Dissertations / Theses on the topic 'Gas Turbine Cooling System'

A novel experimental facility for the testing of modern high pressure nozzle guide vanes, the Annular Sector Heat Transfer Facility, is described in this thesis. Non- dimensionally similar conditions to a thermal paint test are reproduced, in a warm flow field, by the use of actual engine hardware, contoured sidewalls, and an innova- tive system of deswirl vanes in a five-passage annular sector cascade. External Mach and Reynolds numbers, inlet turbulence intensity, and coolant-to-mainstream pres- sure ratio are all matched to engine conditions. The test vanes are heavily cooled both internally (by convection and impingement) and externally (by film cooling). Detailed aerodynamic measurements are discussed, which demonstrate that a peri- odic, transonic, and highly engine-realistic flow is established in the cascade. High resolution full coverage maps of overall cooling effectiveness are presented, acquired on the vane surfaces at steady state conditions by wide-band liquid crys- tals and infrared thermography. Experimental measurements are then scaled to en- gine conditions by a new theoretical procedure, argued from first principles, which extends the principle of superposition to fully-cooled compressible flows. A newly- defined recovery temperature is proposed, which accounts for the redistribution of heat between the internal and external vane flows in a fully-integrated manner. This technique makes the results analogous to those of a thermal paint test, but allows for fundamental research and early and inexpensive cooling system validation. Overall cooling effectiveness measurements are complemented by those of the re- quired cooling flow capacity to achieve them, conducted in a second test rig commis- sioned during this research: the Flow Testing Facility. To conclude, the approach developed is applied to the global thermal assessment of the dendritic geometry, an innovative turbine cooling system. Experimental results show promising benefits over the baseline vane, especially in regions of low coolant-to-mainstream pressure margin.

Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018.
Gas turbines have achieved widespread popularity in industrial fields. This is due to the high power, reliability, high efficiency, and its use of cheap gas as fuel. However, a major draw-back of gas turbines is due to the strong function of ambient air temperature with its output power. With every degree rise in temperature, the power output drops between 0.54 and 0.9 percent. This loss in power poses a significant problem for utilities, power suppliers, and co-generations, especially during the hot seasons when electric power demand and ambient temperatures are high. One way to overcome this drop in output power is to cool the inlet air temperature. There are many different commercially available means to provide turbine inlet cooling. This disserta-tion reviews the various technologies of inlet air cooling with a comprehensive overview of the state-of-the-art of inlet fogging systems. In this technique, water vapour is being used for the cooling purposes. Therefore, the water quality requirements have been considered in this thesis. The fog water is generally demin-eralized through a process of Reverse Osmosis (RO). The drawback of fogging is that it re-quires large amounts of demineralized water. The challenge confronting operators using the fogging system in remote locations is the water scarcity or poor water quality availability. However, in isolated hot areas with high levels of radiation making use of solar PV energy to supply inlet cooling system power requirements is a sustainable approach. The proposed work herein is on the development of a photovoltaic (PV) application for driv-ing the fogging system. The design considered for improved generation of Acaica power plant in Cape Town, South Africa. In addition, this work intends to provide technical infor-mation and requirements of the fogging system design to achieve additional power output gains for the selected power plant.

In modern, low emission, gas turbine combustion systems the amount of air available for cooling of the flame tube liner is limited. This has led to the development of more complex cooling systems such as cooling tiles i.e. a double skin system, as opposed to the use of more conventional cooling slots i.e. a single skin system. An isothennal experimental facility has been constructed which can incorporate 10 times full size single and double skin (cooling tile) test specimens. The specimens can be tested with or without effusion cooling and measurements have been made to characterise the flow through each cooling system along with the velocity field and cooling effectiveness distributions that subsequently develop along the length of each test section. The velocity field of the coolant film has been defined using pneumatic probes, hot-wire anemometry and PIV instrumentation, whilst gas tracing technique is used to indicate (i) the adiabatic film cooling effectiveness and (ii) mixing of the coolant film with the mainstream flow. Tests have been undertaken both with a datum low turbulence mainstream flow passing over the test section, along with various configurations in which large magnitudes and scales of turbulence were present in the mainstream flow. These high turbulence test cases simulate some of the flow conditions found within a gas turbine combustor. Results are presented relating to a variety of operating conditions for both types of cooling system. The nominal operating condition for the double skin system was at a coolant to mainstream blowing ratio of approximately 1.0. At this condition, mixing of the mainstream and coolant film was relatively small with low mainstream turbulence. However, at high mainstream turbulence levels there was rapid penetration of the mainstream flow into the coolant film. This break up of the coolant film leads to a significant reduction in the cooling effectiveness. In addition to the time-averaged characteristics, the time dependent behaviour of the .:coolantfilm was. also investigated. In particular, unsteadiness associated with large scale structures in the mainstream flow was observed within the coolant film and adjacent to the tile surface. Relative to a double skin system the single skin geometry requires a higher coolant flow rate that, along with other geometrical changes, results in typically higher coolant to mainstream velocity ratios. At low mainstream turbulence levels this difference in velocity between the coolant and mainstream promotes the generation of turbulence and mixing between the streams so leading to some reduction in cooling effectiveness. However, this higher momentum coolant fluid is more resistant to high mainstream turbulence levels and scales so that the coolant film break up is not as significant under these conditions as that observed for the double skin system. For all the configurations tested the use of effusion cooling helped restore the coolant film along the rear of the test section. For the same total coolant flow, the minimum value of cooling effectiveness observed along the test section was increased relative to the no effusion case. In addition the effectiveness of the effusion patch depends on the amount of coolant injected and the axial location of the patch. The overall experimental data suggested the importance of the initial cooling film conditions together with better understanding of the possible mechanisms that results in the rapid cooling film break-up, such as high turbulence mainstream flow and scales, and this will lead to a more effective cooling system design. This experimental data is also thought to be ideal for the validation of numerical predictions.

This research concerns the integration of Adaptive Search (AS) technique such as the Genetic Algorithms (GA) with knowledge based software to develop a research prototype of an Adaptive Search Manager (ASM). The developed approach allows to utilise both quantitative and qualitative information in engineering design decision making. A Fuzzy Expert System manipulates AS software within the design environment concerning the preliminary design of gas turbine blade cooling systems. Steady state cooling hole geometry models have been developed for the project in collaboration with Rolls Royce plc. The research prototype of ASM uses a hybrid of Adaptive Restricted Tournament Selection (ARTS) and Knowledge Based Hill Climbing (KBHC) to identify multiple "good" design solutions as potential design options. ARTS is a GA technique that is particularly suitable for real world problems having multiple sub-optima. KBHC uses information gathered during the ARTS search as well as information from the designer to perform a deterministic hill climbing. Finally, a local stochastic hill climbing fine tunes the "good" designs. Design solution sensitivity, design variable sensitivities and constraint sensitivities are calculated following Taguchi's methodology, which extracts sensitivity information with a very small number of model evaluations. Each potential design option is then qualitatively evaluated separately for manufacturability, choice of materials and some designer's special preferences using the knowledge of domain experts. In order to guarantee that the qualitative evaluation module can evaluate any design solution from the entire design space with a reasonably small number of rules, a novel knowledge representation technique is developed. The knowledge is first separated in three categories: inter-variable knowledge, intra-variable knowledge and heuristics. Inter-variable knowledge and intra-variable knowledge are then integrated using a concept of compromise. Information about the "good" design solutions is presented to the designer through a designer's interface for decision support.

This PhD dissertation, conducted as part of a CIFRE research project between TURBOMECA and CERFACS in partnership with the VKI, deals with improving performance of axial turbines from helicopter engines. One of the most critical design points of such engines is the control of the high pressure turbine blade lifetime which face the high temperatures from the combustor. Today, industrial numerical aerothermal predictions of the flows around the blade (in the vein and in its cooling system) are performed with the Reynolds Averaged Navier-Stokes (RANS). Thanks to the increasing computational power, Large Eddy Simulation (LES) becomes affordable to offer further flow predictions. Therefore, this thesis focuses on the capabilities of the LES to estimate the flow in turbine blade internal cooling channels. To simplify this analysis where several physical phenomenon are present, the problem is described in three parts with increasing complexity. The first part addresses simplified typical geometries of cooling channel (U-bend and ribbed channel) in a static configuration. Considering the flow regime, a wall-resolved approach using a hybrid unstructured mesh is proposed in view of the application on an industrial case. The second part extends the study of the ribbed channel in rotation using an inertial reference frame. LES provides mean and unsteady results in good agreement with the available experimental data and previous works, for the flow dynamic and the heat transfer. Finally, the third part presents the application of the method to an industrial case with conjugate heat transfer between a complex cooling channel and the blade. This last section is not present in the public manuscrit for confidential reasons. Results of the use of the wall-resolved approach in rotation in an inertial frame of reference are compared to RANS predictions and show the potential of the method with high local differences.

