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1
Acikalin, Serdar. "Synthesis Of Ferrocenyl Quinones And Ferrocenyl Based Burning Rate Catalysts". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1081256/index.pdf.
Testo completoAbstract (sommario):
Recently, considerable interest has been devoted to the synthesis of new
ferrocene derivatives since properly functionalized ferrocene derivatives could be
potential antitumor substances. For this purpose, we have investigated the synthesis
of ferrocenyl quinones starting from squaric acid. Thermolysis of ferrocenylsubstituted
cyclobutenones, which have been prepared from ferrocenyl
cyclobutenediones and alkenyllithiums, affords hydroquinones, which furnish, upon
oxidation, ferrocenyl quinones. Ferrocenyl cyclobutenediones have been prepared
from known cyclobutenediones by nucleophilic addition of
ferrocenyllithiumfollowed by hydrolysis, Pd/Cu-cocatalyzed cross-coupling with
(tri-n-butylstannyl)ferrocene or Friedel–
Crafts alkylation with ferrocene. A mechanism involving electrocyclic ring opening of alkenyl substituted cyclobutenone to dienylketene and consequent electrocyclic ring closure to cyclohexadienone followed by enolization has been proposed to account for the formation of ferocenyl substituted hydroquinones. Rocket design and production is one of the hottest topics in defense industry. On this subject, significant amount of investments have been done and excellent results were obtained. Among the burning rate catalysts for composite rocket propellants, ferrocene derivatives are one of the most famous ones. Although ferrocene derivatives are superior to some other burning rate catalysts, their use has some drawbacks arising from the tendency of migration in the bulk of the material and their sensitivity toward oxidation by air. With the aim of preventing the negative aspects of ferrocene derivatives, we have investigated the synthesis of EDA (ethylenediamine), TEP (tetraethylenepentamine) and DDI (dimeryl-diisocyanate) based ferrocene derivatives.
2
Bellino, Peter William. "A Study of Spreading and In Situ Burning of Oil in an Ice Channel". Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/1172.
Testo completoAbstract (sommario):
The potential for oil exploration on the Arctic Outer Continental Shelf warrants determination of an efficient method to clean up an oil spill. Traditional spill response equipment may not be practical in an Arctic environment; the presence of ice which may prevent proper deployment of equipment. The remoteness of the areas proposed for oil exploration lack the infrastructure and support networks necessary to stage a response to a large oil spill. These difficulties make it necessary to explore alternative means of oil spill cleanup. In situ burning is one method that may be particularly well-suited for arctic and sub-arctic environments due to the minimal amount of equipment required to achieve an efficient burn, i.e. high mass loss. The Arctic and sub- Arctic environments add an additional level of complexity by introducing a spill medium (ice) that is highly unstable at elevated temperatures. Our experiments sought to calculate the mass loss rate of oil mixtures to determine the efficiency with which they burn within ice channels of varying widths. Since fuel layer thickness is a critical factor in determining the effectiveness of an in situ burn the spread rate of oil along an ice channel was studied. Burning of oil in an ice channel yields low efficiencies (10%) primarily due to the geometric changes of the melting ice channel. The spreading was modeled as a constant flux rectilinear buoyancy-inertia governed flow. The melting causes an increase in the surface area and results in the critical thickness of the oil to be reached sooner. Based on the current bench- scale testing, losses due to ice melting cause the efficiencies of the burning process to be excessively low and not viable to full scale clean up. The results warrant future research to understand how varying other parameters, including starting mass of fuel, influence efficiencies.
3
Farmahini, Farahani Hamed. "A Study on Burning of Crude Oil in Ice Cavities". Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-theses/501.
Testo completoAbstract (sommario):
In situ burning (ISB) is a practical method of oil spill cleanup in icy conditions. This study investigates one example of a likely oil spill scenario; burning oil in an ice cavity. In this situation, unique and unexplored physical processes come into play compared with the classical problem of confined pool fires in vessels. The icy walls of the cavity create a significant heat sink causing notable lateral heat losses especially for small cavity sizes (5-10 cm). Melting of ice because of the heat from the flame causes the geometry of cavity to change. Specifically, the diameter of the pool fire increases as the burning advances. This widening causes the fuel to stretch laterally thereby reducing its thickness at a faster rate. The melted ice water causes the oil layer to rise which causes the ullage height to decrease. The decrease in ullage and increase in diameter counteract the reduction in thickness because of widening or stretching of the fuel layer. There thus exists a strong coupling between the burning rate and the geometry change of the pool and cavity. To explore the problem, experiments were performed in circular ice cavities of varying diameters (5 - 25 cm). The change in shape of the ice cavity and the oil layer thickness are recorded using a combination of visual images, mass loss, and temperature data along the centerline and edge of the cavity. The average burning rate of crude oil in a cavity is greater than the corresponding burning rate in a vessel of equal diameter, yet the burning efficiency (% of fuel consumed during combustion) is lower. For example, the average mass loss rate in a 10 cm ice cavity is 50% higher than a steel vessel of similar size. However, the burning efficiency is lower by 50%. Widening of cavity (170%) contributes to the increase in the average mass burning rate. At the same time heat losses through fuel layer increase because of decrease in fuel thickness by widening of the fuel layer. This coupling is analyzed using a mathematical model which can predict burning rate and efficiency of crude oil in an ice cavity for the range of cavity diameters examined. Extension of the model to larger sizes comparable to realistic situations in the Arctic is discussed.
4
Ward, Nicholas Rhys. "The rate-limiting mechanism for the heterogeneous burning of iron in normal gravity and reduced gravity". Queensland University of Technology, 2007. http://eprints.qut.edu.au/16673/.
Testo completoAbstract (sommario):
This thesis presents a research project in the field of oxygen system fire safety relating to the heterogeneous burning of iron in normal gravity and reduced gravity. Fires involving metallic components in oxygen systems often occur, with devastating and costly results, motivating continued research to improve the safety of these devices through a better understanding of the burning phenomena. Metallic materials typically burn in the liquid phase, referred to as heterogeneous burning. A review of the literature indicates that there is a need to improve the overall understanding of heterogeneous burning and better understand the factors that influence metal flammability in normal gravity and reduced gravity. Melting rates for metals burning in reduced gravity have been shown to be higher than those observed under similar conditions in normal gravity, indicating that there is a need for further insight into heterogeneous burning, especially in regard to the rate-limiting mechanism. The objective of the current research is to determine the cause of the higher melting rates observed for metals burning in reduced gravity to (a) identify the rate-limiting mechanism during heterogeneous burning and thus contribute to an improved fundamental understanding of the system, and (b) contribute to improved oxygen system fire safety for both ground-based and space-based applications. In support of the work, a 2-s duration ground-based drop tower reduced-gravity facility was commissioned and a reduced-gravity metals combustion test system was designed, constructed, commissioned and utilised. These experimental systems were used to conduct tests involving burning 3.2-mm diameter cylindrical iron rods in high-pressure oxygen in normal gravity and reduced gravity. Experimental results demonstrate that at the onset of reduced gravity, the burning liquid droplet rapidly attains a spherical shape and engulfs the solid rod, and that this is associated with a rapid increase in the observed melting rate. This link between the geometry of the solid/liquid interface and melting rate during heterogeneous burning is of particular interest in the current research. Heat transfer analysis was performed and shows that a proportional relationship exists between the surface area of the solid/liquid interface and the observed melting rate. This is confirmed through detailed microanalysis of quenched samples that shows excellent agreement between the proportional change in interfacial surface area and the observed melting rate. Thus, it is concluded that the increased melting rates observed for metals burning in reduced gravity are due to altered interfacial geometry, which increases the contact area for heat transfer between the liquid and solid phases. This leads to the conclusion that heat transfer across the solid/liquid interface is the rate-limiting mechanism for melting and burning, limited by the interfacial surface area. This is a fundamental result that applies in normal gravity and reduced gravity and clarifies that oxygen availability, as postulated in the literature, is not rate limiting. It is also established that, except for geometric changes at the solid/liquid interface, the heterogeneous burning phenomenon is the same at each gravity level. A conceptual framework for understanding and discussing the many factors that influence heterogeneous burning is proposed, which is relevant to the study of burning metals and to oxygen system fire safety in both normal-gravity and reduced-gravity applications.
