Distributed energy production in the form of renewable energy sources are expected to increase in the coming years, a consequence of this is instability of the power grids due to the stochastic nature and lack of inertia of renewable energy sources. In addition, small and local, so called island grids, are on the rise and these system may present an even higher sensitivity to frequency fluctuations. In these applications gas turbines are an attractive option owing to the quick start capabilities, flexible fuel options and reliable operation. The aim of this thesis is to evaluate the transient capabilities of the Siemens SGT-750 double shaft and SGT-800 single shaft industrial gas turbines in island grid settings, through simulations of substantial load increases in varying ambient settings. Furthermore the possibility of using hydrogen fuel as a renewable option to the standard natural gas will be evaluated. This thesis provides a model of a simple island grid for load sharing between two or three turbines. The model was tuned to real life test data for the two gas turbines considered. In order to evaluate the capabilities of the turbines simulations were run in cold (-30 oC), hot (30 oC) and ISO (15 oC) conditions, evaluating the maximum instant load increase capabilities. Case studies were also run on island grids containing two or three turbines in order to determine the frequency response in case of an event. Case A regarded a scenario in which two turbines ran on 50% of rated power and one tripped, case B regarded three turbines working on 33% of rated power and one tripped out. Lastly, the maximum load increase cases with hydrogen fuel mixes (25, 50, 75 and 100% hydrogen by volume) were considered. The results suggest that the SGT-750 and SGT-800 gas turbines are capable of handling scenarios on reasonably dimensioned power systems, with both machines capable of recovering instant load increases of over 50% of the rated power. The findings shows thats hort periods (<10 s.) of allowed overfiring temperatures are necessary for the transient performance for the most extreme scenarios of high ambient temperatures and large loadincreases (around 50% of rated power). Furthermore an empirical κ-parameter, related to inertia and operational stability is discussed in order to compare GT load increase capability. The relevance of inertia and dynamic response is discussed and conceptually simulated to highlight the their role in gas turbine transient response. The hydrogen simulations, aside from the 75% case, showed little difference from natural gas in transient scenarios. The 75% hydrogen fuel consisting of high amounts ofinert gas however, rendered the turbine unable to withstand substantial load increases. The hydrogen simulation results are suggested to be accounted for by the rather simple combustion system and the energy densities of the gases.

No description available.

Intimate knowledge of ammonia fueling gas turbines is of crucial importance for power generation sectors, owing to its carbon-free nature and high hydrogen capacity. Anticipated challenges include, among others, the difficulty to stabilize ammonia flames and on top of that the propensity of ammonia flames to produce large quantities of nitrogen monoxide emissions. In gas turbine devices, combustion in practice occurs in a turbulent swirl flow and at elevated pressure conditions. The stability of ammonia flames and the production of NO emissions are sensitive to such parameters. This body of work focuses on the development of a swirl combustor, ~30kW thermal power, for investigating behaviors of flame stability limits and NO emissions from the combustion of ammonia fuel with mixtures of hydrogen or methane at pressure conditions up to 5 bar. Data show that increasing the ammonia addition increases the equivalence ratio at the lean blowout limit but also reduces the flames’ propensity to flashback. If the volume fraction of ammonia in the fuel blend exceeds a critical value, increasing the equivalence ratio at a fixed bulk velocity does not yield flashback and rich blow-out occurs instead. This significantly widens the range of equivalence ratios yielding stable ammonia flames. Regardless of the fuel blend, increasing the pressure increases the propensity to flashback if the bulk velocity remains constant. Pure ammonia-air flames are stable under elevated pressures, and the stable range of equivalence ratio becomes wider as the pressure increases. The NO emissions are measured for large ranges of equivalence ratios, ammonia fractions, and pressures. Regardless of the ammonia fraction, data show that competitively low NO emissions can be found for slightly rich equivalence ratios. Good NO performance is also found for very lean ammonia-hydrogen-air mixtures, regardless of the pressure. NO mole fractions for lean ammonia mixtures can be reduced as pressure increases, demonstrating the strong potential of fueling gas turbines with ammonia-hydrogen mixtures.

