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1
Romanelli, Mirko. « Modellazione del comportamento di un combustore e turbina aeronautica con fogging ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12374/.
Texte intégralRésumé :
Tra i vari metodi di produzione di energia meccanica le turbomacchine rappresentano sicuramente uno dei metodi più sviluppati e di maggiore interesse per via del loro utilizzo in ambito aeronautico, per la produzione di energia elettrica e la movimentazione di grosse macchine
motrici. A causa della loro diffusione è diventato di fondamentale importanza trovare delle metodologie per aumentarne la potenza, l'ecosostenibilità e i rendimenti. A tale scopo la tecnica del fogging rappresenta una valida opzione per cercare di raggiungere tali obiettivi.
In questo elaborato è stato prima effettuato uno studio in ambiente MatLab del comportamento di un turboalbero Allison 250 C18 variando la portata di acqua iniettata all'interno della motorizzazione cercando di determinare analiticamente, mediante le conoscenze teoriche acquisite,
l'andamento di alcune grandezze fondamentali quali temperatura e pressione per poi confrontare i risultati ottenuti con i dati sperimentali raccolti precedentemente presso il "Laboratorio di macchine e propulsione" della Scuola di Ingegneria e Architettura, sede di Forlì. Successivamente si è passati alla creazione tramite Simulink, un tool di MatLab, di un modello dinamico che ci permettesse di estendere i risultati ottenuti dallo studio di alcuni punti di funzionamento a un range più elevato in modo da avere un quadro completo del comportamento del turboalbero.
2
Gobbato, Paolo. « Studio delle instabilità termoacustiche in un combustore di turbina a gas ». Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3427348.
Texte intégralRésumé :
Combustion instabilities are a major technical problem in most of industrial applications since they cause a performance deterioration of the combustion process. Under unstable operation the large amplitude oscillations of the flow induce many dangerous effects such as large mechanical vibrations, noise, augmented heat transfer rates at the combustor walls and increased pollutant emissions. In the gas turbines, an unstable heat release inside the combustion chamber can damage the hottest components of the combustor and reduce the life of the turbine blades.
This study presents an investigation of the thermoacoustic behaviour of a single can gas turbine combustor. The combustor, originally conceived for operation with liquid and gaseous fossil fuels, was modified by the manufacturer to burn pure hydrogen or hydrogen/natural gas mixtures. Combustor design development was supported by experimental activities performed on a full-scale full-pressure test rig.
A detailed procedure is proposed in this work to study the thermoacoustic instabilities in the combustor. Both hydrogen and natural gas operation are simulated by means of CFD RANS simulations carried out on a finite volume commercial code. The three-dimensional CFD analyses are performed on a coarse grid and take advantage of simplified numerical models to reduce the computation time. Due to this approach, the CFD analyses can simulate the time dependent thermoacoustic reactive flow field for a period of time large enough to capture unstable oscillation regimes, if present. Experimental measurements are used to impose the model boundary conditions and to validate the numerical results.
The pressure signals recorded during the simulated period show a constant low-amplitude oscillation (a limit cycle) which does not affect the combustor performance. This behaviour agrees with the experimental data acquired during the combustion tests.
The final part of this study compares the computed frequency spectra with the measured ones. The good agreement between the numerical results and the experimental values validate the potential of the low computational cost CFD approach to describe the thermoacoustic behaviour of the considered combustor.L'instabilità di combustione peggiora le prestazioni di un combustore a flusso continuo e pertanto deve essere considerata un fenomeno indesiderato. Fluttuazioni della pressione e del rilascio termico possono infatti causare vibrazioni meccaniche, rumore, formazione di punti caldi sulle pareti della camera di combustione e incremento delle emissioni inquinanti. La combustione instabile è particolarmente dannosa nei combustori per turbina a gas nei quali ampie oscillazioni di portata e di rilascio termico possono danneggiare irreparabilmente le parti fisse e rotanti della turbina. Nel lavoro che si presenta viene studiato il comportamento termoacustico di un combustore di turbina a gas. Il combustore esaminato è del tipo tubolare, con singolo bruciatore a fiamma diffusiva ed è stato modificato dal costruttore per essere alimentato non solo a gas naturale ma anche a idrogeno. Il processo di sviluppo è stato supportato da prove di combustione su scala reale eseguite su un banco prova in grado di riprodurre le condizioni di pieno carico. L’analisi termoacustica viene condotta seguendo una procedura di indagine basata sulla simulazione numerica del fenomeno mediante un codice numerico commerciale con modelli di turbolenza di tipo RANS. Nelle analisi numeriche i modelli numerici e le griglie di calcolo sono scelti in modo da minimizzare tempi e risorse di calcolo. In questo modo è possibile simulare un intervallo temporale sufficientemente ampio da consentire al sistema di evolvere liberamente fino alle condizioni di regime per poter così valutare l’eventuale presenza di instabilità termoacustiche. Le misure raccolte durante le prove sperimentali sono impiegate nei calcoli sia per l’imposizione delle condizioni al contorno sia per la valutazione dei risultati. I segnali di pressione registrati durante le simulazioni mostrano la permanenza di oscillazioni di pressione nel combustore caratterizzate da un’ampiezza piuttosto ridotta. Queste oscillazioni sono dunque ampiamente tollerabili dal sistema (la combustione è ovunque completa e non vi sono fenomeni di estinzione di fiamma e di surriscaldamento delle pareti del combustore), in accordo con quanto osservato durante le prove sperimentali. Gli spettri calcolati al termine delle simulazioni sono comparati con gli spettri acquisiti durante le prove di combustione. Dal confronto emerge una sostanziale corrispondenza tra i modi di vibrare calcolati e quelli misurati al banco prova.
3
Khandelwal, Bhupendra. « Development of gas turbine combustor preliminary design methodologies and preliminary assessments of advanced low emission combustor concepts ». Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/9157.
Texte intégralRésumé :
It is widely accepted that climate change is a very serious environmental
concern. Levels of carbon dioxide (CO2) and other emissions in the global
atmosphere have increased substantially since the industrial revolution and now
increasing faster than ever before. There is a thought that this has already led
to dangerous warming in the Earth’s atmosphere and relevant changes around.
