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In this paper, the performance of a compact Three-Fluid Combined Membrane Contactor (3F-CMC) is investigated using Computational Fluid Dynamics (CFD), supported and validated with a good agreement by an experimental campaign made on a fully working prototype. This internally-cooled membrane contactor is the core component of a hybrid air conditioning system for electric vehicles (EVs) developed in a successful H2020 project called XERIC. In the adopted numerical approach, the conjugate heat and mass transfer inside the 3F-CMC is described by non-isothermal incompressible flows and vapor transport through a PTFE hydrophobic membrane. The sensitivity of the 3F-CMC performance to air/desiccant flow rates, temperature, humidity, and desiccant concentration is analyzed numerically through the validated CFD codes. According to this study, the moisture removal increases by the inlet humidity ratio, nearly linearly. Under the considered conditions (where the inlet air temperature is 26.2 &deg, C), when the inlet relative humidity (RH) is 75% the moisture removal is about 450% higher than the case RH = 37%, while the absorption effectiveness declines about 45%. Furthermore, this study shows that the amount of absorbed vapor flux rises by increasing the airflow rate, on the other hand, the higher the airflow rate, the lower is the overall absorption efficiency of the 3F-CMC. This investigation gives important suggestions on how to properly operate a 3F-CMC in order to achieve the requested performance, especially in hot and humid climates.

Die Anforderungen der Industrie an Zerspanungswerkzeuge nehmen durch den Einsatz neuer Werkstoffe und der Forderung nach k��rzeren Bearbeitungszeiten immer mehr zu. Um diesen Anspr��chen, beispielsweise in der Serienfertigung von Automotive-Unternehmen, gerecht werden zu k��nnen, m��ssen Zerspanungswerkzeuge dementsprechend hochwertig ausgef��hrt und st��ndig weiterentwickelt werden. Ein Schneidwerkstoff, der hervorragende Vorteile hinsichtlich Stabilit��t und Verschlei��festigkeit mit sich bringt, und ein gro��es Potential f��r zuk��nftige Entwicklungen von Zerspanungswerkzeugen besitzt, ist der Diamant. Es ist zurzeit das h��rteste bekannte Element und wird f��r die Zerspanung von NE-Metallen und Nichtmetallen eingesetzt. Der aktuell noch gr����te Nachteil von Diamant ist die Einschr��nkung seines Einsatzgebietes. Die Zerspanung von Eisen-Kohlenstoff-Legierungen mit Diamantwerkzeugen ist aufgrund von Diffusionsvorg��ngen, die ab einer Temperatur von 700C auftreten, nur bedingt m��glich. Am Institut f��r Fertigungstechnik und Hochleistungslasertechnik der Technischen Universit��t Wien gibt bzw. gab es bereits einige Forschungsarbeiten, die sich mit der K��hlung von verschiedenen Ausf��hrungen von Wendeschneidplatten besch��ftigen. Mithilfe eines erodierten, internen K��hlkanals in die Wendeschneidplatte konnten auch bereits erste Erfolge in der Bearbeitung von Eisen-Kohlenstoff-Legierungen mit PKD (polykristalliner Diamant) -Werkstoffen erzielt werden. Diese Arbeit besch��ftigt sich mit der Entwicklung einer innovativen K��hlungsmethode, bei der die Drehbearbeitung von Einsen-Kohlenstoff-Legierungen unter Verwendung von PKD-Wendeschneidplatten erm��glicht werden soll. Diese innovative K��hlungsmethode setzt sich aus der Kombination einer internen K��hlung (IK) und einer externen Minimalmengenschmierung (MMS) zusammen. Unter Zuhilfenahme des Simulationsprogramms ANSYS wurde der K��hlkanal f��r die Innenk��hlung sowohl mechanisch als auch str��mungstechnisch optimiert und mittels des Verfahrens des Senkerodierens in die Wendeschneidplatte eingearbeitet. Ebenfalls musste der Drehhalter mit geeigneten Zuund Abf��hrbohrungen f��r den K��hlschmierstoff versehen werden. Neben verschiedenen PKD-Wendeschneidplatten wurden zudem diverse CBN-Wendeschneidplatten mit der eben beschriebenen K��hlungsmethode erprobt. Durch grundlegende Schnittversuche an einem Bearbeitungszentrum (BAZ) wurden die ermittelten Versuchsergebnisse analysiert und miteinander verglichen., The requirements for modern cutting tools in the field of production engineering is constantly rising, due to more efficient processing times and the development of novel material combinations. In order to meet these industrial requirements, cutting tools need to be refined and improved constantly. One of the most advantageous cutting material, which improvable benefits are optimal for the utilization of cutting tools, is diamond. Due to its outstanding characteristic in hardness, its use in the modern industry is indispensable. Diamond is often applied in the machining of non-ferrous metal and nonmetal material. A serious disadvantage of diamond is the limited field of application, as the machining of an iron-carbon alloy is just conditionally possible because of diffusion processes that occur above 700C. The Institute for Production Engineering and Laser Technology of the Vienna University of Technology has already developed a technique for the cooling of various types of cutting inserts. By implementation of a cooling channel by electric discharge machining (EDM), initial successes could have been made in the machining of iron-carbon alloys with PCD (polycrystalline diamond) -tools. The present master thesis is focused on the development of an innovative cooling system to enable the machining (turning, in particular) of iron-carbon alloys by the use of PCD-inserts. This innovative cooling system is made up by the combination of internal cooling with cutting fluid and an external minimum lubrication. The flow-optimized cooling channel for the internal cooling has been assessed, considering mechanical as well as fluid mechanical aspects, by using the simulation program ANSYS. Furthermore, the tool holder had to be modified with bore holes for the feed and discharge system of the internal cutting fluid. Besides the PCD-inserts, the explained cooling system has also been tested on CBN-inserts, to have comparable results between the different tool materials. The results ruling from various experimental cutting tests have been analyzed and evaluated.

