Benchmarking of Computational Models Against Experimental Data for Adiabatic Film-cooling Effectiveness for Large Spacing Compound Angle Full Coverage Film Cooling Arrays PDF Download
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Author: Simon R. Martinez
Publisher:
ISBN:
Category : Adiabatic demagnetization
Languages : en
Pages : 152
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Author: Simon R. Martinez
Publisher:
ISBN:
Category : Adiabatic demagnetization
Languages : en
Pages : 152
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Author: Justin Hodges
Publisher:
ISBN:
Category :
Languages : en
Pages : 118
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This thesis is an experimental and numerical full-coverage film cooling study. The objective of this work is the quantification of local heat transfer augmentation and adiabatic film cooling effectiveness for two full-coverage film cooling geometries. Experimental data was acquired with a scientific grade CCD camera, where images are taken over the heat transfer surface, which is painted with a temperature sensitive paint. The CFD component of this study served to evaluate how well the v2-f turbulence model predicted film cooling effectiveness throughout the array, as compared with experimental data. The two staggered arrays tested are different from one another through a compound angle shift after 12 rows of holes. The compound angle shifts from [beta]=-45° to [beta]=+45° at row 13. Each geometry had 22 rows of cylindrical film cooling holes with identical axial and lateral spacing (X/D=P/D=23). Levels of laterally averaged film cooling effectiveness for the superior geometry approach 0.20, where the compound angle shift causes a decrease in film cooling effectiveness. Levels of heat transfer augmentation maintain values of nearly h/h0=1.2. There is no effect of compound angle shift on heat transfer augmentation observed. The CFD results are used to investigate the detrimental effect of the compound angle shift, while the SST k-[omega] turbulence model shows to provide the best agreement with experimental results.
Author: Greg Natsui
Publisher:
ISBN:
Category :
Languages : en
Pages : 126
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Full-coverage film cooling is investigated both experimentally and numerically. First, surface measurements local of adiabatic film cooling eeffectiveness and heat transfer augmentation for four different arrays are described. Reported next is a comparison between two very common turbulence models, Realizable k-[epsilon] and SST k-[omega], and their ability to predict local film cooling effectiveness throughout a full-coverage array. The objective of the experimental study is the quantification of local heat transfer augmentation and adiabatic film cooling effectiveness for four surfaces cooled by large, both in hole count and in non-dimensional spacing, arrays of film cooling holes. The four arrays are of two different hole-to-hole spacings (P/D = X/D = 14.5; 19.8) and two different hole inclination angles ([alpha] = 30°; 45°), with cylindrical holes compounded relative to the flow ([beta] = 45°) and arranged in a staggered configuration. Arrays of up to 30 rows are tested so that the superposition effect of the coolant film can be studied. In addition, shortened arrays of up to 20 rows of coolant holes are also tested so that the decay of the coolant film following injection can be studied. Levels of laterally averaged effectiveness reach values as high as [eta with line above]= 0.5, and are not yet at the asymptotic limit even after 20-30 rows of injection for all cases studied. Levels of heat transfer augmentation asymptotically approach values of h=h0 [almost equal to] 1.35 rather quickly, only after 10 rows. It is conjectured that the heat transfer augmentation levels off very quickly due to the boundary layer reaching an equilibrium in which the perturbation from additional film rows has reached a balance with the damping effect resulting from viscosity. The levels of laterally averaged adiabatic film cooling effectiveness far exceeding [eta with line above]= 0.5 are much higher than expected. The heat transfer augmentation levels off quickly as opposed to the film effectiveness which continues to rise (although asymptotically) at large row numbers. This ensures that an increased row count represents coolant well spent. The numerical predictions are carried out in order to test the ability of the two most common turbulence models to properly predict full-coverage film cooling. The two models chosen, Realizable k-[epsilon] (RKE) and Shear Stress Transport k-[omega] (SSTKW), are both two-equation models coupled with Reynolds Averaged governing equations which make several gross physical assumptions and require several empirical values. Hence, the models are not expected to provide perfect results. However, very good average values are seen tobe obtained through these simple models. Using RKE in order to model full-coverage filmcooling will yield results with 30% less error than selecting SSTKW.
Author: Michael E. Crawford
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 120
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Author: S. Stephen Papell
Publisher:
ISBN:
Category : Mach number
Languages : en
Pages : 68
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 120
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 31
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The thermal efficiency of gas turbine systems depends largely on the turbine inlet temperature. Recent decades have seen a steady rise in the inlet temperature and a resulting reduction in fuel consumption. At the same time, it has been necessary to employ intensive cooling of the hot components. Among various cooling methods, film cooling has become a standard method for cooling of the turbine airfoils and combustion chamber walls. The University of Minnesota program is a combined experimental and computational study of various film-cooling configurations. Whereas a large number of parameters influence film cooling processes, this research focuses on compound angle injection through a single row and through two rows of holes. Later work will investigate the values of contoured hole designs. An appreciation of the advantages of compound angle injection has risen recently with the demand for more effective cooling and with improved understanding of the flow; this project should continue to further this understanding. Approaches being applied include: (1) a new measurement system that extends the mass/heat transfer analogy to obtain both local film cooling and local mass (heat) transfer results in a single system, (2) direct measurement of three-dimensional turbulent transport in a highly-disturbed flow, (3) the use of compound angle and shaped holes to optimize film cooling performance, and (4) an exploration of anisotropy corrections to turbulence modeling of film cooling jets.
Author: Mark Kenneth Harrington
Publisher:
ISBN:
Category :
Languages : en
Pages : 236
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Author: Katharine Lee Harrison
Publisher:
ISBN:
Category :
Languages : en
Pages : 314
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Film cooling computations and experiments were performed to study heat transfer and adiabatic effectiveness for several geometries. Various assumptions commonly made in film cooling experiments were computationally simulated to test the validity of using these assumptions to predict the heat flux into conducting walls. The validity of these assumptions was examined via computational simulations of film cooling on adiabatic, heated, and conducting flat plates using the commercial code FLUENT. The assumptions were found to be reasonable overall, but certain regions in the domain suffered from poor predictions. Film cooling adiabatic effectiveness and heat transfer coefficients for axial holes embedded in a 1 [hole diameter] transverse trench on the suction side of a simulated turbine vane were experimentally investigated as well to determine the net heat flux reduction. Heat transfer coefficients were determined with and without upstream heating both with and without a tripped boundary layer approach flow. The net heat flux reduction for the trench was found to be much higher than for the baseline row of holes. Two transverse trench geometries and a baseline row of holes geometry were also simulated using FLUENT and the results were compared to experiments by Waye and Bogard (2006). Trends between simulated trench configurations and baseline cylindrical holes without a trench were found to be largely in agreement with experimental trends, suggesting that FLUENT can be used as a tool for studying new trench configurations.
Author: S. Stephen Papell
Publisher:
ISBN:
Category :
Languages : en
Pages : 24
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