Emissions legislations are going to be stringent as the years will pass. Hydro
carbon fuel cost is also increasing substantially; more over this is non-
renewable source of energy.
There is an urgent need for novel combustor technologies for reducing emission
as well as exploring alternative renewable fuels without effecting combustor
performance. Development of novel combustors needs comprehensive
understanding of conventional combustors. The design and development of gas
turbine combustors is a crucial but uncertain part of an engine development
process. At present, the design process relies upon a wealth of experimental
data and correlations. Some major engine manufacturers have addressed the
above problem by developing computer programs based on tests and empirical
data to assist combustor designers, but such programs are proprietary. There is
a need of developing design methodologies for combustors which would lead to
substantial contribution to knowledge in field of combustors. Developed design
methodologies would be useful for researchers for preliminary design
assessments of a gas turbine combustor.
In this study, step by step design methodologies of dual annular radial and axial
combustor, triple annular combustor and reverse flow combustor have been
developed. Design methodologies developed could be used to carry out
preliminary design along with performance analysis for conventional combustion
chambers. In this study the author has also proposed and undertaken
preliminary studies of some novel combustor concepts.
A novel concept of a dilution zone less combustor has been proposed in this
study. According to this concept dilution air would be introduced through nozzle
guide vanes to provide an optimum temperature traverse for turbine blades.
Preliminary study on novel dilution zone less combustor predicts that the length
of this combustor would be shorter compared to conventional case, resulting in
reduced weight, fuel burn and vibrations. Reduced fuel burn eventually leads to
lower emissions.
Another novel concept of combustor with hydrogen synthesis from kerosene
reformation has been proposed and a preliminary studies has been undertaken
in this work. Addition of hydrogen as an additive in gas turbine combustor
shows large benefits to the performance of gas turbine engines in addition to
reduction in NOx levels. The novel combustor would have two stages,
combustion of ~5% of the hydrocarbon fuel would occur in the first stage at
higher equivalence ratios in the presence of a catalyst, which would eventually
lead to the formation of hydrogen rich flue gases. In the subsequent stage the
hydrogen rich flue gases from the first stage would act as an additive to
combustion of the hydrocarbon fuel. It has been preliminary estimated that the
mixture of the hydrocarbon fuel and air could subsequently be burned at much
lower equivalence ratios than conventional cases, giving better temperature
profiles, flame stability limits and lower NOx emissions.
The effect of different geometrical parameters on the performance of vortex
controlled hybrid diffuser has also been studied. It has been predicted that
vortex chamber in vortex controlled hybrid diffuser does not play any role in
altering the performance of diffuser.
The overall contribution to knowledge of this study is development of combustor
preliminary design methodologies with different variants. The other contribution
to knowledge is related to novel combustors with a capability to produce low
emissions. Study on novel combustor and diffuser has yielded application of two
patent applications with several other publications which has resulted in a
contribution to knowledge. A list of research articles, two patents, awards and
achievements are presented in Appendix C.
4
Aslanidou, Ioanna. « Combustor and turbine aerothermal interactions in gas turbines with can combustors ». Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:b1527fd0-8e54-4831-8625-32722141511e.
Texte intégralRésumé :
As the research into the improvement of gas turbine performance progresses, the combustor-turbine interface becomes of increasing importance. In new engine designs components come closer together and the study of the combustor and turbine interactions can prove to be valuable for the improvement of the aerothermal performance of the vane. This thesis presents an experimental and numerical investigation of the aerodynamic and heat transfer aspect of the interactions between the combustor and the nozzle guide vane. In the gas turbine studied the trailing edge of the combustor transition duct wall is found upstream of every second vane. In the experimental measurements carried out in a purpose-built high speed experimental facility, the wake of this wall is shown to increase the aerodynamic loss of the vane. On the other hand, the wall alters secondary flow structures and has a protective effect on the heat transfer in the leading edge-endwall junction, a region that has proven to be detrimental to component life. The effect of different clocking positions of the vane relative to the combustor wall are tested experimentally and shown to alter the aerodynamic field and the heat transfer to the vane. The experimental methods and processing techniques adopted in this work are utilized to highlight the differences between the different cases studied. A new concept of using the combustor wall to shield the nozzle guide vane leading edge is introduced, followed by a proposed design that is numerically analysed, including a new cooling system. This uses continuous cooling slots on the upstream combustor wall to cool the vane leading edge. Coolant to the endwalls is provided from continuous slots on the combustor-turbine interface. The reduction of secondary flow through the removal of the horseshoe vortex in the new design results in improved cooling of the endwalls, with a higher average adiabatic effectiveness than in the original case, using the same coolant mass flow rate. The vane surface and suction side are also successfully cooled using less air than that required for a showerhead. The new vane is tested in the experimental facility. The improved aerodynamic and thermal performance of the shielded vane is demonstrated under engine-representative inlet conditions. The new design is shown to have a lower average total pressure loss than the original vane for all inlet conditions. The heat transfer on the vane surface is overall reduced for all inlet conditions and the peak heat transfer on the vane leading edge-endwall junction is moved further upstream, to a region that can be effectively cooled from the upstream cooling slots on the combustor wall trailing edge and the endwalls.
5
Abraham, Santosh. « Heat Transfer and Flow Measurements on a One-Scale Gas Turbine Can Combustor Model ». Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35177.
Texte intégralRésumé :
Combustion designers have considered back-side impingement cooling as the solution for modern DLE combustors. The idea is to provide more cooling to the deserved local hot spots and reserve unnecessary coolant air from local cold spots. Therefore, if accurate heat load distribution on the liners can be obtained, then an intelligent cooling system can be designed to focus more on the localized hot spots. The goal of this study is to determine the heat transfer and pressure distribution inside a typical can-annular gas turbine combustor. This is one of the first efforts in the public domain to investigate the convective heat load to combustor liner due to swirling flow generated by swirler nozzles. An experimental combustor test model was designed and fitted with a swirler nozzle provided by Solar Turbines Inc. Heat transfer and pressure distribution measurements were carried out along the combustor wall to determine the thermo-fluid dynamic effects inside a combustor. The temperature and heat transfer profile along the length of the combustor liner were determined and a heat transfer peak region was established.