Bu çalışmanın amacı farklı şekil ve dizilimlere sahip iğne-kanat yapılarının ısı transferi ve basınç kaybı üzerindeki etkisini tespit etmektir. Bu çalışma kapsamında; gaz türbinli motorlar için kritik konulardan biri olan türbin soğutma teknolojileri incelenmiştir. Dış ve iç soğutma teknolojileri hakkında genel hatları ile bilgiler verildikten sonra iğne-kanat soğutma konusu üzerinde durulmuştur. Daha sonra konu ile ilgili teorik bilgiler paylaşılmış olup, literatürdeki mevcut çalışmalar özetlenmiş ve literatür taraması sonucunda tespit edilen bir deneysel çalışma; analiz modelini doğrulama çalışması olarak kullanılmıştır. Yapılan doğrulama ve ağdan bağımsızlık çalışmalarıyla; uygulanan modelleme ve analiz yaklaşımının güvenilirliği tespit edilmiş olup, analiz matrisine göre farklı kesit, dizilim, boyut ve Reynolds Sayıları için analizler gerçekleştirilmiştir. Tüm bu çalışmalardan sonra ise; yapılan analizler sonucunda elde edilen bulgular paylaşılmıştır. The aim of this study was to determine the effect of pin-fins having different shapes and configurations on the heat transfer and pressure loss. This scope of work; turbine cooling technologies, which is one of the critical issues for gas turbine engines, were examined. Having provided general information about the external and internal cooling technologies, the pin-fin cooling is emphasized. Then the theoretical information about this topic has been shared and the current studies in the literature are summarized. One of the experimental studies which is determined as a result of literature review, was used for the validation of the analysis model. The reliability of the applied modeling and analysis approach was determined with verification and mesh independence work. For different cross-section, configuration, dimension and Reynolds numbers were analyzed according to the analysis matrix. After all these studies; the results obtained from the analysis were shared. 71

In this contribution, a novel rig was used to assess the heat transfer coefficients on a full internal multi pass cooling scheme. Transient liquid crystal technique was used for the measurement of the heat transfer coefficient (HTC) on channel's internal surfaces. A first set of experiments were performed at engine similar conditions of Re=21000 and Ro=0.074. In order to assess the reliability of the measurement methodology and to explore the thermal behavior at higher rotation numbers, tests were also carried out at Re=17000 and Ro=0.074-0.11. From the spatially resolved HTC maps made available, it is possible to characterize the thermal performances of the whole passage and to highlight the effect of rotation.