There is a constant struggle to increase the efficiency in gas turbines, where one method is to have a higher inlet temperature to the turbine. Often, this results in temperatures higher than the critical temperature of the materials, which makes cooling of the components an important part of the turbine. The cooling air is tapped from the compressor, and has hence required work while being compressed, but since it is removed from the thermodynamic cycle it will not provide any work in the turbine stages. Therefore, it is important to understand the losses in the cooling system to be able to use the smallest amount of cooling air possible, while still cool sufficiently to not decrease the turbine’s lifetime. The pressure losses in the cooling and secondary air systems are due to either friction or minor losses; contractions, expansions and bends. The losses can be described by a discharge coefficient, ; a rate of how close the actual mass flow is to the ideal mass flow, or a pressure loss coefficient, ; a rate of the pressure drop. In the cooling and secondary air systems there are orifices and cooling geometries. These can have different geometrical properties depending on application, and thereby have different heat transfer performances and causing a higher or lower pressure drop. At Siemens Industrial Turbomachinery AB, SIT AB, a one-dimensional in-house program named C3D is used for thermal calculations and calculations of flow properties of internal cooling flow networks. The program uses hydraulic networks consisting of nodes and branches to simulate the flow inside the components. Correlations used for describing pressure losses have been collected and divided depending on their valid ranges, with the aim to make pressure loss calculations easier. A MATLAB code have been developed, which, depending on input parameters, separates the correlations and returns a plot with the correlations that can be used. In order to make the code as useful as possible, a few assumptions were made; curve fitting of correlations which were only available as plots and interpolation to get larger valid ranges for some cases. These assumptions will influence the results, but the code will still be able to give an indication of which correlation to use, and hence, the objective is fulfilled. Simulations in one dimension are commonly used, since it is less time consuming than three-dimensional modelling. Therefore, with focus on the pressure losses, a one-dimensional model of a blade in the in-house program C3D has been evaluated using a three-dimensional model in the CFD program Ansys CFX. Also, two new models were created in C3D; both with geometrical properties and pressure loss coefficients adjusted to the CFX model, but the first model is using the same hydraulic network as in the evaluated, reference, model while the second is using a new network, built according to the streamlines in CFX. The resulting mass flows in the C3D models were compared to the mass flows in the CFX model, which ended in the conclusion that it is hard for the one-dimensional models to understand the complex, three-dimensional flow situations, even when adjusting them to the CFX model. Anyhow, the adjustments made the model somewhat closer to the three-dimensional case, and hence CFX should be used in an earlier stage when developing C3D models.

The Advisory Council of Aeronautical Research in Europe (ACARE) has set record emission reduction targets for 2020, in response to increased awareness of global warming issues and the forecast high level of growth in global air traffic. In order to meet this legislation engine designers have to consider new and unconventional designs. An intercooled aero-engine with a heat exchanger (HX) positioned between the IP and HP compressors has the potential to reduce emissions and/or reduce specific fuel consumption relative to conventional engine cycles. In such an engine a coolant delivery system is required to bleed a proportion of the bypass flow, from behind the fan outlet guide vane (FOGV), rapidly diffuse the flow (to reduce pressure loss through the HX modules) and present it to the intercooler (i.e. heat exchanger) modules for cooling. This spent cooling air is then fed back into the bypass duct. To realise the benefits of the intercooled cycle the coolant delivery system must diffuse the flow, within the geometrical constraints, with minimal pressure loss and present it to the heat exchanger modules with suitable flow characteristics over a range of operating conditions. Therefore, a predominately experimental study, complemented with CFD predictions, was undertaken to investigate the design and performance of a coolant delivery system aimed at providing high pressure recovery in a relatively short length. For this to be achieved some pre-diffusion of the flow is required upstream of the offtake (i.e. by making the offtake larger than the captured streamtube), with a controlled diffuser or hybrid diffuser arrangement located downstream of the offtake. Although targeted at an intercooled aero-engine the concept of a system that produces a high pressure recovery in a limited length is applicable to a variety of applications. Experimental data were obtained on a modified existing low speed isothermal annular test facility operating at nominally atmospheric conditions. The offtake must operate aft of the FOGV in a highly complex flow field environment. Hence, a 1½ stage axial flow compressor (IGV, rotor and modified OGV) was used to simulate the unsteady blade wakes, secondary flows, loss cores and other turbo-machinery features that can significantly influence offtake performance. Preliminary numerical (CFD) studies enabled an offtake configuration to be determined and provided understanding of the governing fluid mechanic processes. A relatively small scale, low speed test facility was designed that had the capability to evaluate aerodynamic processes in isolation (i.e. pre-diffusion, controlled diffusion, hybrid diffusion) and full system modelling to enable the complex interaction between these flow processes to be assessed. Hence an optimal system could be characterised in terms of total pressure loss, static pressure recovery and flow profiles at HX inlet. Measurements and numerical predictions are initially presented for a baseline configuration with no offtake present. This enabled the OGV near field region to be characterised and provided a datum, relative to which the effects of introducing an offtake could be assessed. The results showed that in the near field region (i.e. within one chord downstream of the FOGV) the high velocity gradients in the circumferential direction, and associated turbulent shear stresses, dominate the profile mixing and loss production. There is little mixing out of profiles in the radial direction. Furthermore, the relatively large amount of kinetic energy associated with the compressor efflux and its subsequent mixing to a more uniform profile (i.e. reduced blockage) results in a significant static pressure recovery (Cp=5.5%). With the offtake present a variety of configurations were investigated including different levels of pre-diffusion, prior to the offtake, and different offtake positions. This enabled evaluation of the upstream pressure effects and interaction with the upstream FOGV. For very compact systems of short length, such that the gap between the OGV and offtake is relatively small, the amount of pre-diffusion achievable is limited by the offtake pressure field and its impact on the upstream OGV row. This pressure field is also influenced by parameters such as the non-dimensional offtake height and splitter thickness. For systems of increased length a significant amount of flow pre-diffusion can be achieved with little performance penalty (relative to the datum configuration). Hence, the loss associated with mixing blade wakes and secondary flows in an adverse pressure gradient is relatively small. However, the pre-diffusion level is eventually limited, to approximately 1.5, by the increased distortion and pressure losses associated with the captured streamtube. Further measurements were made with various controlled diffuser and hybrid diffusers (of varying area ratio) downstream of the offtake and various levels of pre-diffusion. The flow profile that is presented to the controlled diffuser is directly influenced by the upstream pre-diffusion process. Hence, in this case the upstream-downstream interaction is relatively strong. Conversely, the downstream-upstream interaction, between the controlled diffuser and pre-diffusion process, is relatively weak and thus has little effect on the upstream flow field. The data enabled an optimal system to be characterised (pre-diffusion/controlled diffusion split) in terms of total pressure loss, static pressure recovery and flow profiles at HX inlet. A total system diffusion of 1.8 was achievable with a pre-diffusion of 1.4 and controlled diffusion of 1.25, with further increases in either the pre-diffusion level or the controlled diffuser area ratio destabilising the system. This was achieved with an absolute mass weighted total pressure loss of 11% measured from FOGV inlet to the controlled diffuser exit plane. Utilising a hybrid bled diffuser, combined with the pre-diffusion, enabled a total system diffusion of 2.24 to be achieved. The system incorporated a 6% bleed from the hybrid diffuser and a system total pressure loss of 13%. Experimental and computational results obtained in the current research have provided an understanding of the governing flow mechanisms and quantified the geometric and aerodynamic interaction of the offtake with the FOGV and between the diffusion processes. This has enabled a design methodology to be outlined that provides approximate information on system geometry and performance (in terms of optimal diffusion split and total pressure loss) for future coolant delivery systems with minimal effort. Preliminary design maps have been developed to define the magnitude of the interaction between the offtake and FOGV in terms of the offtake height, pre-diffusion level, the splitter thickness and the axial distance between the fan OGV and offtake. In this way systems of optimal diffusion split, minimum pressure loss and minimal axial length can be determined.