5
Ward, Nicholas Rhys. "The rate-limiting mechanism for the heterogeneous burning of iron in normal gravity and reduced gravity". Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16673/1/Nicholas_Ward_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis presents a research project in the field of oxygen system fire safety relating to the heterogeneous burning of iron in normal gravity and reduced gravity. Fires involving metallic components in oxygen systems often occur, with devastating and costly results, motivating continued research to improve the safety of these devices through a better understanding of the burning phenomena. Metallic materials typically burn in the liquid phase, referred to as heterogeneous burning. A review of the literature indicates that there is a need to improve the overall understanding of heterogeneous burning and better understand the factors that influence metal flammability in normal gravity and reduced gravity. Melting rates for metals burning in reduced gravity have been shown to be higher than those observed under similar conditions in normal gravity, indicating that there is a need for further insight into heterogeneous burning, especially in regard to the rate-limiting mechanism. The objective of the current research is to determine the cause of the higher melting rates observed for metals burning in reduced gravity to (a) identify the rate-limiting mechanism during heterogeneous burning and thus contribute to an improved fundamental understanding of the system, and (b) contribute to improved oxygen system fire safety for both ground-based and space-based applications. In support of the work, a 2-s duration ground-based drop tower reduced-gravity facility was commissioned and a reduced-gravity metals combustion test system was designed, constructed, commissioned and utilised. These experimental systems were used to conduct tests involving burning 3.2-mm diameter cylindrical iron rods in high-pressure oxygen in normal gravity and reduced gravity. Experimental results demonstrate that at the onset of reduced gravity, the burning liquid droplet rapidly attains a spherical shape and engulfs the solid rod, and that this is associated with a rapid increase in the observed melting rate. This link between the geometry of the solid/liquid interface and melting rate during heterogeneous burning is of particular interest in the current research. Heat transfer analysis was performed and shows that a proportional relationship exists between the surface area of the solid/liquid interface and the observed melting rate. This is confirmed through detailed microanalysis of quenched samples that shows excellent agreement between the proportional change in interfacial surface area and the observed melting rate. Thus, it is concluded that the increased melting rates observed for metals burning in reduced gravity are due to altered interfacial geometry, which increases the contact area for heat transfer between the liquid and solid phases. This leads to the conclusion that heat transfer across the solid/liquid interface is the rate-limiting mechanism for melting and burning, limited by the interfacial surface area. This is a fundamental result that applies in normal gravity and reduced gravity and clarifies that oxygen availability, as postulated in the literature, is not rate limiting. It is also established that, except for geometric changes at the solid/liquid interface, the heterogeneous burning phenomenon is the same at each gravity level. A conceptual framework for understanding and discussing the many factors that influence heterogeneous burning is proposed, which is relevant to the study of burning metals and to oxygen system fire safety in both normal-gravity and reduced-gravity applications.
6
Arvanetes, Jason. "DESIGN AND IMPLEMENTATION OF AN EMISSION SPECTROSCOPY DIAGNOSTIC IN A HIGH-PRESSURE STRAND BURNER FOR THE STUDY OF SOLID PROPELL". Master's thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2820.
Testo completoAbstract (sommario):
The application of emission spectroscopy to monitor combustion products of solid rocket propellant combustion can potentially yield valuable data about reactions occurring within the volatile environment of a strand burner. This information can be applied in the solid rocket propellant industry. The current study details the implementation of a compact spectrometer and fiber optic cable to investigate the visible emission generated from three variations of solid propellants. The grating was blazed for a wavelength range from 200 to 800 nm, and the spectrometer system provides time resolutions on the order of 1 millisecond. One propellant formula contained a fine aluminum powder, acting as a fuel, mixed with ammonium perchlorate (AP), an oxidizer. The powders were held together with Hydroxyl-Terminated-Polybutadiene (HTPB), a hydrocarbon polymer that is solidified using a curative after all components are homogeneously mixed. The other two propellants did not contain aluminum, but rather relied on the HTPB as a fuel source. The propellants without aluminum differed in that one contained a bimodal mix of AP. Utilizing smaller particle sizes within solid propellants yields greater surface area contact between oxidizer and fuel, which ultimately promotes faster burning. Each propellant was combusted in a controlled, non-reactive environment at a range of pressures between 250 and 2000 psi. The data allow for accurate burning rate calculations as well as an opportunity to analyze the combustion region through the emission spectroscopy diagnostic. It is shown that the new diagnostic identifies the differences between the aluminized and non-aluminized propellants through the appearance of aluminum oxide emission bands. Anomalies during a burn are also verified through the optical emission spectral data collected.M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering
7
Tanner, Matthew Wilder. "Multidimensional Modeling of Solid Propellant Burning Rates and Aluminum Agglomeration and One-Dimensional Modeling of RDX/GAP and AP/HTPB". Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2706.pdf.
Testo completo
8
Lundell, Carl. "RESEARCH STUDY: REACTING METAL BIS(TRIMETHYL)AMIDES WITH DOUBLE-BASE PROPELLANT STABILIZERS". Master's thesis, Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/437570.
Testo completoAbstract (sommario):
ChemistryM.A.
During World War II, it was discovered that when lead was added to double-base propellants, it produced beneficial burn rate phenomena. Specifically, the propellant burn rate first increased unexpectedly at low pressures, then the burn rate became independent of pressure, followed lastly by “mesa burning” where the burn rate actually decreased with increasing pressure. This results in a beneficial negative feedback mechanism. Over the past 75 years, researchers have explored different lead complexes to achieve better propellant performance. However, over the last decade, research has shifted to finding an alternative to using lead as an additive to reduce toxicity. Until the attempts detailed herein, researchers had not, to our knowledge attempted to combine double-base propellant stabilizers with various metals to achieve these desired results. In doing so, we prepared two lead complexes, Tetrakis (µ3-(4-methyl-3-nitrophenyl imido lead (II))) 1, and Bis(dinitrophenyl imido lead(II)) 2, that were synthesized by reacting lead bis(trimethylsilyl)amide with a common double-base propellant stabilizer 2-nitrodiphenylamine (NDPA) and 4-methyl-3-nitroaniline. Both complexes formed from protolysis of the trimethylsilylamide ligand by the acidic proton of the amine, and crystallized from tetrahydrofuran (THF). Bomb calorimetry coupled with crystal density structure determined that 1 has a very high energy density of 74.1 MJ/L, more than three times the energy density of conventional nitroamine explosives, whereas 2 was lower at 38.2 MJ/L. The structure, charge and characterization of 1 and 2 are discussed. However, each complex is air sensitive making burn rate experimentation infeasible, so any possible changes to the propellant as an additive remained undetermined. Attempts to use of tin, zinc, or bismuth bis(trimethyl)amides in place of lead, were unsuccessfully characterized, although reactions were likely observed.
Temple University--Theses
9
Jommi, Alessandro. "Studio e ricostruzione delle distribuzioni granulometriche interne al grano in motori a propellente solido". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7829/.
Testo completoAbstract (sommario):
The main purposes of this essay were to investigate in detail the burning rate anomaly phenomenon, also known as "Hump Effect", in solid rocket motors casted in mandrel and the mechanisms at the base of it, as well as the developing of a numeric code, in Matlab environment, in order to obtain a forecasting tool to generate concentration and orientation maps of the particles within the grain. The importance of these analysis is due to the fact that the forecasts of ballistics curves in new motors have to be improved in order to reduce the amount of experimental tests needed for the characterization of their ballistic behavior. This graduate work is divided into two parts. The first one is about bidimensional and tridimensional simulations on z9 motor casting process. The simulations have been carried out respectively with Fluent and Flow 3D. The second one is about the analysis of fluid dynamic data and the developing of numeric codes which give information about the concentration and orientation of particles within the grain based on fluid strain rate information which are extrapolated from CFD software.
10
Gabriel, Vladimir Hallak. "Estudo de modificadores balísticos na formulação de propelentes base dupla visando à otimização de sua velocidade de queima". Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/97/97137/tde-30042014-094502/.
Testo completoAbstract (sommario):
Propelentes sólidos são materiais energéticos que produzem gases em alta pressão por meio de uma reação de combustão. Qualquer propelente sólido inclui dois ou mais dos seguintes componentes: oxidante (nitratos e percloratos); combustível (resinas orgânicas ou polímeros); compostos químicos combinando oxidantes e combustíveis (nitrocelulose ou nitroglicerina); aditivos para facilitar processos de produção ou alterar a taxa de queima e inibidores (fita de etilcelulose), para restringir superfícies de combustão. Pequenas percentagens de aditivos são usadas para modificar diversas propriedades mecânicas, químicas e balísticas dos propelentes sólidos: acelerar ou desacelerar a velocidade de combustão (catalisadores e inibidores de combustão, respectivamente); assegurar a estabilidade química para prevenir a deterioração durante a estocagem; controlar as propriedades de processamento durante a produção de propelente (tempo de cura, fluidez para extrusão ou moldagem, etc.); controlar as propriedades de absorção de radiação no propelente em combustão; aumentar a resistência mecânica e diminuir a deformação elástica; e, finalmente, minimizar a sensibilidade térmica. No caso de propelentes sólidos Base Dupla (mistura de duas bases ativas: a nitrocelulose e a nitroglicerina), é possível alterar sua velocidade de queima principalmente pelo emprego de pequenos teores de modificadores balísticos, em geral sais orgânicos de cobre e chumbo. Neste trabalho, estudou-se a aceleração da velocidade de queima de uma formulação conhecida de propelente Base Dupla - BD, alterando o teor total dos modificadores balísticos cromato de cobre e estearato de chumbo (ou plastabil - nome comercial) na receita original, bem como a proporção entre eles. Estas alterações na formulação original devem, idealmente, preservar os parâmetros de desempenho estabelecidos para as propriedades químicas (estabilidade química) e mecânicas (densidade da massa e ensaios de tração), ao mesmo tempo otimizando o desempenho balístico, pelo aumento da velocidade de queima. Os resultados experimentais mostram que para os parâmetros de qualidade elongação e velocidade de queima a interação entre os fatores, Proporção Sal de Chumbo/Sal de Cobre (Fator A) e Teor de Modificadores Balísticos (Fator B) foram significativos, ou seja, quanto maior os fatores pior o resultado com as propriedades. Com os parâmetros de resistência a tração e densidade da massa, o fator A e B respectivamente influenciam negativamente quando aumentado em sua concentração. Para o parâmetro estabilidade química não houve nenhum sinal de melhora ou influencia dos fatores. No caso da velocidade de queima a interação AB é o que mais influencia. Melhorando significativamente a velocidade de queima.Solid propellants are energetic materials which produce a considerable amount of high-pressure gases by means of a combustion reaction. Any solid propellant formulation includes at least two of the following items: oxidizer (nitrates and perchlorates); fuel (organic resins or polymers); chemical compounds combining oxidizers and fuels (nitrocellulose or nitroglycerine); additives to easy production operations or to modify the burning rate and inhibitors (tape ethyl-cellulose), to restrict the combustion surfaces. Small amounts of additives are employed to modify the mechanical, chemical and ballistic features of the solid propellants: to accelerate or diminish the burning rate (catalysts and inhibitors of burning, respectively); to assure the chemical stability in order to prevent the deterioration during stocking; to control the processing properties during propellant production (curing time, extrusion or casting rheology); to control the radiation absorption in the burning propellant; to enhance the mechanical resistance and to reduce the strain; and, finally, to get the thermal sensitivity to a minimum level. In the case of Double-Base solid propellants (blend of two energetic bases: nitrocellulose and nitroglycerine), it\'s possible to control its burning rate mainly by the use of small amounts of ballistic modifiers, generally copper and lead organic salts. This work has studied the burning rate acceleration of a known Double-Base propellant formulation, by changing the total amount of the ballistic modifiers copper chromate and lead stearate (commercially known as plastabil) in the original formulation, as well as the proportion between them. These changes at the original recipe should preserve, ideally, the performance levels required for the chemical (chemical stability) and mechanical properties (density and stress-strain evaluation), optimizing, at the same time, the ballistic performance, through the burning rate enhancement. Results show that for the parameters of quality and elongation rate of burning the interaction between factors, Proportion of Lead Salt / Salt Copper (Factor A) and content Ballistic Modifiers (Factor B) were significant, ie, the higher the worst factors result with the properties. With the parameters of tensile strength and mass density, the factor A and B respectively negatively influence increased when its concentration. For the chemical stability parameter there was no sign of improvement or influences of factors. In the case of burning rate AB interaction is what most influences. Significantly improving the speed of burning.