Made available in DSpace on 2018-12-11T17:27:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-12-01 The elimination of cutting fluids’ usage is one of the great challenges of sustainable manufacturing. Various devices and alternative techniques have been developed, but their results are limited, as well as their commercial applications. Most of them require drastic changes in the cutting tools or machine tools, or operate with nonevaporative cooling cycles, with low cooling capacity. The aim of this study is to present a device that overcomes these limitations and stands as an alternative to the application of cutting fluid without sacrificing the performance of the machining. Thus, a toolholder is developed that enables the indirect cooling of the cutting tool with a pumped two-phase system using the coolant R141b (vaporization temperature of 32 °C). In this system, the geometry of the cutting tool is not changed and there is no direct contact with the refrigerant, so there is no contamination or piece cleaning necessity. Moreover, the system operates in a closed circuit with only 5 l of coolant that does not require constant treatment. The performance of the proposed method of internal cooling is evaluated by turning tests of AISI 1045 steel under conditions of continuous and interrupted cut. The turning tests compare the lives of the uncoated cemented carbide cutting tools, their temperatures, and wear mechanisms acting during machining with the internal cooling method, or cutting fluid or dry cutting. The results show that the internal cooling is able to extend the life of cutting tools by 58 % in interrupted cutting and by 7 % in continuous cutting in relation to the cutting fluid application and by 13 and by 45 % in relation to the interrupted and continuous dry cutting, respectively. The thermal analysis indicates that the internal cooling method reduces the average surface temperature of the contact zone by 10 % when compared to dry cutting. This device has a great possibility of use by the industry because is an effective and environmentally friendly technology. Department of Mechanical Engineering Sao Paulo State University – Unesp Department of Mechanical Engineering Sao Paulo State University – Unesp

In this paper, the solid desiccant adsorption packed bed with a three-stage internal cooling (ICSPB) has been proposed to improve the dehumidification efficiency and make a comparison with that of non-internal cooling. To investigate the performance of the ICSPB, the dehumidification capacity, dehumidification efficiency, water content of solid desiccant, moisture ratio of solid desiccant, temperature of solid desiccant and inlet and outlet air temperature difference were discussed in different conditions of inlet air and supplying water temperature. It was found that the dehumidification performance of the bed with internal cooling could be improved greatly in the low temperature and low humidity conditions, while in the high temperature and humid, the improvement was not obvious. With internal cooling, the dehumidification efficiency and the water content of the solid desiccant could be improved 59.69% and 110.7%, respectively, and the temperature of solid desiccant could be reduced 2.2 &deg, C when the ICSPB operated at the inlet air temperature of 20 &deg, C, inlet humidity of 55%, and water temperature of 14 &deg, C. Moreover, the dehumidification performance at each stage of ICSPB was studied. It was found that, the first stage played the most important role in the dehumidification process. In addition, the calculation models that can be used to predict the moisture ratio and the temperature of solid desiccant were established on the test results.

Forced convection is a phenomenon already widely investigated in literature. However, there remain potential important improvements on its understanding and numerical prediction. The classical RANS approaches, widely used in industry for the design of cooling systems, are based on a constant turbulent Prandtl number value and isotropic turbulence. This results in a limited fidelity for the prediction of the convective heat transfer coefficient (at best 10-15% of accuracy). The present investigation, therefore, aims at supporting the development of CFD codes by providing detailed and accurate experimental data. Unlike most of the investigations available in literature, which provide the wall heat transfer and/or the velocity fields, the present research addresses the flow temperature. This temperature information allows obtaining the turbulent heat transport term required for the determination of the turbulent Prandtl number value. Laser-Induced Fluorescence (LIF) has the advantage to provide a 2D temperature distribution by a non-intrusive optical approach. Gas-phase measurements, required for a consistent heat transfer investigation, were never applied before in internal flows as in the present application. First of all, the use of a fluorescent tracer is investigated regarding its impact on the Prandtl number value of the gas. After a detailed evaluation of the technique, including the image processing, the first experiments in a static cell show encouraging results of the first two-color measurements. A novel facility was designed and built at the von Karman Institute (VKI) to extend the study to the selected application. For simplicity, the test section is a smooth high aspect ratio duct to investigate a quasi 2D internal flow, as this configuration is closer to a cooling channel. The measurements performed with the one-color methodology and using toluene as the fluorescent tracer show a good agreement between the obtained mean temperature profile and the one resulting from a traversing thermocouple probe. On the other hand, temperature fluctuations are strongly affected by the signal fluctuations recorded by the camera. The facility is prepared for possible nitrogen flow in order to eliminate the undesirable effect of oxygen quenching. Besides, the implementation of a Particle Image Velocimetry (PIV) system allows simultaneous velocity and temperature measurements with results of the turbulent heat transport term. The deep discussion and conclusions allow the author to outline possible future perspectives for further development of this technique. (FSA - Sciences de l'ingénieur) -- UCL, 2018