Constant-heat-flux boundary condition was established using two identical surface heaters, and the Infrared Thermal Imaging system was used to capture the real-time steady-state temperature distribution at the combustor liner wall. Analysis on the flow characteristics was also performed to compare the pressure distributions with the heat transfer results. The experiment was conducted at two different Reynolds numbers (Re 50,000 and Re 80,000), to investigate the effect of Reynolds Number on the heat transfer peak locations and pressure distributions. The results reveal that the heat transfer peak regions at both the Reynolds numbers occur at approximately the same location. The results from this study on a broader scale will help in understanding and predicting swirling flow effects on the local convective heat load to the combustor liner, thereby enabling the combustion engineer to design more effective cooling systems to improve combustor durability and performance.Master of Science
6
Carmack, Andrew Cardin. « Heat Transfer and Flow Measurements in Gas Turbine Engine Can and Annular Combustors ». Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32466.
Texte intégralRésumé :
A comparison study between axial and radial swirler performance in a gas turbine can combustor was conducted by investigating the correlation between combustor flow field geometry and convective heat transfer at cold flow conditions for Reynolds numbers of 50,000 and 80,000. Flow velocities were measured using Particle Image Velocimetry (PIV) along the center axial plane and radial cross sections of the flow. It was observed that both swirlers produced a strong rotating flow with a reverse flow core. The axial swirler induced larger recirculation zones at both the backside wall and the central area as the flow exits the swirler, and created a much more uniform rotational velocity distribution. The radial swirler however, produced greater rotational velocity as well as a thicker and higher velocity reverse flow core. Wall heat transfer and temperature measurements were also taken. Peak heat transfer regions directly correspond to the location of the flow as it exits each swirler and impinges on the combustor liner wall.
Convective heat transfer was also measured along the liner wall of a gas turbine annular combustor fitted with radial swirlers for Reynolds numbers 210000, 420000, and 840000. The impingement location of the flow exiting from the radial swirler resulted in peak heat transfer regions along the concave wall of the annular combustor. The convex side showed peak heat transfer regions above and below the impingement area. This behavior is due to the recirculation zones caused by the interaction between the swirlers inside the annulus.Master of Science
7
Jelercic, David. « Experiments in annular combustors ». Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251891.
Texte intégral
8
Anand, Vijay G. « Rotating Detonation Combustor Mechanics ». University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530798871271548.
Texte intégral
9
Ayache, Simon Victor. « Simulations of turbulent swirl combustors ». Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/243609.
Texte intégralRésumé :
This thesis aims at improving our knowledge on swirl combustors. The work presented here is based on Large Eddy Simulations (LES) coupled to an advanced combustion model: the Conditional Moment Closure (CMC). Numerical predictions have been systematically compared and validated with detailed experimental datasets. In order to analyze further the physics underlying the large numerical datasets, Proper Orthogonal Decomposition (POD) has also been used throughout the thesis. Various aspects of the aerodynamics of swirling flames are investigated, such as precession or vortex formation caused by flow oscillations, as well as various combustion aspects such as localized extinctions and flame lift-off. All the above affect flame stabilization in different ways and are explored through focused simulations. The first study investigates isothermal air flows behind an enclosed bluff body, with the incoming flow being pulsated. These flows have strong similarities to flows found in combustors experiencing self-excited oscillations and can therefore be considered as canonical problems. At high enough forcing frequencies, double ring vortices are shed from the air pipe exit. Various harmonics of the pulsating frequency are observed in the spectra and their relation with the vortex shedding is investigated through POD. The second study explores the structure of the Delft III piloted turbulent non-premixed flame. The simple configuration allows to analyze further key combustion aspects of combustors, with further insights provided on the dynamics of localized extinctions and re-ignition, as well as the pollutants emissions. The third study presents a comprehensive analysis of the aerodynamics of swirl flows based on the TECFLAM confined non-premixed S09c configuration. A periodic component inside the air inlet pipe and around the central bluff body is observed, for both the inert and reactive flows. POD shows that these flow oscillations are due to single and double helical vortices, similar to Precessing Vortex Cores (PVC), that develop inside the air inlet pipe and whose axes rotate around the burner. The combustion process is found to affect the swirl flow aerodynamics. Finally, the fourth study investigates the TECFLAM configuration again, but here attention is given to the flame lift-off evident in experiments and reproduced by the LES-CMC formulation. The stabilization process and the pollutants emission of the flame are investigated in detail.
10
Gray, D. T. « The control of fluidised combustors ». Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373677.
Texte intégral
11
Forster, Robin Norman George. « CFD modelling of vortex combustors ». Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/770204/.
Texte intégralRésumé :
This dissertation examines the suitability of Computational Fluid Dynamics (CFD) modelling for the production of realistic flowfields and temperature fields within a series of vortex combustion chambers of differing geometries and operating under various conditions. Initial validation of the CFD predictions was obtained through modelling of a series of isothermal vortex chambers for which a comprehensive set of experimental data was available. It was observed that CFD did indeed produce representative flowfield predictions for chambers of various geometries and operating conditions. A vortex unit used for the incineration of sewage sludge (US Navy Waste Incinerator) was subsequently investigated, and it was shown that due to the high moisture content of the waste material used, temperature profiles obtained with a modified coal combustion model were similar to those obtained with a more straightforward and computationally less expensive spray drier model. Results from both models were similar to experimentally observed conditions. However, comprehensive validation was not possible. In order that full validation could be provided for a CFD model of a vortex combustion unit, a model was developed of a commercial thermal oxidiser used for the incineration of liquid and gaseous wastes. CFD temperature predictions for the BASF Thermal Oxidiser were validated by a series of experimental measurements obtained from the operating unit. In general, it was found that the Reynolds Stress Model for turbulence produced the most representative velocity flowfields, with the less computationally demanding k-e model being applicable only under certain limited circumstances. Furthermore, insufficient grid refinement resulted in significantly distorted velocity profiles.
12
Ubhi, G. S. « Emissivity measurement of gas turbine combustor ceramic coatings and its influence on combustor design ». Thesis, Cranfield University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378890.
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13
Spencer, A. « Gas turbine combustor port flows ». Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/6883.