11
Beaulieu, Patricia. "Flammability Characteristics at Heat Fluxes up to 200 kW/m2 and The Effect of Oxygen on Flame Heat Flux". Digital WPI, 2005. https://digitalcommons.wpi.edu/etd-dissertations/427.
Testo completoAbstract (sommario):
"This dissertation documents two interrelated studies that were conducted to more fundamentally understand the scalability of flame heat flux. The first study used an applied heat flux in the bench scale horizontal orientation which simulates a large scale flame heat flux. The second study used enhanced ambient oxygen to actually increase the bench scale flame heat flux itself. Understanding the scalability of flame heat flux more fully will allow better ignition and combustion models to be developed as well as improved test methods. The key aspect of the first study was the use of real scale applied heat flux up to 200 kW/m2. An unexpected non-linear trend is observed in the typical plotting methods currently used in fire protection engineering for ignition and mass loss flux data for several materials tested. This non-linearity is a true material response. This study shows that viewing ignition as an inert material process is inaccurate at predicting the surface temperature at higher heat fluxes and suggests that decomposition kinetics at the surface and possibly even in-depth may need to be included in an analysis of the process of ignition. This study also shows that viewing burning strictly as a surface process where the decomposition kinetics is lumped into the heat of gasification may be inaccurate and the energy balance is too simplified to represent the physics occurring. The key aspect of the second study was direct experimental measurements of flame heat flux back to the burning surface for 20.9 to 40 % ambient oxygen concentrations. The total flame heat flux in enhanced ambient oxygen does not simulate large scale flame heat flux in the horizontal orientation. The vertical orientation shows that enhanced ambient oxygen increases the flame heat flux more significantly and also increases the measured flame spread velocity."
12
Spadim, Emanuel Rangel. "Desenvolvimento de dispositivo automático para determinação do índice de combustão de briquetes /". Botucatu, 2020. http://hdl.handle.net/11449/192569.
Testo completoAbstract (sommario):
Orientador: Saulo Philipe Sebastião GuerraResumo: Este trabalho teve como objetivo avaliar o comportamento dos briquetes durante a queima, considerando a possibilidade de se aprimorar o índice de combustão de briquetes de biomassa (aqui denominado ICOMa) com o uso de um aplicativo de computador, de forma que esta nova proposta fosse mais sensível às variações dos dados que o ICOM (já existente na literatura), bem como determinar sua taxa de perda de massa em função do tempo de queima. Com esta nova proposta, também era esperado que se percebesse uma correlação entre o ICOMa e o poder calorífico superior da biomassa ensaiada, possibilitando estimar esta grandeza, ainda que de forma aproximada, sem o uso de uma bomba calorimétrica. A fabricação do dispositivo para obtenção do ICOMa foi baseada em trabalhos prévios obtidos na literatura, usando uma balança com porta de comunicação em protocolo RS 232, um termopar tipo K para medição da temperatura e um dispositivo para aquisição automática dos dados, feita por um aplicativo computacional também desenvolvido neste trabalho. Os briquetes usados nos ensaios foram de casca de algodão, toco de eucalipto, bagaço de cana-de-açúcar e madeira de pinus, e foram produzidos especificamente para a determinação do ICOMa. O aplicativo atendeu às necessidades do ensaio para obtenção das variáveis relacionadas aos índices de combustão. O ICOMa foi mais sensível que o ICOM na observação da relação entre consumo de massa e geração de calor, e permitiu observar diferenças estatisticamente signific... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work aimed to evaluate the behavior of briquettes during burning, considering the possibility of improving the combustion index of biomass briquettes (here called ICOMa) using a software, so that this new proposal to be more sensitive to data variations than ICOM (already existing in the literature), as well as to determine its mass loss rate as a function of burning time. It was also expected with this new proposal, that a correlation between the ICOMa and the higher heating value of the tested biomass could be perceived, making it possible to estimate this magnitude, albeit approximately, without the use of a bomb calorimeter. The manufacture of the device for obtaining the ICOMa was based on previous work obtained in the literature, using a RS 232 communication port scale, a type K thermocouple for temperature measurement, and a device for automatic data acquisition by a computational application, this one developed in this work. The briquettes used in the tests were cotton bark, eucalyptus stump, sugarcane bagasse, and pinewood, and produced specially for the determination of ICOMa. The computational application met the needs of the test to obtain the variables related to the combustion indexes. The ICOMa was more sensitive than the ICOM in observing the relationship between the mass consumption and heat generation, and show a statistical difference between different temperature curves of the materials, unlike the ICOM. The biggest ICOMa found was 0.97 K.h.g-1, and t... (Complete abstract click electronic access below)
Mestre
13
Ruffilli, Davide. "Simulation of the casting process of an Al-AP-HTPB propellant with an open source solver". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Cerca il testo completoAbstract (sommario):
The purpose of this work is to understand and evaluate the phenomena that influence the burning rate. In particular it focuses on the separation between solid and liquid phase during the casting process. To evaluate it an open source solver is used (OpenFOAM) with the addition of formulas that allow to evaluate the difference in concentration of solid particles. The obtained results show a significant agreement between experimental data and previous studies, used as references, and the predicted ones. This work is the starting point from which other future studies can draw inspiration to continue the analysis in more detail.
14
Kalender, Volkan. "Characterization Of Electrolyte And Pyrotechnic Powders And Pellets". Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612959/index.pdf.
Testo completoAbstract (sommario):
Electrolyte and pyrotechnic pellets are two important components of
thermal batteries. Both electrolyte and pyrotechnic pellets are produced by cold
compaction of constituent powders. These compacts are integrated in the battery as
pellets with sufficient green density, green strength, calorific energy and burning
rate (for pyrotechnic only) to provide high performance batteries.
In this study, effects of physical properties of the used powders such as
particle size distribution, average particle size, particle shape and composition of
components and applied compression pressure and their interactions on green
density and green strength of electrolyte pellets and in addition, calorific energy
and burning rate of pyrotechnic pellets were examined.
Statistical experimental designs were constructed to investigate the main
and interaction effects of studied variables. 24 two factorial statistically designed
experiments&rsquoresults for pyrotechnic pellets exhibited that the compression pressure and iron powder morphology were the most significant factors improving green density and break strength of pyrotechnic pellets. It was shown that the compression pressure had a negative effect on burning rate. Both calorific output and burning rate were increased significantly by increasing KClO4 fraction. In addition, decreasing particle size of KClO4 had also a positive effect on burning rate. The maximum calorific output was obtained at maximum KClO4 fraction. 23 two factorial statistically designed green strength and green density experiments&rsquo
results of electrolyte pellets revealed that, compression pressure was again the dominating factor. Moreover, there was a tendency for higher green density with lower MgO fraction and electrolyte powder average particle size. Besides, the positive effect of decreasing average particle size on green strength was investigated distinctly at low green density values. From the thermal battery perspective, main and interaction effects of variables on the characteristics of electrolyte and pyrotechnic pellets were successfully examined.
15
Carney, Ama R. "Concurrent-Flow Flame Spread Over Ultra-Thin Discrete Fuels in Microgravity". Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1586545691969088.
Testo completo
16
Rossetti, Edoardo. "Evaluation of the ballistic properties of a solid propellant from its granulometric composition". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Cerca il testo completoAbstract (sommario):
This work is aimed at evaluating the effect of a solid propellant’s granulometric composition on its burning rate and, more in general, on its ballistic properties, as packing, density, or specific impulse. To evaluate the burning rate, a combustion model is developed in MatLab. To conclude, a model predicting the viscosity of a bimodal propellant is introduced. The obtained results show a significant agreement between experimental data, used as references, and the predicted ones. This work is the starting point from which other works can arise, improving the combustion model and expanding the viscosity estimation also for trimodal propellants.