Thermal efficiency and power output of gas turbines increase with increasing turbine rotor inlet temperature. The rotor inlet temperatures in most gas turbines are far higher than the melting point of the blade material. Hence the turbine blades need to be cooled. In this work, simulations were carried out with the leading edge of gas turbine blade being internally cooled by coolant passages with V-shaped ribs at angles of 30°, 45° or 60° and at three aspect ratios (1:1, 1:2 and 2:3). The trailing edge of the blade was cooled by cylindrical and triangular pin-fin perforations in staggered and inline arrangements. Numerical analyses were carried out for each configuration of the cooling passages. The best cooling passages for leading edge and trailing edge were deduced by comparing the results of these analyses. It was found that using V-shaped ribs and fins induces a swirling flow, which in turn increases the velocity gradient and hence produces an improvement in heat transfer. The results show that under real time flow conditions, the application of V-shaped ribs and pin-fin perforations is a very promising technique for improving blade life.

A great effort has been carried out over the recent years in the understanding of the flow field and heat transfer in the internal cooling channels present in turbine blades. Indeed, advanced cooling schemes have not only lead to the increase of the gas turbine efficiency by increasing the Turbine Inlet Temperature above the material melting temperature, but also the increase of the turbine lifespan. To allow such progresses, modern experimental and numerical techniques have been widely applied in order to interpret and optimize the aerodynamics and heat transfer in internal cooling channels. However, the available data is limited in the case of internal cooling channels in turbine rotor blades. Rotation and temperature gradients introduce Coriolis and centripetal buoyancy forces in the rotating frame of reference, modifying significantly the aerothermodynamics from that of the stationary passages. In the case of turbine rotor blades, most of the investigations are either based on point-wise measurements or are constraint to low rotational regimes. The main objective of this work is to study the detailed flow and heat transfer of an internal cooling channel at representative engine dimensionless operating conditions. This work introduces a laboratory test section that operates ribbed channels over a wide range of Reynolds, Rotation and Buoyancy numbers. In the present work, the Reynolds number ranges from 15,000 to 55,000, the maximum Rotation number is equal to 0.77, and the maximum Buoyancy number is equal to 0.77. The new experimental facility consists in a versatile design that allows the interchangeability of the tested geometry, so that channels of different aspect ratios and rib geometries can be easily fitted. Particle Image Velocimetry and Liquid Crystal Thermography are performed to provide accurate velocity and heat transfer measurements under the same operating conditions, which lead to a unique experimental data set. Moreover, Large Eddy Simulations are carried out to give a picture of the entire flow field and complement the experimental observations. Additionally, the numerical approach intends to provide a robust methodology that is able to provide high fidelity predictions of the performance of internal cooling channels.

