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1
Tajiri, Kazuya. "Simulations of combustion dynamics in pulse combustor". Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12175.
Testo completo
2
Fernandes, Renato. "Metodologia de projeto de queimadores a jato para fornos de clínquer". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264846.
Testo completoAbstract (sommario):
Orientador: Waldir Antônio BizzoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Os queimadores a jato são caracterizados pela elevada quantidade de movimento na direção axial e elevada potência, estes queimadores são muito empregados em fornos rotativos, principalmente na indústria do cimento e da calcinação. O projeto de queimadores a jato é realizado usualmente aproximando o escoamento de ar primário no queimador por um modelo de escoamento compressível isentrópico em um bocal, esta aproximação leva a elevada divergência entre o projeto e a performance do equipamento em operação. Nesta tese foram desenvolvidos e empregados modelos de escoamento compressível com atrito, troca de calor e variação de área de seção para o escoamento do ar primário no interior do queimador, esta modelagem permite integrar todo o projeto do queimador desde a especificação de motores, sopradores, simulação da rede de tubos que compõe queimador, incluindo o manifold, válvulas de controle, placas de orifício, mangotes etc, inclusive relacionando o escoamento do ar primário com o jato formado pelo queimador através do emprego e também do desenvolvimento de índices aerodinâmicos que representem o jato. Os pontos de inovação incluem além da modelagem proposta também o desenvolvimento de modelo para escoamento em swirlers, aplicação da lei de Crocco em escoamentos com mudança súbita de área de seção, aplicação de modelos de entrainment etc. A modelagem matemática proposta foi empregada no desenvolvimento de um sistema computacional na qual foi usado para simular diversos queimadores em escala industrial, e as simulações obtidas foram comparadas com as medições de campo realizadas nos queimadores. Os resultados das simulações foram muito representativos com divergências de no máximo 5,0 % entre as propriedades do escoamento simuladas com as propriedades mensuradas, por exemplo, pressão, temperatura, vazão etc
Abstract: Jet burners are characterized by their high power and their high momentum in the axis direction. For that reason, these burners are widely used in rotary kilns, especially in the cement and calcination industry. The project of jet burners is based on the approximation of the primary air flow in the burner, through the development of an isentropic compressible flow model for one nozzle. This approximation leads to high differences between the project and the actual performance of the equipment. For the purposes of this thesis, models of compressible flow with friction, heat exchange and variable cross section area for primary air flow inside the burner were developed and applied. The application of these models makes possible the integration of the whole burner project, i.e. specification of motors, blowers, and the simulation of the burner's tubing system, which comprises manifold, control valves, orifices flow meters, hoses, etc. These models also provides means to relate the primary air flow to the jet formed by the burner, through the application and development of aerodynamic indexes that represent the jet. Besides proposed modeling techniques, innovations in this thesis include the development of a model for representing flow in swirlers, an application of the Crocco law for flow through sudden changing cross sections, application of entrainment models, etc. Mathematical modeling was applied in the development of a computational system, which was used to simulate diverse industrial burners. Resulting simulations were compared with measures taken from actual burners. Results obtained were highly representative, showing a variance of 5.0% at the most between simulated flow properties and measured properties, i.e. pressure, temperature, flow rate, etc
Mestrado
Termica e Fluidos
Mestre em Engenharia Mecânica
3
Leng, Jing. "Combustion processes within a gas fired pulsed combustor". Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307945.
Testo completo
4
Bishop, Robert Phelps. "Combustion efficiency in internal combustion engines". Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15164.
Testo completoAbstract (sommario):
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: leaf 26.
by Robert Phelps Bishop.
B.S.
5
Hossain, Abu Norman. "Combustion of solid fuel in a fluidized bed combustor". Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1176492911.
Testo completo
6
Hossain, Abu Noman. "Combustion of solid fuel in a fluidized bed combustor". Ohio University / OhioLINK, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1176492911.
Testo completo
7
Lei, Yafeng. "Combustion and direct energy conversion in a micro-combustor". Texas A&M University, 2005. http://hdl.handle.net/1969.1/4311.
Testo completoAbstract (sommario):
The push toward the miniaturization of electromechanical devices and the resulting
need for micro-power generation (milliwatts to watts) with low-weight, long-life devices
has led to the recent development of the field of micro-scale combustion. Since batteries
have low specific energy (~200 kJ/kg) and liquid hydrocarbon fuels have a very high
specific energy (~50000 kJ/kg), a miniaturized power-generating device, even with a
relatively inefficient conversion of hydrocarbon fuels to power, would result in increased
lifetime and/or reduced weight of an electronic or mechanical system that currently
requires batteries for power.
Energy conversion from chemical energy to electrical energy without any moving
parts can be achieved by a thermophotovoltaic (TPV) system. The TPV system requires
a radiation source which is provided by a micro-combustor. Because of the high surface
area to volume ratio for micro-combustor, there is high heat loss (proportional to area)
compared to heat generation (proportional to volume). Thus the quenching and
flammability problems are more critical in a micro-scale combustor. Hence innovative
schemes are required to improve the performance of micro-combustion.
In the current study, a micro-scale counter flow combustor with heat recirculation is
adapted to improve the flame stability in combustion modeled for possible application to a TPV system. The micro-combustor consists of two annular tubes with an inner tube of
diameter 3 mm and 30 mm long and an outer tube of 4.2 mm diameter and 30 mm long.
The inner tube is supplied with a cold premixed combustible mixture, ignited and burnt.
The hot produced gases are then allowed to flow through outer tube which supplies heat
to inner tube via convection and conduction. The hot outer tube radiates heat to the TPV
system. Methane is selected as the fuel. The model parameters include the following:
diameter d , inlet velocity u , equivalence ratio àand heat recirculation efficiency ÷
between the hot outer flow and cold inner flow. The predicted performance results are as
followings: the lean flammability limit increased from 7.69% to 7.86% and the
quenching diameter decreased from 1.3 mm to 0.9 mm when heat recirculation was
employed. The overall energy conversion efficiency of current configuration is about
2.56.
8
Chow, Siu-Kei. "Flow and combustion characteristics of a liquid-fuelled combustor". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46714.
Testo completo
9
Ichihashi, Fumitaka. "Investigation of Combustion Instability in a Single Annular Combustor". University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1299617901.
Testo completo
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Ribeiro, Natália da Silva [UNESP]. "Estudo termogravimétrico da combustão e oxicombustão de misturas carvão mineral-biomassa". Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/149903.
Testo completoAbstract (sommario):
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Nesta dissertação, investiga-se através da análise termogravimétrica o comportamento da combustão de amostras de carvão mineral, bagaço de cana-de-açúcar, bagaço de sorgo biomassa e das misturas de carvão-biomassa. A biomassa e o carvão possuem propriedades físico-químicas diferentes que proporcionam comportamento térmico diferente durante o processo de co-combustão, desta forma o objetivo desta pesquisa é caracterizar o comportamento térmico de misturas de carvão mineral com bagaço de cana-de-açúcar e bagaço de sorgo em atmosferas simuladas de combustão (O2/N2) e oxicombustão (O2/CO2). Os experimentos foram realizados em duplicata em um analisador termogravimétrico utilizando uma razão de aquecimento de 10 °C/min. Foi considerada uma granulometria uniforme para todos os materiais (63 µm) com a finalidade de garantir uma mistura homogênea. Foram estudadas quatro proporções de biomassa na mistura (10, 25, 50 e 75%). A partir das técnicas de termogravimetria (TG) e termogravimetria derivada (DTG) foram determinados parâmetros tais como Índice de combustão, sinergismo e energia de ativação, bem como avaliada a influência da atmosfera de combustão sobre esses parâmetros. Os resultados indicam que o bagaço de cana-de-açúcar apresenta valor de energia de ativação inferior ao registrado para o bagaço de sorgo e desempenho de combustão superior ao do bagaço de sorgo. Para as misturas, os melhores resultados foram registrados até a proporção de 25% de biomassa na mistura. Avaliando individualmente cada material, quando se substitui o N2 por CO2 pode-se observar um aumento na reatividade da reação, uma maior oxidação dos materiais e uma melhora nos parâmetros avaliados. Para ambas as misturas não foram observadas mudanças significativas no perfil de combustão quando o N2 é substituído por CO2. No entanto, a presença da biomassa na co-combustão com o carvão, além dos benefícios econômicos e ambientais, aumentou o desempenho da combustão do carvão mineral em ambas as atmosferas.