The efficiency of air-breathing gas turbine engines improves as the combustion temperature increases. Therefore, modern gas turbines operate at temperatures greater than the melting temperature of hot-gas-path components, and cooling must be introduced in order to maintain mechanical integrity of those components. Two highly effective techniques used in modern designs for this purpose are impingement cooling and use of coolant film on hot-gas-path surface introduced through discrete film or effusion holes. In this study, these two mechanisms are coupled into a single prototype cooling system. The heat transfer capability of this system is experimentally determined for a variety of different geometries and coolant flow rates. This study utilizes Temperature Sensitive Paint (TSP) in order to measure temperature distribution over a surface, which allowed for local impingement Nusselt number, film cooling effectiveness, and film cooling heat transfer enhancement profiles to be obtained. In addition to providing quantitative heat transfer data, this method allowed for qualitative investigation of the flow behavior near the test surface. Impinging jet-to-target-plate spacing was varied over a large range, including several tall impingement scenarios outside the published limits. Additionally, both in-line and staggered effusion arrangements were studied, and results for normal injection were compared to full coverage film cooling with inclined- and compound-angle injection. Effects of impingement and effusion cooling were combined to determine the overall cooling effectiveness of the system. It is shown that low impingement heights produce the highest Nusselt number, and that large jet-to-jet spacing reduces coolant flow rate while maintaining moderate to high heat transfer rates. Staggered effusion configurations exhibit superior performance to in-line configurations, as jet interference is reduced and surface area coverage is improved. Coolant to mainstream flow mass flux ratios greater than unity result in jet blow-off and reduced effectiveness. The convective heat transfer coefficient on the film cooled surface is higher than a similar surface without coolant injection due to the generation of turbulence associated with jet-cross flow interaction.
ID: 030646180; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; .; Thesis (M.S.M.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 171-176).
M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Thermo-Fluids Track

Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) за спеціальністю 05.05.16 "Турбомашини та турбоустановки", (технічні науки). – Національний технічний університету "Харківський політехнічний інститут", Міністерство освіти і науки України, Харків, 2018. Дисертацію присвячено вирішенню важливої науково-технічної задачі вдосконалення систем охолодження газових турбін шляхом подальшого розвитку методів гідравлічного і теплового розрахунку каналів системи охолодження газових турбін. Вивченню структури і властивості потоку в цих елементах, отриманню залежностей, описуючих цей потік. Виконано аналіз науково-технічної літератури, присвяченій проектуванню систем охолодження ГТД, в якому розглянуто міжнародний досвід експериментальних досліджень і обчислювальних експериментів, що до дослідження теплообміну і гідродинаміки течії в обертових елементах. В результаті аналізу літератури показано що, основним напрямом розвитку ефективних і надійних систем охолодження ГТД є підвищення точності розрахунку витратних і гідравлічних характеристик елементів системи охолодження. Показано, що на моделювання процесів впливає геометрія каналу, направлення течії (відцентрове, доцентрове), наявність супутних потоків, параметри і властивості (повітря, масло-повітря) охолоджуючого середовища. Тому від точності, з якою буде змодельований окремий елемент, залежить надійність моделювання всієї системи охолодження. Проведено адаптацію математичних моделей елементів гідравлічних мереж для розрахунку систем охолодження газових турбін, таких як: апарат закручування потоку (АЗ), теплообмінник, канали, що переміщуються. Наведено опис, теоретичні основи моделювання цих елементів гідравлічної схеми, проведені чисельні дослідження по впливу апарата закручування і теплообмінника на ефективність охолодження, складені відповідні моделі систем охолодження. Встановлено, що ефективність охолодження при застосуванні АЗ збільшується на 15%. Запропоновано підхід включення в загальну гідравлічну схему теплообмінника, при загальному наборі початкових даних, які відображають роботу теплообмінника в змінному режимі. Проведено дослідження впливу відцентрового ефекту на можливість подачі повітря в порожнини ротора турбіни. Розглянуті приклади течії повітря в порожнинах, утворених двома паралельними дисками з осьовою або радіальною подачею повітря на периферійному радіусі. Проведений CFD аналіз показав, що в залежності від напрямку подачі повітря істотно змінюється характер течії в порожнині. При радіальній подачі повітря в напрямку осі обертання має місце безвихровий характер течії, при осьовій - з'являється вихор. Проте, відмінність в характері течії майже не позначається на величині протитиску, який перешкоджає переміщенню повітря. Визначено діапазон достовірності результатів методу розрахунку насосного ефекту в придискових порожнинах роторів газових турбін, а саме: відношення ширини порожнини до зовнішнього радіуса диска не перевищує величину 0,17, що дозволяє обґрунтовано використовувати цей метод для розрахунків систем охолодження. Розроблено узагальнений підхід до методу розрахунку коефіцієнтів витрати і гідравлічного опору елементів систем охолодження газових турбін таких, як отвори, потовщені діафрагми, лабіринтові ущільнення, які регламентують витрату охолоджуючого повітря і відповідають за надійність і економічність системи охолодження. Так як розрахунок гідравлічної схеми застосовує коефіцієнти гідравлічного опору кожної ділянки схеми, а експериментальні дані часто представленні коефіцієнтами витрати, тому встановлено зв'язок між ними за допомогою припущень, які враховують різницю між стисливим і нестисливим середовищами. На основі проведених досліджень, обґрунтовано поправку на стисливість до коефіцієнту гідравлічного опору подовжених діафрагм, отворів, лабіринтових ущільнень, яка уточнює коефіцієнт гідравлічного опору до 25%. Розроблено математичну модель розрахунку підшипника, описані підходи до визначення концентрації і термодинамічних характеристик двофазного гомогенного середовища, що дозволило включити підшипник як в гідравлічну, так і теплову моделі систем охолодження газових турбін. Розроблено метод розрахунку гідравлічної мережі для маслоповітряної суміші, який істотно розширив можливості моделювання процесів охолодження роторів і підшипників газових турбін і маслозабезпечення підшипників, що дозволило провести спільний розрахунок системи охолодження ротора турбіни і підшипників. Проведено дослідження системи охолодження ротора високотемпературної газової турбіни за допомогою розроблених методів розрахунку. Встановлено, що методи розрахунку відповідають робочим даним газотурбінного двигуна Д 36.
The dissertation for the degree of Candidate of Technical Sciences (Ph. D.) in the specialty 05.05.16 "Turbomachine and turbine plants", (technical sciences). National Technical University "Kharkiv Polytechnical Institute", Ministry of Science and Science of Ukraine, Kharkiv, 2018. Dissertation is devoted to solving an important scientific and technical task of improving the cooling systems of gas turbines by further developing the methods of hydraulic and thermal calculation of the channels of the cooling system of gas turbines. To study the structure and flow properties of these elements, to obtain the dependences describing this flow. The analysis of scientific and technical literature devoted to the design of cooling systems for gas turbine engines was carried out, in which international experience of experimental studies and computational experiments was considered, to the study of heat transfer and flow hydrodynamics in rotating elements. As a result of the analysis of the literature, it is shown that the main direction of development of efficient and reliable GTE cooling systems is to improve the accuracy of the calculation of the flow and hydraulic characteristics of the elements of the cooling system. It is shown that the modeling of processes is influenced by the channel geometry, flow direction (centrifugal, centripetal), presence of associated flows, parameters and properties (air, oil-air) of the cooling medium. Therefore, the accuracy with which the simulation of the entire cooling system depends on the accuracy with which the individual element will be modeled. Mathematical models of hydraulic network elements have been adapted to calculate gas turbine cooling systems, such as: a device for swirling flow, a heat exchanger, channels that are moved. Description, theoretical bases of modeling of these elements of a hydraulic circuit, the researches carried out on the influence of the apparatus of the twist and the heat exchange apparatus on the efficiency of cooling are given, the corresponding models of cooling systems are made. Impact study conducted of the centrifugal effect on the possibility of air supply in the cavity of the rotor of the turbine has been studied. The considered examples of air flow in cavities formed by two parallel disks with axial or radial air supply at a peripheral radius. CFD analysis showed that, depending on the direction of air supply, the nature of the flow in the cavity is significantly changed. At radial air supply in the direction of the axis of rotation there is a non-vortex nature of the flow, with axial - vortex occurs. However, the difference in the nature of the flow almost does not affect the magnitude of the back pressure, which impedes the movement of air. The range of reliability of the results of the calculation method of the pump effect in the disk cavities of the rotors of the gas turbines is determined, namely: the ratio of the width of the cavity to the external radius of the disk does not exceed the value of 0.17, which allows us to use this method reasonably for calculations of the cooling systems. Developed a generalized approach to the method of calculating the flow coefficients and the hydraulic resistance of elements of the cooling systems of gas turbines such as openings, thickened diaphragms, labyrinth seals, regulating the flow of cooling air, which are responsible for the reliability and economy of the cooling system. In the calculations of the hydraulic circuit, the hydraulic resistance coefficients of each section of the circuit are used, and the experimental data are often represented by flow coefficients. Therefore, a connection is established between them using assumptions that take into account the difference between compressible and incompressible media. On the basis of the research, justified correction for compressibility to the coefficient of hydraulic resistance of elongated diaphragms, holes, labyrinth seals, which specifies the coefficient of hydraulic resistance to 25%. A mathematical model for calculating the bearing has been developed, approaches have been described for determining the concentration and thermodynamic characteristics of a two-phase homogeneous medium, which made it possible to include the bearing in both the hydraulic and thermal models of gas turbine cooling systems.A method was developed for calculating the hydraulic network for the air-oil mixture, which significantly expanded the possibilities for simulating the cooling processes of the rotors and bearings of gas turbines and providing bearings with oil, which made it possible to jointly calculate the cooling system of the turbine rotor and bearings. A study of the cooling system of the rotor of a high-temperature gas turbine was carried out using the developed calculation methods. It is established that the calculation methods correspond to the working data of the D-36 gas turbine engine.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.05.16 – турбомашини та турбоустановки, (технічні науки). – Національний технічний університету "Харківський політехнічний інститут", Міністерство освіти і науки України, Харків, 2018. Розроблено методи розрахунку повітряного охолодження і систем маслозабезпечення, які дозволяють отримати якісно нові результати, що сприяють підвищенню надійності проектування системи охолодження ГТУ. Удосконалено метод розрахунку повітряного охолодження за рахунок введення нових елементів таких, як апарат закручування, теплообмінник які розширюють можливості проектування системи охолодження ГТУ і ГТД. Набув подальший розвиток метод розрахунку гідравлічних мереж систем охолодження газових турбін з урахуванням закручування потоку в міждискових порожнинах. Обґрунтовано надійне застосування методу розрахунку насосного ефекту в придискових порожнинах роторів в діапазоні відношення ширини до зовнішнього радіусу диска s/r₂ = 0,17. Розвинений метод розрахунку гідравлічного опору подовжених діафрагм, отворів, лабіринтових ущільнень з урахуванням стисливості середовища Обґрунтовано поправку на стисливість до коефіцієнту гідравлічного опору, що уточнює коефіцієнт гідравлічного опору до 25%. Розроблена сумісна математична модель і метод розрахунку гідравлічного опору двофазного гомогенного середовища, що дозволяє моделювати процеси охолодження і маслозабезпечення в межах загального методу гідравлічного розрахунку системи охолодження, і проводити спільний розрахунок системи охолодження ротора турбіни і підшипників.
The dissertation for the degree of the Candidate of Technical Sciences (Ph.D.) in the specialty 05.05.16 turbomachine and turbine plants, (technical sciences). National Technical University "Kharkiv Polytechnical Institute", Ministry of Science and Science of Ukraine, Kharkiv, 2018. Developed methods for calculating air cooling and oil supply systems allow us to expand the possibilities by introducing new elements such as heat exchanger, labyrinth seals, bearings, as well as obtaining qualitatively new results that increase the reliability of the design of the cooling system of the GT. The reliable application of the method of calculating the pumping effect in the disk cavities of gas turbine rotors in the range of the ratio of width to the outer disk radius s/r₂ = 0,17 is substantiated. The method is developed for calculating the hydraulic resistance of elongated diaphragms, holes, labyrinth seals, considering the compressibility of the medium. The investigated effect on the hydraulic resistance of the angle of the hole. The correction for compressibility to the coefficient of hydraulic resistance of elongated diaphragms, holes, labyrinth seals is justified, that corrects coefficient of hydraulic resistance to 25%. Developed in conjunction mathematical model and a method for calculating the hydraulic resistance of a two-phase homogeneous medium that significantly expands the modeling capabilities of cooling processes and oil supply within the general method of hydraulic calculation of the cooling system, which allowed a joint calculation of the cooling system of the turbine rotor and bearings.

