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Articles 31 - 48 of 48
Full-Text Articles in Heat Transfer, Combustion
Heat Transfer Due To Unsteady Effects As Investigated In A High-Speed, Full-Scale, Fully-Cooled Turbine Vane And Rotor Stage, Jonathan R. Mason
Heat Transfer Due To Unsteady Effects As Investigated In A High-Speed, Full-Scale, Fully-Cooled Turbine Vane And Rotor Stage, Jonathan R. Mason
Theses and Dissertations
Experiments were conducted to examine the effects of film cooling on a gas turbine engine’s high‐pressure turbine section. The focus for this effort was in the tip/shroud region of a rotor stage and a high pressure turbine vane. A primary goal was to understand the unsteady flow effects. Attempts were also made to characterize the effects as caused by the fully‐cooled rotor stage. Data for this investigation was taken at the U.S. Air Force’s Turbine Research Facility (TRF), a transient blowdown facility with instrumentation fitted to a full‐scale, high‐speed, fully‐cooled vane and rotor stage of proprietary design. Measurements of pressure, …
The Impact Of Heat Release In Turbine Film Cooling, Dave S. Evans
The Impact Of Heat Release In Turbine Film Cooling, Dave S. Evans
Theses and Dissertations
The Ultra Compact Combustor is a design that integrates a turbine vane into the combustor flow path. Because of the high fuel-to-air ratio and short combustor flow path, a significant potential exists for unburned fuel to enter the turbine. Using contemporary turbine cooling vane designs, the injection of oxygen-rich turbine cooling air into a combustor flow containing unburned fuel could result in heat release in the turbine and a large decrease in cooling effectiveness. The current study explores the interaction of cooling flow from typical cooling holes with the exhaust of a fuel-rich well-stirred-reactor operating at high temperatures over a …
Laser Diagnostic System Validation And Ultra-Compact Combustor Characterization, Terry B. Hankins
Laser Diagnostic System Validation And Ultra-Compact Combustor Characterization, Terry B. Hankins
Theses and Dissertations
The AFIT combustion optimization and analysis laser (COAL) lab is now completely operational and is state-of-the-art in combustion diagnostics. The objective of this research is to perform a validation of a laser diagnostic system and to begin the characterization of a small-scale model of an ultra-compact combustor (UCC). Validation of the laser system was accomplished by using planar laser induced fluorescence (PLIF) on a laminar premixed hydrogen-air flame produced by a Hencken burner. OH species concentrations are measured. Flame temperatures are determined with a two line fluorescence technique using different transitions in the (1,0) band of the OH (A-X) electronic …
Validation Of The Afit Small Scale Combustion Facility And Oh Laser-Induced Fluorescence Of An Atmospheric Laminar Premiext Ed Flame, Stephen J. Koether
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
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, …
Branch Detonation Of A Pulse Detonation Engine With Flash Vaporized Jp-8, John David Slack
Branch Detonation Of A Pulse Detonation Engine With Flash Vaporized Jp-8, John David Slack
Theses and Dissertations
Pulse Detonation Engines (PDE) operating on liquid hydrocarbon fuels are limited to operating frequencies of 35 Hz due to long ignition times from a low energy ignition sources. This study shows ignition time of JP-8 can be nearly eliminated by igniting a thrust tube using a secondary detonation. A counter flow heat exchanger attached to a thrust tube utilized waste heat from the detonation process to heat JP-8 to supercritical conditions. The fuel flash vaporized when injected into the air stream of the engine. A detonation was produced by a spark in a 5 cm diameter, 1.37 m long tube. …
Design And Numerical Simulation Of Two Dimensional Ultra Compact Combustor Model Sections For Experimental Observation Of Cavity-Vane Flow Interactions, David S. Moenter
Design And Numerical Simulation Of Two Dimensional Ultra Compact Combustor Model Sections For Experimental Observation Of Cavity-Vane Flow Interactions, David S. Moenter
Theses and Dissertations
