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(1 - 5 of 5)
- Title
- INVESTIGATION ON INTERACTIONS OF UNSTEADY WAKES AND FILM COOLING ON AN ANNULAR ENDWALL.
- Creator
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Golsen, Matthew, Kapat, Jayanta, University of Central Florida
- Abstract / Description
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In recent decades, greater interest in the effect of rotational wakes on gas turbine film cooling applications has produced increasing numbers of studies on these unsteady phenomena. Wakes are primarily shed from upstream components such as transition duct walls, stator vanes, and rotors. Studies have shown that in areas of unsteady flow, the best performing parameters in conventional steady investigations may not be the best for unsteady applications. One common method of modeling the...
Show moreIn recent decades, greater interest in the effect of rotational wakes on gas turbine film cooling applications has produced increasing numbers of studies on these unsteady phenomena. Wakes are primarily shed from upstream components such as transition duct walls, stator vanes, and rotors. Studies have shown that in areas of unsteady flow, the best performing parameters in conventional steady investigations may not be the best for unsteady applications. One common method of modeling the unsteady wake interaction in subsonic flows is the use of spoke wheel type wake generators using cylindrical rods to produce the velocity detriment and local increase in turbulence intensity. Though the impact of wakes have been studied for decades on airfoil losses and boundary layer transition, only recently has the film cooling and wake interaction been investigated. The existing work is primarily on leading edge models and airfoil cascades. The primary parameter characterizing the unsteady wakes is the dimensionless or reduced frequency known as the Strouhal number. The film cooling jet itself has dominant frequencies resulting from the shear and the jet trailing wake shedding, depending on the injectant flow rate. There exist great deficiencies in the fundamental understanding of the interaction of these two frequencies. Heat transfer considerations are also relatively recent being studied only since the early 1990's. Heat transfer coefficients and film cooling effectiveness have been reported for leading edge and linear airfoil cascades. In the case of the linear cascade, no data can be taken near the endwall region due to the varying tangential velocity of wake generating rod. The current work expands on this initiative incorporating a sector annular duct as the test setting for the rotating wakes focusing on this endwall region. Studies in to the effect of the rods in this alternate orientation include film cooling effectiveness using temperature sensitive paint, impact of wake rod to film cooling hole diameter ratio, and time accurate numerical predictions and comparisons with experimental work. Data are shown for a range of momentum flux ratios and Strouhal numbers. The result of this work sets the stage for the complete understanding of the unsteady wake and inclined jet interaction.
Show less - Date Issued
- 2011
- Identifier
- CFH0004094, ucf:44796
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004094
- Title
- Aeroelastic Investigation of a Circumferentially Varying Tip Gap in an Axial Compressor Rotor.
- Creator
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Canon, Ornan, Kapat, Jayanta, Vasu Sumathi, Subith, Kauffman, Jeffrey, Mackie, Kevin, Kiesow, Hans-jurgen, University of Central Florida
- Abstract / Description
-
The tip leakage flow in axial compressors is a significant factor in engine performance and a subject of investigation over the last several decades. Many studies have already shown that the vortices generated by this tip leakage can have a negative impact on the surrounding flow field and overall performance, and could potentially lead to excitations as well. This study examines the effect of these vortices on aeroelasticity. Specifically, it looks at the effect from a circumferentially...
Show moreThe tip leakage flow in axial compressors is a significant factor in engine performance and a subject of investigation over the last several decades. Many studies have already shown that the vortices generated by this tip leakage can have a negative impact on the surrounding flow field and overall performance, and could potentially lead to excitations as well. This study examines the effect of these vortices on aeroelasticity. Specifically, it looks at the effect from a circumferentially varying tip gap, such as that produced by casing ovalization.For this project, the casing ovalization of an industrial gas turbine compressor was modeled using a frequency domain solver, without the need for a full wheel model. Both the vibratory and aerodynamic calculations were conducted in order to assess the aeroelastic response of the blade, as well as the aerodynamic impact. Engine test data was implemented in order to model realistic levels of casing ovalization and to calibrate the analytical models. Comparisons to a well-established method are also conducted to further calibrate the models. The calculations showed that for the gap variations imposed, the instantaneous effects aligned with expectations. However, the variation from small and large gaps had a canceling effect on each other over the cycle of oscillation around the engine.
Show less - Date Issued
- 2016
- Identifier
- CFE0006682, ucf:51926
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006682
- Title
- Experimental and Numerical Investigation of Aerodynamic Unsteadiness in a Gas Turbine Midframe.
- Creator
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Golsen, Matthew, Kapat, Jayanta, Vasu Sumathi, Subith, Sultanian, Bijay, University of Central Florida
- Abstract / Description
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As modern gas turbines implement more and more complex geometry to increase life and efficiency, attention to unsteady aerodynamic behavior becomes more important. Computational optimization schemes are contributing to advanced geometries in order to reduce aerodynamic losses and increase the life of components. These advanced geometries are less representative of cylinder and backward facing steps which have been used as analogous geometries for most aerodynamic unsteadiness research. One...