17
Zayed, Abdel-Nasser Abdel-Hamid. "Computed tomography applications in ballistics". Thesis, Cranfield University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282474.
Testo completo
18
Söderström, Hanna. "Semipermeable membrane devices as integrative tools for monitoring nonpolar aromatic compounds in air". Doctoral thesis, Umeå University, Chemistry, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-378.
Testo completoAbstract (sommario):
Air pollutants pose a high risk for humans, and the environment, and this pollution is one of the major environmental problems facing modern society. Active air sampling is the technique that has been traditionally used to monitor nonpolar aromatic air pollutants. However, active high volume samplers (HiVols) require a power supply, maintenance and specialist operators, and the equipment is often expensive. Thus, there is a need to develop new, less complicated sampling techniques that can increase the monitoring frequency, the geographical distribution of the measurements, and the number of sites used in air monitoring programs. In the work underlying this thesis, the use of semipermeable membrane devices (SPMDs) as tools for monitoring gas phase concentrations of nonpolar aromatic compound was evaluated using the compound classes polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs (alkyl-PAHs) and nitrated PAHs (nitro-PAHs) as test compounds.
High wind-speeds increased the uptake and release in SPMDs of PAHs and PCBs with log KOA values > 7.9, demonstrating that the uptake of most nonpolar aromatic compounds is controlled by the boundary layer at the membrane-air interface. The use of a metal umbrella to shelter the SPMDs decreased the uptake of PAHs and PCBs by 38 and 55 percent, respectively, at high wind/turbulence, and thus reduced the wind effect. Further, the use of performance reference compounds (PRCs) to assess the site effect of wind on the uptake in SPMDs reduced the between-site differences to less than 50 percent from as much as three times differences in uptake of PCBs and PAHs. However, analytical interferences reduced the precision of some PRCs, showing the importance of using robust analytical quality control.
SPMDs were shown to be efficient samplers of gas phase nonpolar aromatic compounds, and were able to determine local, continental and indoor spatial distributions of PAHs, alkyl- PAHs and nitro-PAHs. In addition, the use of the SPMDs, which do not require electricity, made sampling possible at remote/rural areas where the infrastructure was limited. SPMDs were also used to determine the source of PAH pollution, and different approaches were discussed. Finally, SPMDs were used to estimate the importance of the gas phase exposure route to the uptake of PAHs in plants. The results demonstrate that SPMDs have several advantages compared with HiVols, including integrative capacity over long times, reduced costs, and no need of special operators, maintenance or power supply for sampling. However, calibration data of SPMDs in air are limited, and spatial differences are often only semi-quantitatively determined by comparing amounts and profiles in the SPMDs, which have limited their use in air monitoring programs. In future work, it is therefore important that SPMDs are properly sheltered, PRCs are used in the sampling protocols, and that calibrated sampling rate data, or the SPMD-air partition data, of specific compounds are further developed to make determination of time weighted average (TWA) concentrations possible.
19
Sulaiman, Shaharin Anwar. "Burning rates and instabilities in the combustion of droplet and vapour mixtures". Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435896.
Testo completo
20
Balfour, Victoria Nairn. "The effect of forest fires on runoff rates the role of duff removal and surface sealing by vegetative ash, western Montana /". Diss., [Missoula, Mont.] : The University of Montana, 2007. http://etd.lib.umt.edu/theses/available/etd-12202007-181528/.
Testo completo
21
Prado, Gustavo Faibischew. "Impactos cardiopulmonares e inflamatórios da exposição à poluição da queima de biomassa em cortadores de cana queimada e em voluntários saudáveis do município de Mendonça". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/5/5150/tde-01122011-150351/.
Testo completoAbstract (sommario):
A colheita não-mecanizada da cana-de-açúcar, precedida por sua queima, expõe os trabalhadores e pessoas de cidades vizinhas a altas concentrações de poluentes. Este estudo foi desenvolvido para avaliar os impactos cardiopulmonares e os biomarcadores de estresse oxidativo e atividade inflamatória sistêmica desencadeados pela exposição à poluição proveniente da queima da cana. Cortadores de cana (safristas, n = 113) e voluntários saudáveis da cidade de Mendonça - São Paulo, Brasil - (população de referência, n = 109) foram avaliados com espirometria, variabilidade da frequência cardíaca (VFC), enzimas antioxidantes, dosage do nível plasmático do malonaldeído e de interleucinas pró-inflamatórias durante a pré-safra e a safra. A concentração de PM2.5 aumentou de 8g/m3 durante a pré-safra para 23.5g/m3 na área urbana e 61g/m3 nas plantações de cana, durante a safra. Na safra, evidenciou-se uma diminuição mais acentuada na VFC, função pulmonar e da atividade das enzimas antioxidantes entre os cortadores de cana, em comparação com os voluntários da população de referência. Houve elevação do Malonaldeído em ambos os grupos durante a safra, com um maior aumento entre os safristas. Além disso, encontramos um aumento na pressão diastólica apenas nos cortadores de cana. Tanto os cortadores de cana quanto os voluntários da população local exibiram impactos cardiopulmonares e metabólicos da exposição à poluição durante a safra, com maior magnitude dessas alterações entre os safristas, o que destaca o impacto deletério da poluição atmosférica na população exposta. Esses achados pré-clínicos podem sinalizar processos fisiopatológicos desencadeados pela poluição advinda da queima de biomassa nas populações estudadasNon-mechanized sugarcane harvesting preceded by burning exposes workers and people of neighboring towns to high concentrations of pollutants. This study was designed to assess cardiopulmonary impacts and biomarkers of oxidative stress triggered by exposure to pollution from sugarcane burning. Sugarcane workers (n=113) and healthy volunteers of a reference population (n=109) from the city of Mendonça (São Paulo, Brazil) were evaluated with spirometry, heart rate variability (HRV), antioxidant enzymes, plasma malonaldehyde and proinflammatory interleukins during non-harvest and harvest periods. Concentration of PM2.5 increased from 8g/m3 during nonharvest to 23.5g/m3 in the urban area and to 61g/m3 in sugarcane fields, during harvest. It was evidenced a more remarkable decrease in lung function, HRV and in activity of antioxidant enzymes among sugarcane workers, compared to individuals from the reference population. Malonaldehyde had elevated in both groups during harvest, with a higher increase among sugarcane workers. Furthermore, we found an increase in diastolic pressure only in sugarcane workers. Both sugarcane workers and volunteers from the local population exhibited significant cardiopulmonary and metabolic impacts of exposure to outdoor air pollution during harvest, with a higher magnitude of these alterations among sugarcane workers, which highlights the deleterious impact of air pollution. These preclinical findings may signal pathophysiological processes triggered by biomassburning outdoor pollution in the populations studied
22
Nansalmaa, Erdenekhuu. "Evaluation on Health Impact of Government Support for GER (Traditional Dwelling) District's Electricity Night Rates in Ulaanbaatar City". Digital Archive @ GSU, 2011. http://digitalarchive.gsu.edu/iph_theses/161.
Testo completoAbstract (sommario):
During the last 10 years, air pollution has become one of the major public health problems in Ulaanbaatar city of Mongolia, and concentrations of pollutants were measured 3 to 50 times higher than WHO recommendation. This devastating air pollution is produced mostly by thousands of families who migrated from countryside and live in gers (traditional dwellings) in the suburban area which is not connected to the central heating system, and nearly all of them burn coal to keep them warm. Due to air pollution, residents living in Ulaanbaatar city suffer health problems that equal to the smoking of 4-5 packs of cigarettes. During the winter time, PM10 hourly average concentrations increased to 2,300 μg/m3, and daily average became over than 1,000 μg/m3 in the most polluted parts of the city. At present, Mongolian government has accepted that the health of Mongolian residents has deteriorated at an alarming level.
In January of 2011, Mongolian Parliament approved the Law on Reduction of Air Pollution in the Capital City to control air pollution and eliminate the gaps in practice. One main provision of this law was to improve ger district electricity transmission and distribution network and reduce the night-time price of electricity by 50 percent. Therefore, this study aimed to estimate direct health benefits of Government Provision on cutting electricity payment by 50 percent during the night time and analyze the efficiency of this program on reducing air pollution and its related health impact.
The study result showed when this new regulation is fully implemented in the ger districts, the annual consumption of coal and wood would be decreased by about 550,000 tons and 415,000 tons, accompanied by massive reduction of the emission. These changes would lead into noteworthy health benefits such as 15.7 and 17.4 percent of reduction of total and infant mortality rates and 4.3 and 4.7 percent decrease of cardiovascular and respiratory disease morbidity cases, annually.
23
Christopherson, John Ostler 1956. "Effects of prescribed fire on fuel accumulation rates and selected soil nutrients". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277123.
Testo completoAbstract (sommario):
Fuel accumulation rate and total soil nitrogen, phosphorus, and sulfur following prescribed fires were studied. Three prescribed fires were conducted in S.E. Arizona ponderosa pine stands during the summers of 1979, 1980, and 1981. Samples of forest floor and larger diameter fuel and soil from the surface 1.5 inches and 1.5 to 3.0 inch layers were collected in the summer of 1981. Forest floor and total fuel accumulation averaged 5.4 to 6.7 and 6.3 to 8.9 tons/acre/year, respectively. Total nitrogen, phosphorus, and sulfur in the surface three inches of mineral soil were not significantly affected by burning. Soil nitrogen, phosphorus, and sulfur content averaged 0.21%, 344 ppm and 150 ppm, respectively, in the surface 1.5 inches and 0.11%, 285 ppm and 74 ppm, respectively, in the 1.5 to 3.0 inch layer.