Texte intégralRésumé :
Competitive pressure and stringent emissions legislation have placed an urgent demand on research to improve our understanding of the gas turbine combustor flow field. Flow through the air admission ports of a combustor plays an essential role in determining the internal flow patterns on which many features of combustor performance depend. This thesis explains how a combination of experimental and computational research has helped improve our understanding, and ability to predict, the flow characteristics of jets entering a combustor. The experiments focused on a simplified generic geometry of a combustor port system. Two concentric tubes, with ports introduced into the inner tube's wall, allowed a set of radially impinging jets to be formed within the inner tube. By investigating the flow with LDA instrumentation and flow visualisation methods a quantitative and qualitative picture of the mean and turbulent flow fields has been constructed. Data were collected from the annulus, port and core regions. These data provide suitable validation information for computational models, allow improved understanding of the detailed flow physics and provide the global performance parameters used traditionally by combustor designers. Computational work focused on improving the port representation within CFD models. This work looked at the effect of increasing the grid refinement, and improving the geometrical representation of the port. The desire to model realistic port features led to the development of a stand-alone port modelling module. Comparing calculations of plain-circular ports to those for more realistic chuted port geometry, for example, showed that isothermal modelling methods were able to predict the expected changes to the global parameters measured. Moreover, these effects are seen to have significant consequences on the predicted combustor core flow field.
14
Motsamai, Oboetswe Seraga. « Optimisation techniques for combustor design ». Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-04072009-222336/.
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15
Asere, Abraham Awolola. « Gas turbine combustor wall cooling ». Thesis, University of Leeds, 1986. http://etheses.whiterose.ac.uk/2590/.
Texte intégralRésumé :
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.
16
Gogebakan, Yusuf. « Simulation Of Circulating Fluidized Bed Combustors ». Phd thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607775/index.pdf.
Texte intégralRésumé :
A dynamic mathematical model for simulation of atmospheric circulating fluidized bed combustors has been developed on the basis of first principles and empirical correlations. The model accounts for dense and dilute zone hydrodynamics, volatiles release and combustion, char particles combustion and their size distribution, and heat transfer from/to gas, particles, waterwalls and refractory.
Inputs to the model include configuration and dimensions of the combustor and its internals, air and coal flows, coal analysis, all solid and gas properties, inlet temperatures of air, cooling water, and feed solids, size distribution of feed solidswhereas outputs include transient values of combustor temperatures, gas concentrations, char and inert hold-ups and their size distributions. The solution procedure employs method of lines approach for the governing non-linear partial differential equations and combined bisection and secant rule for non-linear algebraic equations. The initial conditions required for the model are provided from the simultaneous solution of governing equations of dynamic model with all temporal derivatives set to zero. By setting all temporal derivatives to zero, model can also be utilized for steady state performance prediction. In order to assess the validity and predictive accuracy of the model, it was applied to the prediction of the steady state behavior of Technical University of Nova Scotia 0.3 MWt CFBC Test Rig and predictions were compared with measurements taken on the same rig. Comparison of model predictions at steady state conditions revealed that the predictions of the model are physically correct and agree well with the measurements and the model is successful in qualitatively and quantitatively simulating the processes taking place in a circulating fluidized bed combustor.
17
Cavaliere, Davide Egidio. « Blow-off in gas turbine combustors ». Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/265575.
Texte intégralRésumé :
This thesis describes an experimental investigation of the flame structure close to the extinction and the blow-off events of non-premixed and spray flames stabilized on an axisymmetric bluff body in a confined swirl configuration. The comparison of flames of different canonical types in the same basic aerodynamic field allows insights on the relative blow-off behaviour. The first part of the thesis describes several velocity measurements in non-reacting and reacting flows. The main usefulness of this data is to provide the aerodynamic flow pattern and some discussion on the velocity field and the related recirculation zones. The velocity and turbulence information obtained are particularly useful for providing data, which is crucial for validation of computational models. The second part describes an experimental investigation of non-premixed stable flames very close to the blow-off condition. The measurements included visualisation of the blow-off transient with 5 kHz OH* chemiluminescence, which allowed a quantification of the average duration of the blow-off transient. OH-PLIF images at 5 kHz for flames far from and close to extinction showed that the non-premixed flame intermittently lifts-off the bluff body, with increasing probability as the fuel velocity increases. The flame sheet shows evidence of localised extinctions, which are more pronounced as approaching blow-off. The measurements include blow-off limits and their attempted correlation. It was found that a correlation based on a Damkohler number does a reasonable job at collapsing the dataset. The final part examines the blow-off behaviour of swirling spray flames for two different fuels: n-heptane and n-decane. The measurements include blow-off limits and their att~mpted correlation, visualisation of the blow-off transient with 5 kHz OH* chemiluminescence, and the quantification of the average duration of the blow-off transient. It was found that the average duration of the blow-off event is in order of the tens of ms for both spray flames (10-16 ms). The blow-off event is therefore a relatively slow process for the spray ~ames using n-heptane and decane fuels. This suggests that control measures, such as fast fuel injection, coupled with appropriate detection, such as with chemiluminescence monitoring, may have a reasonable chance of success in keeping the flame alight very close to the blow-off limit. These results, together with those obtained for the non-premixed gaseous case form a wide body of experimental data available for the validation of turbulent flame models. The quantification of some properties during the blow-off transient can assist studies of extinction based on large-eddy simulation that have a promise of capturing combustion transients.
18
Wyse, Saffron Gale. « Automated optimisation of gas turbine combustors ». Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612335.
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Matteucci, Simona. « Numerical Modelling of a Flameless Combustor ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Trouver le texte intégralRésumé :
Flameless combustion can be adopted as a low-emission combustion regime in the aviation sector, which is one of the biggest contributors to NOx emissions and is expected to grow in the near future. Nevertheless, several issues must be solved before any practical applications. Effective design procedure must deal with either combustion or heat transfer phenomena occurring at extremely low—temperature conditions. To this aim, experimental and numerical analyses focused on the characterization of fuel/oxidant behaviour are strongly needed and represent an essential step for further development.
Besides, the complexity of the analysed technological system requires advanced tools for the definition of the chemical kinetics, for the burner designs and more in general for the definition of aviation equipment design. In this light, the thesis has been addressed to the study of flameless combustion mechanisms within a combustion chamber prototype developed in the Faculty of Aerospace Engineering at TU Delft. In particular, the temperature and species concentration fields have been analysed. The CFD tool which will be used is Ansys Fluent together with two detailed reaction mechanisms (KIBO and RDM19).