This dissertation investigates by thermogravimetric analysis the behavior of the combustion of coal, sugarcane bagasse, sorghum biomass bagasse and coal-biomass blends. The biomass and coal have different physicochemical properties that provide different thermal behavior during the process of co-combustion, thus the aim of this research is to characterize the thermal behavior of coal mixed with sugarcane bagasse and sorghum bagasse in simulated atmospheres of combustion (O2/N2) and oxycombustion (O2/CO2). The experiments were performed in duplicate in a thermogravimetric analyzer using a heating rate of 10 ° C/min. A uniform particle size for all materials (63 μm) in order to ensure a homogeneous mixture was considered. Four biomass ratios were studied in the blend (10, 25, 50 and 75%). From the techniques of Thermogravimetry (TG) and Derivative Thermogravimetry (DTG) curves were determined parameters such as: Combustion index, synergism and activation energy and evaluated the influence of combustion atmosphere on these parameters. The results indicate that the sugarcane bagasse presents a lower activation energy value than sorghum bagasse and combustion performance higher than sorghum bagasse. For mixtures, best results were recorded up to 25% proportion of biomass in the blend. Individually evaluating each material, when replacing N2 by CO2 can be seen an increase in the reactivity of the reaction, the increased oxidation of the materials and an improvement in the evaluated parameters. For both blends, no significant changes in combustion profile when N2 substituted by CO2. However, the presence of biomass in co-combustion with coal in addition to economic and environmental benefits increased the combustion performance of coal in both atmospheres.
CNPq: 134366/2015-8
11
Bai, Tiejun. "Combustion of liquid fuels in a Rijke type pulse combustor". Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/12491.
Testo completo
12
Deppe, Martin W. "Combustion efficiency in a dual-inlet side-dump ramjet combustor". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA283564.
Testo completo
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LI, GUOQIANG. "EMISSIONS, COMBUSTION DYNAMICS, AND CONTROL OF A MULTIPLE SWIRL COMBUSTOR". University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1092767684.
Testo completo
14
Metzger, Brian. "Glycerol Combustion". NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-07312007-153859/.
Testo completoAbstract (sommario):
As worldwide production of biodiesel fuel increases, one of the largest concerns is the abundance of waste glycerol. The price of crude glycerol has fallen drastically and many large biodiesel producers are currently paying to landfill this large waste stream. In the search to find a value added alternative, glycerol combustion may be one of the simplest solutions. Heat recovered from glycerol oxidation could easily be used to reduce heating costs inherent to large-scale biodiesel production. It has been stated ?Combustion of glycerol would be an elegant solution, if it worked?. Clean combustion of glycerol is difficult due to its high viscosity, high auto ignition temperature, and concerns of hazardous emissions. In particular, most in the biodiesel producing community share a fear that burning glycerol could produce acrolein, an aldehyde which is a thermal decomposition product of glycerol and is toxic at very low concentrations. This report will detail the design of a burner that can safely and easily burn crude glycerol for process heating. Emissions testing in the burner using glycerol sources of varying quality confirm that this burner design completely oxidizes the glycerol into CO2 and H2O with very low levels of pollutants, typical of other hydrocarbon fuels. These results show that safe, clean, and efficient combustion of a wide range of glycerol purities is possible with a properly designed burner.
15
Radhakrishnan, Arun. "Self-sustained combustion of low grade solid fuels in a stagnation-point reverse-flow combustor". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50275.
Testo completoAbstract (sommario):
This thesis investigates the use of the Stagnation-Point Reverse-Flow (SPRF) combustor geometry for burning low-grade solid fuels that are attractive for specific industrial applications because of their low cost and on-site availability. These fuels are in general, hard to burn, either because of high moisture and impurity-content, e.g. biomass, or their low-volatiles content, e.g., petroleum-coke. This results in various challenges to the combustor designer, for example reduced flame stability and poor combustion efficiency. Conventional solutions include preheating the incoming flow as well as co-firing with high-grade fuels. The SPRF combustor geometry has been chosen because it was demonstrated to operate stably on standard gaseous and liquid-fuels corresponding to ultra fuel-lean conditions and power densities at atmospheric-pressure around 20-25 MW/m3. Previous studies on the SPRF combustor have proven that the unique, reverse flow-geometry allows entrainment of near-adiabatic products into the incoming reactants, thereby enhancing the reactivity of the mixture. Further, the presence of the stagnation-end created a region of low mean velocities and high levels of unsteadiness and mixing-rates that supported the reaction-zones. In this study, we examine the performance of the SPRF geometry on a specific low grade solid fuel, petroleum coke.
There are three main goals of this thesis. The first goal is the design of a SPRF combustor to operate on solid-fuels based on a design-scaling methodology, as well as demonstration of successful operation corresponding to a baseline condition. The second goal involves understanding the mode of operation of the SPRF combustor on solid-fuels based on visualization studies. The third goal of this thesis is developing and using reduced-order models to better understand and predict the ignition and quasi-steady burning behavior of dispersed-phase particles in the SPRF combustor.
The SPRF combustor has been demonstrated to operate stably on pure-oxygen and a slurry made from water and petroleum-coke, both at the baseline conditions (125 kW, 18 g/s, ~25 µm particles) and higher power-densities and powder sizes. For an overall combustor length less than a meter, combustion is not complete (global combustion efficiency less than 70%). Luminance imaging results indicate the incoming reactant jet ignites and exhibits intense burning at the mid-combustor region, around 15 jet diameters downstream of the inlet, most likely due to enhanced mixing as a result of the highly unsteady velocity field. This roughly corresponds to the location of the reaction zones in the previous SPRF combustors operating on gas and liquid fuels. Planar laser visualization of the reacting flow-field using particle-scattering reveals that ignition of a significant amount of the reactants occurs only after the incoming jet has broken into reactant packets. Post-ignition, these burning packets burn out slowly as they reverse direction and exit the combustor on either side of the central injector. This is unlike the behavior in liquid and gas-fueled operation where the incoming reactants burned across a highly corrugated, thin-flame front. Based on these findings, as well as the results of previous SPRF studies, an idealized model of combustor operation based on a plug flow reactor has been developed. The predictions suggest that fuel-conversion efficiency is enhanced by the combustor operating pressure and lowered by the heat-losses.
Overall, this effort has shown the SPRF geometry is a promising compact-combustor concept for self-sustained operation on low-grade solid-fuels for typical high-pressure applications such as direct steam-generation. Based on these findings, it is recommended that future designs for the specific application previously mentioned have a shorter base-combustor with lower heat-losses and a longer steam-generation section for injection of water.
16
YAMAMOTO, Kazuhiro, Satoshi INOUE, Hiroshi YAMASHITA, Daisuke SHIMOKURI e Satoru ISHIZUKA. "Flow Field of Turbulent Premixed Combustion in a Cyclone-Jet Combustor". The Japan Society of Mechanical Engineers, 2007. http://hdl.handle.net/2237/9384.
Testo completo
17
Awosope, Iyiola Olumide. "Flameless oxidation combustion modelling and application to a gas turbine combustor". Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419936.