24
Singh, Siddarth. "Energy Release Rate Based Mechanism for the wear of Punches in Precision Blanking of High Strength Steel". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306850203.
Testo completo
25
Soltesz, Douglas Brandon. "Use of (3He,n) Reactions to Constrain Nuclear Reaction Rates in the Hydrogen and Helium Burning Environments of Type-I X-ray Bursts". Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou161592153252756.
Testo completo
26
Barnes, Duncan Martin. "Selling the modern day tribe: The commodification of rave culture". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2018. https://ro.ecu.edu.au/theses/2107.
Testo completoAbstract (sommario):
This thesis examines youth and rave culture from the late 1980s to the present. It considers the history as well as the global and local impact of rave. I provide a visual ethnographic study from 1999-2014, based on my work as a commercial photographer of the Perth, Western Australian scene. While critically reflecting on existing subcultural research this thesis adds another dimension – the effect that global corporations have had in reshaping subcultural practices, specifically the commodification of rave culture in the form of the contemporary electronic dance festival.
The research incorporates both qualitative and quantitative data to interrogate media coverage on rave culture as well as interviews and first hand experience within the rave scene. I analyse mainstream print and electronic media reporting of rave as a deviant youth subcultural practice linked to the use of the drug ecstasy. I consider the effect this had on rave and it’s rebranding to become known in contemporary times as EDM (electronic dance music). As a result I examine how rave has shifted from a youth subcultural activity to being not only mainstream and commercial, but also owned and controlled by global corporations. My discussion of the conventions of festival/music scenes will demonstrate how rave, which once operated outside ‘acceptable’ boundaries, has become a part of the conventional norm.
A unique aspect of this thesis is the inclusion and analysis of my photographs taken over a 15 year period that document the changes that occurred as rave transitioned from a subversive underground scene to corporate run multimillion dollar events. The photographs are also compiled into an accompanying monograph. The monograph allows for an immersive visual experience of non-staged event images and predetermined studio and location photographs. The book offers what words alone cannot fully engage with – a representation of what was and remains a highly visual scene, based on fashion, performance and settings.
27
Linget, Héloïse. "Programmation de cristaux dopés en ions terres rares pour le traitement du signal : application au renversement temporel et à l'analyse spectrale large bande instantanée de signaux RF". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS132/document.
Testo completoAbstract (sommario):
Dans de nombreux systèmes de traitement de l'information, le signal est numérisé, traité informatiquement, puis reconverti dans le domaine analogique. La faible bande passante de ces étapes de conversion numérique/analogique limite considérablement le débit d'informations traitées. Une solution purement analogique améliorerait donc considérablement le temps de traitement et la bande passante. Notre approche consiste à transférer le signal RF à traiter sur une porteuse optique puis à procéder à son traitement dans le domaine optique. L'étape de traitement est assurée par la traversée d'un cristal dopé en ions terres rares convenablement "programmé". Cette étape de programmation consiste à graver dans le profil d'absorption du cristal une fonction caractéristique de l'opération de traitement du signal à réaliser. Deux opérations ont ainsi été implémentées : 1) le renversement temporel de signaux RF : c'est l'opération consistant à générer analogiquement le signal renversé temporellement s(−t) d'un signal incident s(t). La fonction à graver dans le profil d'un cristal d'Er:YSO est alors un réseau spectral de pas variable. 2) l'analyse spectrale large bande instantanée : c'est l'opération permettant d'accéder au contenu spectral d'un signal. On impose au protocole de fournir instantanément le spectre d'un signal large bande. La fonction à graver dans le profil d'un cristal de Tm:YAG est alors un réseau spectro-spatial de pas variableMany signal processing devices rely on the digitalization of the incoming signal. After being processed by a computer, the signal needs to be converted back to its original analog form. Due to the limited bandwidth of analog-to-digital and digital-to-analog stages, the data flow rate is significantly limited. A purely analog solution would then significantly improve the processing time and bandwidth. In our approach, we first transfer the incoming RF signal on an optical carrier, allowing us to process it in the optical domain. For the processing stage, we propose to engrave the absorption profile of a rare earth ion-doped crystal with different shapes (each shape is specific to one processing operation). In this work, two operations are implemented: 1) time reversal of RF signals: we analogically generate the time reversed replica s(−t) of an incoming signal s(t). For this purpose, the shape to be engraved in the absorption profile of a Er:YSO crystal is a non-periodic spectral grating. 2) instantanous broadband spectral analysis: we want to instantaneously access the spectral components of a broadband signal. For this purpose, the shape to be engraved in the absorption profile of a Tm:YAG crystal is a spectro-spatial grating with a variable period
28
Attal, Yoann. "Processeurs atomiques utilisant la propriété de creusement spectral : modélisation et application à l’analyse spectrale radiofréquence large bande sur porteuse optique". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS161/document.
Testo completoAbstract (sommario):
La propriété de creusement spectral, que l’on retrouve dans certains cristaux dopés aux ions de terres rares refroidis à basse température offre des possibilités prometteuses pour le traitement analogique de signaux radiofréquence. En effet, celle-ci permet de programmer des fonctions de traitement dans le spectre d’absorption du cristal.Partant des premières démonstrations de principe d’un analyseur spectral radiofréquence large bande instantanée, l’objectif est d’en améliorer les performances, ce qui requiert une modélisation précise de l’interaction laser-matière et de l’ensemble des perturbations inhérentes à la montée en maturité technologique du dispositif. Nous avons par conséquent développé un modèle et cherché à étendre son domaine de validité pour qu’il s’applique à un maximum de protocoles.Nous l’avons ensuite appliqué à un matériau en particulier, à savoir un cristal de Tm³ ⁺ :YAG. Après avoir effectué une série de mesures des différentes caractéristiques intrinsèques à ce cristal, nous avons choisi un protocole d’application relativement proche de celui de l’analyseur spectral que nous cherchons à optimiser, à savoir la création de réseaux spectraux large bande. La comparaison des résultats expérimentaux à ceux de notre modèle nous a permis de démontrer sa validité.Nous avons finalement appliqué notre modèle au cas précis de l’analyseur spectral radiofréquence. Les simulations nous ont permis de déterminer théoriquement comment optimiser ses performances, en particulier la dynamique, avec des paramètres réalistes, atteignables expérimentalementThe Spectral Hole Burning property, found in some rare-earth ion-doped crystals at low temperature is particularly relevant for analogic processing of radiofrequency signals. Indeed, it enables processing functions to be programmed in the crystal’s absorption spectrum.Starting with the first demonstrations of a wideband radiofrequency spectrum analyser, we aim at improving its performances, which requires an accurate modelling of the light-matter interaction and all the perturbations arising from the upgrade in TRL (Technology Readiness Level). Therefore, we have developed a model and extended its validity domain to a broad variety of SHB-based protocols.We applied this model on a particular material, namely a Tm³ ⁺:YAG crystal. After measuring experimentally the relevant intrinsic parameters of this crystal, we applied our model to a protocol which is quite similar to the one of the spectrum analyser we aim at optimizing, namely the engraving of wideband spectral gratings. The comparison of our experimental results to the simulations from our model proved its validity.Finally we applied it to the exact case of the radiofrequency spectrum analyser. With the simulations, we determined how to improve its performances, and particularly increase the dynamic range with realistic experimental parameters
29
Venet, Caroline. "Développement d’un filtre spectral ultra résolu pour l’imagerie acousto-optique". Thesis, Paris Sciences et Lettres (ComUE), 2019. https://pastel.archives-ouvertes.fr/tel-02929318.
Testo completoAbstract (sommario):
L'imagerie médicale optique est limitée par la perte de résolution spatiale due à la diffusion des tissus biologiques. L'imagerie acousto-optique permet de palier à ce problème car elle utilise à la fois de lumière et des ondes ultrasonores. Par conséquent elle donne accès au contraste optique local en profondeur dans les tissus biologiques avec la résolution submillimétrique des ultrasons. Diverses méthodes interférométriques ont été développées pour détecter le signal acousto-optique, mais elles ne sont pas adaptées à l'imagerie in vivo. Au cours de cette thèse nous avons développé un filtre spectral intrinsèquement robuste à une mise en œuvre in vivo et capable de filtrer le signal de photons marqués. Ce filtre est basé sur le phénomène de creusement spectral, il est réalisé dans un cristal de grenat d'yttrium aluminium dopé au thulium (Tm:YAG) sous champ magnétique. Le manuscrit décrit d'abord la caractérisation du filtre spectral en condition d'imagerie. Ensuite nous présentons le montage expérimental qui a permis d' imager un gel diffusant simulant un tissu biologique. Dans la suite nous avons changé le laser principal et nous l'avons asservi en fréquence dans le but d'augmenter le niveau de maturation de la technologie. Enfin, la dernière partie du manuscrit détaille comment l'expérience a été compactée pour être apportée à un laboratoire pharmaceutique afin de lancer une campagne d'imagerie in vivoOptical imaging for Medicine is limited by the spatial resolution loss due to light scattering in turbid media. A hybrid imaging method called ultrasound optical tomography can overcome this botteneck. Indeed the simultaneous use of light and ultrasound gives access to optical contrast in depth within scattering medium with the ultrasounds resolution. Several interferometric methods have been developed in order to detect an acousto-optic signal. However, none of them is adapted to in vivo imaging. For this reason a filter created with spectral hole burning is of special interest. This thesis presents the development of an ultra-narrow filter based on spectral hole burning in a thulium doped yttrium aluminum garnet crystal (Tm:YAG) under magnetic field. The first part of the manuscript describes the characterization of the filter in the imaging setup. Next, the actual imaging of a scattering gel is described. The following part presents the change of the main laser and its frequency stabilization for technological maturation. The last part of the manuscript details how the experiment have been compacted to be bring in a pharmacetical laboratory in order to launch in vivo imaging trials
30
Rambaud, Christophe. "Etude, par spectroscopie optique, de la délocalisation quantique de protons dans des cristaux d'acide benzoi͏̈que". Grenoble 1, 1989. http://www.theses.fr/1989GRE10103.