Submitted by Renan Luis Fragelli null (renan.fragelli@gmail.com) on 2017-03-28T15:54:09Z No. of bitstreams: 1 Dissertação de Mestrado - Renan Fragelli.pdf: 5490064 bytes, checksum: 80c3b38563331cc9ef7e88ff192c5c8b (MD5) Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-03-29T20:46:29Z (GMT) No. of bitstreams: 1 fragelli_rl_me_bauru.pdf: 5490064 bytes, checksum: 80c3b38563331cc9ef7e88ff192c5c8b (MD5) Made available in DSpace on 2017-03-29T20:46:29Z (GMT). No. of bitstreams: 1 fragelli_rl_me_bauru.pdf: 5490064 bytes, checksum: 80c3b38563331cc9ef7e88ff192c5c8b (MD5) Previous issue date: 2017-03-16 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Este trabalho surgiu a partir da necessidade de produzir avanços em projeto que trata do desenvolvimento de um porta-ferramentas refrigerado internamente através de um fluido em mudança de fase e, na tentativa de minimizar a alta temperatura na ferramenta de corte através desse sistema de circulação. A utilização de nanofluidos surgiu como uma alternativa para a otimização da transferência térmica entre fluido e ferramenta de corte. A pesquisa consiste em avaliar a influência da adição de nanopartículas de prata numa solução de etilenoglicol e água deionizada, e também, da adição de nanopartículas de hematita (Fe2O3) no fluido refrigerante R141b. Em ambos os casos, as nanopartículas possuíam formato esférico, diâmetro médio de 30nm e foram avaliadas em concentrações. Além disso, as duas soluções foram submetidas a um campo elétrico na região de transferência térmica para analisar a influência do efeito eletrohidrodinâmico e, por fim, considerando as propriedades magnéticas da hematita, este nanofluido foi testado sob influência de um campo magnético. Os testes mostraram que as nanopartículas realmente influenciaram as propriedades dos fluidos e, por consequência, a quantidade de calor transferido. O nanofluido Ag/ETG+H2O(l) (0,023 vol%) resultou num incremento de 11% no valor do coeficiente de transferência térmica convectivo (h) quando sujeito ao campo elétrico. Para o caso do nanofluido Fe2O3/R141b, o valor de h aumentou em 30,3%, porém, quando sob efeito do campo magnético ou elétrico, o coeficiente foi prejudicado, resultando num valor menor que o do controle. Ao final, tem-se a proposta de um possível modelo desse porta-ferramentas. This work arose from the need to produce advances in design development of an internally cooled toolholder through a phase change fluid. In order to minimize the high temperature in the cutting tool by this circulation system, using nanofluids emerged as an alternative to optimize heat transfer between the fluid and the cutting tool. The research consists in evaluate the influence of addition of silver nanoparticles in an ethylene glycol and deionized water solution, and also the addition of hematite nanoparticles (Fe2O3) in the refrigerant R141b. In both cases, nanoparticles had spherical shape, diameter of 30nm, and they were evaluated in different concentrations. Moreover, both nanofluids were subjected to an electric field in the heat transfer region to evaluate the influence of electrohydrodynamic effect and, finally, considering the magnetic properties of hematite, this nanofluid was tested under the influence of a magnetic field. The tests have shown that the nanoparticles really influence the properties of the fluids and, therefore, the amount of heat transferred. The nanofluid Ag/ETG+H2O(l) also presented a positive influence of the electric field, further enhancing the value of the convective heat transfer coefficient (h) in 11% (0,039 vol%). In the case of Fe2O3/R141b nanofluid, the h value increased 30.3%. However, when the nanofluid was under magnetic or electric effect, the value of h was deteriorated, resulting in a lesser value than the control. As conclusion, a new toolholder prototype is presented.

The contribution describes part of the work carried out on a wider research project aimed to set up a new tool to study rotational effects on the heat transfer distribution inside realistic cooling passages for gas turbine blades. Transient thermochromic liquid crystals (TLC) measurement technique is chosen in order to obtain spatially resolved heat transfer data. This obliges to perform the transient measurements with a cold temperature step on the coolant flow, in order to replicate correctly the buoyancy effects induced by rotation. This target is achieved by a new facility which components and working principle have been the subject of previous contributions. In the present paper, the progresses made in the development of the data processing methodology are described at first. Successively, a first step into the demanding rig and methodology validation process is commented by exploiting the results of a wide test campaign on a simple cooling channel geometry.

The present work deepens the analysis of the flow field inside a triangular equilateral channel with turbulence promoters, perpendicular to the radial direction, on both leading and trailing sides, under rotation and both isothermal and nonisothermal conditions (i.e. with centrifugal buoyancy forces). Simulations have been performed at constant Re = 10,000, Ro = 0–0.2–0.6, and Bo = 0–0.08–0.7, the latter corresponding to 80℃ temperature difference between fluid and walls. These conditions match those of the particle image velocimetry measurements, used for comparison against predictions. After proper validation, the numerical modeling helped with the assessment of the flow field evolution along the radial extension of the cooling channel. It has been possible to determine the path of the coolant throughout the channel and localize where the heat transfer would have been enhanced/decreased by secondary flow structures, with respect to the stationary case. Furthermore, a rather Bo-independency of the flow field in this kind of geometry has been confirmed. The analysis presented in this paper finds support from the thermal data available from the open literature, which is rich of thermal analysis indeed, but lacks a detailed description of internal flow fields.