Testo completo
18
Weber, Matthew F. "Characterization of Combustion Dynamics in a Liquid Model Gas Turbine Combustor Under Fuel-Rich Conditions". University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1562060065192189.
Testo completo
19
Hilbert, Renan. "Etude de la combustion turbulente non prémélangée et partiellement prémélangée par simulations numériques directes". Châtenay-Malabry, Ecole centrale de Paris, 2002. http://www.theses.fr/2002ECAP0856.
Testo completoAbstract (sommario):
Ce travail présente l’étude de flammes turbulentes non-prémélangées et partiellement prémélangées par simulations numériques directes (DNS) en utilisant des modèles détaillés de chimie de transport. L’interaction entre une flamme H2/Air et un champ de turbulence est simulée et l’influence de la diffusion différentielle sur la structure de la flamme est qualifiée. On note en particulier l’absence de corrélation entre la température de flamme et le taux de dissipation scalaire quand un modèle de transport élaboré est utilisé, ainsi qu’une modification de la limite d’équilibre. Le ré-établissement de l’équation de flammelettes avec la prise en compte d’un nombre de Lewis non unitaire pour la fraction de mélange Z permet de prendre en compte, au moins partiellement, cet effet. Une simulation de l’interaction entre une flamme non-prémélangée H2/Air et une paire de tourbillons avec des modèles détaillés de chimie et de transport a été réalisée, post traitée et analysée. Une extinction de la flamme est observée et la structure partiellement prémélangée au bord de la zone réactive est étudiée. On montre que le radical OH est un bon traceur de la zone d’extinction de la flamme, mais qu’il ne « voit » pas l’intensification de l’activité chimique dans les zones partiellement prémélangées. L’auto-allumage d’une flamme turbulente non prémélangée a été examiné. Les résultats de DNS permettent d’extraire des informations sur la prévision de la localisation du premier site d’autoallumage, sur l’influence du modèle de transport et sur la structure partiellement prémélangée observée. La répétition des calculs permet une étude statistique de l’influence de la turbulence sur le temps d’allumage. Le test a priori d’un nouveau modèle de combustion turbulente basé sur le concept de densité de surface de flamme généralisée donne de premiers résultats prometteurs.
20
Hillion, Mathieu. "Contrôle de combustion en transitoires des moteurs à combustion interne". Phd thesis, École Nationale Supérieure des Mines de Paris, 2009. http://pastel.archives-ouvertes.fr/pastel-00005749.
Testo completoAbstract (sommario):
Cette thèse traite le problème du contrôle de combustion des moteurs automobiles à combustion interne. On propose une méthode complétant les stratégies de contrôle existantes reposant sur des cartographies calibrées en régime stabilisé. Pendant les transitoires, cette méthode de contrôle utilise des variations de la variable rapide (moment d'allumage ou d'injection) pour compenser les déviations des conditions initiales des variables thermodynamiques dans les cylindres (variables lentes) par rapport à leurs valeurs optimales. Les corrections sont calculées grâce à une analyse de sensibilité d'un modèle de combustion. La stratégie de contrôle en résultant est utilisable en temps réel et, de manière intéressante, ne requiert ni capteur additionnel, ni phase de calibration supplémentaire. Plusieurs cas d'´etudes sont exposés: un moteur essence, un moteur Diesel dilué dans un cadre d'injection monopulse puis multipulse. Des simulations ainsi que des résultats experimentaux obtenus sur banc moteurs et véhicules mettent en valeur l'interêt de la méthode proposée.
21
Ghorbali, Ali. "Cyclic variation in combustion in a constant volume combustion chamber". Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6757.
Testo completoAbstract (sommario):
Cycle to cycle variations in combustion and turbulence characteristics in a swirling flow were measured in a cylindrical vessel. The vessel was charged by rapid tangential injection using a shrouded valve for two valve lifts (7 mm and 12 mm). A premixed lean mixture of propane and air ($\phi$ = 0.8) was ignited at quarter radius from the center. Pressure rise as a function of time was measured using a pressure transducer. Mean flow, turbulence intensity and Taylor microscale were estimated by statistical analysis of a single hot wire anemometer signal using ensemble averaging and cyclic analysis. Results obtained indicate that changing the valve lift changes turbulence characteristics at mid-radius. However, turbulence characteristics at quarter radius from center and quarter radius to wall were found to be independent of valve lift. Mean time, standard deviation of mean time delay and Taylor microscale were estimated using combustion pressure traces. Results indicate that the mean time and the standard deviation ignition are weak functions of mean flow and turbulence intensity and strong functions of the Taylor microscale as implied by the Tennekes model. Cyclic variations at ignition were observed to contribute the most to cyclic variations.
22
Sone, Kazuo. "Unsteady simulations of mixing and combustion in internal combustion engines". Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12171.
Testo completo
23
Heising, Raymond. "Effectiveness of pulsed spray combustion for suppression of combustion instabilities". Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/16682.
Testo completo
24
Shah, Priti. "Mathematical modelling of flow and combustion in internal combustion engines". Thesis, University of Greenwich, 1989. http://gala.gre.ac.uk/8703/.
Testo completoAbstract (sommario):
The research work reported herein addresses the problem of mathematical modelling of fluid flow and combustion in internal combustion engines. In particular, the investigation of three topics that constitute prime sources of uncertainty, in current numerical models, namely turbulence modelling, inaccuracies in the solution procedure specific to moving grids, and combustion modelling. Two and three-dimensional computations of the in-cylinder turbulent flow in a diesel engine are described first, with emphasis on the modifications made to the standard k- model of turbulence to account for rapid compression/expansion, and on the k-W model also used in the computations. It is concluded that the standard k- model may lead to poor predictions when used for internal combustion engine simulations, and that the modified model leads to more reasonable length-scale distributions, improving significantly the overall agreement of velocity predictions with experiment. It is also demonstrated that the k-W model provides better turbulence predictions than the unmodified k- model for the cases considered. The moving boundary within a reciprocating engine poses the problem that as it moves toward the cylinder head it compresses the computational grid cells, creating large aspect ratios that can adversely affect the numerical accuracy and convergence. A conservative scheme has therefore been devised that allows for the removal or addition of grid cells during the simulation, so as to maintain reasonable aspect ratios. It is concluded that with the proposed scheme convergence is obtained within fewer iterations, computational cost is therefore reduced, and that the results are generally in better agreement with experimental data. The third part of this study investigates and compares the performance of the two most commonly used combustion models (the eddy-break-up and the Arrhenius models) and proposes a new formulation of a flame-front model. Calculations have been performed for a one-dimensional test case and for a representative spark-ignition engine in order to determine the grid and time step requirements for numerical accuracy, the sensitivity of results to empirical input and the physical realism of the predictions by comparison with experimental data. It has been found for the cases considered that neither the eddy-break-up nor the Arrhenius models are appropriate for predicting engine combustion. The Arrhenius model does not represent well the combustion process for the cases considered. The eddy-break-up model is not capable of predicting the observed flame front, and the empirical constants in the model require extensive tuning to obtain predictions that match experiments. The flame-front model however, in spite of many simplifications, produces much more realistic flame-front propagation and the empirical input of the model, i.e. the flame speed, can in principle be obtained by other means other than ad-hoc tuning. It is concluded that the flame-front model requires refinement, but for the cases considered, it provides the basis of a very promising combustion model for predicting premixed combustion in engines.
25
Alganash, Blaid Sasi Abozeid. "Numerical investigation of the combustion processes of various combustion regimes". Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/7124/.