The need for better methods of cooling gas turbine combustors and a review of current cooling techniques have been presented. Three cooling methods are investigated: (a) Full Coverage Discrete Hole Film Cooling (Effusion), (b) Impingement/Effusion Hybrid Cooling Systems, and (c) Transpiration Cooling. The aim of these cooling techniques is to effectively and efficiently cool gas turbine combustors with a significant reduction in current cooling air requirements. The range of test conditions were coolant temperature, Tc, of 289 < Tc 710 K and combustion gases temperature, Tg, of 500 Tg N< 1900 K. The discharge coefficients of the effusion and the impingement/effusion systemshave also been studied. A detailed analysis has been made of the heat transfer of the cooling systems, jet penetration into the cross-stream, prediction of the cooling jet temperatures at various stages in the cooling process and the cooling film heat transfer coefficient. The results of the discharge coefficient (Cd) indicate a decreasing C with increasing wall thickness to diameter ratio, t/D, and a weak effect of cross-stream flow. The results of both the effusion and the impingement/effusion hybrid systems indicate a high cooling performance of similar magnitude to that of the transpiration system. Graphical design correlations for the cooling wall have been made. The optimum hole geometries for both cooling configurations have been developed. The influence of the coolant to hot gas density ratio has been studied over the range 1.4-3.4. In the design of effusion and impingement/effusion cooling systems, wall thickness, hole density, hole diameter and wall design pressure loss are significant parameters for cooling performance maximisation.

A first part of a ”Heat Transfer Handbook” about correlations for internal cooling of gas turbine vanes and blades has been created. The work is based on the cooling of vanes and blades 1 and 2 on different Siemens Gas Turbines. The cooling methods increase the heat transfer in the cooling channels by increasing the heat transfer coefficient and/or increasing the heat transfer surface area. The penalty paid for the increased heat transfer is higher pressure losses.

Three cooling methods, called rib turbulated cooling, matrix cooling and impingement cooling were investigated. Rib turbulated cooling and impingement cooling are typically used in the leading edge or mid region of the airfoil and matrix cooling is mostly applied in the trailing edge region.

Literature studies for each cooling method, covering both open literature and internal reports, were carried out in order to find correlations developed from tests. The correlations were compared and analyzed with focus on suitability for use in turbine conditions. The analysis resulted in recommendations about what correlations to use for each cooling method.

For rib turbulated cooling in square or rectangular ducts, four correlations developed by Han and his co-workers [3.5], [3.8], [3.9] and [3.6] are recommended, each valid for different channel and rib geometries. For U-shaped channels, correlations of Nagoga [3.4] are recommended.

Matrix cooling is relatively unknown in west, but has been used for many years in the former Soviet Union. Therefore available information in open literature is limited. Only one source of correlations was found. The correlations were developed by Nagoga [4.2] and are valid for closed matrixes. Siemens Gas Turbines are cooled with open matrixes, why further work with developing correlations is needed.

For impingement cooling on a flat target plate, a correlation of Florschuetz et al. [5.7] is recommended for inline impingement arrays. For staggered arrays, both the correlations of Florschuetz et al. [5.7] and Höglund [5.8] are suitable. The correlations for impingement on curved target plate gave very different results. The correlation of Nagoga is recommended, but it is also advised to consult the other correlations when calculating heat transfer for a specific case.

Another part of the work has been to investigate the codes of two heat transfer programs named Q3D and Multipass, used in the Siemens offices in Finspång and Lincoln, respectively. Certain changes in the code are recommended.

The successful design of cooling systems for gas turbine engines is a key factor to feasibility of new projects, as the trend for increasing turbine entry temperatures implies requirements for more sophisticated cooling methods. This work focuses on the prediction of cooling performance of turbines, starting from local heat transfer effects at the surface of blades and vanes and expanding to performance simulation of cooled high pressure turbines and engines. In this context, this thesis establishes a new method that investigates the following topics: • The connection between the gas flow field around a cooled blade or vane and the prediction of cooling requirements of the setup. • The connection between a detailed gas flow field around a cooled blade or vane and a preliminary estimation of its metal temperature. • The effect that blade cooling requirements prediction has towards the performance simulation of a cooled turbine and the difference in results between turbine models of different axial resolution. • A simulation platform that includes the aforementioned topics under a web-based gas turbine performance simulation program. The first two objectives are tackled by developing a preliminary cooling design framework, which performs the needed convective and conductive heat transfer calculations between the gas and the blade, the blade and the coolant, and within the blade material. The method divides the geometry into a finite number of volumes, where heat transfer calculations are performed for steady-state conditions. One- and two-dimensional results show a good agreement with previous experimental work. The results suggest that chord resolution for blade heat transfer prediction is essential for a more accurate coolant temperature and mass flow rate prediction. In addition, conduction modelling has a dominant effect in heat transfer prediction of blades with steep temperature gradients. The third objective is achieved by associating the coolant state before mixing with the main stream and the results in turbine performance. The coolant temperature and mass flow rate prediction have a significant impact on turbine work and thermodynamic efficiency, figures highlighted as well for different turbine axial resolution methods. The results suggest that as the coolant heats up through a blade or vane and eventually mixes with the main flow, it contributes significantly towards the predicted turbine work, affecting as well the overall engine performance results, such as specific fuel consumption and specific thrust. A multistage turbine model is most suitable for capturing these effects, but it requires a number of additional inputs. Finally, the thesis suggests that a simulation framework such as the aforementioned, it can be of high usability and applicability if implemented on the cloud, rather than locally installed.

