You are here

Surface Measurements and Predictions of Full-Coverage Film Cooling

Download pdf | Full Screen View

Date Issued:
2012
Abstract/Description:
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 transferaugmentation 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 η = 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 ≈ 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 = 0.5 aremuch higher than expected. The heat transfer augmentation levels off quickly as opposed tothe 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 mostcommon turbulence models to properly predict full-coverage film cooling. The two models chosen, Realizable k-epsilon (RKE) and Shear Stress Transport k-omega (SSTKW), areboth two-equation models coupled with Reynolds Averaged governing equations which makeseveral gross physical assumptions and require several empirical values. Hence, the modelsare 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.
Title: Surface Measurements and Predictions of Full-Coverage Film Cooling.
26 views
15 downloads
Name(s): Natsui, Gregory, Author
Kapat, Jayanta, Committee Chair
Raghavan, Seetha, Committee Member
Vasu Sumathi, Subith, Committee Member
, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2012
Publisher: University of Central Florida
Language(s): English
Abstract/Description: 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 transferaugmentation 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 η = 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 ≈ 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 = 0.5 aremuch higher than expected. The heat transfer augmentation levels off quickly as opposed tothe 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 mostcommon turbulence models to properly predict full-coverage film cooling. The two models chosen, Realizable k-epsilon (RKE) and Shear Stress Transport k-omega (SSTKW), areboth two-equation models coupled with Reynolds Averaged governing equations which makeseveral gross physical assumptions and require several empirical values. Hence, the modelsare 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.
Identifier: CFE0004580 (IID), ucf:49221 (fedora)
Note(s): 2012-12-01
M.S.A.E.
Engineering and Computer Science, Mechanical and Aerospace Engineering
Masters
This record was generated from author submitted information.
Subject(s): Film Cooling -- Adiabatic Film Cooling Effectiveness -- Full-Coverage Film Cooling -- Multi-Row Film Cooling -- Heat Transfer Augmentation -- Convective Heat Transfer -- Experimental -- Temperature Sensitive Paint -- Modeling -- CFD
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0004580
Restrictions on Access: public 2012-12-15
Host Institution: UCF

In Collections