The legislations on greenhouse gas emissions are getting tougher and tougher every year. This drives the demand for energy efficient gas turbines with as low emissions as possible. This poses the challenge to manufacturers of constructing gas turbines with lessened environmental impact, but with maintained performance. To obtain this, there is a need of optimization of current principles along with completely new ideas and solutions. One part of developing new, improved gas turbine configurations is to create prototypes and test them. However, creating and testing a gas turbine is a both expensive and time consuming. They are large in every sense of the word: they are long, heavy, demand lots of fuel, create massive air flows and generate a lot of energy. Designing, building and testing new turbine configurations are therefore risky, as it requires investing lots of time and money. This means that it is highly profitable to have accurate, dependable simulation models. This thesis uses Matlab Simulink to create a dynamic model of a single axis gas turbine with nine stage compressor and a single stage turbine. The modeling of the compressor composes a large part of the work in the thesis, where the Ellipse compressor model is introduced and implemented on a gas turbine compressor. The Ellipse model creates a parametric model of each of the nine compressor stages by the use of elliptic equations. The goal is to provide an alternative to the look-up table model of compressors, which are common to find in modeling papers today. In the design of the compressor, a single stage map is scaled nine different ways to mimic the design of a real life nine stage compressor. The stage scaling principle is based on a linear model that correlates stage size with maximum available pressure ratio at optimal speed. The constructed compressor model is put in a simulated test bench and a compressor map is created. The map is found to in most aspects resemble a general compressor map. Furthermore, the thesis contains a run-through of the sub-models of the rest of the turbine, namely combustion chamber and fuel injection, compressor turbine and torque dynamics. For each sub-model, the most important equations and inspirations for these are presented. Finally, a description of the simulation scenarios and the simulation software, Matlab Simulink, is provided. The model is tested in steady-sate operation around its optimal operating point, as well as during a transient in a benign operating zone, in terms of efficiency. The results of these simulations are analyzed and a flaw in the control strategy is pinpointed. An alternate control strategy is proposed, described and implemented. A comparison is made between the original and alternative control strategies, and it is concluded that the new controller manages to mitigate the problems identified in the original simulations. / I takt med att lagstiftningen skärps mer och mer på utsläppsområdet ställs större krav på gasturbiners miljöpåverkan. Tillverkare vill som följd av detta minimera utsläppen, men ändå bibehålla prestanda. För att uppnå detta krävs optimeringar av befintliga principer och i vissa fall helt nya tankar, lösningar och idéer. Ett led i att ta fram nya, bättre gasturbiner är att skapa prototyper och testköra dessa. Det är emellertid en kostsam process att konstruera och testköra en gasturbin, vilket gör vinsterna med pålitliga simuleringsmodeller påtagliga både tidsmässigt och ekonomiskt. Detta arbete innefattar huvudsakligen konstruktionen av en dynamisk modell av en gasturbin. Den modellerade gasturbinen har nio kompressorsteg, en roterande axel samt ett turbinsteg. Modelleringen av kompressorn utgör en stor del av arbetet, där Ellipsemodellen introduceras och implementeras på gasturbinskompressorer. Ellipsemodellen parametriserar en inmatad kompressormapp med elliptiska ekvationer och möjliggör ett steg från den sedvanliga modelleringen av kompressorer som lookup-tables som annars är förhärskande i gasrtubinmodellering. Kompressorns nio steg skalas och modelleras individuellt med en inbördes skalningsprincip som bygger på de respektive stegens maximala tryckkvot vid optimal hastighet. Den konstruerade kompressorn sätts i en simulerad testbänk och en kompressormapp skapas, vilken inses i mångt och mycket likna en allmän kompressormapp. En detaljerad genomgång ges av alla gasturbinens submodeller av kompressor, förbränning och bränsleinsprutning samt turbin och rotationsdynamik. De viktigaste ekvationerna som styr respektive modell, samt inspirationskällor till dessa föredras under modelleringskapitlet. Vidare avhandlas simuleringsscenario och den använda programvaran Matlab Simulink beskrivs i korthet. Den totala gasturbinmodellen testas i stationär drift och en längre transient genom dess föredragna arbetsområde. Resultaten därifrån utvärderas och en alternativ regulatorstruktur föreslås och implementeras. Resultaten med den alternativa regulatorstrukturen diskuteras och jämförs med de identifierade bristerna som skulle åtgärdas, och det konstateras att den nya regulatorn lyckas åtgärda de identifierade bristerna i den ursprungliga designen.