An improved computational fluid dynamics (CFD) model was developed for numerical simulation of the Ultra Compact Combustor (UCC) concept to enhance turbulent flow characterization of the circumferentially traveling, centrifugal-force enhanced combustion, cavity flow into the engine main flow passage via a radial cavity in the turbine axial guide vanes. The CFD model uses a dense grid on a 60° periodic, axisymmetric combustor section, with the RNG κ-ε turbulence model to resolve turbulent flow details. An overall analysis and performance evaluation of the experimentally tested UCC configuration and an axially shortened cavity baseline configuration was conducted at various experimentally documented operating …
Numerical Investigation Of Cavity-Vane Interactions Within The Ultra Compact Combustor, Jonathan F. Anisko
Numerical Investigation Of Cavity-Vane Interactions Within The Ultra Compact Combustor, Jonathan F. Anisko
Theses and Dissertations
A numerical analysis and design optimization of the Ultra Compact Combustor (UCC) has been conducted. The UCC is a combustor designed to incorporate high-g loadings to increase flame propagation speed while reducing flame length, thereby helping to significantly reduce the size of a combustor. A commercial CFD package with a k-Ⲉ turbulence model has been used to develop design rules for the construction of future UCCs. There have been several versions of UCC that have been designed, built and tested by AFRL/PRTC. Since real experimental tests are expensive and construction time is prohibitive to test many different design configurations, CFD …
Design, Build And Validation Of A Small-Scale Combustion Chamber Testing Facility, Eric R. Dittman
Design, Build And Validation Of A Small-Scale Combustion Chamber Testing Facility, Eric R. Dittman
Theses and Dissertations
This study investigated the design parameters necessary for the construction and use of a testing facility built to test the combustor section of engines. User inputs were acquired by interview and used in the decisions made in arrangement of pieces of machinery and how different systems were to interact. The design was then carried out as the various parts of the facility were built and installed. Software was designed which controlled the different parts of the combustion process and monitored the different products of combustion as well as the properties of the air and fuel used in the combustion. These …
Optimization Of A Low Heat Load Turbine Nozzle Guide Vane, Jamie J. Johnson
Optimization Of A Low Heat Load Turbine Nozzle Guide Vane, Jamie J. Johnson
Theses and Dissertations
Often turbomachinery airfoils are designed with aerodynamic performance foremost in mind rather than component durability. However, future aircraft systems require ever increasing levels of gas-turbine inlet temperature causing the durability and reliability of turbine components to be an ever more important design concern. As a result, the need to provide improved heat transfer prediction and optimization methods presents itself. Here, an effort to design an airfoil with minimized heat load is reported. First, a Reynolds-Averaged Navier-Stokes (RANS) flow solver was validated over different flow regimes as well as varying boundary conditions against extensive data available in literature published by the …
Performance Measurements Of Direct Air Injection In A Cavity-Based Flameholder For A Supersonic Combustor, Scott G. Edens
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 …
Variable Area Inlet For Vehicle Thermal Control, Thomas R. Layne, Milton E. Franke, Darrell B. Ridgedly
Variable Area Inlet For Vehicle Thermal Control, Thomas R. Layne, Milton E. Franke, Darrell B. Ridgedly
AFIT Patents
A variable area inlet structure for a vehicle utilizing ram air for coolant is described which comprises a variable area inlet device in the ram air inlet in the form of a butterfly valve, damper, shutter, or similar structure, a temperature sensor in thermal contact with a component within the vehicle to be cooled by ram air flow, a controller and actuator, responsive to the temperature sensor and operatively connected to the variable area device, for controlling the inlet area in response to the component temperature.