There are two critical stages of grain refinement during solidification: above and below the liquidus temperature. The key to improve the refinement potential is ensuring the nucleation sites precipitate in large quantities and dispersed in the melt above liquidus. In this work, internal cooling with annular electromagnetic stirring was applied to an Al-Zn-Mg-Cu-Zr alloy at a temperature above liquidus. A systematic experimental study on the grain refining potential was performed by combining different melt treatments and pouring temperatures. The results indicate that internal cooling with annular electromagnetic stirring (IC-AEMS) had a significantly superior grain refining potency for the alloy compared to traditional electromagnetic stirring (EMS). In addition, homogeneous and refined grains were achieved at high pouring temperatures with IC-AEMS. The possible mechanisms for the enhanced grain refinement above the liquidus temperature are explained as the stable chilling layer around the cooling rod in IC-AEMS providing undercooling for the precipitation of Al3Zr nucleant particles and the high cooling rate restraining the growth rate of these particles. At the same time, forced convection promotes a more homogeneous distribution of nucleant particles.

By merging two standard swirl chambers, an alternative cooling configuration named double swirl chambers (DSC) has been developed. In the DSC cooling configuration, the main physical phenomena of the swirl flow in swirl chamber and the advantages of swirl flow in heat transfer augmentation are maintained. Additionally, three new physical phenomena can be found in DSC cooling configuration, which result in a further improvement of the heat transfer: (1) impingement effect has been observed, (2) internal heat exchange has been enhanced between fluids in two swirls, and (3) “∞” shape swirl has been generated because of cross effect between two chambers, which improves the mixing of the fluids. Because of all these improvements, the DSC cooling configuration leads to a higher globally-averaged thermal performance parameter (Nu¯¯/Nu∞/(f/f0)1/3) than standard swirl chamber. In particular, at the inlet region, the augmentation of the heat transfer is nearly 7.5 times larger than the fully developed non-swirl turbulent flow and the circumferentially averaged Nusselt number coefficient is 41% larger than the standard swirl chamber. Within the present work, a further investigation on the DSC cooling configuration has been focused on the influence of geometry parameters e.g. merging ratio of chambers and aspect ratio of inlet duct on the cooling performance. The results show a very large influence of these geometry parameters in heat transfer enhancement and pressure drop ratio. Compared with the basic configuration of DSC cooling, the improved configuration with 20% to 23% merging ratio shows the highest globally-averaged thermal performance parameter. With the same cross section area in tangential inlet ducts, the DSC cooling channel with larger aspect ratio shows larger heat transfer enhancement and at the same time reduced pressure drop ratio, which results in a better globally-averaged thermal performance parameter.

