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Heat transfer on nozzle guide vane end wallsHarvey, Neil William January 1991 (has links)
No description available.
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Aerodynamics and Heat Transfer for a Modern Stage and One-Half TurbineKrumanaker, Matthew Lee 05 February 2003 (has links)
No description available.
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Predictions and Measurements of Film-Cooling on the Endwall of a First Stage VaneKnost, Daniel G. 15 October 2003 (has links)
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
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Experimental investigation of film cooling effectiveness on gas turbine bladesGao, Zhihong 15 May 2009 (has links)
The hot gas temperature in gas turbine engines is far above the permissible metal temperatures. Advanced cooling technologies must be applied to cool the blades, so they can withstand the extreme conditions. Film cooling is widely used in modern high temperature and high pressure blades as an active cooling scheme. In this study, the film cooling effectiveness in different regions of gas turbine blades was investigated with various film hole/slot configurations and mainstream flow conditions. The study consisted of four parts: 1) effect of upstream wake on blade surface film cooling, 2) effect of upstream vortex on platform purge flow cooling, 3) influence of hole shape and angle on leading edge film cooling and 4) slot film cooling on trailing edge. Pressure sensitive paint (PSP) technique was used to get the conduction-free film cooling effectiveness distribution. For the blade surface film cooling, the effectiveness from axial shaped holes and compound angle shaped holes were examined. Results showed that the compound angle shaped holes offer better film effectiveness than the axial shaped holes. The upstream stationary wakes have detrimental effect on film effectiveness in certain wake rod phase positions. For platform purge flow cooling, the stator-rotor gap was simulated by a typical labyrinth-like seal. Delta wings were used to generate vortex and modeled the passage vortex generated by the upstream vanes. Results showed that the upstream vortex reduces the film cooling effectiveness on the platform. For the leading edge film cooling, two film cooling designs, each with four film cooling hole configurations, were investigated. Results showed that the shaped holes provide higher film cooling effectiveness than the cylindrical holes at higher average blowing ratios. In the same range of average blowing ratio, the radial angle holes produce better effectiveness than the compound angle holes. The seven-row design results in much higher effectiveness than the three-row design. For the trailing edge slot cooling, the effect of slot lip thickness on film effectiveness under the two mainstream conditions was investigated. Results showed thinner lips offer higher effectiveness. The film effectiveness on the slots reduces when the incoming mainstream boundary layer thickness decreases.
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Experimental investigation of film cooling effectiveness on gas turbine bladesGao, Zhihong 15 May 2009 (has links)
The hot gas temperature in gas turbine engines is far above the permissible metal temperatures. Advanced cooling technologies must be applied to cool the blades, so they can withstand the extreme conditions. Film cooling is widely used in modern high temperature and high pressure blades as an active cooling scheme. In this study, the film cooling effectiveness in different regions of gas turbine blades was investigated with various film hole/slot configurations and mainstream flow conditions. The study consisted of four parts: 1) effect of upstream wake on blade surface film cooling, 2) effect of upstream vortex on platform purge flow cooling, 3) influence of hole shape and angle on leading edge film cooling and 4) slot film cooling on trailing edge. Pressure sensitive paint (PSP) technique was used to get the conduction-free film cooling effectiveness distribution. For the blade surface film cooling, the effectiveness from axial shaped holes and compound angle shaped holes were examined. Results showed that the compound angle shaped holes offer better film effectiveness than the axial shaped holes. The upstream stationary wakes have detrimental effect on film effectiveness in certain wake rod phase positions. For platform purge flow cooling, the stator-rotor gap was simulated by a typical labyrinth-like seal. Delta wings were used to generate vortex and modeled the passage vortex generated by the upstream vanes. Results showed that the upstream vortex reduces the film cooling effectiveness on the platform. For the leading edge film cooling, two film cooling designs, each with four film cooling hole configurations, were investigated. Results showed that the shaped holes provide higher film cooling effectiveness than the cylindrical holes at higher average blowing ratios. In the same range of average blowing ratio, the radial angle holes produce better effectiveness than the compound angle holes. The seven-row design results in much higher effectiveness than the three-row design. For the trailing edge slot cooling, the effect of slot lip thickness on film effectiveness under the two mainstream conditions was investigated. Results showed thinner lips offer higher effectiveness. The film effectiveness on the slots reduces when the incoming mainstream boundary layer thickness decreases.
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Experimental investigation of turbine blade platform film cooling and rotational effect on trailing edge internal coolingWright, Lesley Mae 02 June 2009 (has links)
The present work has been an experimental investigation to evaluate the
applicability of gas turbine cooling technology. With the temperature of the mainstream
gas entering the turbine elevated above the melting temperature of the metal components,
these components must be cooled, so they can withstand prolonged exposure to the
mainstream gas. Both external and internal cooling techniques have been studied as a
means to increase the life of turbine components.