20
Bengtsson, Karl. « ThermoacousticInstabilities in a Gas Turbine Combustor ». Thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226530.
Texte intégralRésumé :
Stationary gas turbines are widely used today for power generation and mechanical drive applications. The introduction of new regulations on emissions in the last decades have led to extensive development and new technologies used within modern gas turbines. The majority of the gas turbines sold today have a so called DLE (Dry Low Emission) combustion system that mainly operates in the leanpremixed combustion regime. The lean-premixed regime is characterized by low emission capabilities but are more likely to exhibit stability issues compared to traditional non-premixed combustion systems. Thermoacoustic instabilities are a highly unwanted phenomena characterized by an interaction between an acoustic eld and a combustion process. This interaction may lead to self-sustained large amplitude oscillations which can cause severe structural damage to the gas turbine if it couples with a structural mode. However, since a coupled phenomena, prediction of thermoacoustic stability is a complex topic still under research. In this work, the mechanisms responsible for thermoacoustic instabilities are described and a 1- dimensional stability modelling approach is applied to the Siemens SGT-750 combustion system. The complete combustor is modelled by so called acoustic two-port elements in which a 1-dimensional ame model is incorporated. The simulations is done using a generalized network code developed by Siemens. The SGT-750 shows today excellent stability and combustion performance but a deeper knowledge in the thermoacoustic behaviour is highly valued for future development. In addition, measurement data from an engine test is evaluated, post-processed and compared with the results from the 1-dimensional network model. The results are found to be in good agreement and the thermoacoustic response of the SGT-750 is found to be dominated by both global modes including all cans as well as local modes within the individual cans.
21
Murthy, J. N. « Gas turbine combustor modelling for design ». Thesis, Cranfield University, 1988. http://hdl.handle.net/1826/2626.
Texte intégralRésumé :
The design and development of gas turbine combustors is a crucial but uncertain part of an engine development process. Combustion within a gas turbine is a complex interaction of, among other things, fluid dynamics, heat and mass transfer and chemical kinetics. At present, the design process relies upon a wealth of experimental data and correlations. The proper use of this information requires experienced combustion engineers and even for them the design process is very time consuming.
Some major engine manufacturers have attempted to address the above problem by developing one dimensional computer programs based on the above test and empirical data to assist combustor designers. Such programs are usually proprietary. The present work, based on this approach has yielded DEPTH, a combustor design program. DEPTH ( Design and Evaluation of Pressure, Temperature and Heat transfer in combustors) is developed in Fortran-77 to assist in preliminary design and evaluation of conventional gas turbine combustion chambers.
DEPTH can be used to carry out a preliminary design along with prediction of the cooling slots for a given metal temperature limit or to evaluate heat transfer and temperatures for an existing combustion chamber. Analysis of performance parameters such as efficiency, stability and NOx based on stirred reactor theories is also coupled. DEPTH is made sufficiently interactive/user-friendly such that no prior expertise is required as far as computer operation is concerned. The range of variables such as operating conditions, geometry, hardware, fuel type can all be effectively examined and their contribution towards the combustor performance studied. Such comprehensive study should provide ample opportunity for the designer to make the right decisions. It should also be an effective study aid. Returns in terms of higher thermal efficiencies is an incentive to go for combined cycles and cogeneration. In such cases, opting for higher cycle pressures together with a second or reheat combustor promise higher thermal efficiencies and exhaust temperatures and hence such designs are likely to be of interest. The concepts that are needed for understanding a double or reheat combustor are also addressed using the programme. A specific application of the programme is demonstrated through the design of a double combustor.
22
Soon, Lee Aik. « Two Combustor Engine for Military Applications ». Thesis, Cranfield University, 2009. http://hdl.handle.net/1826/4491.
Texte intégralRésumé :
The key requirements for military aircraft are high survivability and mission
success rate: the former will “exponentially” increase the latter. The survivability
of the aircraft depends crucially on its performance and energy signatures, to
which its propulsion system contributes significantly. Therefore this imposes
demands upon future propulsion systems for a better aerothermodynamics
performance with a lower energy signature.
However, the performances
achievable with conventional engine cycles
may be reaching their limits.
Therefore, the author was motivated to investigate the potential of the two combustor
engine for military fighter
applications; with respect to its
aerothermodynamics performance and infrared signature.
An extensive literature survey was conducted to identify the uptodate
research for the two combustor
engine. Based on the collected information,
systematic approaches were formatted with proven analytical methodologies for
conducting the present study. A proven conventional engine (i.e. F100PW229
engine, based on “open publication”),
for powering military fighter aircraft, was
selected for benchmarking purposes in order to identify the prospect of the two combustor
engine. With an engine performance-simulation
program of high
fidelity and a detail engine model, the accuracy of the predictions of the engines’
performances are greatly improved. The key contribution is the establishment on
the influences of the two combustor
engine on the performances of the selected
fighter aircraft, in particular the transient behaviour, steady state
flight
characteristics (e.g. flight envelope)
and infrared signatures. This research relates
the performance of the two combustor
engine to that of the aircraft, which was not
found in any uptodate
publication. The availability of this research will allow
engine and aircraft studies to include two combustor
solution in a more secure
way than it was possible.
In this investigation, the main analytical tool employed is a Cranfield
University inhouse
developed engine performance-simulation
program,
TURBOMATCH. The author has implemented various subprograms
to interface
with TURBOMATCH in order to conduct specific simulations, e.g. transient behaviour
predictions. All the analyses have been undertaken using data from the
published literature.
23
Hao, Beilene 1973. « Effect of variability on combustor performance ». Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/82779.
Texte intégral
24
Goodro, Robert Matthew. « Improved understanding of combustor liner cooling ». Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:51596540-f4cf-480c-aa40-7fc5b9a97abb.