This thesis is a collaboration between Siemens Industrial Turbomachinery(SIT) and Royal Institute of Technology(KTH). It is aimed to study and compare the outputs of two different computational approaches in axial gas turbine design procedure with the data obtained from experimental work on a test turbine. The main focus during this research is to extend the available test databank and to further understand and investigate the turbine stage efficiency, mass flow parameters and reaction degree under different working conditions. Meanwhile the concept and effect of different loss mechanisms and models will be briefly studied.  The experimental part was performed at Heat and Power  Technology department on a single stage test turbine in its full admission mode. Three different pressure ratios were tested. For the medium pressure ratio a constant temperature anemometry (CTA) method was deployed in two cases, with and without turbulence grid, to determine the effect of free-stream turbulence intensity on the investigated parameters. During the test campaign the raw gathered data was processed with online tools and also they served as boundary condition for the computational codes later.  The computational scope includes a one-dimensional design approach known as mean-line calculation and also a two-dimensional method known as throughflow calculation. An in-house SIT software, CATO, generated the stage geometry (vane, blade and the channel) and then two other internal computational codes, MAC1 and BETA2, were employed for the one-dimensional and two-dimensional computations respectively. It was observed that to obtain more accurate mass flow predictions a certain level of channel blockage should be implemented to represent the boundary layer development and secondary flow which is typically around 2%. The codes are also equipped with two options to predict the friction loss: One is a more empirical correlation named as the Old approach in SIT manuals and the other works based on allocation of boundary layer transition point, named as BL in the present thesis. Simulations were done by use of both approaches and it turned out that the latter works more accurately if it is provided with appropriate transition point and blockage estimation.  The measured data also suggests the idea that the transition point of the vane and blade is not affected by a change in turbulence intensity at least up to 6% in the tested Reynolds numbers, . Amongst different solutions the one which used BL approach and constant transition point (while the turbulence intensity changed) managed to predict this behavior. Also it was investigated and revealed that the codes inherently predict poor results in off-design loadings which is mainly due to positive incidence angle in addition to high spanwise gradient of the flow parameters.

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 streamline curvature (SLC) throughflow numerical model was assessed and modified to better approximate the flow fields of highly transonic fans typical of military fighter applications. Specifically, improvements in total pressure loss modeling were implemented to ensure accurate and reliable off-design performance prediction. The assessment was made relative to the modeling of key transonic flow field phenomena, and provided the basis for improvements, central to which was the incorporation of a physics-based shock loss model. The new model accounts for shock geometry changes, with shock loss estimated as a function of inlet relative Mach number, blade section loading (flow turning), solidity, leading edge radius, and suction surface profile. Other improvements included incorporation of loading effects on the tip secondary loss model, use of radial blockage factors to model tip leakage effects, and an improved estimate of the blade section incidence at which minimum loss occurs. Data from a single-stage, isolated rotor and a two-stage, advanced-design (low aspect ratio, high solidity) fan provided the basis for experimental comparisons. The two-stage fan was the primary vehicle used to verify the present work. Results from a three-dimensional, steady, Reynolds-averaged Navier-Stokes model of the first rotor of the two-stage fan were also used to compare with predicted performance from the improved SLC representation. In general, the effects of important flow phenomena relative to off-design performance of the fan were adequately captured. These effects included shock loss, secondary flow, and spanwise mixing. Most notably, the importance of properly accounting for shock geometry and loss changes with operating conditions was clearly demonstrated. The majority of the increased total pressure loss with loading across the important first-stage tip region was shown to be the result of increased shock loss, even at part-speed. Overall and spanwise comparisons demonstrated that the improved model gives reasonable performance trends and generally accurate results, indicating that the physical understanding of the blade effects and the flow physics that underlie the loss model improvements are correct and realistic. The new model is unique in its treatment of shock losses, and is considered a significant improvement for fundamentally based, accurate throughflow numerical approximations. The specific SLC model used here is employed in a novel numerical approach — the Turbine Engine Analysis Compressor Code (TEACC). With implementation of the improved SLC model and additional recommendations presented within this report, the TEACC method offers increased potential for accurate analysis of complex, engine-inlet integration issues, such as time-variant inlet distortion. / Ph. D.

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No description available.

Engine development has been in the direction of increased turbine inlet temperatures to improve efficiency and power output. Secondary flows develop as a result of a near-wall pressure gradient in the stagnating flow approaching the inlet nozzle guide vane as well as a strong cross-passage gradient within the passage. These flow structures enhance heat transfer and convect hot core flow gases onto component surfaces. In modern engines it has become critical to cool component surfaces to extend part life. Bypass leakage flow emerging from the slot between the combustor and turbine endwalls can be utilized for cooling purposes if properly designed. This study examines a three-dimensional slot geometry, scalloped to manipulated leakage flow distribution. Statistical techniques are used to decouple the effects of four geometric parameters and quantify the relative influence of each on endwall cooling levels and near-wall total pressure losses. The slot geometry is also optimized for robustness across a range of inlet conditions. Average upstream distance to the slot is shown to dominate overall cooling levels with nominal slot width gaining influence at higher leakage flow rates. Scalloping amplitude is most influential to near-wall total pressure loss as formation of the horseshoe vortex and cross flow within the passage are affected. Scalloping phase alters local cooling levels as leakage injection is shifted laterally across the endwall. / Ph. D.