In the past few decades, the operating temperatures of gas turbine engines have increased significantly with a view towards increasing the overall thermal efficiency and specific power output. As a result of increased turbine inlet temperatures, the hot gas path components downstream of the combustor section are subjected to high heat loads. Though materials with improved temperature capabilities are used in the construction of the hot gas path components, in order to ensure safe and durable operation, the hot gas path components are additionally supplemented with thermal barrier coatings (TBCs) and sophisticated cooling techniques. The present study focusses on two aspects of gas turbine cooling, namely augmented internal cooling and external film cooling. One of the commonly used methods for cooling the vanes involves passing coolant air bled from the compressor through serpentine passages inside the airfoils. The walls of the internal cooling passages are usually roughened with turbulence promoters like ribs to enhance heat transfer. Though the ribs help in augmenting the heat transfer, they have an associated pressure penalty as well. Therefore, it is important to study the thermal-hydraulic performance of ribbed internal cooling passages. The first section of the thesis deals with the numerical investigation of flow and heat transfer characteristics in a ribbed two-pass channel. Four different rib shapes- 45° angled, V-shaped, W-shaped and M-shaped, were studied. This study further aims at exploring the performance of different rib-shapes at a large rib pitch-to-height ratio (p/e=16) which has potential applications in land-based gas turbines operating at high Reynolds numbers. Detailed flow and heat transfer analysis have been presented to illustrate how the innate flow physics associated with the bend region and the different rib shapes contribute to heat transfer enhancement in the two-pass channel. The bend-induced secondary flows were observed to significantly affect the flow and heat transfer distribution in the 2nd pass. The thermal-hydraulic performance of V-shaped and 45° angled ribs were better than W-shaped and M-shaped ribs. The second section of the study deals with the analysis of film cooling performance of different hole configurations on the endwall upstream of a first stage nozzle guide vane. The flow along the endwall of the airfoils is highly complex, dominated by 3-dimensional secondary flows. The presence of complex secondary flows makes the cooling of the airfoil endwalls challenging. These secondary flows strongly influence endwall film cooling and the associated heat transfer. In this study, three different cooling configurations- slot, cylindrical holes and tripod holes were studied. Steady-state experiments were conducted in a low speed, linear cascade wind tunnel. The adiabatic film cooling effectiveness on the endwall was computed based on the spatially resolved temperature data obtained from the infrared camera. The effect of mass flow ratio on the film cooling performance of the different configurations was also explored. For all the configurations, the coolant jets were unable to overcome the strong secondary flows inside the passage at low mass flow ratios. However, the coolant jets were observed to provide much better film coverage at higher mass flow ratios. In case of cylindrical ejection, the effectiveness values were observed to be very low which could be because of jet lift-off. The effectiveness of tripod ejection was comparable to slot ejection at mass flow ratios between 0.5-1.5, while at higher mass flow ratios, slot ejection was observed to outperform tripod ejection. Master of Science

Nickel-based superalloys such as Waspaloy are used for engine components and in the nuclear industry, where considerable strength and corrosion resistance at high operating temperatures are called for. These characteristics of such alloys cause increases in cutting temperature and resultant tool damage, even at low cutting speeds and low feed rates. Thus, they are classified as difficult-to-cut materials. This article presents a cooling method to be used in metal cutting based on a tool holder with a closed internal cooling system with cooling fluid circulating inside. Hence, a green cooling method that does not harm the environment and is efficient in removing heat from the cutting zone was developed. A series of cutting experiments were conducted to investigate the practicality and effectiveness of the internally cooled tool model. The developed system achieved up to 13% better surface quality than with dry machining, and tool life was extended by 12%. The results clearly showed that with the reduced cutting temperature of the internal cooling, it was possible to control the temperature and thus prevent reaching the critical cutting temperature during the turning process, which is vitally important in extending tool life during the processing of Waspaloy.

Zusammenfassung in englischer Sprache, Abweichender Titel nach ��bersetzung der Verfasserin/des Verfassers

Nowadays, it is common practice to expose engine components to main annulus air temperatures exceeding the thermal material limit in order to increase the overall engine performance and to minimise the engine specific fuel consumption. To prevent overheating of the materials and thus the reduction of component life, an internal flow system is required to cool and protect the critical engine parts. Previous studies have shown that the insertion of a deflector plate in turbine cavities leads to a more effective use of reduced cooling air, since the coolant is fed more effectively into the disc boundary layer. This paper describes a flexible design parameterisation of an engine representative turbine stator well geometry with stationary deflector plate and its implementation within an automated design optimisation process using automatic meshing and steady-state CFD . Special attention and effort is turned to the flexibility of the parameterisation method in order to reduce the number of design variables to a minimum on the one hand but increasing the design space flexibility & generality on the other. Finally the optimised design is evaluated using a coupled FEA / CFD method and compared against the baseline design.