Дисертацію присвячено удосконаленню методів керування неусталеними неізотермічними режимами газотранспортних систем на компресорних станціях і в лінійній частині трубопроводу. Проведено аналітичні дослідження термогазодинамічних процесів у складних системах. Встановлено закономірності розподілу потоку газу при змінних геометричних характеристиках і характеру гідравлічного опору, що дозволило створити новий концептуальних підхід до створення моделі керування режимами: а) математичну модель транспортної мережі з використанням методу ув’язки по вузлам; б) математичну модель газотранспортної мережі без компресорних станцій з використанням методу ув’язки по контурах із урахуванням та вибором початково-граничних умов. Створена модель керування газопотоками і формування параметрів оптимального керування. Встановлено характерні зв’язки між параметрами нестаціонарних процесів у газотранспортних системах для визначення критеріїв нестаціонарності режимів роботи лінійної частини газопроводу, а також введені критерії нестаціонарності при розрахунках режимів роботи газотранспортної системи в цілому. Розроблено класифікацію експлуатаційних режимів та розроблено методику розрахунку нестаціонарних режимів за критерієм мінімальної тривалості перехідних режимів. На основі цих математичних моделей побудовані алгоритми і програми розрахунку нестаціонарних режимів роботи газопроводів при наявності компресорних станцій і відводів, а також проведено розрахунок мінімальної витрати наливного газу для підтримки заданого тиску. Проведені аналітичні дослідження процесів пуску і зупинки компресорних станцій для вибору математичних моделей нестаціонарних процесів і врахування температурних режимів з метою забезпечення оптимального керування експлуатаційними режимами. Даний підхід дозволив розробити моделі і принципи їх реалізації для режимів роботи складної газотранспортної системи, рівномірного завантаження різнотипних газоперекачувальних агрегатів на компресорних станціях з метою мінімальних витрат паливного газу при максимальних поставках газу споживачам.
Диссертация посвящена усовершенствованию методов управления неустановившимися неизотермическими режимами газотранспортных систем на компрессорных станциях и в линейной части трубопровода. Во вступлении обоснована актуальность темы исследований, показана ее связь с научными планами, программами, освещены научная новизна и задачи исследований, научное и практическое значение полученных результатов, дается общая характеристика работы. Приведена информация об апробации работы, ее внедрении, раскрыв личный вклад автора. Подытоживая выполненные исследования можно сделать вывод: полная математическая модель дает возможность зафиксировать ряд явлений, которые возникают во время пуска газопровода - это колебание газа в начальный момент, перемещение нагретого газа вдоль участка магистрального газопровода, колебание температуры в произвольном сечении трубы после прохождения фронта нагретого газа й много других факторов. На основании разработанных математических моделей построены алгоритмы и программы расчета нестационарных режимов работы газопроводов при наличии компрессорных станций и от водов, а также проведен расчет минимальных затрат топливного газа для поддержания заданного давления. Проведены аналитические исследования процессов пуска - остановки компрессорных станций для выбора математических моделей нестационарных процессов и учета температурных режимов с целыо обеспечения оптимальною управления эксплуатационными режимами. Данный подход позволил разработать модели и принципы их реализации для управления режимами работы сложной газотранспортной системы, равномерной загрузки разнотипных газоперекачивающих агрегатов на компрессорных станциях с целью минимальных расходов топливного газа при максимальных поставках газа потребителям.
Dissertation is dedicated to the improvement of gas transporting systems unsettled non-isothermal modes management methods in the compressor stations and linear parts ol the pipelines. Analytical research of the thermal-gas-dynamic processes in complex systems has been conducted. Gas streams distribution regulations under conditions of changing geometrical characteristics and the character of hydraulic resistance have been exposed, that allowed to create the mathematical model of gas-transporting network computation by using the method of binding contour and the method of binding nodes, taking into consideration various initial and boundary conditions. The mathematical model of gas streams control and optimum gas streams management parameters forming has been created. The distinctive correlation between non-stationary processes in the gas-transporting systems parameters have been determined, that allowed to establish the criteria of non-stationary behavior of the linear part of the pipeline operating modes, ai well as to determine the complete gas-transporting system operating modes non-stationari criteria. The gas-transporting systems operating modes classification has been developed as well as the methodology of computation of the non-stationary operating modes of the gas-transporting systems using the criteria of transitory modes minimal duration have beer created. The given approach allowed developing models and principles of their realization for the complex gas-transporting system operating modes, and equal load of differen types of compressor stations gas-pumping equipment with the purpose of gas fuel minimal consumption and maximal gas delivery to the customers.

This thesis presents CFD predictions of gas turbine film and effusion cooling. The dearth of detailed experimental adiabatic effusion cooling data led to the validation of the computational procedures against the experimental adiabatic cooling effectiveness data for a single row of inclined round film cooling holes. This showed that the overall best agreement of the CFD predictions with experimental data was for the realizable k-e turbulence model with enhanced wall function. This was also shown to give good predictions of experimental results for trench outlet film cooling. This film cooling CFD work was extended .to demonstrate trench outlet lip geometries that could further improve the cooling effectiveness. The limitation of the CFD model was at higher blowing rates, M, when the film jet lifted off from the surface, where the CFD did not accurately predict the adiabatic cooling effectiveness close to the hole. For attached jets at lower M the agreement was good. The same CFD procedures were used for all the effusion cooling conjugate heat transfer (CHT) predictions. The hot metal wall effusion cooling experimental data base of Andrews and co-workers (1983-1995) was used to validate the CHT effusion cooling predictions. This database was for combustor flat wall cooling with mainly 90° injection holes. The overall effusion cooling effectiveness was measured and this required conjugate heat transfer CFD predictions. The adiabatic film cooling effectiveness was also predicted, by using a gas tracer in the cooling air and predicting its concentration at the effusion wall. For each effusion hole configuration, the coolant mass flow rate, G kg/srrr2bar, was varied from 0.1 to 1.5 and each G required a separate computation. The influence of the number of holes at a constant X!D of 4.6 and the hole size at fixed X were investigated. The agreement between the predictions and experimental data was good. Finally, the influence of the effusion coolant jets flow direction to the hot-gas crossflow on effusion cooling performance was investigated. This included 30° inclined opposed-flow jets effusion wall, which was predicted to be the best effusion jets flow pattern. The addition of the filleted shape trench outlet to effusion cooling was predicted to improve the cooling performance with reduced coolant mass flow rate, due to the improved adiabatic film cooling.

In this study, a new gas turbine monitoring system being able to carry out appropriate run process is set up for a gas turbine with 250 kW power rating and its accessories. The system with the mechanical and electrical connections of the required sub-parts is transformed to a kind of the test stand. Performance test result calculation method is described. In addition that, performance evaluation software being able to apply with the completion of the preliminary performance tests is developed for this gas turbine. This system has infrastructure for the gas turbine sub-components performance and aerothermodynamics research. This system is also designed for aviation training facility as a training material for the gas turbine start and run demonstration. This system provides the preliminary gas turbine performance research requirements in the laboratory environment.