Show moreAs modern gas turbines implement more and more complex geometry to increase life and efficiency, attention to unsteady aerodynamic behavior becomes more important. Computational optimization schemes are contributing to advanced geometries in order to reduce aerodynamic losses and increase the life of components. These advanced geometries are less representative of cylinder and backward facing steps which have been used as analogous geometries for most aerodynamic unsteadiness research. One region which contains a high degree of flow unsteadiness and a direct influence on engine performance is that of the MidFrame. The MidFrame (or combustor-diffuser system) is the region encompassing the main gas path from the exit of the compressor to the inlet of the first stage turbine. This region contains myriad flow scenarios including diffusion, bluff bodies, direct impingement, high degree of streamline curvature, separated flow, and recirculation. This represents the most complex and diverse flow field in the entire engine. The role of the MidFrame is to redirect the flow from the compressor into the combustion system with minimal pressure loss while supplying high pressure air to the secondary air system. Various casing geometries, compressor exit diffuser shapes, and flow conditioning equipment have been tested to reduce pressure loss and increase uniformity entering the combustors. Much of the current research in this area focuses on aero propulsion geometries with annular combustors or scaled models of the power generation geometries. Due to the complexity and size of the domain accessibility with physical probe measurements becomes challenging. The current work uses additional measurement techniques to measure flow unsteadiness in the domain. The methodology for identifying and quantifying the sources of unsteadiness are developed herein. Sensitivity of MidFrame unsteadiness to compressor exit conditions is shown for three different velocity profiles. The result is an extensive database of measurements which can serve as a benchmark for radical new designs to ensure that the unsteadiness levels do not supersede previous successful levels.
Show less - Date Issued
- 2013
- Identifier
- CFE0004851, ucf:49682
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004851
- Title
- EFFECTS OF TRANSPORT PROPERTIES AND FLAME UNSTEADINESS ON NITROGEN OXIDES EMISSIONS FROM LAMINAR HYDROGEN JET DIFFUSION FLAMES.
- Creator
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Park, Doyoub, Chen, Ruey-Hung, University of Central Florida
- Abstract / Description
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Experimental studies on the coupled effects of transport properties and unsteady fluid dynamics have been conducted on laminar, acoustically forced, hydrogen jet diffusion flames diluted by argon and helium. The primary purpose of this research is to determine how the fuel Lewis number and the flow unsteadiness play a combined role in maximum flame temperature and affect NOx emission from jet diffusion flame. The fuel Lewis number is varied by increasing/decreasing the mole fraction of...
Show moreExperimental studies on the coupled effects of transport properties and unsteady fluid dynamics have been conducted on laminar, acoustically forced, hydrogen jet diffusion flames diluted by argon and helium. The primary purpose of this research is to determine how the fuel Lewis number and the flow unsteadiness play a combined role in maximum flame temperature and affect NOx emission from jet diffusion flame. The fuel Lewis number is varied by increasing/decreasing the mole fraction of diluents in the fuel stream. Therefore, maximum flame temperatures and then NOx emission levels were expected to differ for Ar- and He-diluted flames. In an investigation of unsteady flames, two different frequencies (10 and 100 Hz) were applied to observe a behavior of NOx emission levels and flame lengths by changes of unsteady fluid dynamics and transport properties.
Show less - Date Issued
- 2005
- Identifier
- CFE0000646, ucf:46535
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000646
- Title
- The Study of an Impinging Unsteady Jet - Fluid Mechanics and Heat Transfer Analysis.
- Creator
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Osorio, Andrea, Kapat, Jayanta, Kinzel, Michael, Raghavan, Seetha, University of Central Florida
- Abstract / Description
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The high heat transfer capabilities of impinging jets have led to their widespread use in industrial applications, such as gas turbine cooling. These impinging jets are usually manufactured on the walls of super-alloy metals and are influenced by being positioned with a confined setting. Studies have been shown to enhance the heat transfer of impinging jets by fluctuating the flow which will be analyzed in this project with two designs. The first design is a self-sustaining stationary fluidic...
Show moreThe high heat transfer capabilities of impinging jets have led to their widespread use in industrial applications, such as gas turbine cooling. These impinging jets are usually manufactured on the walls of super-alloy metals and are influenced by being positioned with a confined setting. Studies have been shown to enhance the heat transfer of impinging jets by fluctuating the flow which will be analyzed in this project with two designs. The first design is a self-sustaining stationary fluidic oscillator that causes a sweeping motion jet to impinge on the surface. This is investigated using Particle Image Velocimetry (PIV) to study the flow field as well as copper- block heated surface to study the heat transfer. The second design involves pulsating the jet through a rotating disk that opens and closes the jet hole, providing a pulsing impingement on the surface. This is examined using hot-wire anemometry for understanding the fluid mechanics and copper-block heated surface to study the heat transfer. Both configurations are tested at a constant Reynolds number of 30,000 with the oscillator tested at normalized jet-to-surface spacings of 3, 4, 6 and the pulsing mechanism tested at jet-to-surface spacing of 3. The results for the fluidic oscillator indicate: Reynolds stress profiles of the jet demonstrated elevated levels of mixing for the fluidic oscillator; heat transfer enhancement was seen in some cases; a confined jet does worse than an unconfined case; and the oscillator's heat removal performed best at lower jet-to- surface spacings. The results for the pulsing mechanism indicate: lower frequencies displayed high turbulence right at the exit of the jet as well as the jet-to-surface spacing of 3; the duty cycle parameter strongly influences the heat transfer results; and heat transfer enhancement was seen for a variation of frequencies.
Show less - Date Issued
- 2018
- Identifier
- CFE0007353, ucf:52102
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007353
