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Articles 1 - 30 of 48
Full-Text Articles in Heat Transfer, Combustion
Investigation Of The Flow Field Morphology Of Film Cooling In Supersonic Flow, Umberto Sandri, Massimiliano Ferro, Alessio Picchi, Antonio Andreini, Bruno Facchini, Marc D. Polanka
Investigation Of The Flow Field Morphology Of Film Cooling In Supersonic Flow, Umberto Sandri, Massimiliano Ferro, Alessio Picchi, Antonio Andreini, Bruno Facchini, Marc D. Polanka
Faculty Publications
Film cooling is widely implemented in highly thermally stressed gas turbine components. Its performance has been extensively investigated for several decades and many results are available in the literature. In conventional gas turbines, regions of supersonic flow are not prevalent and should generally be avoided. For this reason, results relative to film cooling in supersonic flow are limited. Nevertheless, a new interest related to Rotating Detonation Combustors (RDC) and supersonic turbines is growing. The implementation of those engine components in a gas turbine is likely to need film cooling for thermal protection. In this context, it becomes crucial to gain …
Enhancing Crossflow Dynamics Through The Gas Injection From Multiple Cylinders, Sahrish B. Naqvi, Sadia Siddiqa, Maciej Matyka, Rama S. R. Gorla, Md. Mamum Molla
Enhancing Crossflow Dynamics Through The Gas Injection From Multiple Cylinders, Sahrish B. Naqvi, Sadia Siddiqa, Maciej Matyka, Rama S. R. Gorla, Md. Mamum Molla
Faculty Publications
We investigate unsteady, two-dimensional laminar fluid flow around cylinders, focusing on understanding the impact of injecting methane gas through two diametrically opposite arcs on the cylinder in the crossflow of the second fluid. This study encompasses applications in mixing and dispersion, which are crucial in various technological and natural processes. Our analysis addresses velocity field’s contribution to the spatiotemporal distribution of transported quantities. We observed that mixing induces a transition from laminar to turbulent flow. Depending on the injected-to-crossflow velocity ratios, the wake vortices downstream of cylinder arrays separate from or connect to the injected gas. This phenomenon significantly impacts …
Effects Of Fluid Slip On Heat Transfer In The Thin Film Region In A Microchannel, Rama S. R. Gorla, John Brewer, Abdeel Roman
Effects Of Fluid Slip On Heat Transfer In The Thin Film Region In A Microchannel, Rama S. R. Gorla, John Brewer, Abdeel Roman
Faculty Publications
A theoretical study was undertaken to investigate the influence of interfacial slip on evaporation of a thin liquid film in a microfluidic channel. The disjoining pressure and the capillary force which drive the liquid flow at the liquid-vapor interface in thin film region are adopted. The evaporating thin film region is an extended meniscus beyond the apparent contact line at a liquid/solid interface. Thin film evaporation plays a key role in a highly efficient heat pipe. Slip length was found to affect the heat transfer in the microchannel by altering the thin film geometry.
Turbine Cooling System With Energy Separation, James L. Rutledge, Matthew N. Fuqua, Carol M. Bryant
Turbine Cooling System With Energy Separation, James L. Rutledge, Matthew N. Fuqua, Carol M. Bryant
AFIT Patents
A method and system for cooling an engine and/or vehicle using energy separation is disclosed herein. An energy separation device is operable for separating a compressed gaseous coolant stream into a first relatively cooler coolant flow stream and a second relatively hotter coolant flow stream. The relative cooler coolant flow stream is directed to a first region requiring increased cooling and the relative hotter coolant flow stream is directed to a second region requiring lower cooling than the first region in the engine or vehicle.