Testo completoAbstract (sommario):
Les transitions optiques des molecules de thioindigo dopant des cristaux d'acide benzoique, sont sensibles au transfert des protons par effet tunnel le long des liaisons hydrogene intradimeres de la matrice. Mesure dans le cas d'un acide carboxylique des niveaux d'energie des protons delocalises et de l'element de matrice d'effet tunnel. Sensibilite du systeme a transfert de protons aux contraintes internes et externes. Deduction des vitesses de relaxation des protons delocalises, comparaison avec des calculs theoriques indiquant l'importance des processus a plusieurs phonons dans cette relaxation. Utilisation de l'effet d'un champ electrique pour influencer la delocalisation des protons
31
Chang, Hsiu-Ming, e 張修銘. "Burning Rate of Premixed Flames in an Accelerative Flow". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/82480284918553415626.
Testo completoAbstract (sommario):
碩士國立清華大學
動力機械工程學系
87
The influence of flow acceleration in the normal on the burning rate of premixed flames is investigated numerically. The results reveal that the burning rate and the flame thickness of premixed flame decrease and increases with the flow acceleration, respectively. Besides the flame stretch, the structure of premixed flame is modified by the flow acceleration. This finding is important for the combustion of premixed flames.
32
Chang, Hao-Ming, e 張皓閔. "Measurement of the Burning Rate of Solid Sugar Rocket Propellant". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/61403447630811437350.
Testo completoAbstract (sommario):
碩士國立交通大學
機械工程系所
104
Solid rocket is nearly impossible for throttling capability, therefore designing a motor which can produce a desired thrust curve is necessary. In order to precisely predict a thrust curve, a realistic burning rate correlation is very important. The burning rate is a function of combustor pressure and is described by the burning rate equation (r = a*Pn). The parameters “a” and “n” is generally obtained from experimental data. Usually, there are two methods of measurements, which include Crawford strand burner and Ballistic Evaluation Motor (BEM). Crawford strand burner can quickly acquire the data in the laboratory and BEM can create realistic environment of combustion chamber. BEM is selected as the method for measuring the burning rate of solid sugar propellant in this study. The propellant used in this study is composed of Sorbitol and Potassium nitrate (KNO3). Sorbitol is the major fuel which also acts as a binder of propellant and KNO3 is the oxidizer. Iron oxide was also added for its catalytic effect. This type of propulsion system has already been used in several flight missions in our group.. Two different types of experimental combustors (single-port, end burning) were used in this study to investigate the burning rate of the stated propellant at different chamber pressures. These combustors are designed to operate at different chamber pressures with minimal adjustments. Nozzles with various throat diameters were used to produce the desired chamber pressures. After acquiring the real-time thrust and chamber pressure, with the assumption that all propellant regression is normal to the grain surface, the propellant consumption rate and the regression rate are both estimated by the pressure curve. Therefore, burning rate equation can be used to correlate the regression rate with combustor pressure. The results show that burning rate of propellant undulates under 12 atm. and then increase along with pressure increase after 12 atm. Since real motor is used in this study, it is easy to obtain the relationship between burning area and chamber pressure. With the results, we can conclude that the relationship between burning area and chamber pressure is positively correlated. In general, the present measurements agree reasonably well with previous published data. Since the thrust curve of motor is acquired during test, these data can be also used to predict the performance parameters like specific impulse (Isp)、characteristic exhaust velocity (C*) and thrust coefficient (CF) and use these coefficients to analyze the performance of motor.
33
Liu, Weng Sheng, e 劉文聖. "A Study on 2.75 Inch High burning Rate Rocket Igniter". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/75642504127615076401.
Testo completoAbstract (sommario):
碩士國防大學理工學院
兵器系統工程碩士班
101
A front-end rocket ignition system is investigated. This system can be operated at low voltage 9V for 2.75 inch rocket propellant instant detonation. When the igniter is detonated, the output temperature, pressure, burning rate and heat flux are critical to rocket ignition success. This study uses the K-type thermocouple, filter amplifier, high-speed data transient processor and GPIB controller to construct a high-temperature measurement system. The high-speed camera uses a built-in CMOS sensor chip with the PFV high-speed image processing software to build a high-speed dynamic visualization system. A piezoelectric crystal pressure sensor, charge amplifier and homemade combustion chamber are used to construct the pressure measurement system. Igniter quality can be measured by establishing the burning rate, temperature and pressure as a reference to improve the quality. A Kalman filter with recursive estimation is used to estimate the igniter heat flux. In design for igniter, gunpowder formula is critical. Keywords: Igniter, Heat flux, Thermocouple, High-speed camera.
34
Zhang, Dong-Ke. "The ignition, burning rate and reactivity of pulverized fuel particles". Thesis, 1992. http://hdl.handle.net/1959.13/1335934.
Testo completoAbstract (sommario):
Research Doctorate - Doctor of PhilosophyLaboratory scale measurements and theoretical investigations have been made on the ignition and combustion behaviour of pulverized fuel particles. The aims of the experimental study were to: measure the critical (gas or particle) temperatures and energy requirements for the ignition of the pulverized fuel particles; determine the ignition mechanisms; evaluate the combustion reactivity of these fuels; and compare results obtained using various experimental techniques. The objectives of the theoretical study were to develop models for ignition and compare model predictions with experimental results in order to establish possible ignition mechanisms.
35
Rosyadi, Basthiyan Sidqi Fidari, e 貝璽嚴. "Bio-fuel Droplet Combustion: Burning Rate Constants and Microexplosion Phenomena Measurements". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/84390695526398273851.
Testo completoAbstract (sommario):
碩士國立中央大學
機械工程學系
102
論文探討兩種不同生質燃料(生質柴油和葵花油)，以及它們分別與柴油混合燃料(生質燃料體積濃度比從5%到75%)，在常壓靜止條件下之液滴燃燒實驗。對稱球形微小液滴可由自製的壓電驅動液滴產生器所產生，液滴直徑(d)範圍從0.45 mm到0.60 mm，將小液滴懸浮在兩條非常細水平定位且相互垂直呈十字狀直徑為20 μm之陶瓷纖維上。加熱器為一對直徑為0.2 mm 之Khantal 導線，呈半橢圓形狀並將其水平地置放於懸浮小液滴的兩側邊，用來點燃液滴。一旦點燃後當火焰包圍液滴時，加熱器即斷電移開，此時液滴的直徑訂為初始直徑(d0)，由高速攝影機所決定。由液滴燃燒過程所攝之時序圖，我們以(d/d0)2對時間t的最佳擬合斜率(即d2-law)，來決定液滴的燃燒率常數(K)。研究結果顯示，當 d0值下降時，K值會上升，對所有本研究所使用之燃料均如是。100%生質柴油比一般商用柴油有較高的K值。後者沒有微爆現象，而前者在燃燒後期即將完成液滴燃燒前，有弱微爆現象，這可能是由於少量的甲基亞油酸(4.92wt%)存在於生質柴油中所導致。此外，複雜但有趣的微爆現象，可以在純葵花油和其與柴油之混合生質燃料中被觀察到，我們找到兩個不同K值於液滴燃燒的過程中。當葵花油在混合燃料中體積比超過50%時，混合液滴會經歷一轉變，從第一階段的規律燃燒(K1)到第二階段液滴燃燒後期(K2)的強膨脹和微爆現象，其中K1 < K2。但是當混合燃料中含有較少量葵花油(< 50%)時，前述轉變順序正好相反，換句話說，在液滴燃燒開始不久的第一階段，強微爆即發生，其中K1 > K2。這種微爆的反向過程，可能可以歸因於在葵花油中，具有不同揮發成分的脂肪酸所致。我們發現在液滴燃燒中，擴散過程為主導因素，因為具有不同(d/d0)2 vs. t曲線可以被擬合成單一的曲線，當時間(t)以無因次tdiff = d02/α，其中α為液滴燃料的熱擴散係數。前述結果，有助我們對生質燃料燃燒之了解，其對未來汽車和航空工業上使用生質燃料替代化石液體燃料，將有所助益。
36
Cheng, Kun Fu, e 鄭昆福. "Studies on the Burning Rate Pressure Exponent of the Composite Solid Propellants". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/69644824653291936279.