Testo completoAbstract (sommario):
This thesis concerns numerical investigations of the combustion behaviour of various combustion regimes. The simulations are based on modelling the flow of the fuels in the combustion devices. Computational fluid dynamics (CFD) modelling and analysis were used in three different works. FLUENT software, which is based on the finite volume method, is used to carry out all the simulations. Firstly, numerical simulations were carried out to investigate the turbulent non-premixed combustion of a mixture of methane (CH4) 90% and nitrogen (N2) 10%, on volume basis, inside an axis-symmetric cylindrical chamber (base case). The objective is to investigate the turbulent flow, flame propagation, temperature and species concentration and evaluate the effects of different reduced reaction mechanisms of methane and the influence of various turbulence models on them. The turbulent combustion inside the chamber occurs under a condition for which the equivalence ratio (ɸ) of 1.04 is used. Instead of using fully detailed chemical kinetics schemes and to reduce the computational costs, four global reduced chemical kinetics mechanisms are employed in the combustion model and they are named as (M-I, M-II, M-III and M-IV). The simulations, in which M-I is used, are performed by Renolds-Averaged Navier Stokes (RANS) approach with the three two-equation k-ϵ closures (standard, realizable and RNG) employed to model the turbulent flow. Concerning the chemistry-turbulence interaction, the finite-rate/eddy-dissipation model (FR/ED) is used. The first two of the above kinetics schemes are two-step reaction mechanisms and the other two are first-step and five-step reaction mechanisms, respectively. The latter one is used to assess the capability of FR/ED model for modeling such a mechanism. The influence of thermal radiation is also investigated by means of P-1 model. The standard k-ϵ model and realizable k-ϵ model are also modified and used in the course of simulations. Moreover, the reaction mechanism (M-II) is optimized to see its effects on the combustion process. The results are compared with the experimental data and gave good agreement. It is found that the best results are generally obtained using the modified standard k-ϵ model. Moreover, the simulation results using the realizable turbulence model are found to have large discrepancies compared to the experimental data. In comparison with the experimental data, the optimization of M-II (Em = 1.6x108 J/kmol) is found to have good results in terms of temperature. Increasing the dilution of the fuel by N2 is investigated. Four cases, CH4 (85, 80, 75 and 100%) on volume basis, are performed. The latter one concerns the combustion of pure methane. The results are compared with the base case and found that the base case is the best compromise to obtain the highest temperature in inside the chamber. Secondly, an axis-symmetric combustion model based on the Euler-Lagrange approach was formulated to model the combustion of pulverized bituminous coal. Three cases with three different char oxidation models are presented. In case1 and case 2, the diffusion and kinetic/diffusion global char models are used, respectively. Whereas, to model char oxidation in case 3, the multi-surface reactions model is used. The volatiles released during the devolatilization stage, which is modelled using a single kinetic rate model, are treated as one species and its combustion is modelled using the FR/ED model. The predicted results have good agreement with the available experimental data and the best predictions are obtained from case 3. The results showed that the combustion inside the reactor was affected by the particulate size. It is found that the burnout of the particle with the diameter of 16 μm at the exit of the furnace is 100%. Whereas, the burnout of the particles with diameters of 84, 154, 222, 291 μm is approximately 86, 75, 35, 33, 29 %, respectively. A number of simulations were carried out to find the best values of parameters suitable for predicting NOx pollutants. The chemical formation and reduction rates of NO are calculated by post-processing data obtained from the previously reacting flow simulations. This method is computationally efficient. For volatile-N is assumed that the nitrogen is released via the intermediates HCN and NH3. For char-N path way, it is assumed that all the nitrogen is released via the intermediate HCN. It is found that the assumption of the partition of volatile-N by 52% HCN, 10% NH3 and 38% NO has the best agreement with the experiment data. The influence of different operating parameters on the combustion process and NOx formation was investigated as well. For the same operating conditions and the same particles size distribution, the combustion of pulverised biomass alone, represented by straw, was investigated followed by the investigation of its firing with coal. The former one show a promising results under such operating conditions. It is found that the temperature distribution when burning straw particles is nearly the same as that obtained from burning coal because all the saw particles are completely burned out inside the furnace when compared with the coal particles. The NOx model, in which the ratio of HCN to NH3 is suggested to be for the partitioning of volatile-N, shows that NO formation is reduced by approximately 20% for case I and 26% for case II at the exit of the furnace when compared to coal. For the latter one the results of co-firing blends of coal with 10, 20, 30 and 40% share of biomass are presented and show the influence of co-firing on the combustion process. Co-firing of straw with coal enhances the combustion behaviour and increases the burnout of coal particles compared to that of coal firing only. It is seen that the burnout of the particles with sizes 84, 154 and 222 μm is remarkably increased. On the other hand, the burnout of the other two particles (291 μm and 360 μm) does not show a great change. The share of 10% of straw shows the highest temperature. Thirdly, Two-phase computational modelling based on the Euler–Euler was developed to investigate the heterogeneous combustion processes of carbon particles inside a newly designed combustion chamber. A transient simulation was carried out for a small amount of carbon powder situated in a cup which was located at the centre of the combustion chamber. A heat source was provided to initiate the combustion with the air supplied by three injection nozzles. The combustion simulations are performed for particle sizes with different diameters (0.5mm, 1mm, 1.5mm, 2mm, 2.5mm and 3mm). The particle of 1mm diameter is assigned to the baseline case. The results show that the combustion is sustained in the chamber, as evidenced by the flame temperature. It is shown that, up to a time of 0.55 s, the higher temperature was gained from the case of carbon particles with the diameter of 3 mm and burning the carbon particles with a diameter of 0.5 mm produces lower temperature. This may be attributed to the residence time of the carbon particles and the design of the burner. The larger particles stay longer than the smaller ones inside the chamber. This may due to the reason that the smaller particles follow the streamlines of the continuous phase and increasing the particle size leads to that the larger particles may deviate from the streamlines of the continuous phase and their slip velocity may increase resulting in enhancing convective transports of heat and species concentrations. The influence of the chamber design was also investigated. The height of the chamber is doubled. With the same operating conditions, up to a time of approximately 0.55 s, it is found that burning carbon particles in the doubled height chamber produces higher temperature than the baseline case (particle diameter 1 mm) and after this time the opposite takes place. Most of the other cases do so.
26
Du, Jianyi. "Combustion CFD simulation". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/NQ56437.pdf.
Testo completo
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Strand, Carina Renée. "Catalytic combustion control". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-21120.
Testo completoAbstract (sommario):
A mathematical model representing the dynamic behaviour observed at the actual catalytic incineration plant at Perstorp was derived. The model equations for the two main process units, the heat exchanger and the incinerator, were based on the lumped systems approach in order to avoid using partial differential equations. The model was written in Matlab and implemented in Simulink using s-functions for the dynamic study. By analyzing the dynamic data from the actual plant, it was discovered that the possible source of the ocassional large temperature variations in the incinerator is the periodic variations in the inlet compositions, amplified the overly agressive air valve controller combined with a significant dead time. This results in oscillations due to overshooting. This behaviour was successfully reproduced using the derived model. Two possibilities for improving the control performance were investigated, both using already existing sensors and actuators. The first control improvement involved reducing the proportional gain according to the SIMC tuning rules for PI controllers. This resulted in a significant reduction in the amplitude of the oscillations in the temperatures throughout the reactor, and thus a more stable performance. Finally, cascade control was implemented using the faster-responding catalyst bed temperature for the inner loop, and the reactor outlet temperature for the outer loop. This provided the most optimal results with the best disturbance rejection as it is able to compensate for the disturbance before it is detected in the outlet temperature.
28
Martin, Kendrick. "Switchgrass combustion studies". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29537.
Testo completoAbstract (sommario):
This thesis presents fundamental research about the combustion gas products and solid phase residue of switch grass combustion. To identify the compounds released during the combustion phase, tests were conducted using a Thermogravimetric Analyzer (TGA) coupled to a Fourier Transform Infrared Spectrometer. These test revealed that aromatic compounds as well as carbon dioxide and water were released.High Pressure Liquid Chromatography (HPLC) and GCMS/GCFID were also used to identify and semi-quantify polycyclic aromatic hydrocarbons (PAH) and benzene derivatives. From these analyses it was concluded that thermal synthesis was not occurring within an oxidative environment and as such no PAHs were found.