Investigation Of The Effect Of Internal Reynolds Number And Advective Capacity Ratio On Gas Turbine Film Cooling Parameters, John P. Di Lella
Investigation Of The Effect Of Internal Reynolds Number And Advective Capacity Ratio On Gas Turbine Film Cooling Parameters, John P. Di Lella
Theses and Dissertations
The desire for more powerful engines drives higher turbine inlet temperatures and a greater need to cool them. Experimentalists attempt to match cooling effectiveness between two conditions by matching several non-dimensional parameters, one of which is the coolant warming factor. The first investigation of this study examines the effect of the internal Reynolds number and the advective capacity ratio on the coolant warming factor by making use of a computational model and four different gases. It indicates the non-negligible and opposing effects of external convection and solid conduction on the coolant warming factor at matched internal Reynolds number and advective …
Detonation Confinement In A Second-Generation Radial Rotating Engine, John T. Ursino
Detonation Confinement In A Second-Generation Radial Rotating Engine, John T. Ursino
Theses and Dissertations
In recent years, Rotating Detonation Engines (RDEs) have been coupled with turbomachinery to harness the benefits of detonative combustion. A novel type of RDE, referred to as the disk or Radial RDE (RRDE), has been developed in pursuit of length and weight savings compared to a traditional annular flow RDE. This design includes a disk-shaped device within which reactants flow from the outer radius, detonate, and exit the inner radius. In this paper several modifications have been made to a previously tested RRDE to address issues that arose with the original design. The combustion chamber diameter has been increased to …
Turbine Cooling System With Energy Separation, James L. Rutledge, Matthew Fuqua, Carol M. Bryant
Turbine Cooling System With Energy Separation, James L. Rutledge, Matthew Fuqua, Carol M. Bryant
AFIT Patents
A method and system for cooling an engine and/or vehicle using energy separation is disclosed herein. An energy separation device is operable for separating a compressed gaseous coolant stream into a first relatively cooler coolant flow stream and a second relatively hotter coolant flow stream. The relative cooler coolant flow stream is directed to a first region requiring increased cooling and the relative hotter coolant flow stream is directed to a second region requiring lower cooling than the first region in the engine or vehicle.
Disk Engine With Circumferential Swirl Radial Combustor, Brian Bohan, Marc Polanka, Bennett Staton
Disk Engine With Circumferential Swirl Radial Combustor, Brian Bohan, Marc Polanka, Bennett Staton
AFIT Patents
A disk engine and system configured to provide high power at a reduced axial length is disclosed herein. The disk engine includes a radial compressor, a compressor discharge manifold positioned circumferentially about compressor, a combustion chamber positioned within the discharge manifold and a radial turbine positioned radially inward of the combustion chamber.
Injection Studies On A Small-Scale Rotating Detonation Engine With Improved Flow Control, Jonathan J. Wyatt
Injection Studies On A Small-Scale Rotating Detonation Engine With Improved Flow Control, Jonathan J. Wyatt
Theses and Dissertations
The Rotating Detonation Engine (RDE) has gained increasing attention in recent years for its potential advantages over typical deflagration combustion. A Micro-RDE design with an outer diameter of 28mm operating on Nitrous Oxide and Ethylene was recently developed, which stretched the limits of small-scale detonation engines. The testing on this rig has shown a stable one wave mode detonation with frequencies reaching 16.8 kHz. Key parameters that influence the detonation wave mode are cell size, fill height, and wave speed, which are heavily influence d by injection schemes. Previous testing utilized a partially premixed jets in crossflow (JIC) injection scheme, …
Thermal Ignition Of A Combustible Over An Inclined Hot Plate, Salaika Parvin, Nepal Chandra Roy, Rama S. R. Gorla
Thermal Ignition Of A Combustible Over An Inclined Hot Plate, Salaika Parvin, Nepal Chandra Roy, Rama S. R. Gorla
Faculty Publications
In this study, the ignition characteristics and the flow properties of the mixed convection flow are presented. Detailed formulations of the forced, natural and mixed convection problems have been discussed. In order to avoid inconvenient switch between the forced and natural convection we introduce a continuous transformation in the mixed convection. We make a comparison between these situations which reveal a good agreement. For mixed convection flow, the ignition distance is explicitly expressed as a function of the Prandtl number, reaction parameter and wall temperature. It has been observed that owing to the increase of the aforesaid parameters, the thermal …
Effects Of High Freestream Turbulence And Conduction On Film Cooling Effectiveness Of Shaped Holes, Richard A. Macias Jr.