Texte intégralRésumé :
Heat management is an essential part of combustor design, as operating temperatures within the combustor generally exceed safe working temperatures of the materials employed in its construction. Two principal methods used to manage this heat are impingement and film cooling. Impingement heat transfer refers to jets of impinging fluid delivered by orifices integrated into internal structures in order to remove undesired heat. This mode of heat transfer has a relatively high effectiveness, making it an attractive method of heat management. As such, a considerable number of studies have been done on the subject providing a substantial body of useful knowledge. However, there are innovative cooling configurations being used in gas turbines which generate compressibility and temperature ratio effects on heat transfer which are currently unexplored. Presented here are data showing that these effects have a significant impact on heat transfer and new correlations are presented to account for temperature ratio and Mach number effects for a range of conditions. These findings are significant and can be applied to impinging flows in other areas of a gas turbine engine such as turbine blades and vanes. Film cooling refers to the injection of coolant onto a surface through an array of sharply angled holes. This is done in a manner that allows the coolant to remain close to the surface where it provides an insulating layer between the hot gas freestream and the cooler surface. In order to improve turbine efficiency, research efforts in film cooling are directed at reducing film cooling flow without decreasing turbine inlet temperatures. Both impingement cooling and film cooling are heavily utilized in combustor liners. Frequently, cooling air first impinges against the back side of the liner, then the spent impingement fluid passes through film cooling holes. This arrangement combines the convective heat transfer of the impinging jets convection as the coolant passes through the film cooling holes and the benefits that come from having a thin film of cool air between the combustor wall and the combustion products. In order to improve the understanding of internal cooling in gas turbine engines, the influence of previously unexplored physical parameters such as compressible flow effects and temperature ratio in impingement flows and variable blowing ratio in a film cooling array must be examined. Prior to this work, there existed in the available literature only an extremely limited exploration of compressibility effects in impingement heat transfer and the results of separately examining the effects of Mach number and Reynolds number. The film cooling literature provides no information for a full array of film cooling holes along a contraction at high blowing ratios. Exploring these effects and conditions adds to the body of available data and allows the validation of numerical predictions.
25
Hall, Benjamin F. « Combustor simulators for scaled turbine experiments ». Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:9c8e46e6-218f-4715-b2bd-8c8abbee446a.
Texte intégralRésumé :
Gas turbine combustors employing a single lean combustion stage represent the next generation of design for reduced NOXemissions. These lean-burn combustors rely on swirl-stabilised flames resulting in highly non-uniform outflows. Non-uniform conditions adversely affect high-pressure turbine performance. 3D numerical simulations provide a means to understand and optimise engine design, however, the modelling of turbulence means experimental validation is crucial. Turbine test facilities operating at scaled, non-reacting conditions, with simulated combustor flows are an important source of validation data. This thesis presents advances in combustor simulator design, testing and instrumentation relevant to the challenges of modern, highly-integrated turbine testing. The design of a lean-burn combustor simulator, characterised by swirl and non-uniform temperature, is presented. The design was based on measurements and predictions of engine conditions. Unsteady numerical simulations were employed as a predictive design tool. An engine-scale combustor simulator was manufactured and characterised experimentally in a bespoke facility. Surveys of flow structure are presented, focusing on experimental turbine inlet data. These data confirmed that the combustor simulator reproduces the important features of a lean-burn combustor; e.g. swirling mainstream flow and high turbulence intensity. The lean-burn combustor simulator will be the first of its kind to be implemented in a rotating turbine test facility, and will provide important validation data. Measurement techniques were developed alongside the core work. Miniaturised five-hole probe rakes for turbine inlet measurements were developed using additive manufacturing (AM). Building on this work, an open source AM five-hole probe design is presented with experimental validation. The problem of estimating pressure probe bandwidth was also addressed, and a simplified model is presented. These tools have direct applications in turbomachinery research.
26
Orain, Mikaël. « Experiments with gas and liquid-fuelled flames ». Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252000.
Texte intégral
27
Fabbri, Federico. « Controllo multiparametro della combustione ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5121/.
Texte intégral
28
Reuter, Dierk Martin. « Investigation of combustion instability in ramjet combustors ». Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/12271.
Texte intégral
29
Au-Yeung, Hok Wang. « NOx formation in gas-fired pulse combustors ». Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/10384.
Texte intégralRésumé :
The main focus of this investigation was to get a greater understanding of the effect of combustion frequency, positive pressure amplitude, relative air:fuel ratio (A), water jacket temperature and input firing rates on the emissions of NO from pulse combustors. This study was carried out by a programme of experimental work combined with the development of a one-dimensional model. Results obtained in this study from experimental measurement, revealed evidence that a Schmidt tube has the ability to operate over a wide range of parameters (such as operating frequency, positive pressure amplitude, relative air:fuel ratio, water jacket temperature and input firing rates) with variable NO emissions. It was found that the level of NO emissions became lower with increasing operating frequency and positive pressure amplitude. As an example, when the rig was operated at input firing rate 25 kW and a positive pressure amplitude of 0.12 bar, increasing the frequency from 35 Hz to 73 Hz produced a monotonic reduction in NO emissions from 61 ppm to 29 ppm (dry, 3% O2). An'increase in positive pressure amplitude from 0.05 to 0.12 bar produced a change in NO emissions from 46 ppm to 34 ppm. It was also found that the values of NO emissions fell. with increasing excess air for A> 1.1. However, NO emissions increased with increasing water jacket temperature (Tw) along the length of tail pipe and with increasing input firing rates. Experimental results showed that the positive pressure amplitude was not dependent on the wall jacket temperature. However, the operating range of stable pressure oscillation could be extended from [...continued].
30
Bradshaw, Sean D. (Sean Darien) 1978. « Probabilistic aerothermal design of gas turbine combustors ». Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36286.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006.Includes bibliographical references (p. 87-89).
This thesis presents a probability-based framework for assessing the impact of manufacturing variability on combustor liner durability. Simplified models are used to link combustor liner life, liner temperature variability, and the effects of manufacturing variability. A probabilistic analysis is then applied to the simplified models to estimate the combustor life distribution. The material property and liner temperature variations accounted for approximately 80 percent and 20 percent, respectively, of the combustor life variability. Furthermore, the typical combustor life was found to be approximately 20 percent less than the life estimated using deterministic methods for these combustors, and the probability that a randomly selected combustor will fail earlier than predicted using deterministic methods is approximately 80 percent. Finally, the application of a sensitivity analysis to a surrogate model for the life identified the leading drivers of the minimum combustor life and the typical combustor life as the material property variability and the variability of the near-wall combustor gas temperature, respectively.
by Sean Darien Bradshaw.
