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 Title
 TOWARD INCREASING PERFORMANCE AND EFFICIENCY IN GAS TURBINES FOR POWER GENERATION AND AEROPROPULSION: UNSTEADY SIMULATION OF ANGLED DISCRETEINJECTION COOLANT IN A HOT GAS PATH CROSSFLOW.
 Creator

Johnson, Perry, Kapat, Jayanta, University of Central Florida
 Abstract / Description

This thesis describes the numerical predictions of turbine film cooling interactions using Large Eddy Simulations. In most engineering industrial applications, the ReynoldsAveraged NavierStokes equations, usually paired with twoequation models such as k[epsilon] or k[omega], are utilized as an inexpensive method for modeling complex turbulent flows. By resolving the larger, more influential scale of turbulent eddies, the Large Eddy Simulation has been shown to yield a significant...
Show moreThis thesis describes the numerical predictions of turbine film cooling interactions using Large Eddy Simulations. In most engineering industrial applications, the ReynoldsAveraged NavierStokes equations, usually paired with twoequation models such as k[epsilon] or k[omega], are utilized as an inexpensive method for modeling complex turbulent flows. By resolving the larger, more influential scale of turbulent eddies, the Large Eddy Simulation has been shown to yield a significant increase in accuracy over traditional twoequation RANS models for many engineering flows. In addition, Large Eddy Simulations provide insight into the unsteady characteristics and coherent vortex structures of turbulent flows. Discrete hole film cooling is a jetincrossflow phenomenon, which is known to produce complex turbulent interactions and vortex structures. For this reason, the present study investigates the influence of these jetcrossflow interactions in a timeresolved unsteady simulation. Because of the broad spectrum of length scales present in moderate and high Reynolds number flows, such as the present topic, the high computational cost of Direct Numerical Simulation was excluded from possibility.
Show less  Date Issued
 2011
 Identifier
 CFH0004086, ucf:44798
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFH0004086
 Title
 Thermoacoustic Reimann Solver Finite Volume Method with Application to Turbulent Premixed Gas Turbine Combustion Instability.
 Creator

Johnson, Perry, Kapat, Jayanta, Ilie, Marcel, Vasu Sumathi, Subith, Shivamoggi, Bhimsen, University of Central Florida
 Abstract / Description

This thesis describes the development, verification, and validation of a three dimensional time domain thermoacoustic solver. The purpose of the solver is to predict the frequencies, modeshapes, linear growth rates, and limit cycle amplitudes for combustion instability modes in gas turbine combustion chambers. The linearized Euler equations with nonlinear heat release source terms are solved using the finite volume method. The treatment of mean density gradients was found to be vital to the...
Show moreThis thesis describes the development, verification, and validation of a three dimensional time domain thermoacoustic solver. The purpose of the solver is to predict the frequencies, modeshapes, linear growth rates, and limit cycle amplitudes for combustion instability modes in gas turbine combustion chambers. The linearized Euler equations with nonlinear heat release source terms are solved using the finite volume method. The treatment of mean density gradients was found to be vital to the success of frequency and modeshape predictions due to the sharp density gradients that occur across deflagration waves. In order to treat mean density gradients with physical fidelity, a nonconservative finite volume method based on the wave propagation approach to the Riemann problem is applied. For modelling unsteady heat release, user input flexibility is maximized using a virtual class hierarchy within the OpenFOAM C++ library. Unsteady heat release based on time lag models are demonstrated. The solver gives accurate solutions compared with analytical methods for onedimensional cases involving mean density gradients, crosssectional area changes, uniform mean flow, arbitrary impedance boundary conditions, and unsteady heat release in a onedimensional Rijke tube. The solver predicted resonant frequencies within 1% of the analytical solution for these verification cases, with the dominant component of the error coming from the finite time interval over which the simulation is performed. The linear growth rates predicted by the solver for the Rijke tube verification were within 5% of the theoretical values, provided that numerical dissipation effects were controlled. Finally, the solver is then used to predict the frequencies and limit cycle amplitudes for two lab scale experiments in which detailed acoustics data are available for comparison. For experiments at the University of Melbourne, an empirical flame describing function was provided. The present simulation code predicted a limit cycle of 0.21 times the mean pressure, which was in close agreement with the estimate of 0.25 from the experimental data. The experiments at Purdue University do not yet have an empirical flame model, so a general vortexshedding model is proposed on physical grounds. It is shown that the coefficients of the model can be tuned to match the limit cycle amplitude of the 2L mode from the experiment with the same accuracy as the Melbourne case. The code did not predict the excitation of the 4L mode, therefore it is concluded that the vortexshedding model is not sufficient and must be supplemented with additional heat release models to capture the entirety of the physics for this experiment.
Show less  Date Issued
 2013
 Identifier
 CFE0005098, ucf:50730
 Format
 Document (PDF)
 PURL
 http://purl.flvc.org/ucf/fd/CFE0005098