Finally an infrared microscope and a scanning electron microscope were used to study functional group, morphology and metal content change resulting from the combustion process.
This research provided information about the combustion mechanism of switch grass and laid the foundation for pilot-scale testing.
29
Cairns, Malcolm. "Titanium particle combustion". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86572.
Testo completoAbstract (sommario):
In order to increase the validity of numerical models of the detonation of heterogeneous titanium explosives, experimental results are needed. The combustino of titanium is studied using two experimental techniques. The first technique is the study of the burn time for a single particle over a wide range of initial diameters while altering the oxygen concentration. To accomplish this a new flat flame burner to study particle burn time has been designed. Luminous tracks caused by the light emitted by the combustion of the particles are analyzed and burn time is inferred. Burn time in air and in an oxygen enriched atmosphere were determined. A second experiment involves the study of large scale detonation of heterogeneous charges. The charges are filled with nitromethane and a packed bed of titanium particles. The titanium particles varied in morphology and particles size. A critical charge diameter for charge ignition (CDPI) was found for irregularly shaped particles but was not found for spherical particles.Pour augmenter la validit des modles numriques sur dtonation d'explosifs htrognes contenants du titane , des rsultats exprimentaux sont ncessaires. Le combustino de titane est tudi en utilisant deux techniques exprimentales. La premire technique est l'tude du temps brle pour une particule sur une large gamme de diamtres initiaux en changeant la concentration d'oxygne. Pour l'accomplir un nouveau brleur de flamme plat pour tudier la particule brle le temps a t conu. Les empreintes lumineuses provoques par la lumire mise par la combustion des particules sont analyses et brlent le temps est dduit. Brlez le temps dans l'air et dans l'atmosphre enrichie d'un oxygne ont t dtermins. Une deuxime exprience implique l'tude de grande dtonation d'chelle de charges htrognes. Les charges sont remplies de nitromethane et un lit emball de particules de titane. Les particules de titane variaient dans la grandeur de particules et la morphologie. Un diamtre de charge critique pour l'ignition de charge (CDPI) a t trouv pour les particules irrgulirement en forme de, mais n'a pas t trouv pour pour les particules irrgulirement en forme de mais n'a pas t trouv pour les particules sphriques.
30
Bhidayasiri, Roongrueng. "Control of combustion". Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286243.
Testo completo
31
Williams, R. "Submerged flame combustion". Thesis, Swansea University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636655.
Testo completoAbstract (sommario):
The objective of this work is to better understand the operation of Submerged Flame Burners, commonly known as Submerged Combustion Burners. Two main aspects require consideration, namely: practical applications of the technology in industry; secondly, theoretical modelling of the flame behaviour within the Submerged Combustion Burner in order to ensure flame stability in the burner and hence heat transfer efficiency and reliable operation. The current status of the Submerged Combustion Technology has been reviewed, detailing the separation equipment items that, overall, make up an industrial Submerged Combustion package. The functionality of the different items has been considered in the context of the primary objective of the equipment, i.e. the establishment of a stable flame within the Submerged Burner. Cases detailing specific instances of the application of Submerged Combustion technology in industry are presented in order that practical aspects of the operation of such units can be better appreciated. The flame system within the Submerged Burner has been modelled using a commercially available Computational Fluid Dynamic Package. A simplified model was used in order to represent the processes occurring within the burner for the combustion of methane with air as the oxidant. The K- turbulence model was used for the prediction of turbulence behaviour within the system. The results of the Computational Fluid Dynamic modelling cover a range of operating parameter values that might be expected to be encountered in industrial applications of Submerged Combustion. The results of the theoretical analysis have been considered in terms of the significance to the design and operation of industrial Submerged Combustion units. The discussions of the practical application of the technology have also led to recommendations being made in respect of the design of the ancillary equipment associated with the Submerged Combustion Burners. The observations made and conclusions drawn in this work provide a better understanding of the processes involved with the production of a stable flame within a Submerged Combustion Burner. Recommendations have been made for future work building on the work reported here.
32
Pearce, Steven Mitchell. "Hydrogen enhanced combustion". Thesis, University of Canterbury. Mechanical Engineering, 2000. http://hdl.handle.net/10092/6047.
Testo completoAbstract (sommario):
Current four stroke engine research objectives focus on increasing part load thermal efficiency while reducing exhaust emissions. Methods currently employed to achieve this are homogeneous charge lean burn technology, stratified charge lean burn technology and the use of alternative fuels. Of all possible alternative fuels hydrogen is viewed by many as being, ultimately, the fuel of the future. Methanol is regarded as being a likely transitional fuel between the current petroleum transport fuels and hydrogen. Hydrogen is known to be effective in extending the operating lean limit of an engine when used in small amounts in conjunction with conventional fuels.
This thesis presents the results of an investigation into the use of hydrogen as a supplementary fuel in a methanol fuelled Ricardo E6 engine. Three methods of introducing supplementary hydrogen into the engine were investigated: Untimed manifold injection, early direct injection and injection through a modified spark-plug.
Suitable injection systems were designed and tested on the Ricardo E6 engine. An engine management system, data acquisition system and post processing software were developed to enable data to be acquired and analyzed. The direct injection systems were the subject of schlieren visualization investigations of injected gas distribution to improve performance and elucidate engine related phenomena. Results detailing the effects of hydrogen supplementation on the engine performance, combustion and exhaust gas emissions are presented and discussed.
The early direct injection of hydrogen through a dedicated cylinder head tapping proved to be the least effective method of introducing supplementary hydrogen in the Ricardo E6 engine. The position of the injector diametrically opposite the spark-plug coupled with low levels of bulk mixture motion in the cylinder resulted in the formation of an inversely stratified charge (lean near spark-plug) even when injection commenced very early in the compression stroke. The inversely stratified charge resulted in a given level of hydrogen supplementation not being as effective as was the case in the other two fuelling systems.
The homogeneous air/fuel mixture formed by the untimed manifold injection of hydrogen was found to have a beneficial effect on both the combustion and emissions of the engine especially in lean air/fuel mixtures. Introducing supplementary hydrogen into the inlet manifold of the engine was however found to reduce the volumetric efficiency of the engine, reducing the level of output power produced by the engine.
Injecting hydrogen through a modified spark-plug was found to be the most effective way of introducing supplementary hydrogen. The improved performance of the modified spark-plug system over the other two systems was found to be due to the presence of a localized hydrogen/air mixture at the spark-plug electrodes at the time of ignition. Extension of the lean limit past that possible with methanol alone was demonstrated whilst maintaining both a high thermal efficiency and low indicated specific unburned hydrocarbon emissions.
Direct injection of supplementary hydrogen into the combustion chamber, either with the aim of forming a homogeneous charge, or forming a richer air/fuel mixture in the vicinity of the spark-plug without the use of a pre-chamber, has not been reported previously in the published literature. The investigation of both of these fuelling methods is presented in this thesis and constitutes an original contribution to the field of engine research.
33
Harding, Stephen C. "Investigation into mixing and combustion in an optical, lean, premixed, prevaporised combustor". Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359964.
Testo completo
34
Venkatesh, Vishnu P. (Vishnu Pravin). "Thermal design and analysis of a recuperative combustor for gas-turbine combustion". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/101313.
Testo completo
35
Wan, Ab Karim Ghani Azlina. "Co-combustion of biomass fuels with coal in a fluidised bed combustor". Thesis, University of Sheffield, 2006. http://etheses.whiterose.ac.uk/14891/.