Ph.D.
31
Underwood, David Scott. « Primary zone modeling for gas turbine combustors ». Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/32700.
Texte intégralRésumé :
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1999."June 1999."
Includes bibliographical references (p. 107-110).
Gas turbine combustor primary zone flows are typified by swirling flow with heat release in a variable area duct, where a central toroidal recirculation zone is formed. The goal of the research was to develop reduced-order models for these flows in an attempt to gain insight into, and understanding of the behavior of swirling flows with combustion. The specific research objectives were (i) to develop a quantitative understanding and ability to compute the behavior of swirling flows with heat addition at conditions typical of gas turbine combustors, (ii) to assess the relative merits of various reduced-order models, and (iii) to define the applicability of these models in the design process. To this end, several reduced-order models of combustor primary zones were developed and assessed. The models represent different levels of modeling approximations and complexity. The models include a quasi-one-dimensional control volume analysis, a streamline curvature model, a quasi-one- dimensional model with recirculation zone capturing (CFLOW), and an axisymmetric Reynolds averaged Navier-Stokes code (UTNS). The models were evaluated through inter-comparison, and comparison with experiment. Following this evaluation, CFLOW was applied to a lean-premixed combustor for which three-dimensional Navier-Stokes solutions existed. These simplified analyses/models were able to capture the features of swirling flows with heat release across flow regimes of interest in gas turbine combustors, provide insight into the underlying physics, and yield guidelines for design purposes. Cross-comparison of the reduced-order models highlighted the aspects of these flows that need to be described accurately. Specifically, modeling of the mixing on the downstream boundary of a recirculation zone is crucial for accurate computation of these flows, with both Reynolds stresses and bulk transport across the interface being accounted for in order to capture recirculation zone closure. The simplified mixing and heat release models used had limitations arising from the need to input empirically-derived parameters. Calibration of these parameters with higher-fidelity computations and experiments allowed comparison of the models across the flow regimes of interest. Following calibration of the mixing and heat release models, CFLOW was able to compute recirculation zone volumes to within 25% of those given by both the axisymmetric and three-dimensional Navier-Stokes codes for swirl ratios between 0.5 and 1.0 and equivalence ratios between 0.0 and 0.8.
by David Scott Underwood.
Sc.D.
32
Redemann, Kai. « Ash management in circulating fluidized bed combustors ». Aachen Shaker, 2008. http://d-nb.info/991096231/04.
Texte intégral
33
Rowan, Scott A. « Viscous drag reduction in a scramjet combustor / ». St. Lucia, Qld, 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17438.pdf.
Texte intégral
34
David, Jiri. « Emissions from a gas-burning pulse combustor ». Thesis, Middlesex University, 1993. http://eprints.mdx.ac.uk/10176/.
Texte intégralRésumé :
The pulse combustor has a number of attractive features for heating applications. These include simplicity of construction, compactness for a given heat input rate, enhanced exhaust gas heat transfer and most importantly low CO and NOx emissions. With more stringent air quality and emissions standards soon to be in force in many countries, the latter has received much attention among the producers of gas appliances. This study investigates the performance of and emissions from a Helrnholtz-type pulse combustor with varying parameters such as gas input rate, tailpipe length, combustion chamber volume and composition I)f the natural gas being used as a fuel. The experimental work was primarily focused on the measurements of O2, CO2, CO and NOx concentrations in the pulse combustor exhaust gas; such data are difficult to find in the general literature. Measurements of the aspirated combustion air flow rate and operating frequency were also made. Initially some modifications to the natural-gas-fired pulse burner of 5kW output constructed by A. Suthenthiran were made and new gas sampling ports and probes were designed and constructed. An orifice plate flow meter and air-box were also designed and constructed in an attempt to measure the pulsating air flow of the combustor. It was found, however, that the combustor would not operate with the air-box fitted. The air/fuel ratios of the combustor were therefore calculated from the measured exhaust gas analysis by means of a specially written computer program. Much attention was also given to the selection of reliable gas analysis equipment and as a result five different gas analyzers were tested. It was found that the investigated pulse combustor was capable of operation only under fuel-lean conditions since the stoichiometric air/fuel ratio was never reached. Percentage excess air levels when using the mains gas (NGA) as a fuel were typically found in the range of 5 - 40 % The variation of carbon monoxide exhaust levels with gas flow rate displayed, in most cases, a characteristic 'U' shaped curve gently sloping down and reaching minimum CO concentration (typically below 300 ppm), before rising steeply as stoichiometry was approached. It was also found that in the lower and middle operating range CO levels were notably reduced with increase in combustion chamber volume and slightly reduced with increase in tailpipe length. Furthermore, the CO/C02 ratio did not exceed the maximum permissible limit of 0.02 set by appliance safety standards for any of the conducted trials. Test results for all investigated variables indicated that production of nitrogen oxides was strongly temperature dependent; a finding which is consistent with the literature. In addition, NOx emissions were observed to rise with increase in gas flow rate, tailpipe length and combustion chamber volume respectively. With measured NOx levels below 60 ppm our results agree with the values reported elsewhere. Furthermore, oxides of nitrogen monitored in this study consisted mainly of thermal NO formed by the Zeldovich mechanism. The pulse combustor was operated on family 2H test gases ie. NGA (mains), NGB, NGC (high in Hz) and NGD (high in N2 ) in order to evaluate the effect of changes in fuel composition on its performance. A conventional method based on the modified Harris & Lovelace diagram was used to define an acceptable area within which all family 2H gases would be interchangeable. Propane was found not to be interchangeable with the reference gas NGA.
35
Stowe, Robert Alan. « Performance prediction of a ducted rocket combustor ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ65434.pdf.
Texte intégral
36
Tajiri, Kazuya. « Simulations of combustion dynamics in pulse combustor ». Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12175.
Texte intégral
37
Poppe, Christian. « Scalar measurements in a gas turbine combustor ». Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264987.
Texte intégral
38
Menzies, Kevin Robert. « Grid adaptation for gas trubine combustor calculations ». Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504933.