Testo completoAbstract (sommario):
碩士國防大學中正理工學院
應用化學研究所
91
The burning rate pressure exponent (n) is the most important index in composite solid propellants. Various factors which affect this property and a number of different manufacturing processes for controlling the pressure exponent in composite solid propellants of AP/RDX/HTPB/Al system are discussed. They include the effects of (1) different content of HTPB and DOA, (2) the particle size of Al and RDX, (3) the particle size distribution of AP, (4) NQ replacing RDX, and (5) the ballistic modifier additives. The burning rate was measured in a strand burner at 21℃ and 15~105 kg/cm2of nitrogen pressure.From the results of the burning rate analysis, the pressure exponent (n) of propellants：(1) decreased with increasing content of HTPB and DOA, (2) decreased with increasing Al particle size, (3) increased with increasing RDX particle size, (4) increased with decreasing AP particle size, but for the propellants made from the different AP particle sizes, the feeding order and the mixing extent during different manufacturing processes would also affect the burning rate and the pressure exponent, (5) decreased with increasing NQ content which suppressed the burning rate of propellant, and (6) increased with increasing Fe2O3 of ballistic modifier additive, or decreased with increasing C-black, TiO2 and CaCO3 of ballistic modifier additive. The effect of the initial temperature of the 30 mm Al powder propellant on the burning rate also was discussed.
37
CHEN, KUEI-CHI, e 陳貴奇. "Interference Rocket Ignition Composition with High Thermal Energy: High Burning Rate Performance". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/06038694360647481119.
Testo completoAbstract (sommario):
碩士國防大學理工學院
兵器系統工程碩士班
104
This interference rocket ignition composition is composed of zirconium, ferric oxide and silica. The zirconium powder is the main combustion ingredient and widely used in various ammunitions. The ignition composition plays an important role in gunpowder chain ignition with the MLRS affecting the overall rocket launch and target destruction success. If the interference rocket ignition composition formula is changed, using NASA research and development NASA-Lewis Code (CET86) analog the CR-201 ignition composition pressure and temperature changes. First of all, the energy required for powder combustion ignition is provided by quantitative ignition module system which a stable heat and quantifiable source. The K-type thermocouple, filter amplifier, signal processing board and high-speed data transient processor are used to construct a high-temperature-speed measurement system. A pressure sensor, charge amplifier and homemade combustion chamber are used to construct the pressure measurement system. The high-speed camera uses a built-in CMOS sensor chip with the PFV image processing software to build a high-speed imaging and photography system. A Kalman filter with recursive estimation is used to estimate the ignition composition heat flux, and forward derived analog temperature. The experimental measurement data is useful as an ignition powder formula for MLRS formula improvement and testing reference.
38
Shih, Chun-Chi, e 施純祺. "Combustion Performance of Zirconium-Nickel Alloy Delay Composition with Middle Burning Rate". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/72310144262471569218.
Testo completoAbstract (sommario):
碩士國防大學理工學院
兵器系統工程碩士班
101
This study investigates combustion performance of Zirconium-Nickel alloy delay composition with middle burning rate. Zirconium-Nickel alloy delay composition is composed of four constituents: barium chromate, potassium perchlorate, Zirconium -Nickel alloy (70/30) and Zirconium -Nickel alloy (30/70). If the Zirconium-Nickel alloy delay composition formula is changed, using NASA-Lewis Code (CET-86) analog the igniter pressure and temperature changes. This is an important basis of Zirconium-Nickel alloy delay composition formula design. A Kalman filter with recursive estimation is used to estimate the Zirconium-Nickel alloy delay composition heat flux. The experimental models are based on the tube of Zirconium-Nickel alloy delay composition. The quantitative ignition components provide quantitative energy and then ignite the delay composition. A fast response thermocouple was utilized to measure the extrusive temperature. The phenomena of combustion along the delay composition in the glass tube was recorded by using a high-speed camera. Finally, the result will provide design applications, measurement and analysis in the field of the delay composition.
39
Shou-Ming, Hsiao, e 蕭首銘. "Analysis and Research on Delay Characteristics with High Burning Rate of M557 Fuze". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/57281179048223498050.
Testo completoAbstract (sommario):
碩士國防大學理工學院
兵器系統工程碩士班
101
This study is based on experimental methods using temperature and visual imaging techniques to construct M557 delay composition performance experimental measurement equipment. The ignition point, burning rate and output, are investigated to build a M557 fuze reference database. The Taguchi method L_4 〖(2〗^3) level orthogonal 4 is employed to adjust the variation in set conditions. The NASA-Lewis Code (CET86) database format combustion thermodynamic theory of balanced analog computing is used to evaluate the influence of released combustion energy from 4 different proportional delay composition formulations. The M557 fuze is composed of Zirconium, Trioxide, Chromium trioxide and glue (Zr+MoO_3+Cr_2 O_3+Viton). This fuze has a high burning rate delay composition. Electronic scales are used to fix the experimental delay weight composition. The experimental ignition device components and temperature measurement system are filled into a quartz tube with the auto-transformer and timer. An electric wire is energized to ignite the device. The rapidly burning temperature is measured with the K Type fine style exposed-type thermocouple. This transient high-temperature curve retrieves the records using a high-speed data acquisition system (MultiPro120). Visual imaging technology using high speed camera captures the rapid burning process. Additionally, we placed copper plate in the bottom of quartz tube. The inverse heat transfer theory estimates the rapidly burning pulse heat flux of the M557 delay composition. Comparing the measured and simulated temperatures, the results show that the heat flux estimation method is feasible. Experiments verify the feasibility and practicality of the measurement method, and establish reference of the M557 fuze. The results also provide design application of pyrotechnics field.
40
Lin, Chin-Nan, e 林景楠. "Effect of Zr-Ni Particles Size for Burning Rate of Military Delay Composition System". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/81093294974280064283.
Testo completoAbstract (sommario):
碩士元智大學
化學工程學系
91
The thermal behaviors of the ignition and burning rate characteristics of the Zr-Ni-KClO4-BaCrO4 system have been widely used in the delay system employed in a number of important army fuses. Therefore, the main objectives of the present study were to investigate the effects of the Zr-Ni Alloy particle sizes according to wet grinding times and then test the effects of the burning rates of delay composition system (DCS) of the fuses. Experimentally, the key parameters of the preparation for Zr-Ni alloy nano- or micro-particles and test of DCS are described as following: wet grinding time, particle size distribution, composition of DCS, and delay burning rates or times. The experimental data showed the burning times of DCS were fast and the performance of the fuses had met the standard test. The particle sizes of Zr-Ni alloys decreased with the increasing wet grinding times. It was also found that the well-controlled manufacturing process can promote the validity and reliability of the fuses. The XRPD patterns and FE-SEM microscopes revealed the composition and properties were still unchanged except the particle size distributions. The XRPD, XANES and EXAFS spectra also indicated the valences of nickel elements in Zr-Ni alloy nano- and micro-particles were both zero. The relationship of Zr-Ni alloy particle sizes and burning rates or times can be confirmed by the fuse performance and dish burning tests. In addition, the DCS burning test was like an explosion when the wet grinding time was 14 hr with the Zr-Ni alloy particle size of 2.1 μ. The kinetics of burning the Zr-Ni alloy micro- or nano-particles by TGA method showed the Zr-Ni alloy microparticles might have a pseudo-first-order reaction and an activation energy of 211.5~337.6 kJ/mol. On the contrary, the reaction order and the activation energy were 2 and 23.74 kJ/mol, respectively for the nanopahse Zr-Ni alloy. In addition, the process of DCS manufacturing had been improved on having a delay burning time of fuse perform test of 4.62 sec. It will also assure the quality and reliability that can meet the military standard of 4-5 sec. Furthermore, the Zr-Ni alloy nanoparticles may have the opportunities to improve the explosive energy for enhancing the attack power on the battlefield in the future.
41
Ghrayeb, Shadi Z. Ivanov Kostadin N. "Investigations of thorium based fuel to improve actinide burning rate in S-PRISM reactor". 2008. http://etda.libraries.psu.edu/theses/approved/PSUonlyIndex/ETD-3505/index.html.
Testo completo
42
Chang, Chin-Hua, e 張誌華. "Study on the Formulas and Combustion Characteristics of Alloy Delay Composition with Low Burning Rate". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/54413233117988856493.
Testo completoAbstract (sommario):
碩士國防大學中正理工學院
應用化學碩士班
99
The objective of this research was to explore the reaction characteristics and the burning properties of titanium/carbon (Ti-C), nickel oxide/zirconium (Ni2O3/Zr) and ferric oxide/aluminum (Fe2O3/Al) type alloy delay compositions. In the first place, the initial reaction temperature and reaction heat of these delay compositions during the reaction were measured by means of differential scanning calorimetry (DSC). Afterward the delay compositions of different formulas were processed to be cylindrical pellets to measure their burning properties. In the experiments, the cylindrical pellets were packed into a heat-resisting quartz tube and were ignited by an electrical-heating wire. A high-speed video camera and a digital-image processing device were used for simultaneously recording of their combustion phenomena. In addition, the output flame temperature was detected by placing a thermocouple at the end of the quartz tube. The influence of each ingredient of the formula on the reaction characteristics and the burning properties was analyzed from the experimental results. These research results will contribute to improving the formulas of alloy delay compositions.
43
(5930867), Forrest J. Son. "Piezoelectric Inkjet Printed Aluminum Bismuth (III) Oxide: The Effects of Printing Parameters on Burning Rate". Thesis, 2020.