Testo completoAbstract (sommario):
Co-combustion of biomass with coal has been investigated in a 0.15 m diameter and 2.3 m high fluidised bed combustor under various fluidisation and operating conditions. Biomass materials investigated were chicken waste, rice husk, palm kernel shells and fibres, refuse derived fuel and wood wastes. These were selected because they are produced in large quantities particularly in the Far East. The carbon combustion efficiency was profoundly influenced by the operating and fluidising parameters in the decreased following order: fuel properties (particle size and density), coal mass fraction, fluidising velocity, excess air and bed temperature. The smaller particle size and lower particle density of the fuels (i.e. coal/chicken waste, coal/rice husk and coal/wood powder), the higher carbon combustion efficiency obtained in the range of 86-90%, 83-88%, 87-92%, respectively. The carbon combustion efficiency increases in the range of 3% to 20% as the coal fraction increased from 0% to 70%, under various fluidisation and operating conditions. Also, the carbon combustion efficiency increases with increasing excess air from 30- 50% in the range of 5 - 12 % at 50% coal mass fraction in the biomass mixture. However, further increased of excess air to 70% will reduced the carbon combustion efficiency. Relatively, increasing fluidising velocity contributed to a greater particle elutriation rate than the carbon to CO conversion rate and hence increased the unburned carbon. Furthermore, the bed temperature had insignificant influence of carbon combustion efficiency among the biomass fuels. Depending upon excess air ranges, fluctuations of CO emissions between 200 - 1500 ppm were observed when coal added to almost all biomass mixtures. In ash analyses, the percentages of unburned carbon were found to have increased in the range 3 to 30% of the ash content with the increases of coal fraction in the coal! biomass mixture. Furthermore, no fouling, ash deposition and bed agglomeration was observed during the combustion runs for all tests due to lower operating bed temperature applied. Lastly, a simple model was developed to predict the amount of combustion in the freeboard. This study demonstrated the capability of co-firing biomass with coal and also demonstrated the capability to be burnt efficiently in existing coal-fired boilers with minimum modification.
36
Xu, Min. "Chemical looping combustion : cold model hydrodynamics and modeling of methane combustion". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27743.
Testo completoAbstract (sommario):
A novel interconnected fluidized bed (IFB) reactor with a bypass line for chemical looping combustion (CLC) has been developed to overcome the problem of short residence time of oxygen carrier in the air reactor.
A comprehensive hydrodynamic study was carried out on the cold-flow model of the proposed reactor. Detailed mapping of the operating conditions for the reactor system was studied. Pressure transducers were applied to investigate the pressure loops and the cross-sectional average solids hold-up along the air reactor. Solids circulation flux between the two reactors was measured using butterfly valves by estimating the time interval for collecting a given volume of solids. Helium was used as gas tracer for gas leakage measurement. The experiments examined the gas leakage from air reactor to fuel reactor, from fuel reactor to air reactor, from loop-seals to fuel reactor and from fuel reactor to the cyclone.
For scaling consideration, the cold-flow reactor was operated with fluidizing gas mixture of helium and air to simulate the hydrodynamics of the hot unit. The effect of density ratio of solids to gas on the solids circulation flux, pressure loops and voidage distribution along the air reactor was investigated. The connection between cold unit and hot unit is achieved by applying a scaling law. It can be stated that the cold-flow model operated with fluidizing gas mixture of 96 vol% helium and 4 vol% air can be used to simulate the hydrodynamics of an atmospheric CLC hot unit.
A comprehensive model for the investigation of the reactor is introduced by combining fluidization properties and a particle population balance for calculation of the bed particle conversion, considering the chemical reaction of a single particle. The dimensionless parameters, Mrfuel and Mrair, which represent the mass ratio of input oxidized-particles to the input fuel in unit time for the fuel reactor and the mass ratio of reduced-particles to the input oxygen in unit time for the air reactor, respectively, are introduced. The model shows that Mrfuel should be more than 50 for achieving fuel conversion of 90% in the fuel reactor and Mrair should be more than 60 for achieving oxygen conversion of 85% in the air reactor.
A procedure for optimizing the performance of the atmospheric CLC reactor is developed. The modeling analysis indicated that the optimum operating condition of an atmospheric CLC reactor hot unit should be chosen as follows: fuel capacity is 80 kW, Ua0=6.6 m/s, Uf0= 0.076 m/s, UA1=4Umf, UA2=1Umf, and the temperature in air reactor is 1223 K and in fuel reactor is 1173 K.
37
Forsberg, Peter. "Combustion Valve Wear : A Tribological Study of Combustion Valve Sealing Interfaces". Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-204636.
Testo completoAbstract (sommario):
The exhaust valve system of combustion engines experiences a very complex contact situation of frequent impact involving micro sliding, high and varying temperatures, complex exhaust gas chemistry and possible particulates, etc. In addition, the tribological situation in the exhaust valve system is expected to become even worse due to strict future emission regulations, which will require enhanced combustion and cleaner fuels. This will substantially reduce the formation of combustion products that might ease the contact conditions by forming tribofilms on the contacting surfaces. The lack of protective films is expected to result in increased wear of the contact surfaces. The aim of the work presented in this thesis has been to increase the tribological understanding of the valves. The wear that takes place in the valve sealing interface and how the change in operating conditions affects it have been studied. Such understanding will facilitate the development of future valve designs. A test rig has been developed. It has a unique design with the ability to insert ppm amounts of media into a hot air flow, in order to simulate different environmental changes, e.g. varying amount and composition of combustion residue particles. PVD coated valves were evaluated in a dry atmosphere. It was concluded that although some of the coatings showed potential, the substrate could not support the thin, hard coatings. Investigations with an addition of different oils have been performed. Fully formulated oils proved to build up a protective oil residue tribofilm. This tribofilm has been in-depth analysed and proved to have similar composition and appearance as tribofilms found on low wear field tested valves. With a non-additivated oil, wear particles from the valve seat insert formed a wear particle tribofilm on top of the valve sealing surface. Without any oil the surfaces showed severe wear with wear particles spread over the surfaces. The results presented give a hint about what to be expected in the future, when the engine oils are replaced with ash less oils with reduced amount of additives and the consumed amount of oil within the cylinders are reduced.
38
Farrow, Timipere Salome. "A fundamental study of biomass oxy-fuel combustion and co-combustion". Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/27633/.
Testo completoAbstract (sommario):
While oxy-fuel combustion research is developing and large scale projects are proceeding, little information is available on oxy-biomass combustion and cocombustion with coal. To address this knowledge gap, this research conducted has involved comprehensive laboratory based fundamental investigation of biomass firing and co-firing under oxy-fuel conditions and compared it to conventional air firing conditions. First, TGA was employed to understand the fundamental behaviour of biomass devolatilisation, char combustion and nitrogen partitioning between volatiles and residual char. The results revealed that C02 did not have effect on the devolatilisation of sawdust at temperatures below 1100 grad. C due to higher mass transfer resistance of primary volatiles in C02 than in N2 at low temperatures. Secondly,. by optimising the devolatilisation procedure in a combustion system that simulates closely to an industrial scale such as drop tube furnace (DTF), the devolatilisation/char combustion characteristics of sawdust was investigated. The effect of CO2 on volatile yields, nitrogen partitioning and char burnout were all significant in relation to N2• While coal combustion additives are being used to enhance coal burnout, this study observed improved coal char burnout when biomass char was co-fired with coal char, again a faster burnout was observed in oxy-firing condition compared to air firing. This was due to the catalytic effect of biomass inherent alkali and alkaline earth metals. Similarly, improved volatile yields were observed during codevolatilisation. These fundamental results have provided insight into oxybiomass' firing and co-firing and the data can be used in appropriate CFD modelling to aid the design of oxy-biomass co-firing burners.
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Horning, Marcus. "Feedback Control for Maximizing Combustion Efficiency of a Combustion Burner System". University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1459356183.