The present study aims at conducting a numerical investigation of the classic film cooling scheme of transpiration film cooling and effusion film cooling for validation through computational methods. Steady-state simulations were performed and the flow was considered incompressible with low turbulence. The CFD package FLUENT 6.2.16 was used to solve the Navier-Stokes equations numerically, and the pre-processor, Gambit 2.2.30, was used to generate the required grid. The research aims at perfonning computational predictions on the film cooling performance and the aerodynamics aspect of flat plate film cooling ·on the transpiration and effusion film cooling. It was determined that the proposed scheme and type of geometry, coupled with the hybrid mesh generation, can validate the classic experimental results. with reasonable agreement. Computational predictions on the transpiration film cooling have shown that different boundary conditions used for the porous media may lead to different results, whether it is over-prediction or under-prediction results in comparison with the experimental data. It has been observed for the effusion film cooling, on the case of co-flow coolant , . ejection into the mainstream, that the adiabatic film cooling effectiveness continuously increases with the axial distance towards the leading edge where the flow of the coolant is fully-developed. Furthermore, the streamwise cooling uniformity was better than in the upstream region at the middle region of the test wall. In contrast, the adiabatic film cooling effectiveness for the opposed flow coolant ejection into the mainstream flow was gradually decreasing with the axial distance. Coflow coolant ejection into the mainstream has provide better cooling effectiveness but the oppose flow coolant ejection from the cooling holes has proved to be good aerodynamics in protecting the adjacent wall due to the large area of the film cooling coverage of the combustor wall. The present study was concerned only with the downstream effectiveness aspect on the performance of the coolant mass flow on the geometrical parameters effects; for transpiration film cooling - the pore size, and effusion film cooling - hole diameter, film cooling hole arrangement, number of holes, inclination and orientation of cooling hole with respect to the mainstream flow. The performance related to the heat transfer coefficient and conjugate heat transfer is a prospective topic for future studies. Advanced and innovative cooling techniques are essential in order to improve the efficiency and output power of the gas turbines. The CFD predictions performed have utilised a scalar tracer gas in the coolant flow and has been very effective at visualizing the coolant to the mainstream mixing phenomenon, determining the boundary layer development and directly predicting the adiabatic film cooling effectiveness. Current methods in determining the film cooling effectiveness using the scalar tracer gas concentration facilitate the future study on the conjugate heat transfer pred,iction where the temperature profiles cannot be used because conjugate heat transfer is highly affected by the effect ofthe temperature in the system. The technique· of providing an alternative method using the heat and mass transfer analogy in quantify the cooling effectiveness combines the advantages of using a scalar tracer gas in determining the cooling effectiveness and also provide clear insight into the film cooling structure in the cooling hole and coolant interaction in the mainstream when the experimental method is at 'off-limit'. The results of the present investigations performed were used to validate the computation model. Therefore, this study is of value for those interested in gas turbine cooling.

In gas turbine development, the direction has been toward higher turbine inlet temperatures to increase the work output and thermal efficiency. This extreme environment can significantly impact component life. One means of preventing component burnout in the turbine is to effectively use film-cooling whereby coolant is extracted from the compressor and injected through component surfaces. One such surface is the endwall of the first stage nozzle guide vane.

This thesis details the design, prediction, and testing of two endwall film-cooling hole patterns provided by leading gas turbine engine companies. In addition a flush, two-dimensional slot was included to simulate leakage flow from the combustor-turbine interface.

The slot coolant was found to exit in a non-uniform manner leaving a large, uncooled ring around the vane. Film-cooling holes were effective at distributing coolant throughout much of the passage, but at low blowing rates were unable to provide any benefit to the critical vane-endwall junction both at the leading edge and along the pressure side. At high blowing ratios, the increased momentum of the jets induced separation at the leading edge and in the upstream portion of the passage along the pressure side, while the jets near the passage exit remained attached and penetrated completely to the vane surface.

Computational fluid dynamics (CFD) was successful at predicting coolant trajectory, but tended to under-predict thermal spreading and jet separation. Superposition was shown to be inaccurate, over-predicting effectiveness levels and thus component life, because the flow field was altered by the coolant injection.
Master of Science

Modern gas turbine engines run at extremely high temperatures which require the high pressure turbine blades to be extensively cooled in order to reach life requirements. This must be done using the minimum amount of coolant in order to reduce the negative impacts on the cycle efficiency. In the design process the cooling configuration and stress distribution must be carefully considered before verification of the design is conducted. Improvements to all three of these blade design areas are presented in this thesis which investigates internal cooling systems in the form of ribbed, radial passages and leading edge impingement systems. The effect of rotation on the heat transfer distribution in ribbed radial passages is investigated. An engine representative triple-pass serpentine passage, typical of a gas turbine mid-chord HP blade passage, is simulated using common industrial RANS CFD methodology with the results compared to those from the RHTR, a rotating experimental facility. The simulations are found to perform well under stationary conditions with the rotational cases proving more challenging. Further study and simulations of radial passages are undertaken in order to understand the salient flow and heat transfer features found, namely the inlet velocity profile and rib orientation relative to the mainstream flow. A consistent rib direction gives improved heat transfer characteristics whilst careful design of inlet conditions could give an optimised heat transfer distribution. The effect of rotation on the heat transfer distribution in leading edge impingement systems is investigated. As for the radial passages, RANS CFD simulations are compared and validated against experimental data from a rotating heat transfer rig. The simulations provide accurate average heat transfer levels under stationary and rotating conditions. The full target surface heat transfer in an engine realistic leading edge impingement system is investigated. Experimental data is compared to RANS CFD simulations. Experimental results are in line with previous studies and the simulations provide reasonable heat transfer predictions. A new method of combined thermal and mechanical analysis is presented and validated for a leading edge impingement system. Conjugate CFD simulations are used to provide a metal temperature distribution for a mechanical analysis. The effect of changes to the geometry and temperature profile on stress levels are studied and methods to improve blade stress levels are presented. The thermal FEA model is used to quantify the effect of HTC alterations on different surfaces within a leading edge impingement system, in terms of both temperature and stress distributions. These are then used to provide improved target HTC distributions in order to increase blade life. A new method using Gaussian process regression for thermal matching is presented and validated for a leading edge impingement case. A simplified model is matched to a full conjugate CFD solution to test the method's quality and reliability. It is then applied to two real engine blades and matched to data from thermal paint tests. The matches obtained are very close, well within experimental accuracy levels, and offer consistency and speed improvements over current methodologies.

During hot days, gas turbine power output deteriorates significantly. Among various means to augment gas turbine output, inlet air fog cooling is considered as the simplest and most costeffective method. During fog cooling, water is atomized to micro-scaled droplets and introduced into the inlet airflow. In addition to cooling the inlet air, overspray can further enhance output power by intercooling the compressor. However, there are concerns that the water droplets might damage the compressor blades and increased mass might cause potential compressor operation instability due to reduced safety margin. Furthermore, the two-phase flow thermodynamics during wet compression in a rotating system has not been fully established, so continued research and development in wet compression theory and prediction model are required. The objective of this research is to improve existing wet compression theory and associated models to accurately predict the compressor and the entire gas turbine system performance for the application of gas turbine inlet fog cooling. The following achievements have been accomplished: (a) At the system level, a global gas turbine inlet fog cooling theory and algorithm have been developed and a system performance code, FogGT, has been written according to the developed theory. (b) At the component level, a stage-stacking wet compression theory in the compressor has been developed with known airfoil configurations. (c) Both equilibrium and non-equilibrium water droplet thermal-fluid dynamic models have been developed including droplet drag forces, evaporation rate, breakup and coalescence. A liquid erosion model has also been developed and incorporated. (d) Model for using computational fluid dynamics (CFD) code has been developed to simulate multiphase wet compression in the rotating compressor stage. In addition, with the continued increase in volatility of natural gas prices as well as concerns regarding national energy security, this research has also investigated employing inlet fogging to gas turbine system fired with alternative fuels such as low calorific value synthetic gases. The key results include discovering that the saturated fogging can reduce compressor power consumption, but overspray, against conventional intuition, actually increases compressor power. Nevertheless, inlet fogging does increase overall net power output.

This work focuses on a comparative analysis among three compressor inlet air cooling techniques using a thermodynamic approach to simulate the gas turbine cycle. Firstly, a Base Case is tested to determine the gas turbine performance without any cooling method. The effect of site altitude on the power output gas turbine even without any cooling technique is also simulated. After, the evaporative cooling, absorption and mechanical refrigeration chillers are studied under different ambient temperature and relative humidity. Results showed that the cooling potential of the evaporative system is dependent of its effectiveness, while the absorption chiller cooling load is determined by pre-established compressor inlet air temperature. For the mechanical chiller method, however, it is necessary also to consider the power demand required by the vapour refrigerant compression. It is important to observe that although the absorption chiller has been the more suitable cooling method, it is only a realizable solution if the exhaust gases heat are available and with adequate discharge temperature. Furthermore, the gas turbine analysis is carried out at two brazilian locations: Campos/RJ and Goiania/GO. The monthly power output gain offered by the evaporative cooling method is low due to its intrinsic limitation, the ambient wet-bulb temperature. Further, the mechanical chiller system provided a considerable improvement in power output monthly results. However, the best power output increment is reached when the absorption chiller system is employed. Besides, a preliminary economic analysis showed that evaporative cooling offered the lowest unit electric energy cost, but associated with the lesser incremental power generation potential. On the other hand, the chillers systems are more expensive, while provide larger values of incremental electric energy. Results also showed that the cooling techniques allow obtaining a considerable increase in power generation with a lower cost in comparison with the gas turbine plant without any cooling method.