The heat transfer in the system piston - piston rod - crosshead of reciprocating compressors can be influenced by a fluid enclosed in an internal cavity. Thus, heat is transferred by the fluid flow inside the hollow parts utilizing the reciprocating motion. Subsequently, the high working frequency of such compressors can lead to an improved cooling of the high temperature compressor parts in comparison with conventional solid material designs.  For the experimental examination of this cooling concept a test rig has been set up at the Technische Universität Dresden which comprises a vertically oscillating hollow rod that is heated at its upper end and cooled at its lower end. Among other factors the heat transfer of this cooling concept is affected by the internal diameter of the piston rod. In order to quantify the influence of the internal diameter on the axial heat transfer three different hollow rods with varying internal diameters where investigated by means of temperature measurements.  The experimental results are presented and the influence of the size of the cavity is discussed. Furthermore, the measured temperatures are used for numerical simulations of the test rig in order to derive the axial heat flux of the fluid inside the cavity. Based on the resulting values the heat transfer capability of the investigated cooling concept can be examined with respect to the internal diameter and the benefit for the cooling of different compressor components can be estimated.

Cooling of gas turbine blades is critical to long term durability. Accurate prediction of blade metal temperature is a key component in the design of the cooling system. In this design space, spatial distribution of heat transfer coefficients plays a significant role. Large-Eddy Simulation (LES) has been shown to be a robust method for predicting heat transfer. Because of the high computational cost of LES as Reynolds number (Re) increases, most investigations have been performed at low Re of O(104). In this paper, a two-pass duct with a 180° turn is simulated at Re = 100,000 for a stationary and a rotating duct at Ro = 0.2 and Bo = 0.5. The predicted mean and turbulent statistics compare well with experiments in the highly turbulent flow. Rotation-induced secondary flows have a large effect on heat transfer in the first pass. In the second pass, high turbulence intensities exiting the bend dominate heat transfer. Turbulent intensities are highest with the inclusion of centrifugal buoyancy and increase heat transfer. Centrifugal buoyancy increases the duct averaged heat transfer by 10% over a stationary duct while also reducing friction by 10% due to centrifugal pumping. Published version

In order to reach desired levels of efficiency and power output of jet engines, advanced gas turbine and compressor blades made from Ti‐6AL‐4V alloy operate at very high temperatures (up to 600°C) and speeds (up to 10000 rpm) [3–4]. Pressure of springing streams and inertial forces are main reasons of stress appearance in the blades. Besides that, blade usually could be out of action after one's edges had become damaged under temperature or foreign object hit negative influence. High cycle fatigue (HCF) accounts for 56% of major aircraft engine failures and ultimately limits the service life of most critical rotating components. Extensive inspection and maintenance programs have been developed to detect, renew and replace defected blades, to avoid catastrophic engine failure. Various modern technologies including laser cladding (filling layers of sprayed material) allow prolongation of blades’ life by damaged part's renovation with alternate material. The general aim of the present work concludes of blades’ mechanical bahavour comparison before and after renewal. Suremontuotos dujų turbinos ir kompresoriaus menčių analizė Santrauka.Šiame darbe aprašoma, kaip buvo atliekama suremontuotų turbinos ir kompresoriaus menčių atsparumo analizė. Svarbiausia buvo palyginti ekvivalentinių įtampų rezultatus iki ir po menčių renovavimo alternatyvia medžiaga. Modelių, kurie buvo suprojektuoti kompiuterine programa SolidWorks, medžiaga buvo keičiama tose darbinės mentės briaunos vietose, kur buvo galimi eksploataciniai defektai. Reikšminiai žodžiai: turbinos mentė, kompresoriaus mentė, modeliavimas, srautai, vidinis vėdinimas, nuostolių simuliavimas, medžiagų pakitimas, Von Mise ekvivalentinis stresas, pajėgumas, eksperimentas, rezultatų palyginimas. First Published Online:14 Oct 2010

It is well known that turbine engine efficiency can be improved by increasing the turbine inlet gas temperature. This causes an increase of heat load to the turbine components. Current inlet temperature level in advanced gas turbine is far above the melting point of the vane material. Therefore, along with high temperature material development, sophisticated cooling scheme must be developed for continuous safe operation of gas turbine with high performance. Gas turbine blades are cooled internally and externally. Internal cooling is achieved by passing the coolant through passages inside the blade and extracting the heat from outside of the blade. This paper focuses on turbine vanes internal cooling. The effect of arrangement of rib and parabolic fin turbulator in the internal cooling channel and numerical investigation of temperature distribution along the vane material has been presented. The formulations for the internal cooling for the turbine vane have been done and these formulated equations are solved by MacCormack's technique.