Testo completo
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Mohanraj, Rajendran. "Modeling of combustion instabilities and their active control in a gas fueled combustor". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/12089.
Testo completo
41
Silva, Nerivaldo Rodrigues da. "Metodologia para determinação da potencia indicada em motores de combustão interna". [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263004.
Testo completoAbstract (sommario):
Orientador: Caio Glauco SanchezDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Neste trabalho buscou-se desenvolver um método para a determinação da potência indicada em motores de combustão interna e medição da pressão de combustão com um osciloscópio. Para isto é necessário conhecer a curva de pressão de combustão do cilindro em função d posição angular do virabrequim e os dados da geometria do mecanismo biela-manivela. Utilizou-se a pressão de combustão do cilindro para calcular o trabalho transferido pelo gás ao pistão do motor. A pressão de combustão foi medida com um transdutor de pressão piezoelétrico. O efeito piezoelétrico é devido ao fenômeno que ocorre com o cristal de quartzo que quando submetido a uma pressão gera uma carga elétrica. Essa carga é convertida em um sinal de tensão linear e proporcional. Este sinal pode ser analisado por um osciloscópio ou ser condicionado por um sistema de aquisição de dados. Obtidos os dados, estes foram analisados através dos diagramas Log P-Log v, para verificar sua qualidade e se representavam o fenômeno físico medido. A curva da pressão do cilindro versus volume calculado foram plotadas, gerando os diagramas P-v. A área do diagrama P-v durante o tempo de compressão e expansão, que corresponde ao trabalho indicado liquido, foi determinada por integração numérica. A pressão média indicada calculada foi comparada com o valor obtido com o indicador de pressão Indiset 620 da AVL e apresentou resultado satisfatório. Os demais resultados obtidos foram analisados e comparados com os dados da revisão da literatura e apresentaram uma boa concordância. As tecnologias disponíveis para medição da pressão de combustão e os métodos para avaliação da performance são de maior importância para o estudo do processo da combustão, visando o desenvolvimento de motores com alta potência, baixo consumo de combustíveis e baixas emissões tóxicas dos gases de escapamento
Abstract: In this thesis, we were looking for a method to determinate the indicated power in a combustion engine and measurement of combustion pressure using an oscilloscope. To achieve that, it was necessary to know the curve of combustion pressure for each cylinder according to the crankshaft 's angular position and geometric data of connecting rod and crank shaft¿s mechanism. We used the cylinder¿s combustion pressure to calculate the work transferred by the gas to the engine¿s piston. The combustion pressure was measured by a piezoelectric pressure transducer. The piezoelectric effect occurs when a crystal of quartz, that under a certain pressure, generates an electrical signal. This signal is converted to a proportional and linear signal that can be analyzed by an oscilloscope or a data acquisition system. Once we obtained the data, we analyzed it thru a Log P-Log v diagram, verifying its quality and if it represents the measured physical effect. The curve of cylinder¿s pressure versus calculated area was plotted, generating the P-v diagrams. The diagram P-v area, during a certain time of compression and expansion, which correspond to the work indicated, was originated of a numerical integration. The indicated and calculated average pressure was compared to the value obtained from an AVL¿s Indiset 620 pressure indicator, showing satisfactory results. All the other results obtained were analyzed and compared to literature¿s revision data showing a good concordance. The available technologies to measure the combustion pressure and the methods to check performance, are very important to study the combustion process, aiming the development of higher power engines, lower consumption of fuel and lower toxic gas emission
Mestrado
Termica e Fluidos
Mestre em Engenharia Mecânica
42
Botura, César Augusto [UNESP]. "Desenvolvimento de um sistema de incineração de resíduos sólidos para utilização com combustão pulsante". Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/106449.
Testo completoAbstract (sommario):
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Universidade Estadual Paulista (UNESP)
Este trabalho tem a finalidade de investigar a incineração de resíduos sólidos na presença de ondas acústicas para incrementar o processo de combustão. Para tanto foi projetado e construído um forno rotativo para incineração de resíduo sólido industrial. Um combustor do tipo sintonizável foi desenvolvido e acoplado ao forno rotativo para indução de oscilações acústicas, além de outros acessórios utilizados no processo de combustão (alimentador de resíduos, ejetor, sonda para análise de gases). Os resultados obtidos mostram que a presença do campo acústico melhora o processo de combustão. Estes resultados foram avaliados principalmente através da análise de gases de combustão, permitindo uma redução da quantidade de combustível utilizado.
This work has the objective of investigating the incineration of solid wastes with acoustics oscillations to improve the combustion process. A rotary kiln was designed and built for the research. A tunable combustor was developed and connected to the rotary kiln for induction of the acoustics oscillations. Accessories were also built and used in the combustion process (feeder of waste, air ejector, probe for gas analysis). The results show that the presence of the acoustic field improves the combustion process. These results had been evaluated mainly through the analysis of gas combustion, allowing a reduction of the amount of used fuel.
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Tongroon, Manida. "Combustion characteristics and in-cylinder process of CAI combustion with alcohol fuels". Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4501.
Testo completoAbstract (sommario):
Controlled auto-ignition (CAI) combustion in the gasoline engine has been extensively studied in the last several years due to its potential for simultaneous improvement in fuel consumption and exhaust emissions. At the same time, there has been increasing interest in the use of alternative fuels in order to reduce reliance on conventional fossil fuels. Therefore, this study has been carried out to investigate the effect of alcohol fuels on the combustion characteristics and in-cylinder processes of CAI combustion in a single cylinder gasoline engine. In order to study the effect of alcohol fuels, combustion characteristics were investigated by heat releases analysis in the first part. The combustion process was studied through flame structure and excited molecule by chemiluminescence imaging. Furthermore, in-cylinder gas composition was analysis by GC-MS to identify the auto-ignition reactions involved in the CAI combustion. In addition, the influence of spark-assisted ignition and injection timings were also studied. Alcohol fuels, in particular methanol, resulted in advanced auto-ignition and faster combustion than that of gasoline. In addition, their use could lead to substantially lower HC, NOX and CO exhaust emissions. Spark-assisted ignition assisted gasoline combustion by advancing ignition timing and initiating flame kernel at the centre of combustion chamber but it had marginal effect on alcohol fuels. Auto-ignition always took place at the perimeter of the chamber and occurred earlier with alcohol fuels. Fuel reforming reactions during the NVO period were observed and they had significant effect on alcohol combustion.
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Chung, Nguyen Thai. "Pre-integrated non-equilibrium combustion-response mapping for internal combustion engine emissions". Thesis, University of Glasgow, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412952.
Testo completo
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Turner, Dale Michael. "The combustion and emissions performance of fuel blends in modern combustion systems". Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1165/.
Testo completoAbstract (sommario):
The combustion and emissions performance of fuel blends in modern combustion systems has been investigated with the intention of reducing emissions, improving efficiency and assessing the suitability of future automotive fuels. The combustion systems used in this study include Homogeneous Charge Compression Ignition (HCCI) and Direct Injection Spark Ignition (DISI). By adding a small quantity (10%) of diesel to gasoline, the HCCI combustion of this ‗Dieseline‘ mixture shows a 4% increase in the maximum and a 16% reduction in the minimum loads (IMEP) achievable. The NOX emissions are reduced, with greater than 30% savings seen for high engine loads. The addition of bio-fuels (ethanol and 2,5 di-methylfuran) to gasoline in HCCI combustion resulted in reduced ignitability giving rise to a 0.25 bar IMEP reduction of the maximum load. A 70% increase in NOX emissions is seen at an engine load of 3.5 bar IMEP. The addition of ethanol and to a lesser extent 2,5 di-methylfuran (DMF) to gasoline in DISI combustion shows increased combustion efficiency. The NOX emissions are reduced with ethanol, but are increased with the addition of DMF. At wide open throttle the bio-fuels show up to a 3 percentage point increase in efficiency through the use of more favourable spark timings brought about by the increased octane ratings and enthalpies of vaporisation. The PM emissions from DISI combustion can be reduced by up to 58% (mass) with the addition of ethanol. The soluble organic fraction forms a significant part of the total PM, particularly for the higher ethanol blends at wide open throttle. The addition of DMF however increases the total PM by up to 70% (mass) through the incomplete combustion of the ring structure.