The Large Eddy Simulation approach is employed to predict the flow physics and heat transfer characteristics of a film-cooling problem that is formed from the interaction of a coolant jet with a hot mainstream flow. The film-cooling technique is used to protect turbine blades from thermal failure, allowing the gas inlet temperature to be increased beyond the failure temperature of the turbine blade material in order to enhance the efficiency of gas turbine engines. A coolant fluid is injected into the hot mainstream through several rows of injection holes placed on the surface of a gas turbine blade in order to form a protective coolant film layer on the blade surface. However, due to the complex, unsteady and three-dimensional interactions between the coolant and the hot gases, it is difficult to achieve the desired cooling performance. Understanding of this complex flow and heat transfer process will be helpful in designing more efficiently cooled rotor blades. A comprehensive numerical investigation of a rotating film-cooling performance under different conditions is conducted in this thesis, including film-cooling on a flat surface and film-cooling on a rotating gas turbine blade. The flow-governing equations are discretised based on the finite-volumes method and then solved iteratively using the well-known SIMPLE and PISO algorithms. An in-house FORTRAN code has been developed to investigate the flat plate film-cooling configuration, while the gas turbine blade geometry has been simulated using the STAR-CCM+ CFD commercial code. The first goal of the present thesis is to investigate the physics of the flow and heat transfer, which occurs during film-cooling from a standard film hole configuration. Film-cooling performance is analysed by looking at the distribution of flow and thermal fields downstream of the film holes. The predicted mean velocity profiles and spanwise-averaged film-cooling effectiveness are compared with experimental data in order to validate the reliability of the LES technique. Comparison of adiabatic film-cooling effectiveness with experiments shows excellent agreement for the local and spanwise-averaged film-cooling effectiveness, confirming the correct prediction of the film-cooling behaviour. The film coverage and film-cooling effectiveness distributions are presented along with discussions of the influence of blowing ratio and rotation number. Overall, it was found that both rotation number and blowing ratio play significant roles in determining the film-cooling effectiveness distributions. The second goal is to investigate the impact of innovative anti-vortex holes on the film-cooling performance. The anti-vortex hole design counteracts the detrimental kidney vorticity associated with the main hole, allowing coolant to remain attached to the blade surface. Thus, the new design significantly improves the film-cooling performance compared to the standard hole arrangement, particularly at high blowing ratios. The anti-vortex hole technique is unique in that it requires only readily machinable round holes, unlike shaped film-cooling holes and other advanced concepts. The effects of blowing ratio and the positions of the anti-vortex side holes on the physics of the hot mainstream-coolant interaction in a film-cooled turbine blade are also investigated. The results also indicate that the side holes of the anti-vortex design promote the interaction between the vortical structures; therefore, the film coverage contours reveal an improvement in the lateral spreading of the coolant jet.

Transpiration cooling as potential replacement of multi-hole effusion cooling for gas turbine engines combustion liner application is investigated by comparing their cooling film effectiveness based on the mass transfer analogy (CFEM). Pressure sensitive paint was used to measure CFEM over PM surfaces which was found to be on average 40% higher than multi-hole effusion cooling. High porosity PM with low resistance to flow movement were found to offer uneven distribution of exiting coolant, with large amounts leaving the trailing edge, leading to lopsided CFEM. Design of anisotropic PM based on PM properties (porosity, permeability, and inertia coefficient) were investigated using numerical models to obtain more uniform CFEM. Heat transfer analysis of different PM showed that anisotropic samples offered better thermal protection over isotropic PM for the same porosity. Comparison between cooling film effectiveness obtained from temperatures CFET against CFEM revealed large differences in the predicted protection. This is attributed to the assumptions made to apply CFEM, nonetheless, CFEM remains a good proxy to study and improve transpiration cooling. A method for creating a CAD model of designed PM is proposed based on critical characteristics of transpiration cooling for future use in 3D printing manufacturing.

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Bachelors
Engineering and Computer Science
Aerospace Engineering

A higher demand in power output from modern land based gas turbines has resulted in an increase in combustor exit temperatures. High temperatures in turn have resulted in flatter profiles at the combustor exit warranting the need for sufficient cooling of the endwall region. Endwall cooling is affected by the coolant flow through certain design features. A typical endwall design includes a leakage slot at the interface between the combustor and the vane, a leakage slot at the vane-to-vane interface and film-cooling holes. In addition, with the increase in energy demands and depletion of natural gas resources, alternate fuels such as coal derived synthetic gas are being used in gas turbines. Coal derived fuels, however, contain traces of ash and other contaminants that deposit on endwall surfaces, thereby altering its surface conditions. The purpose of this study was to investigate the effects of realistic endwall features and surface conditions on leading edge endwall cooling. Endwall designs like placing film-cooling holes in a trench, which provide an effective means of improving cooling were also studied at the leading edge. An infrared camera was used to obtain measurements of adiabatic effectiveness levels and a laser Doppler velocimeter was used for flowfield measurements. This study was done on a large scale, low-speed, recirculating wind tunnel operating at a Reynolds number of 2.1e+5 and an inlet mainstream turbulence level of 1%. Endwall measurements were taken for coolant flow through varying slot width at the combustor-vane interface. A constant coolant mass flow and a narrower combustor-turbine interface slot caused the coolant to exit uniformly whereas increasing the slot width had an opposite effect. Measurements were also taken with hole blockage and spallation, which showed a 10-25% decrease in the effectiveness levels whereas near hole deposition showed a 20% increase in effectiveness levels. A comparison of the cooling effectiveness due to placement of film-cooling holes in a trench was made to film-cooling holes not placed in a trench. Measurements indicated a superior performance of trenched holes to holes without a trench. Trenched holes showed a 60% increase in effectiveness levels due to decreased coolant jet separation.
Ph. D.

In the design of mechanical components, numerical simulations and experimental methods are commonly used for design creation (or modification) and design optimization. However, a major challenge of using simulation and experimental methods is that they are time-consuming and often cost-prohibitive for the designer. In addition, the simultaneous interactions between aerodynamic, thermodynamic and mechanical integrity objectives for a particular component or set of components are difficult to accurately characterize, even with the existing simulation tools and experimental methods. The current research and practice of using numerical simulations and experimental methods do little to address the simultaneous “satisficing” of multiple and often conflicting design objectives that influence the performance and geometry of a component. This is particularly the case for gas turbine systems that involve a large number of complex components with complicated geometries. Numerous experimental and numerical studies have demonstrated success in generating effective designs for mechanical components; however, their focus has been primarily on optimizing a single design objective based on a limited set of design variables and associated values. In this research, a multiobjective design optimization framework to solve a set of user-specified design objective functions for mechanical components is proposed. The framework integrates a numerical simulation and a nature-inspired optimization procedure that iteratively perturbs a set of design variables eventually converging to a set of tradeoff design solutions. In this research, a gas turbine engine system is used as the test application for the proposed framework. More specifically, the optimization of the gas turbine blade internal cooling channel configuration is performed. This test application is quite relevant as gas turbine engines serve a critical role in the design of the next-generation power generation facilities around the world. Furthermore, turbine blades require better cooling techniques to increase their cooling effectiveness to cope with the increase in engine operating temperatures extending the useful life of the blades. The performance of the proposed framework is evaluated via a computational study, where a set of common, real-world design objectives and a set of design variables that directly influence the set of objectives are considered. Specifically, three objectives are considered in this study: (1) cooling channel heat transfer coefficient, which measures the rate of heat transfer and the goal is to maximize this value; (2) cooling channel air pressure drop, where the goal is to minimize this value; and (3) cooling channel geometry, specifically the cooling channel cavity area, where the goal is to maximize this value. These objectives, which are conflicting, directly influence the cooling effectiveness of a gas turbine blade and the material usage in its design. The computational results show the proposed optimization framework is able to generate, evaluate and identify thousands of competitive tradeoff designs in a fraction of the time that it would take designers using the traditional simulation tools and experimental methods commonly used for mechanical component design generation. This is a significant step beyond the current research and applications of design optimization to gas turbine blades, specifically, and to mechanical components, in general.
Ph.D.
Doctorate
Industrial Engineering and Management Systems
Engineering and Computer Science
Industrial Engineering

The cooling effectiveness with the skin cooled micro cooling of a single gas turbine blade is analyzed numerically. The study use Hypermesh to generate a comprehensive 3D mesh of the domain that consists of air around the blade, skin layer of the blade, the cooling channels that wrap around the blade and the core metallic blade inner core. The micro channels were rectangular channel width of 2.54 mm x 0.39mm and heat transfer coefficient varying from (800and 1100 W/m2K) with the channel inlet velocity being constant. The study examined the flow pattern and the local heat transfer effect on the blade temperature. The results show the comparison of the channel HTC of 800 W/m²k and 1100 W/m²K and the effect of coolant inlet temperature on the blade bulk temperature.

