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- Title
- STUDY OF HEAT TRANSFER CHARACTERISTICS OF IMPINGING AIR JET USING PRESSURE ANDN TEMPERATURE SENSITIVE LUMINESCENT PAINT.
- Creator
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Liu, Quan, Kapat, Jayanta, University of Central Florida
- Abstract / Description
-
Luminescent coating measurement system is a relatively new technology for quantitative pressure and temperature measurement. Usually referred to as Pressure Sensitive Paint (PSP) and Temperature Sensitive Paint (TSP), luminescent coatings contain sensor molecules, which undergoes a luminescent transition when excited with light of proper wavelength. The reaction is pressure and/or temperature sensitive. The image of TSP or PSP coated model surface can be captured with a scientific grade...
Show moreLuminescent coating measurement system is a relatively new technology for quantitative pressure and temperature measurement. Usually referred to as Pressure Sensitive Paint (PSP) and Temperature Sensitive Paint (TSP), luminescent coatings contain sensor molecules, which undergoes a luminescent transition when excited with light of proper wavelength. The reaction is pressure and/or temperature sensitive. The image of TSP or PSP coated model surface can be captured with a scientific grade camera and then processed to obtain full field temperature and pressure distribution with very high fidelity. The preparation time of the technique is short. The measurement system offers an economic alternative to conventional testing methods using large number of pressure taps and thermocouples. The purpose of the experiment in this thesis is to take the benefits of the TSP and PSP technique, develop a well-controlled process and then apply the technique for a fundamental study on jet impingement heat transfer. First, Uni-Coat TSP and Binary-FIB PSP purchased from ISSI Inc. are calibrated to high accuracy. The calibration uncertainty of TSP and PSP are found to be ±0.93 °C and ±0.12 psi over temperature and pressure ranges of 22 to 90 ° C and 5 to 14.7 psia, respectively. The photodegradation of TSP is then investigated with the same calibration system. The photodegradation refers to the phenomenon of decreasing emission intensity as the luminescent paint is exposed to the illumination light during testing. It was found that photodegradation rate is a strong function of temperature and the optical power of illumination lighting. The correlation developed in this work is expected to compensate the degradation of TSP to achieve high measurement accuracy. Both TSP and PSP were then applied in the flow and heat transfer measurement of single round impinging air jet. Various separation distance (Z/D) and jet Reynolds number are tested. Pressure measurement on the jet impinged target surface using PSP clearly shows the boundary of jet impingement zone, which broadens with separation distance. In heat transfer experiment using TSP, the "second peak" in local heat transfer occurring at radial distance r/D around 2 is clearly observed when the separation distance Z/D is shorter than the length of jet potential core. The slight variation in radial location and the amplitude of the "second peak" are captured as Z/D and jet Reynolds number change. The optimum Z/D of stagnation point heat transfer is found to be around 5. The effect of jet nozzle configuration is investigated. It is found that the heat transfer rate associated with "tube jet" is generally higher than that of "plate jet". The difference in heat transfer between the two jet configurations is related to the weaker entrainment effect associated with "plate jet", where the entrainment of surrounding air is confined by the injection plate, especially under small Z/D circumstances. When compared with the benchmark data in the literature, the averaged heat transfer data of "tube jet" matches the empirical data better than those of "plate jet". The maximum difference is 3.3% for tube jet versus 15.4% for plate jet at Reynolds number of 60000 and Z/D of 5. The effect of surface roughness on jet impingement heat transfer is also studied. Heat transfer can be significantly increased by the enhanced roughness of the target surface. The largest roughness effect is achieved near stagnation point at high jet Reynolds number. Compared to the heat transfer to a smooth plate, as high as 30.9% increase in area-averaged Nusselt number is observed over a rough surface at r/D=1.5 and jet Reynolds number of 60000. The most significant advance of the present work is that both temperature and pressure measurement be obtained with the same measurement system and with accuracy comparable to traditional testing methods. The procedures that were employed in this work should be easy to apply in any university or industrial testing facility. It provides a rapid testing tool that can help solve complex problems in aerodynamics and heat transfer
Show less - Date Issued
- 2006
- Identifier
- CFE0000960, ucf:46747
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000960
- Title
- Adiabatic Film Cooling Effectiveness of a Transpiration-Cooled Leading Edge Fabricated by Laser Additive Manufacturing.
- Creator
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Calderon, Luisana, Kapat, Jayanta, Raghavan, Seetha, Mingareev, Ilya, University of Central Florida
- Abstract / Description
-
Laser additive manufacturing (LAM) is an emerging technology capable of fabricating complex geometries not possibly made by investment casting methods for gas turbine applications. LAM techniques consist of building parts in a layer-by-layer process by selectively melting metal powders. In the present study, a mock leading edge segment of a turbine blade fabricated by LAM of Inconel 718 powders is investigated. For this particular design, the traditional showerhead film cooling holes have...
Show moreLaser additive manufacturing (LAM) is an emerging technology capable of fabricating complex geometries not possibly made by investment casting methods for gas turbine applications. LAM techniques consist of building parts in a layer-by-layer process by selectively melting metal powders. In the present study, a mock leading edge segment of a turbine blade fabricated by LAM of Inconel 718 powders is investigated. For this particular design, the traditional showerhead film cooling holes have been replaced by two strips containing engineered-porous regions with the purpose of simulating the effect of transpiration cooling. Transpiration cooling has been considered a promising external convective cooling method capable of providing a more uniform film and higher adiabatic film cooling effectiveness than conventional discrete film cooling. In addition, many studies have shown that this technique can yield high firing temperatures with much less coolant consumption than discrete film cooling. In this current study, adiabatic film cooling effectiveness is investigated by means of mass transfer using pressure sensitive paint (PSP). The experiments are conducted for blowing ratios ranging between M = 0.03 and M = 0.28 for a nominal density ratio of 1.5. The density ratio is obtained by using air as the mainstream flow and CO2 as the secondary flow (or coolant source). Results indicate higher coverage and film cooling effectiveness when increasing blowing ratio at the expense of higher pressure drop. In addition, the experimental results are compared to numerical analyses performed using steady state Reynolds Average Navier Stokes (RANS) simulations.
Show less - Date Issued
- 2018
- Identifier
- CFE0007315, ucf:52117
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007315