Texte intégral
39
Bradshaw, Sean D. (Sean Darien) 1978. « Physics-based, reduced-order combustor flow modeling ». Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/82215.
Texte intégral
40
Peck, Jhongwoo 1976. « Development of a liquid-fueled micro-combustor ». Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45271.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2008.Includes bibliographical references (p. 177-184).
Advances in Micro-Electro-Mechanical Systems (MEMS) have made possible the development of shirtbutton-sized gas turbine engines for use as portable power sources. As part of an effort to develop a microscale gas turbine engine, this thesis presents the modeling, design, fabrication, and experimental characterization of a microcombustor that catalytically burns JP8 fuel. Due to high energy densities stored in hydrocarbon fuels, microscale heat engines based on them are estimated to have specific energies about one order of magnitude higher than those of current battery systems. In addition, utilizing a commonly available logistics fuel would provide advantages for military applications. Thus, a microengine burning JP8 fuel is attractive as a portable power source and potential replacement for batteries. The thesis first presents a number of models developed to design the fuel vaporizer, the fuel-air mixing chamber, and the combustion chamber. Among these is a reduced-order mass transfer model that simulates catalytic combustion of a slow diffusing hydrocarbon fuel. A two-phase heat transfer model was also developed to design an on-board fuel vaporizer with an array of micro-channels. Using the model results, a liquid-fueled micro-combustor test rig with a combustion chamber volume of 1.hcc and an overall die size of 36.4 mm x 36.4 mm x 6.5 mm was built. This device is a hybrid structure composed of silicon, sapphire, and glass. Deep reactive ion etching was mainly used to fabricate the silicon parts. The sapphire and glass parts were built by ultrasonic machining. The liquid-fueled micro-combustor was then experimentally characterized. Two configurations were tested and compared; one with the whole combustion chamber filled with a catalyst, and the other with a catalyst filling the chamber only partially.
(cont.) In the fully-loaded configuration, JP8 combustion was stably sustained at mass flow rates up to 0.1 g/sec, and an exit gas temperature of 780 K, an overall combustor efficiency of 19%, and a power density of 43 MW/m" were achieved. The primary limitation on increasing the mass flow rates and temperatures further was structural failure of the device due to thermal stresses. With the partially-loaded configuration, a mass flow rate of 0.2 g/sec, and a corresponding power density of 54 MW/mrn were obtained. The exit gas temperature for the partially-loaded configuration was as high as 720 K, and the maximum overall efficiency was over 22%. Although the reduced amount of catalyst led to incomplete combustion, smaller thermal losses resulted in an increase in the overall combustor efficiencies and power densities. The overall efficiency and the exit gas temperature were lower than the operational requirement of the microengine in both of the device configurations. A non-dimensional operating map was constructed based on the experiment, and suggestions for future liquid fueled micro-combustors were made; to achieve maximum efficiency for a volume as small as possible, improving the thermal efficiency would be necessary. Thesis keywords: Power-MEMS, microengine, micro-combustor, catalytic combustion, JP8 combustor, micro fuel vaporizer, micro-fabrication, deep reactive ion etching
by Jhongwoo Jay Peck.
Ph.D.
41
Moscahlaidis, George. « Investigation of air control on chunkwood combustor ». Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43101.
Texte intégralRésumé :
Many small scale agricultural operations such as greenhouses, peanut drying and tobacco curing,
use significant quantities of thermal energy. Direct combustion of biomass is a potential source of heat energy for those agricultural applications to substitute for the electricity or fossil fuels (principally LP gas) currently used. However, small scale combustion equipment often operates with low efficiency and high emissions.
A prototype chunkwood combustor was installed and tested. The basis for controlling heat output,
was the modulation of air supplied to the primary and secondary combustors. Exhaust gas CO and
CO2 concentrations, combustor efficiency, and useful heat output were measured. The cleannest
burn was achieved during a forty minute test, where 50 percent of stoichiometric air was introduced
at the primary, and 170 percent at the secondary, for a total of 220 percent stoichiometric. The
overall average CO/CO2 ratio for this test was 0.084, and 0.1 is considered to be an average rating for a combustion in a wood stove. Moreover, the efficiency during this test was 52 percent.Master of Science
42
Mescher, Ann M. « Flame structures in a pulverized coal combustor / ». The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487862399449444.
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43
St, George Andrew. « Development and Testing of Pulsed and Rotating Detonation Combustors ». University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1458893231.
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44
Zanotti, Giacomo. « L'impiego del sensore di pressione in camera di combustione per il controllo della combustione ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
Trouver le texte intégralRésumé :
Il sensore di pressione ha un notevole potenziale per il controllo della combustione di un motore.
Il costo elevato, che ne ha impedito la diffusione su larga scala in veicoli di serie, negli ultimi anni si è notevolmente abbassato e la misura della pressione in camera può risultare un elemento essenziale per soddisfare le sempre più stringenti norme relative all'inquinamento e ai consumi.
L'obiettivo di questo elaborato è investigare su tutti i controlli possibili a partire dalla misura della pressione in camera di combustione, sia per motori ad accensione per compressione sia per motori ad accensione comandata.
In particolare in motori Diesel è stato studiato il controllo di CA50, IMEP ed EGR e sono stati visti due modelli per la stima della massa aspirata al momento della chiusura delle valvole di aspirazione e di stima del rapporto aria/combustibile. Per motori ad accensione comandata sono invece stati studiati il controllo della fasatura della combustione (CA50) e il controllo della combustione.
45
Morgan, D. J. « Characteristics of non slagging cyclone combustors for solid fuels ». Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292580.
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Ahmed, Mahbub. « Investigation on the flame dynamics of meso-combustors ». To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Arunajatesan, Srinivasan. « Numerical modeling of waste incineration in dump combustors ». Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/12332.
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Kandamby, Naminda Harisinghe. « Mathematical modelling of gasifier fuelled gas turbine combustors ». Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267305.
Texte intégral
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Dolan, Brian. « Flame Interactions and Thermoacoustics in Multiple-Nozzle Combustors ». University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479822588098224.
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50
Wischnewski, Reiner. « Simulation of large-scale circulating fluidized bed combustors ». Aachen Shaker, 2008. http://d-nb.info/993341691/04.
Texte intégral