Effects Of High Freestream Turbulence And Conduction On Film Cooling Effectiveness Of Shaped Holes, Richard A. Macias Jr.
Theses and Dissertations
With technological advancements allowing higher turbine temperatures, film cooling continues to be an important research area. The Film Cooling Rig (FCR) was fitted with a turbulence generator to vary freestream turbulence intensity and length scale, enabling the effects of high freestream turbulence on overall effectiveness to be studied. A cylindrical hole and laidback fan-shaped hole were investigated over a range of Advective Capacity Ratio (ACR) for freestream turbulence intensities of 2%, 10%, and 15%. For a given ACR, increasing the turbulence intensity resulted in lower overall effectiveness values due to the larger heat transfer coefficient that comes from turbulent ow. …
Detonation Confinement In A Radial Rotating Detonation Engine, Kavi Muraleetharan
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
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
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 …
Examination Of Flow Dynamics And Passive Cooling In An Ultra Compact Combustor, Tylor C. Rathsack
Examination Of Flow Dynamics And Passive Cooling In An Ultra Compact Combustor, Tylor C. Rathsack
Theses and Dissertations
The Ultra Compact Combustor (UCC) promises to greatly reduce the size of a gas turbine engine’s combustor by altering the manner in which fuel is burnt. Differing from the common axial flow combustor, the UCC utilizes a rotating flow, coaxial to the engine’s primary axis, in an outboard circumferential cavity as the primary combustion zone. The present study investigates two key UCC facets required to further this combustor design. The first area of investigation is cooling of the Hybrid Guide Vane (HGV). This UCC specific hardware acts as a combustor center body that alters the exit flow angle and acts …
Combustion Dynamics And Heat Transfer In An Ultra Compact Combustor, Brian T. Bohan
Combustion Dynamics And Heat Transfer In An Ultra Compact Combustor, Brian T. Bohan
Theses and Dissertations
The Ultra Compact Combustor (UCC) is an innovative combustion system alternative to a traditional turbine engine burner with the potential to improve engine efficiency with a reduced combustor volume. The UCC shortens the axial length of the combustor, and therefore reduces engine weight, by burning in an annulus and swirling the reactants in the circumferential direction. These length and weight improvements can directly lead to an increased thrust-to-weight rating of the engine. The present research included five objectives which advanced the UCC concept on four fronts; cooling UCC turbine vanes, advanced computational modeling of UCC systems, system air split control …
Numerical Simulation Of Heat Transfer And Chemistry In The Wake Behind A Hypersonic Slender Body At Angle Of Attack, Matthew J. Satchell, Jeffrey M. Layng, Robert B. Greendyke
Numerical Simulation Of Heat Transfer And Chemistry In The Wake Behind A Hypersonic Slender Body At Angle Of Attack, Matthew J. Satchell, Jeffrey M. Layng, Robert B. Greendyke
Faculty Publications
The effect of thermal and chemical boundary conditions on the structure and chemical composition of the wake behind a 3D Mach 7 sphere-cone at an angle of attack of 5 degrees and an altitude of roughly 30,000 m is explored. A special emphasis is placed on determining the number density of chemical species which might lead to detection via the electromagnetic spectrum. The use of non-ablating cold-wall, adiabatic, and radiative equilibrium wall boundary conditions are used to simulate extremes in potential thermal protection system designs. Non-ablating, as well as an ablating boundary condition using the “steady-state ablation” assumption to compute …
Flow Field Dynamics In A High-G Ultra-Compact Combustor, Andrew E. Cottle
Flow Field Dynamics In A High-G Ultra-Compact Combustor, Andrew E. Cottle
Theses and Dissertations
The Ultra Compact Combustor (UCC) presents a novel solution to the advancement of aircraft gas turbine engine performance. A high-g UCC design operates by diverting a portion of the axial compressor flow into a circumferential combustion cavity positioned about the engine outer diameter. The circumferential cavity (CC) provides the necessary residence length and time for combustion within reduced axial lengths; furthermore, high rates of centrifugal acceleration termed high-g loading are imposed upon the swirling cavity flow. These high-g conditions are hypothesized to increase flame speed, reduce flame length, and improve lean blow-out performance. Work at AFIT was sponsored by the …
