This research has a small portion focused on interior serpentine channels, with the primary focus on improving the effectiveness of the film cooling technique through the use of a new approach to film cooling. This new approach uses a set of three holes sharing the same inlet and diverging from the central hole to form a three-legged, or tripod, design. The tripod design is examined in depth, in terms of geometric variations, through the use of flat plate and cascade rigs, with both transient and steady-state experiments. The flat plate tests provide a simplified setting in which to test the design in comparison to other geometries, and establish a baseline performance in a simple flow field that does not have the complications of surface curvature or mainstream pressure gradients. Cascade tests allow for testing of the design in a more realistic setting with curved surfaces and mainstream pressure gradients, providing important information about the performance of the design on suction and pressure surfaces of airfoils. Additionally, the cascade tests allow for an investigation into the aerodynamic penalties associated with the injection hole designs at various flow rates. Through this procedure the current state of film cooling technology may be improved, with more effective surface coverage achieved with reduced coolant usage, and with reduced performance penalties for the engine as a whole. This research has developed a new film hole design that is manufacturable and durable, and provides a detailed analysis of its performance under a variety of flow conditions. This cooling hole design provides 40% higher cooling effectiveness while using 50% less coolant mass flow. The interior serpentine channel research provides comparisons between correlations and experiments for internal passages with realistic cross sections. / Ph. D.

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 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

No description available.

Heat transfer inside rotating coolant channels have a significant impact in design of gas turbine airfoils and other rotating components such as generator windings.  The effects of the Coriolis acceleration and centrifugal buoyancy have a significant impact on heat transfer behavior inside such rotating coolant channels due to the complex flow patterns of coolant.  Detailed heat transfer knowledge greatly enhances the designers\' ability to validate numerical models of newly designed channels. A rotating experimental rig was designed and built to model scaled up coolant channels at speeds up to 750 rotations per minute (rpm).  A camera is mounted onto the rotating test section and a transient liquid crystal technique is used to measure detailed heat transfer coefficients on a surface of interest.  The experimental set-up is innovative, as it involves no surface heating of the test section, very little instrumentation beyond a few thermocouples and a spray coating of thermochromic liquid crystals on the test surface.  To validate the test rig and the experimental method, multipass coolant channels with rib turbulators, large diameter radially outward channels with rib turbulators, and jet impingement cooling schemes are studied during rotation.  90deg, W, and M-shaped rib enhancements are studied and detailed heat transfer measurements clearly capture the heat transfer enhancement mechanisms with and without rotation.  Jet impingement schemes with single and double rows, normal and off-angle jets, and a cross flow outlet condition are all studied under rotation.  Non-rotating studies are also performed for baseline comparisons to rotating conditions.  Large aspect ratio, diverging channels with dimple and rib turbulators are studied in a stationary condition.  Results for all different test geometries show good comparisons with published studies indicating that the rotating rig and experimental method are valid.  Jet impingement schemes produce higher heat transfer compared to the two-pass channels with ribs, however pressure losses are significantly higher.  The fewer the jets and H/d=1 produces the highest pressure losses with no significant gain in heat transfer.  Off angle jets at H/d=1 produces very high pressure losses with no heat transfer advantage.  A final study with radially outward coolant channels is performed with the highest rotation speeds.  The structure, test section, and camera are thoroughly designed to withstand the exceptional g-forces.  Heat transfer in the radial channels with and without rotation show very little effect of rotation due to the small rotation number. / Ph. D.

Design of internal cooling channels for gas turbine blade is critical to system performance. To achieve maximum efficiency, i.e. maximum cooling with minimum coolant usage, intensive research is required to optimize heat transfer enhancement features. The present study aims at experimental and numerical investigation of two heat transfer augmentation techniques for internal cooling, viz. dimple and swirl induced jet impingement. Dimples are suitable candidates for high performance enhancement as they impose a low pressure drop penalty. The present study aims at experimentally measuring heat transfer on all the walls of diamond, triangular, square and cylindrical shaped dimples in a staggered configuration at three flow conditions in a high aspect ratio channel. A thermal-hydraulic performance factor was evaluated to characterize each dimple shape. Numerical simulations were conducted to visualize flow patterns which was correlated with heat transfer distribution. The results were in good agreement with previous studies. Triangular dimples showed the highest overall performance due to lowest pressure drop penalty, but heat transfer was low inside the dimples. In rotating channels, Coriolis Effect and centrifugal buoyancy significantly affect heat transfer distribution. There is a need to develop a cooling geometry that benefits from rotation and provides consistent cooling. A new geometry was derived from a past study, consisting of two channels divided by a wall with angled holes to provide jet impingement from inlet to outlet channel. Liquid crystal technique was used for heat transfer measurements. It was found that at high rotational speeds, heat transfer increased in the inlet channel, while it decreased in the outlet channel. Additional testing at even higher speeds may provide insight into replacing a traditional U-bend channel in a turbine blade. / Master of Science

Gas turbine components for cooling purposes including other unique and complex three-dimensional designs could be made explicitly possible through additive manufacturing using SLM technology in contrary to the conventional machining processes. Nevertheless, the surface roughness and subsequently the friction factor governs thepressure drop in these components implicitly, thus, influencing the secondary air flow system of a gas turbine. Research studies to understand and predict flow behaviours through especially AM parts are still in a budding stage, and thus, in this scope of thesis, the same has been attempted through experimentation to quantifypressure losses in additively manufactured rectangular orices. With the purpose of a brief analogy, a set of aluminium circular samples were also tested which were manufactured by the conventional process of machining. A total of 9 rectangular MA247 samples of different lengths and hydraulic diameters were tested as continuation to the ongoing research at Siemens Industrial Turbomachinery AB and further on to that, 5 Aluminium Alloy- AW-6082 T6 material samples of circular geometry with varying lengths were tested. The on-going research focuses on the additively manufactured geometries for both rectangular and circular, and hence, the data for circular orifices were used to draw a comparison with its Aluminium counterpart. Pressure losses here were described using the coefficient of discharge and the investigations on roughness were by calculating Darcy frictional factor and Colebrooks equation. Classical theories such as the boundary layer theory, Hagen's power law, Ward-Smith's theory for vena contracta and other works by previous researchers were used to validate the results. The coefficient of discharge could be deployed to restrict and measure the mass flow in the secondary air systems, whereas the results from the calculated frictional factors could be held to simulate the flow distribution in cooling geometries. / <p>E-presentation via Zoom due to the pandemic.</p> / Part of the on-going research on pressure loss study for Gas Turbine cooling purposes by Siemens Energy

This study focused on experimentally determining the cooling performance of a fully cooled, scaled-up model of a C3X turbine vane. The primary objective was to determine the differences in overall effectiveness in the presence and absence of a hot mainstream flowing over the vane. Overall effectiveness was measured using a thermally scaled matched Biot number vane with an impingement plate providing the internal cooling. This is the first study focused on investigating the effect of removing the mainstream flow and comparing the contour and laterally-averaged effectiveness data in support of the development of an assembly line thermal testing method. It was found that the proposed method of factory floor testing of turbine component cooling performance did not provide comparable information to traditional overall effectiveness test methods. A second experiment was performed in which the effect of altering the angle of attack of a flow into a passive turbulence generator was investigated. Measurements in the approach flow were taken using a single wire hot-wire anemometer. This study was the first to investigate the effects such a setup would have on fluctuating flow quantitates such as turbulence intensity and integral length scale rather than simply the mean quantities. It was found that both the downstream turbulence intensity and the turbulence integral length scale increase monotonically with approach flow incidence angle at a specified distance downstream of the turbulence generator. / text