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Milovanović, Nebojša. "A study of controlled auto ignition (CAI) combustion in internal combustion engines". Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/19906.
Testo completoAbstract (sommario):
Controlled Auto Ignition (CAI) combustion is a new combustion principle in internal combustion engines which has in recent years attracted increased attention. In CAI combustion, which combines features of spark ignition (SI) and compression ignition (CI) principles, air/fuel mixture is premixed, as in SI combustion and auto-ignited by piston compression as in CI combustion. Ignition is provided in multiple points, and thus the charge gives a simultaneous energy release. This results in uniform and simultaneous auto-ignition and chemical reaction throughout the whole charge without flame propagation. CAI combustion is controlled by the chemical kinetics of air/fuel mixture with no influence of turbulence. The CAI engine offers benefits in comparison to spark ignited and compression ignited engines in higher efficiency due to elimination of throttling losses at part and idle loads. There is a possibility to use high compression ratios since it is not knock limited, and in significant lower NOx emission (≈90%) and particle matter emission (≈50%), due to much lower combustion temperature and elimination of fuel rich zones. However, there are several disadvantages of the CAI engine that limits its practical application, such as high level of hydrocarbon and carbon monoxide emissions, high peak pressures, high rates of heat release, reduced power per displacement and difficulties in starting and controlling the engine. Controlling the operation over a wide range of loads and speeds is probably the major difficulty facing CAI engines. Controlling is actually two-components as it consists of auto-ignition phasing and controlling the rates of heat release. As CAI combustion is controlled by chemical kinetics of air/fuel mixture, the auto-ignition timing and heat release rate are determined by the charge properties such as temperature, composition and pressure. Therefore, changes in engine operational parameters or in types of fuel, results in changing of the charge properties. Hence, the auto-ignition timing and the rate of heat release. The Thesis investigates a controlled auto-ignition (CAI) combustion in internal combustion engines suitable for transport applications. The CAI engine environment is simulated by using a single-zone, homogeneous reactor model with a time variable volume according to the slider-crank relationship. The model uses detailed chemical kinetics and distributed heat transfer losses according to Woschini's correlation [1]. The fundamentals of chemical kinetics, and their relationship with combustion related problems are presented. The phenomenology and principles of auto-ignition process itself and its characteristics in CAI combustion are explained. The simulation model for representing CAI engine environment is established and calibrated with respect to the experimental data. The influences of fuel composition on the auto-ignition timing and the rate of heat release in a CAI engine are investigated. The effects of engine parameters on CAI combustion in different engine concepts fuelled with various fuels are analysed. The effects of internal gas recirculation (IEGR) in controlling the auto-ignition timing and the heat release rate in a CAI engine fuelled with different fuels are investigated. The effects of variable valve timings strategy on gas exchange process in CAI engine fuelled with commercial gasoline (95RON) are analysed.
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Ranasinghe, D. J. "Modelling partially premixed turbulent combustion in a spark ignited internal combustion engine". Thesis, University of Cambridge, 2000. https://www.repository.cam.ac.uk/handle/1810/272095.
Testo completo
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Garba, Mohammed Umar. "Prediction of ash deposition for biomass combustion and coal/biomass co-combustion". Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/4373/.
Testo completoAbstract (sommario):
In this thesis, a model that couples a reduced alkali kinetic mechanism for alkali sulphate formation during biomass combustion with an ash deposition model using computational fluid dynamics (CFD) techniques has been presented. Starting with a detailed gas-phase kinetic mechanism for the alkali chemistry, a systematic reduction procedure has been performed using a sensitivity analysis to reduce the reaction mechanism to a level that can be implemented into a CFD calculation. An ash deposition model that takes into consideration the ash-sticking probability and the condensation of potassium salts has been developed. The reduced mechanism and the deposition model developed are implemented into a CFD model to predict ash depositions in a 10 MWth biomass grate furnace. Also, a CFD model to predict the deposition rates for the co-combustion of coal with biomass has been developed. This deposition model is based on the combined sticking probabilities of the ash particle viscosity and the melting behaviour of the ash particles. A Numerical Slagging Index (NSI) is also employed to estimate the degree of the sintering of the deposits. Experimental data from the Entrained Flow Reactor (EFR) at Imperial College, London, have been used to validate the models. The predicted results from both the ash deposition models agreed with the experimental measurements, and the NSI has successfully ranked the investigated coal-biomass mixtures according to their degree of sintering.
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Okon, Aniekan. "Combustion dynamics in a lean premixed combustor with swirl forcing and fuel conditions". Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/108265/.
Testo completoAbstract (sommario):
Fossil fuels still account for a large percentage of global energy demand according to available statistics. Natural gas is increasingly gaining the share of these fuels due to the retired coal and nuclear plants. The more stringent emission standards have also put natural gas ahead of other fuels as a result of its efficiency, cost, environmental attributes as well as the operational efficiency of the gas turbine, an engine that uses this fuel. A standard low emission combustion technique in gas turbines is the dry low NOx combustion, with lean fuel and fuel-air premixed upstream of the flame holder. However, this condition is highly susceptible to combustion instabilities characterised by large amplitude oscillations of the combustor’s acoustic modes excited by unsteady combustion processes. These pressure oscillations are detrimental both to the efficiency of performance as well as the hardware of the system. Although the processes and mechanisms that result in instabilities are well known, however, the current challenges facing gas turbine operators are the precise understanding of the operational conditions that cause combustion instabilities, accurate prediction of the instability modes and the control of the disturbances. In a bid to expand this knowledge frontier, this study uses a 100kW swirl premixed combustor to examine the evolution of the flow structures, its influence on the flame dynamics, in terms of heat release fluctuation and the overall effects on the pressure field, under different, swirl, fuel and external excitation conditions. The aim is to determine the operational conditions whose pressure oscillation is reduced to the barest minimum to keep the system in an excellent running condition. The results of this study are expected to contribute towards the design of a new control system to damp instabilities in gas turbines.
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Dody, Joseph W. "Study of biomass combustion characteristics for the development of a catalytic combustor/gasifier". Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/43039.
Testo completoAbstract (sommario):
The research reported here explored, a "new" approach to biomass
energy conversion for small-scale process heat-applications. The conversion process uses close-coupled catalytic. combustion to burn combustibles in effluent generated by primary combustion or gasification of biomass fuels. Computer control of primary and secondary air flow rates allow control of the devices output power while maintaining fuel-lean or stoichiometric conditions in the effluent entering the catalytic combustion zone. The intent of the secondary combustion system is to ensure "clean" exhaust (i.e., promote complete combustion).
A small-scale combustor/gasifier was built and instrumented.
Characteristics of combustion were studied for three biomass fuels so
that primary and secondary air flow control strategies could be devised. A bang-bang type controller was devised for primary air flow
control. Secondary air as controlled based on feedback signals from an inexpensive automobile exhaust gas oxygen sensor. The control strategies and catalytic combustion were implemented on prototype combustor/gasifier and the device was tested with good results.
Power turn down ratios of 4 to 1 and 3 to 1 were achieved. The
zitconia-type automobile exhaust gas oxygen sensors adapted well to the combustion environment of biomass fuel, at least for short periods (long term durability tests were not conducted). The secondary air control system was able to maintain fuel-lean flows for the most part and, the secondary combustion system provided reductions of approximately three fourths in carbon monoxide emissions.Master of Science