Investigation Of Thermal Scaling Effects For A Turbine Blade Leading Edge And Pressure Side Model, Ryan A. Lynch
Investigation Of Thermal Scaling Effects For A Turbine Blade Leading Edge And Pressure Side Model, Ryan A. Lynch
Theses and Dissertations
Recent experiments have attempted to quantify the overall cooling effectiveness at elevated temperature conditions. The Film Cooling Rig (FCR) at the Air Force Institute of Technology has been modified to better match the configuration of a similar large scale, low temperature rig at the Air Force Research Laboratory. This has enabled comparison and trend identification of how various properties scale from the low to high temperature condition. Various internal cooling and hole geometry configurations were investigated over a range of temperatures while utilizing the thermal scaling capability of Inconel 718. Film cooling trends and measures of overall effectiveness were matched, …
Method For Determining Time-Resolved Heat Transfer Coefficient And Adiabatic Effectiveness Waveforms With Unsteady Film Cooling, James L. Rutledge, Jonathan F. Mccall
Method For Determining Time-Resolved Heat Transfer Coefficient And Adiabatic Effectiveness Waveforms With Unsteady Film Cooling, James L. Rutledge, Jonathan F. Mccall
AFIT Patents
A new method for determining heat transfer coefficient (h) and adiabatic effectiveness (η) waveforms h(t) and η(t) from a single test uses a novel inverse heat transfer methodology to use surface temperature histories obtained using prior art approaches to approximate the h(t) and η(t) waveforms. The method best curve fits the data to a pair of truncated Fourier series.
Minimization Of The Effects Of Secondary Reactions On Turbine Film Cooling In A Fuel Rich Environment, Andrew T. Shewhart
Minimization Of The Effects Of Secondary Reactions On Turbine Film Cooling In A Fuel Rich Environment, Andrew T. Shewhart
Theses and Dissertations
The demand for increased thrust, higher engine efficiency, and reduced fuel consumption has increased the turbine inlet temperature and pressure in modern gas turbine engines. The outcome of these higher temperatures and pressures is the potential for unconsumed radical species to enter the turbine. Because modern cooling schemes for turbine blades involve injecting cool, oxygen rich air adjacent to the surface, the potential for reaction with radicals in the mainstream flow and augmented heat transfer to the blade arises. This study evaluated various configurations of multiple cylindrical rows of cooling holes in terms of both heat release and effective downstream …
Operational Characteristics Of An Ultra Compact Combustor, Christopher J. Damele
Operational Characteristics Of An Ultra Compact Combustor, Christopher J. Damele
Theses and Dissertations
Ultra Compact Combustors offer unique solutions to minimize engine size and weight. They accomplish this by reducing the number of components in the engine core and perform the combustion in a circumferential cavity that encircles the core flow. Within this cavity, the fuel is injected rich. Burning continues to occur in the vane passage beneath the circumferential cavity which must be completed in a controlled manner prior to the inlet plane of the turbine rotor. Furthermore, the temperature distribution at the exit of the vane passage must be controlled to generate high work extraction from the turbine. The primary metrics …
Film Cooling In Fuel Rich Environments, Jacob J. Robertson
Film Cooling In Fuel Rich Environments, Jacob J. Robertson
Theses and Dissertations
The ultra compact combustor is a high performance gas turbine design concept that portends reduced weight for future weapons platforms. A natural outcome of the design is the continual presence of fuel-rich air in the turbine component of the engine. Because modern cooling schemes for hot section turbine blades involve injecting cool, oxygen-rich air adjacent to the surface, the potential arises for reaction with the unconsumed radicals in the mainstream ow and augmented heat transfer to the blade. This outcome is contrary to the purpose of film cooling, and can lead to early life-cycle turbine failure. This study examined the …
Design And Testing Of An H2/O2 Predetonator For A Simulated Rotating Detonation Engine Channel, Stephen J. Miller
Design And Testing Of An H2/O2 Predetonator For A Simulated Rotating Detonation Engine Channel, Stephen J. Miller
Theses and Dissertations
