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- Title
- AN EXPERIMENTAL AND NUMERICAL STUDY OF SECONDARY FLOWS AND FILM COOLING EFFECTIVENESS IN A TRANSONIC CASCADE.
- Creator
-
Kullberg, James, Kapat, Jayanta, University of Central Florida
- Abstract / Description
-
In the modern world, gas turbines are widely used in aircraft propulsion and electricity generation. These applications represent a massive use of energy worldwide, so even a very small increase in efficiency would have a significant beneficial economic and environmental impact. There are many ways to optimize the operation of a gas turbine, but a fundamental approach is to increase the turbine inlet temperature to increase the basic thermodynamic efficiency of the turbine. However, these...
Show moreIn the modern world, gas turbines are widely used in aircraft propulsion and electricity generation. These applications represent a massive use of energy worldwide, so even a very small increase in efficiency would have a significant beneficial economic and environmental impact. There are many ways to optimize the operation of a gas turbine, but a fundamental approach is to increase the turbine inlet temperature to increase the basic thermodynamic efficiency of the turbine. However, these temperatures are already well above the melting temperature of the components. A primary cooling methodology, called film cooling, creates a blanket of cool air over the surface and is an effective way to help protect these components from the hot mainstream gasses. This paper focuses on the effect of the film holes upstream of the first row of blades in the turbine because this is the section that experiences the highest thermal stresses. Many factors can determine the effectiveness of the film cooling, so a complete understanding can lead to effective results with the minimum flow rate of coolant air. Many studies have been published on the subject of film cooling, but because of the difficulty and expense of simulating turbine realistic conditions, many authors introduce vast simplifications such as low speed conditions or linear cascades. These simplifications do not adequately represent the behavior of a turbine and therefore their results are of limited use. This study attempts to eliminate many of those simplifications. The test rig used in this research is based on the NASA-GE E3 design, which stands for Energy Efficient Engine. It was introduced into the public domain to provide an advanced platform from which open-literature research could be performed. Experimental tests on a transonic annular rig are time-consuming and expensive, so it is desirable to use experimental results to validate a computational model which can then be used to extract much more information. The purpose of this work is to create a numerical model that can be used to simulate many different scenarios and then to apply these results to experimental data.
Show less - Date Issued
- 2011
- Identifier
- CFH0003772, ucf:44728
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0003772
- Title
- Numerical Simulation of Non-Premixed and Premixed Axial Stage Combustor at High Pressure.
- Creator
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Worbington, Tyler, Ahmed, Kareem, Bhattacharya, Samik, Vasu Sumathi, Subith, University of Central Florida
- Abstract / Description
-
Axial-staged combustors represent an important concept that can be applied to reduce NOx emissions throughout a gas turbine engine. There are four main CFD models presented in this study that describe a highly turbulent jet-in-crossflow (JIC) simulation of partially premixed and non-premixed jets with a constant chamber pressure of 5 atm absolute. The equivalence ratio of the partially premixed jet was held constant at rich conditions with a ?_jet of 4 while the main stage varied from ?_1 and...
Show moreAxial-staged combustors represent an important concept that can be applied to reduce NOx emissions throughout a gas turbine engine. There are four main CFD models presented in this study that describe a highly turbulent jet-in-crossflow (JIC) simulation of partially premixed and non-premixed jets with a constant chamber pressure of 5 atm absolute. The equivalence ratio of the partially premixed jet was held constant at rich conditions with a ?_jet of 4 while the main stage varied from ?_1 and ?_2 of 0.575 and 0.73 with an average headend temperature of 1415K and 1545K, respectively. Chemistry was reduced by tabulation of eight main species using the equilibrium calculation of the software Chemkin. The centerline temperatures entering the JIC stage were measured experimentally and used as the starting point of a radial temperature profile that follows a parabolic trend. Comparison between the uniform and radial temperature profiles showed that the latter had a higher penetration depth into the vitiated crossflow due to a direct relationship between temperature and velocity. To capture the combustion process, Flamelet Generated Manifold (FGM) model was used. The progress variable source uses Turbulent Flame Speed Closure (TFC) to calculate flame propagation and position. There are two distinct flame positions of stability, the windward and leeward sides of the jet. The leeward flame positions for the two equivalence ratios showed that the richer condition sits closer to the jet due to the hotter equilibrium temperature; while the windward flame position is shifted upstream for the leaner case due to more availability of oxygen. The total temperature rise for ?_1 = 0.575 and ?_2 = 0.73 are ?T = 239 K and 186 K, respectively. The non-premixed simulations used a Steady Laminar Flamelet (SLF) approach with a headend equivalence ratio of ?_non = 0.6 and a detailed prediction of CH4 usage, CO production, and temperature increase throughout the jet-in-crossflow domain. Methane was shown to be consumed at a high amount, at almost 90% conversion with a temperature rise of ?T = 149 K. The heat release is below the calculated equilibrium ?T with the main reason pointed out that a significant amount of CH4 is only partially oxidized to CO due to limited oxygen availability with a fuel only configuration. Realizable K-Epsilon, SST K-Omega ?-Re?, and Reynolds Stress Transport (RST) turbulence models were used and compared. RST turbulence model showed to over predict the penetration depths and dissipation of the jet in the downstream domain when compared to literature and experimental data.
Show less - Date Issued
- 2019
- Identifier
- CFE0007880, ucf:52772
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007880