Heat Transfer To The Inclined Trailing Wall Of An Open Cavity, Orval A. Powell
Heat Transfer To The Inclined Trailing Wall Of An Open Cavity, Orval A. Powell
Theses and Dissertations
Experimental and computational heat transfer investigations were performed on a cavity with an inclined trailing wall (20-degrees to the horizontal), simulating one under investigation for use in a scramjet engine. Heat transfer data are reported in the form of Stanton number obtained using a curve fit to the recorded transient surface temperature history under cold flow conditions. Ascending from the reattachment point, the Stanton number increased by nearly 50% due to flow compression. This effect of flow compression was also evident at the junction of the cavity floor and inclined trailing wall, where the Stanton number also increased by 50%. …
Effects Of Liquid Transpiration Cooling On Heat Transfer To The Diverging Region Of A Porous-Walled Nozzle, Daniel J. Schieb
Effects Of Liquid Transpiration Cooling On Heat Transfer To The Diverging Region Of A Porous-Walled Nozzle, Daniel J. Schieb
Theses and Dissertations
This research effort investigated the effects of evaporation of water on the heat transferred to the wall of the diverging portion of a porous walled nozzle The AFIT High Pressure Shock Tube was used with a two-dimensional Mach 3 nozzle. One flat surface of the nozzle was fitted with a layer of porous stainless steel from the nozzle throat to the exit. This porous material was saturated with water to simulate liquid transpiration cooling. Surface temperature data was taken in this region using fast response coaxial thermocouple. Heat transfer was determined from the surface temperature history. Data was taken for …
Numerical Analysis Of Two And Three Dimensional Recessed Flame Holders For Scramjet Applications, Douglas L. Davis
Numerical Analysis Of Two And Three Dimensional Recessed Flame Holders For Scramjet Applications, Douglas L. Davis
Theses and Dissertations
This study investigated the flame holding properties of recessed cavities in supersonic flow using numerical analysis techniques. A simplified analytical model indicated that an important property for flame holding was the lower residence time. Several chemical kinetic rate models for hydrogen and hydrocarbon combustion were compared. The perfectly stirred reactor model also indicated that trace species diffusion should increase flame spreading rate, and that heat loss reduces flame holding limits. After nonreacting calibration, two-dimensional simulations confirmed the perfectly stirred reactor results for blowout limits. Also, the effect of trace species diffusion on flame spreading was shown to be negligible, and …
An Investigation Of The Characteristics Of Regenerative Heat Exchangers, Timothy J. Murphy
An Investigation Of The Characteristics Of Regenerative Heat Exchangers, Timothy J. Murphy
Theses and Dissertations
The objective of the current research was to investigate the effects of reducing screen thickness on the volume and compactness factor of stacked, wire-screen regenerators. An improved transient step-change method was devised which integrated experimental data with a numerical model of the flow to determine the heat transfer coefficient and friction factor. The improvements to the approach are: (1) the measured inlet temperature trace is used, (2) the heat transfer coefficient is based on a parameter called the sponge effect delay time, and (3) the important effect of the tube surrounding the matrix is included in the numerical model. The …
Effects Of Blowing Ratios On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Fu-Jung Chen
Effects Of Blowing Ratios On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Fu-Jung Chen
Theses and Dissertations
The effects of transpiration cooling on heat transfer in the throat region of a porous-walled nozzle were investigated. The experiments were performed in the AFIT low speed shock tube fitted with a Mach 2 nozzle. A blowing region was limited to the area from 1.3 cm prior to the throat to 1.2 cm downstream of the throat. The blowing ratios from -0.0002 (suction) to 0.0117 (blowing) of the main stream flow were studied. Heat flux data were taken from both sides of the nozzle. One side was transpiration cooled by secondary air injection through a porous wall, while the other …
Effects Of Blowing Ratio On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Joseph L. Lenertz
Effects Of Blowing Ratio On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Joseph L. Lenertz
Theses and Dissertations
This experiment analyzed the effects of blowing ratio on heat transfer to the throat region of a porous-walled nozzle, using the AFIT low speed shock tube. Heat flux data were taken from both sides of a two-dimensional Mach 2.0 Re-m=5.2x107 nozzle using thin film resistance thermometers. One side was transpiration-cooled by secondary air injection through a sintered wall, while the other side served as a control. Control results were validated using empirical relations, and cooled side results showed up to a 14% reduction in heat transfer coefficient at blowing ratios of only 0.51%. The linear nature of cooling effectiveness …