A study is presented on the relationship between a pre-detonator and a detonation channel of an RDE. Testing was conducted on a straight narrow channel made of clear polycarbonate windows connected to an H2/O2 pre-detonator to simulate the RDE initiation scheme and allow for flow visualization. A comparison is made on decoupling distance and wave velocities for a range of pre-detonator designs, inclination angles, equivalence ratios and geometries placed within the simulated channel. Regardless of inclination angle or equivalence ratio the detonation wave decoupled within 25 mm from the pre-detonator exit into the channel. A step change in diameter 25 …
Characterization Of Centrifugally-Loaded Flame Migration For Ultra-Compact Combustors, Kenneth D. Lebay
Characterization Of Centrifugally-Loaded Flame Migration For Ultra-Compact Combustors, Kenneth D. Lebay
Theses and Dissertations
The Air Force Research Laboratory (AFRL) has designed an Ultra Compact Combustor (UCC) showing viable merit for significantly reducing gas turbine combustor length making it a viable candidate for implementation as an inter-turbine burner and realization of efficiency benefits from the resulting near constant temperature cycle. This concept uses an off-axis combustor cavity and projects approximately 66% length reduction over a conventional combustor. The annular nature of the cavity creates high angular acceleration levels, on the order of 500-3500 g's, resulting in strong centrifugal and buoyant forces. This unique combination works to significantly reduce the required burn time and subsequently …
Numerical Investigation Of Pre-Detonator Geometries For Pde Applications, Robert T. Fievisohn
Numerical Investigation Of Pre-Detonator Geometries For Pde Applications, Robert T. Fievisohn
Theses and Dissertations
A parametric study was performed to determine optimal geometries to allow the successful transition of a detonation from a pre-detonator into the thrust tube of a pulse detonation engine. The study was performed using a two-dimensional Euler solver with progress variables to model the chemistry. The geometrical configurations for the simulations look at the effect of shock reflections, flow obstructions, and detonation diffraction to determine successful geometries. It was observed that there are success and failure rates associated with pre-detonators. These success rates appear to be determined by the transverse wave structure of a stably propagating detonation wave and must …
Investigation Of Thermal Management And Metamaterials, Calvin T. Roman
Investigation Of Thermal Management And Metamaterials, Calvin T. Roman
Theses and Dissertations
Thermal metamaterials are materials composed of engineered, microscopic structures that exhibit unique thermal performance characteristics based primarily on their physical structures and patterning, rather than just their chemical composition or bulk material properties. The heat transfer performance attributes of a thermal metamaterial are such that similar performance cannot be obtained using conventional materials or compounds. Thermal metamaterials are an emerging technology, and are just now beginning to be acknowledged and developed by the microelectronics and material sciences community. This thesis effort analyzed the current state of thermal metamaterial research, examined the physics and theory of heat transfer and electrical conductivity …
Discrete Film Cooling In A Rocket With Curved Walls, Jonathan F. Mccall
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 …
Ceramic Matrix Composite Characterization Under A Combustion And Loading Environment, Andrew R. Nye
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 …
Laser-Induced Fluorescence And Performance Analysis Of The Ultra-Compact Combustor, Patrick J. Lakusta
Laser-Induced Fluorescence And Performance Analysis Of The Ultra-Compact Combustor, Patrick J. Lakusta
Theses and Dissertations
The AFIT Combustion Optimization and Analysis Laser (COAL) lab’s modular design and state-of-the-art diagnostic systems make it a flexible and important facility for the analysis of combustion processes. The objectives of the current research are to install several enhancements in the lab, validate the laser diagnostic system, characterize the igniter for AFIT’s Ultra-Compact Combustor (UCC) sections, and perform a non-intrusive laser diagnostic, performance, and high-speed video analysis of a flat-cavity UCC section. Validation of the laser system was accomplished using OH Planar Laser-Induced Fluorescence (PLIF) in a laminar hydrogen-air flame produced by a Hencken burner. Results are compared to previous …