high temperature environment. N720/A consisted of an 8-harness satin weave of NextelTM aluminum oxide/silicon oxide fibers bound …

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Hyperspectral Imaging Of A Turbine Engine Exhaust Plume To Determine Radiance, Temperature, And Concentration Spatial Distributions, Spencer J. Bowen Mar 2009

Hyperspectral Imaging Of A Turbine Engine Exhaust Plume To Determine Radiance, Temperature, And Concentration Spatial Distributions, Spencer J. Bowen

Theses and Dissertations

The usefulness of imaging Fourier transform spectroscopy (IFTS) when looking at a rapidly varying turbine engine exhaust scene was explored by characterizing the scene change artifacts (SCAs) present in the plume and the effect they have on the calibrated spectra using the Telops, Inc.-manufactured Field-portable Imaging Radiometric Spectrometer Technology, Midwave Extended (FIRST-MWE). It was determined that IFTS technology can be applied to the problem of a rapidly varying turbine engine exhaust plume due to the zero mean, stochastic nature of the SCAs, through the use of temporal averaging. The FIRST-MWE produced radiometrically calibrated hyperspectral datacubes, with calibration uncertainty of 35% …

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An Analysis Of Multiple Configurations Of Next-Generation Cathodes In A Low Power Hall Thruster, John E. Rotter Mar 2009

An Analysis Of Multiple Configurations Of Next-Generation Cathodes In A Low Power Hall Thruster, John E. Rotter

Theses and Dissertations

The research presented here is an effort to integrate an existing hollow cathode design with a low power production Hall thruster in multiple geometries. Both externally- and internally-mounted cathodes were fabricated and operated in conjunction with a Busek BHT-1500 Hall thruster. Three insert materials were evaluated; Cerium Hexaboride (CeB6), Lanthanum Hexaboride (LaB6), and impregnated tungsten. The thruster was operated at a single operating condition for all testing. The operating specifications for the discharge were 300 V and 2.25 A, giving a total power of 675 W. The boride-based cathodes were tested in both geometries while the tungsten-based cathode was only …

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