Detailed film cooling effectiveness distributions have been obtained on the
turbine blade platform with a variety of cooling configurations. Because the newly
developed pressure sensitive paint (PSP) technique has proven to be the most suitable
technique for measuring the film effectiveness, it was applied to a variety of platform
seal configurations and discrete film flows. From the measurements it was shown
advanced seals provide more uniform protection through the passage with less potential
for ingestion of the hot mainstream gases into the engine cavity.
In addition to protecting the outer surface of the turbine components, via film
cooling, heat can also be removed from the components internally. Because the turbine blades are rotating within the engine, it is important to consider the effect of rotation on
the heat transfer enhancement within the airfoil cooling channels. Through this
experimental investigation, the heat transfer enhancement has been measured in narrow,
rectangular channels with various turbulators. The present experimental investigation
has shown the turbulators, coupled with the rotation induced Coriolis and buoyancy
forces, result in non-uniform levels of heat transfer enhancement in the cooling channels.
Advanced turbulator configurations can be used to provide increased heat transfer
enhancement. Although these designs result in increased frictional losses, the benefit of
the heat transfer enhancement outweighs the frictional losses.
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Parametric Study of Turbine Blade Internal Cooling and Film CoolingRallabandi, Akhilesh P. 2010 August 1900 (has links)
Gas turbine engines are extensively used in the aviation and power generation
industries. They are used as topping cycles in combined cycle power plants, or as
stand alone power generation units.
Gains in thermodynamic efficiency can be realized by increasing the turbine
inlet temperatures. Since modern turbine inlet temperatures exceed the melting
point of the constituent superalloys, it is necessary to provide an aggressive cooling
system. Relatively cool air, ducted from the compressor of the engine is used to
remove heat from the hot turbine blade. This air flows through passages in the
hollow blade (internal cooling), and is also ejected onto the surface of the blade to
form an insulating film (film cooling).
Modern land-based gas turbine engines use high Reynolds number internal flow
to cool their internal passages. The first part of this study focuses on experiments
pertaining to passages with Reynolds numbers of up to 400,000. Common turbulator
designs (45degree parallel sharp-edged and round-edged) ribs are studied. Older
correlations are found to require corrections in order to be valid in the high Reynolds
number parameter space.
The effect of rotation on heat transfer in a typical three-pass serpentine channel
is studied using a computational model with near-wall refinement. Results from this
computational study indicate that the hub experiences abnormally high heat transfer under rotation. An experimental study is conducted at Buoyancy numbers similar to
an actual engine on a wedge shaped model trailing edge, roughened with pin-fins and
equipped with slot ejection. Results show an asymmetery between the leading and
trailing surfaces due to rotation - a difference which is subdued due to the provision
of pin-fins.
Film cooling effectiveness is measured by the PSP mass transfer analogy technique
in two different configurations: a flat plate and a typical high pressure turbine
blade. Parameters studied include a step immediately upstream of a row of holes; the
Strouhal number (quantifying rotor-stator interaction) and coolant to mainstream
density ratio. Results show a deterioration in film cooling effectiveness with on increasing
the Strouhal number. Using a coolant with a higher density results in higher
film cooling effectiveness.
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Unsteady Characterization of Film Cooling Flows on a Rotating High-Pressure TurbineSperling, Spencer Jordan January 2021 (has links)
No description available.
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Optimisation gas coolers for CO2 refrigeration applicationSantosa, I. Dewe January 2015 (has links)
Carbon dioxide (CO2) is a natural, low cost refrigerant with good thermo-physical properties. CO2 is a good alternative for replacing HFC refrigerants that possess high global warming potential and reducing the direct impacts of refrigeration systems on the environment. However, CO2 refrigeration systems operate at relatively high condenser/gas cooler pressures and this imposes special design and control considerations. The gas cooler is a very important part of the system and can have significant influence on its performance. In sub-critical operation, good gas cooler/condenser design can reduce the condenser pressure and delay switching to supercritical operation which increases system efficiency. In supercritical operation optimum design and control can enable the system to operate at pressures that maximise system efficiency. In air cooled systems, gas coolers/condensers are of the finned-tube type. This type of heat exchanger is well established in the HVAC and refrigeration industries. The large changes in the CO2 properties in the gas cooler, however, during supercritical operation impose special design and manufacturing considerations. This research project considered the influence of the unique heat transfer characteristics of CO2 on the design and performance of finned tube air cooled condensers/gas coolers for CO2 refrigeration applications. A combined experimental and modelling approach using Computational Fluid Dynamics (CFD) was employed. A CO2 condenser/gas cooler test facility was developed for the experimental investigations. The facility employs a ‘booster’ hot gas bypass CO2 refrigeration system, with associated condenser/gas cooler test rig and evaporator load simulation facility. A series of experimental tests were carried out with two gas coolers which incorporated horizontal and horizontal-vertical slit fins and was obtained adequate experimental data concerning gas cooler performance. CFD modelling was used to study the performance of the gas coolers. The model was validated against test results and was shown to predict the air outlet temperature and heat rejection of the gas cooler with an accuracy of within ±5%. The model was subsequently used to evaluate the effect of a fin slit between the 1st and 2nd row of tubes of the gas cooler as well as a vertical slit on the 1st row before the last tube of the section. The results showed a 6%-8% increase in the heat rejection rate of the gas cooler compared to the performance without the horizontal slit. The vertical slit in the fin of the last tube has resulted in an additional increase in heat rejection over and above that for the horizontal slit of 1%-2%. CFD modelling was also used to investigate the variation of the refrigerant side, air side and overall heat transfer coefficient along the heat exchanger. The results showed that the refrigerant heat transfer coefficient increases with the decreasing of bulk refrigerant temperature and reaches its maximum when the specific heat of the refrigerant is highest. Furthermore, increasing the refrigerant mass flux, increases the refrigerant side heat transfer coefficient and heat rejection. This can reduce the size of the gas cooler for a given capacity at the expense of higher pressure drop and compressor power consumption. Air side and overall heat transfer coefficient correlations were developed for the specific gas cooler designs which were investigated and showed the heat transfer coefficients increase with increasing Reynolds Number.
