Engineering Commons^™

Direct Simulation And Reduced-Order Modeling Of Premixed Flame Response To Acoustic Modulation, Zheng Qiao

Theses and Dissertations

This dissertation introduces a general, predictive and cost-efficient reduced-order modeling (ROM) technique for characterization of flame response under acoustic modulation. The model is built upon the kinematic flame model–G-equation to describe the flame topology and dynamics, and the novelties of the ROM lie in i) a procedure to create the compatible base flow that can reproduce the correct flame geometry and ii) the use of a physically-consistent acoustic modulation field for the characterization of flame response. This ROM addresses the significant limitations of the classical kinematic model, which is only applicable to simple flame configurations and relies on ad-hoc models …

Development Of A Converging-Channel Drop Tower For Sphere Symmetric Isolated Single Droplet Combustion, Nicholas Alexander Demaio

Theses and Dissertations

The dawn of a new Space Age is upon us; Microgravity combustion of hydrocarbon fuels is a popular method of research and characterization. This allows for a one-dimensional analysis by suppressing the buoyancy forces produced by gravity and the large temperature differential between the flame boundary and the surrounding air. The current testing methods are expensive and require extensive preparation on the researchers behalf. There is a need to investigate an alternative method that is inexpensive, repeatable, and comparable to the other approaches that coincides with the literature.

A low-cost converging-channel drop tower was designed and fabricated for sphero-symmetric single …

Detonation Confinement In A Radial Rotating Detonation Engine, Kavi Muraleetharan

Theses and Dissertations

Radial Rotating Detonation Engines (RRDE) have provided an opportunity for use of a pressure-gain combustor in a more compact form compared to an axial RDE. A successfully tested RRDE has operated over a wide range of test conditions and produced detonation modes with one, two, and three waves. The presence of multiple waves located the detonation waves to the outer radius, while one wave modes operated closer to the inner radius. Locating the detonation wave closer to the inner diameter resulted in less time for combustion prior to the radial turbine. Subsequently, this tended to decrease efficiency. To attempt to …

Design And Analysis Of A Compact Combustor For Integration With A Jetcat P90 Rxi, Daniel Holobeny

Theses and Dissertations

Ultra Compact Combustors are a novel approach to modern gas turbine combustor designs that look to reduce the overall combustor length and weight. A previous study integrated an Ultra Compact Combustor into a JetCat P90 RXi turbine engine and achieved self-sustained operation with a length savings of 33% relative to the stock combustor. However, that combustor could not operate across the full stock engine performance range due to flameout at increased mass ow rates as reactions were pushed out of the primary zone. To ensure reactions stayed in the primary zone, a new design with a larger combustor volume was …

Flow Behavior In Radial Rotating Detonation Engines, Scott A. Boller

Theses and Dissertations

Recent progress has been made in demonstrating Radial Rotating Detonation Engine (RRDE) technology for use in a compact Auxiliary Power Unit with a rapid response time. Investigation of RRDEs also suggests an increase in stable operating range, which is hypothesized to be due to the additional degree of freedom in the radial direction which the detonation wave can propagate. This investigation seeks to determine if the detonation wave is in fact changing its radial location. High speed photography was used to capture chemiluminescence of the detonation wave within the channel to examine its radial location, which was found to vary …

Reconstruction Of The 3d Temperature And Species Concentration Spatial Distribution Of A Jet Engine Exhaust Plume Using An Infrared Fourier Transform Spectrometer Hyperspectral Imager, Mason D. Paulec

Theses and Dissertations

The measurement of combustion byproducts is useful for determining pollution of any fuel burning application, efficiency of combustion, and determining detectability of aircraft exhausts. Both intrusive and non-intrusive techniques have been utilized to measure these quantities. For the majority of the non-intrusive techniques, the absorption and emission spectra of the gases are utilized for measurements. For this research, the use of the Telops Infrared Fourier Transform Spectrometer (IFTS) Hyperspectral Imager (HSI) was explored within the scope of combustion diagnostic methods, as an option for remote measurements of a jet turbine to determine concentration of species and temperature of the combustion …

Tunable Diode Laser Absorption Spectroscopy Verification Analysis For Use In The Combustion Optimization And Analysis Laser Laboratory, Christina R. Serianne

Theses and Dissertations

The AFIT Combustion Optimization and Analysis Laser (COAL) laboratory has state-of-the-art laser diagnostic capability for combustion process. The research for this thesis served to enhance the COAL lab's capability. Currently, there are no known commercially available tunable diode lasers that produce Ultra-Violet radiation required for this analysis. Sum-frequency generation at 313.5 nm was utilized for high speed OH absorption and temperature measurements at a rate of 2kHz. The Tunable Diode Laser Absorption Spectroscopy system was validated by comparison with theoretical and well characterized experimental data by operating the system over a wide range of conditions for an H2 laminar flame …

Pylon Effects On A Scramjet Cavity Flameholder Flowfield, Andrew B. Freeborn

Theses and Dissertations

Cavity flameholders in supersonic combustion ramjet (scramjet) combustors, while effective, fail to take advantage of the full combustor volume. Adding a pylon to the leading edge of a cavity flameholder generates a flowfield increasing mass exchange between the cavity and main combustor flow, increasing the mixing interface between flameholder products and main combustor flow, and exhibiting minimal Reynolds number effects. To demonstrate this modified flowfield driven by supersonic expansion behind the pylon, pylon-cavity flameholder flowfield data were obtained through a combination of wind tunnel experimentation and steady-state computational fluid dynamics (CFD). Flowfield effects of the pylon-cavity were examined at a …

Validation Of The Afit Small Scale Combustion Facility And Oh Laser-Induced Fluorescence Of An Atmospheric Laminar Premiext Ed Flame, Stephen J. Koether

Theses and Dissertations

Construction in the AFIT combustion facility is complete and the objective of this report is to explain the steps taken to make the laboratory operational. The infinite radius Ultra-Compact Combustor (UCC) sectional model has been delivered and is fully installed with all fuel, air and instrument lines. Every major system in the lab has been tested and is functioning properly. Laboratory operating procedure has been established to ensure both safety and continuity in experimental results. Finally, the lab has been certified through official safety channels and combustion experiments are underway. The unique capability of the AFIT combustion laboratory is the …

Design, Construction, And Validation Of The Afit Small Scale Combustion Facility And Section Model Of The Ultra-Compact Combustor, Wesley S. Anderson

Theses and Dissertations

The AFIT small-scale combustion facility is complete and its first experiment designed and built. Beginning with the partially built facility, detailed designs have been developed to complete the laboratory in order to run small-scale combustion experiments at atmospheric pressure. A sectional model of the Ultra-Compact Combustor has also been designed and built. Although the lab's specific design intent was to study the UCC's cavity-vane interaction, facility flexibility has also been maintained for future work. The design enabled the completion of liquid fuel and air delivery systems, power and control systems, and test equipment. The design includes failsafe operation, remote control, …

Performance Measurements Of Direct Air Injection In A Cavity-Based Flameholder For A Supersonic Combustor, Scott G. Edens

Theses and Dissertations

For several years the Air Force Research Lab Propulsion Directorate has been studying the difficulties in fueling supersonic combustion ramjet engines with hydrocarbon based fuels. Recent investigations have focused on the use of direct air injection into a directly-fueled cavity-based flameholder. Direct air injection has been shown qualitatively to be a valuable tool for improving cavity combustion. Little quantitative data is available that characterizes the performance of cavity-based flameholders. The objective of this research was to quantitatively determine the specific advantages and disadvantages of the direct air injection scheme. This was accomplished via intrusive probing into a supersonic free stream …