Gas turbine engines for propulsion operate under harsh conditions including gas temperatures that exceed the melting point of the metal, high mechanical stresses, and particulate ingestion such as sand. To maintain a low and uniform metal temperature to extend the life of a turbine component, a complex scheme of internal convective cooling and external film-cooling is required. Gas turbine engines operated in sandy or dusty environments can ingest a large quantity of sand into the mainstream and, more importantly, into the cooling system. Sand ingested into the coolant system has the potential to reduce or block off the flow intended to cool the turbine blades or vanes. If the source of coolant air to a critical region of a turbine blade were partially blocked, it would result in a substantial reduction in component life. This study includes establishing a methodology for testing sand ingestion characteristics on a simulated turbine component with film-cooling holes at room temperature and engine temperatures. The study evaluates a simple array of laser drilled film-cooling holes, similar to a showerhead on the leading edge of an airfoil. The blocking characteristics of this design indicate that increasing the airflow or decreasing the sand amount results in a decreased blockage. It was also determined that as the metal temperature increases, the blockage from a given amount of sand increases. The methodology used in the primary portion of this thesis was modified to test sand ingestion characteristics on actual turbine blades with film-cooling holes at room temperature and engine temperatures. The study evaluated the blockage performance of several different turbine blades including the F-100-229-full, F-100-229-TE, and the F-119 with a new trailing edge cooling methodology know as a microcircuit. It was shown that increasing the airflow or pressure ratio, or decreasing the sand amount would result in decreased blockage. It was also shown that over a certain metal and coolant temperature, the blockage is significantly worsened. However, it was also shown on the F-119 turbine blade that below a given metal temperature, there is no impact of metal or coolant temperature on sand blockage.
Master of Science

In the modern advanced gas turbines, the turbine inlet temperature may exceed 1500°C as a requirement to increase power output and thermal efficiency. Therefore, it is imperative that the blades and vanes are cooled so they can withstand these extreme temperatures. Film cooling is a cooling technique widely used in high-performance gas turbines. However, the film cooling effectiveness has almost reached plateau, resulting in a bottleneck for continuous improvement of gas turbines' efficiency. In this study, an innovative cooling scheme, mist film cooling is investigated through experiments. A small amount of tiny water droplets with an average diameter about 10-15 µm (mist) is injected into the cooling air to enhance the cooling performance. A Phase Doppler Particle Analyzer (PDPA) system is used for droplet measurements. Mist film cooling performance is evaluated and compared against air-only film cooling. This study continues the previous work by (a) adding fan-shaped holes and comparing their cooling performance with the round holes, (b) extending the length of the test section to study the performance farther downstream the injection holds, and (c) using computational simulation to investigate the feasibility of transporting mist to the film cooling holes through gas turbine inside passages. The results show that, with an appropriate blowing ratio, the fan-shaped holes performs about 200% better than round holes in cooling effectiveness and adding 10% (wt.) mist can further enhance cooling effectiveness 170% in average. Farther downstream away from the injection holes (X/D> 50), mist cooling enhancement prevails and actually increases significantly. PDPA measurements have shed lights to the fundamental physics of droplet dynamics and their interactions with thermo-flow fields. These experimental results lead to either using lower amount of cooling air or use fewer number of cooing holes rows. This means higher gas turbine power output, higher thermal efficiency, and longer components life which will reflect as a cheaper electricity bill. Computational Fluid Dynamics (CFD) showed that it is feasible to transport the water mist, with initial diameters ranging from 30 µm-50 µm and mist ratio of 10-15%, to the cooling holes on the surface of the turbine vanes and rotors to provide the desired film cooling. Key words: Gas Turbines, Heat Transfer, Film / mist Cooling, Experimental Study, Mist Transport, CFD, PDPA.

Siemens Industrial Turbomachinery AB produce five gas turbines models. The SGT-700 can currently only start on gases which contain low amounts of inert gases. It is therefore of interest to widen the fuel range which the SGT-700, as well as other gas turbines, can start on. This report investigates the maximum limit of inert gases the SGT-700 will be able to start on, but also investigates if it is possible to start on liquid fuel (diesel) by making a few modifications to the gas turbine. To investigate this, the atmospheric combustion rig available at Siemens in Finspång has been used with a standard burner, igniter and ignition unit for the SGT-700. For the liquid fuel, the igniter was replaced by a torch igniter specially made for liquid fuels. Four different gases were evaluated; methane, propane, CO2 and N2 in order to see the effect of both various hydrocarbons and various inert gases. A model was developed for the gaseous experiments to estimate the limit for the maximum amount of inert gases the gas turbine would be able to start on. The model suggested that CO2 would require a larger amount of energy than N2 for the same amount in the composition, but that varying hydrocarbons did not have any effect if looking at the mass % of inert gas in the composition. The model was also extended with ethane and hydrogen but no experiments were performed with these gases. The model gave satisfying results. It overestimated the maximum amount of inert gases which could be mixed with propane, but agreed well when comparing the two inert gases with each other. Other interesting results were that an increased fuel flow decreased the minimum ignition energy and that an increased air flow gave a minor decrease in the maximum amount of inert gases that was possible to ignite. The torch igniter for the liquid fuel worked in a satisfying way. The ignition energy was however too low, so the ignition reliability was low. A new ignition unit with larger energy output therefore needs to be implemented. The igniter was fairly insensitive to variations in burner air flow and the ignition delay was small enough to provide a sustainable flame.

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.

A thermal tip clearance control system provides a robust and flexible means of manipulating the closure between the casing and the rotating blade tips in a jet engine, reducing undesirable tip leakage flows. This may be achieved using an impingement cooling scheme on the external casing of the engine in conjunction with careful thermal management of internal over-tip seal segment cavity. For a reduction in thrust specific fuel consumption, the mass flow rate of air used for cooling must be minimised, be at as low a pressure as possible and delivered through a light weight structure surrounding the rotating components in the turbine. This thesis first characterises the effectiveness of a range of external impingement cooling arrangements in typical engine casing closure system. The effects of jet-to-jet pitch, number of jets, inline and staggered alignment of jets, arrays of jets on flange, on an engine representative casing geometry are assessed through comparison of the convective heat transfer coefficient distributions in a series of numerical studies. A baseline case is validated experimentally. The validation data allowed the suitability of different turbulence closure models to be assessed using a commercial RANS solver. Importantly for each configuration the thermal contraction of an idealised engine casing is predicted using thermo-mechanical finite element models, at a series of operating conditions representing engine idle to maximum take-off conditions. Cooling is provided by manifolds attached to the outside of the engine. The assembly tolerance of these components leads to variation in the standoff distance between the manifold and the casing. For cooling arrangements with promising performance, the study is extended to characterise the variation in closure with standoff distance. It is shown that where a sparse array of non-interacting jets is used the system can be made tolerant of large build misalignments. The casing geometry itself contributes to the thermal response of the system, and, in an additional study, the effect of casing thickness and circumferential thermal control flanges are investigated. Restriction of the passage of heat into the flanges was seen to be dramatically change their effectiveness and slight necking of the flanges at their root was shown to improve the performance disproportionally. High temperature secondary air flowing past the internal face of the engine casing tends to heat the casing, causing it to grow. Experimental and numerical characterisation of a heat transfer within a typical over-tip segment cavity heat transfer is presented in this thesis for the first time. A simplified modelling strategy is proposed for casing and a means to reduce the casing heat pickup by up to 25 % was identified. The overall validity of the modelling approach used is difficult to validate in the engine environment, however limited data from a test engine temperature survey became available during the course of the research. By modelling this engine tip clearance control system it was shown that good agreement to the temperature distribution in the engine casing could be achieved where full surface external heat transfer coefficient boundary conditions were available.