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Herstellung und Eigenschaften hydridbasierter Verbundwerkstoffe mit hoher Energie- und Leistungsdichte für die WasserstoffspeicherungPohlmann, Carsten 10 November 2014 (has links) (PDF)
In dieser Arbeit werden kompaktierte Verbundwerkstoffe aus verschiedenen Speichermaterialien mit expandiertem Naturgraphit (ENG) in Hinblick auf die Anwendung als dynamische Wasserstofffeststoffspeichermaterialien untersucht. Pulverförmige hydridbildende Ausgangsmaterialien wurden mit bis zu 25 Masse-% ENG vermischt und bei Pressdrücken bis 600 MPa kompaktiert. Um einen weiten Anwendungsbereich abzudecken wurden ein Niedrigtemperaturmaterial (Ti-Mn-basierte Legierung; 0°C bis 100°C), zwei Mitteltemperaturmaterialien (Amid- und Alanatsystem; 100°C bis 200°C) und ein Hochtemperaturmaterial (Magnesium-Nickel-Legierung; 250°C bis 400°C) basierend auf einer umfangreichen Literaturrecherche gewählt. Die Verbundwerkstoffe weisen eine erhöhte radiale Wärmeleitfähigkeit auf und zeichnen sich im Vergleich zu herkömmlich verwendeten Pulverschüttungen durch höhere volumetrische Wasserstoffspeicherdichten aus.
Im Fokus der Untersuchungen stehen vor allem die im Hinblick auf Anwendungstauglichkeit wesentlichen Eigenschaften der Verbundwerkstoffe. So wurde z.B. der Wasserstoffdruck während der Dehydrierung variiert, um sicher zu stellen, Verbraucher mit üblichen Überdrücken versorgen zu können. Darüber hinaus wurde die Stabilität, Gaspermeabilität, Wärmeleitfähigkeit und Porosität der Presslinge im Verlauf zyklischer Hydrierung evaluiert und diskutiert. Insgesamt zeichnet sich ein hohes Potenzial ab, derartige Presslinge als Wasserstoffspeichermaterial für verschiedene Anwendungen entsprechend der jeweiligen Arbeitstemperaturen und weiteren Randbedingungen (z.B. Systemmasse, Tankvolumen etc.) zu verwenden. Diesbezüglich konnte mittels eines Tankdemonstrators basierend auf dem Ti-Mn-System ein Wasserstofffahrzeug erfolgreich betrieben und somit auch die Praxistauglichkeit der Hydrid-Graphit-Verbundmaterialien gezeigt werden. / Compacted composites of solid-state hydrogen storage materials and expanded natural graphite (ENG) are investigated in view of their potential for hydrogen storage applications. Powdery hydride-forming materials were blended with up to 25 weight-% ENG and compacted with up to 600 MPa compaction pressure. In order to cover a wide range of possible applications one low-temperature material (Ti-Mn-based alloy; 0°C to 100°C), two mid-temperature materials (amide and alante system; 100°C to 200°C) and one high-temperature material (magnesium-nickel alloy; 250°C to 400°C) were chosen based on a thorough literature review. The composites result in an increased radial thermal conductivity and are superior in their volumetric hydrogen storage density compared to commonly used loose powder beds.
The research is focused on the applicability of suchlike prepared composites. In this regard, the dehydrogenation back-pressures were varied to ensure a sufficient supply pressure of common consumer loads. Furthermore, the stability, gas permeability, thermal conductivity and porosity throughout cyclic hydrogenation were evaluated and discussed. Overall, a high potential to use suchlike composite materials for hydrogen storage applications regarding the specific working conditions (temperature, system mass, available volume etc.) is found. In this regard, a demonstrator tank equipped with Ti-Mn-based system was successfully supplying a hydrogen driven vehicle, which proves the feasibility of these hydride-graphite composite materials.
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