Cerca il testo completoAbstract (sommario):
This thesis presents work on the deposition of nanothermite using a piezoelectric inkjet printer, focusing on the effects of printing parameters and sample geometry on burning rate. The ability of the printer to produce consistent droplet size and spacing was shown to have repeatable droplet size and sub-millimeter precision in droplet spacing. The droplet-droplet interaction of the nanothermite ink was examined, and a printing frequency of 10 Hz was shown to produce smooth and consistent geometry in the printed samples. The primary printing parameter varied in this study was the pixel pitch (i.e., the distance between printed droplets). As pixel pitch decreased (i.e., the droplets are printed closer together) in both directions (x- and y-directions), the burning rate increased, and as sample width increased the burning rate increased. A significant number of samples (476) were printed and demonstrated consistent, energetic performance; this indicated favorable high-volume production capabilities. A thermal model was developed based on an energy balance for the printed nanothermite samples. The model accurately predicted the burning rate trends observed in the experimental results. This result indicated that the increase in heat generation in both the thicker (pixel-pitch studies) and wider samples decreased the significance of heat loss to the environment. The statistically significant results presented in this work, along with a descriptive thermal model, increase the fundamental understanding of the effects of printed geometry and droplet spacing on nanothermite energetic performance.
44
Warren, William. "Experimental Techniques for the Study of Liquid Monopropellant Combustion". Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-11072.
Testo completoAbstract (sommario):
Propellants based on hydroxylammonium nitrate (HAN) have shown promise as a hydrazine replacement because of their comparably low toxicity, low vapor pressure, high specific impulse and high density. Herein, the recent history of advanced monopropellant research is explored, and new experimental techniques are presented to investigate the combustion behavior of a potential hydrazine replacement propellant. Nitromethane, a widely available monopropellant with a recent resurgence in research, is utilized in the current study as a proof of concept for the newly designed equipment and as a step towards investigating more-advanced, HAN-based monopropellants.
A strand bomb facility capable of supporting testing at up to 340 atm was employed, and experiments were performed between 28 atm and 130 atm. Burning rate data for nitromethane are calculated from experiments and a power correlation is established as r(mm/s) = 0.33[P(MPa)]^1.02.
A comparison with available literature reveals this correlation to be very much in agreement to other studies of nitromethane. Other physical characteristics of nitromethane combustion are presented. Updates to the facility and new methods to examine the combustion of liquid propellant are described in detail. Special focus is given to procedures and safety information.
45
(5929820), Shourya Jain. "Burning Behaviors of Solid Propellants using Graphene-based Micro-structures: Experiments and Simulations". Thesis, 2018.
Cerca il testo completoAbstract (sommario):
Enhancing the burn rates of solid propellants and energetics is a crucial step towards improving the performance of several solid propellant based micro-propulsion systems. In addition to increasing thrust, high burn rates also help simplify the propellant grain geometry and increase the volumetric loading of the rocket motor, which in turn reduces the overall size and weight. Thus, in this work, burn rate enhancement of solid propellants when coupled to highly conductive graphene-based micro-structures was studied using both experiments and molecular dynamic (MD) simulations.
The experiments were performed using three different types of graphene-structures i.e. graphite sheet (GS), graphene nano-pellets (GNPs) and graphene foam (GF), with nitrocellulose (NC) as the solid propellant.
For the NC-GS samples, propellant layers ranging from 25 µm to 170 µm were deposited on the top of a 20 µm thick graphite sheet. Self-propagating combustion waves were observed, with burn rate enhancements up to 3.3 times the bulk NC burn rate (0.7 cm/s). The burn rates were measured as a function of the ratio of fuel to graphite layer thickness and an optimum thickness ratio was found corresponding to the maximum enhancement. Moreover, the ratio of fuel to graphite layer thickness was also found to affect the period and amplitude of the combustion wave oscillations. Thus, to identify the important non-dimensional parameters that govern the burn rate enhancement and the oscillatory nature of the combustion waves, a numerical model using 1-D energy conservation equations along with simple first-order Arrhenius kinetics was also developed.
For the GNP-doped NC lms, propellant layers, 500 30 µm thick, were deposited on the top of a thermally insulating glass slide with the doping concentrations of GNPs being varied from 1-5% by mass. An optimum doping concentration of 3% was obtained for which the burn rate enhancement was 2.7 times. In addition, the effective thermal conductivities of GNP-doped NC lms were also measured experimentally using a steady state, controlled, heat flux method and a linear increase in the thermal conductivity value as a function of the doping concentration was obtained.
The third type of graphene structure used was the GF - synthesized using a chemical vapor deposition (CVD) technique. The effects of both the fuel loading ratio and GF density were studied. Similar to the GNPs, there existed an optimum fuel loading ratio that maximized the burn rates. However, as a function of the GF density, a monotonic decreasing trend in the burn rate was obtained. Overall, burn rate enhancement up to 7.6 times was observed, which was attributed to the GF's unique thermal properties resulting from its 3D interconnected network, high thermal conductivity, low thermal boundary resistance and low thermal mass. Moreover, the thermal conductivity of GF strut walls as a function of the GF density was also measured experimentally.
Then as a next step, the GF structures were functionalized with a transition metal oxide (MnO2). The use of GF-supported catalyst combined the physical eect of enhanced thermal transport due to the GF structure with the chemical effect of increased chemical reactivity (decomposition) due to the MnO2 catalyst, and thus, resulted in even further burn rate enhancements (up to 9 times). The burn rates as a function of both the NC-GF and MnO2-NC loadings were studied. An optimum MnO2-NC loading corresponding to the maximum burn rate was obtained for each NC-GF loading. In addition, thermogravimetric (TG) and differential scanning
calorimetry (DSC) analysis were also conducted to determine the effect of NC-GF and MnO2-NC loadings on the activation energy (E) and peak thermal decomposition (PTD) temperatures of the propellant NC.
In addition to the experimental work, molecular dynamics simulations were also conducted to investigate the thermal transport and the reactivity of these coupled solidpropellant/graphene-structures. A solid monopropellant, Pentaerythritol Tetranitrate (PETN), when coupled to highly conductive multi-walled carbon nanotubes (MWCNTs) was considered. The thickness of the PETN layer and the diameter of the MWCNTs were varied to determine the effect of PETN-MWCNT loading on the burn rates obtained. Burn rate enhancement up to 3 times was observed and an optimal PETN-MWCNT loading of 45% was obtained. The enhancement was attributed to the faster heat conduction in CNTs and to the layering of PETN molecules around the MWCNTs surface. Moreover, the CNTs remained unburned after the combustion process, conrming that these graphene-structures do not take part in the chemical reactions but act only as thermal conduits, transferring heat from the burned to the unburned portions of the fuel.
A long-pursued goal, which is also a grand challenge, in nanoscience and nanotechnology is to create nanoscale devices, machines and motors that can do useful work. However, loyal to the scaling law, combustion would be impossible at nanoscale because the heat loss would profoundly dominate the chemical reactions. Thus, in addition to the solid propellant work, a preliminary study was also conducted to understand as how does the heat transfer and combustion couple together at nano-scales.
First, an experimental study was performed to understand the feasibility of combustion at nano-scales for which a nano-scale combustion device called "nanobubbles" was designed. These nanobubbles were produced from short-time (< 2000 µs) water electrolysis by applying high-frequency alternating sign square voltage pulses (1-500 kHz), which resulted in H2 and O2 gas production above the same electrode. Moreover, a 10 nm thick Pt thermal sensor (based on resistance thermometry) was also fabricated underneath the combustion electrodes to measure the temperature changes obtained. A signicant amount of bubble production was seen up to 30 kHz but after that the bubble production decreased drastically, although the amount of faradaic current measured remained unchanged, signifying combustion. The temperature changes measured were also found to increase above this threshold frequency of 30 kHz.
Next, non-reactive molecular dynamic simulations were performed to determine as how does the surface tension of water surrounding the electrodes is affected by the presence of dissolved external gases, which would in turn help to predict the pressures inside nanobubbles. Knowing the bubble pressure is a perquisite towards understanding the combustion process. The surface tension of water was found to decrease with an increase in the supersaturation ratio (or an increase in the external gas concentration), thus, the internal pressure inside a nanobubble is much smaller than what would have been predicted using the planar-interface surface tension value of water. Once the pressure behavior as a function of external gas supersaturation was understood, then as a next step, reactive molecular dynamic simulations were performed to study the effects of surface-assisted dissociation of H2 and O2 gases and initial system pressure on the ignition and reaction kinetics of the H2/O2 system at nano-scales. A signicant amount of hydrogen peroxide (H2O2), 6-140 times water (H2O), was observed in the combustion products. This was attributed to the low temperature(~300 K) and high pressure (2-80 atm) conditions at which the chemical reactions were taking place. Moreover, the rate at which heat was being lost from the combustion chamber (nanobubble) was also compared to the rate at which heat was being released from the chemical reactions and only a slight rise in the reaction temperature was observed (~68 K), signifying that, at such small-scales, heat losses dominate.
46
Su, Chung-Hui, e 蘇忠會. "Study The Effects Of Burning-Rate Modifiers On Thermal Decomposition Behaviors Of Ammonium Perchlorate With Different Particle Sizes And Containing Mixtures Same". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/63954799405606304141.
Testo completoAbstract (sommario):
碩士國防大學理工學院
化學工程碩士班
100
In this thesis, the thermal decomposition characteristics of different sizes ammonium perchlorate (AP) particles and its mixture with the addition of various burning-rate modifiers were explored. The thermochemical properties of samples were measured by means of differential scanning calorimetry and thermogravimetry analysis, and then the effects of the various burning-rate modifiers on the thermal decomposition of those samples were also evaluated. The research results showed that the peak temperature of the high-temperature thermal decomposition of AP particles with/without burning-rate modifiers are increased with increasing the particle sizes. Furthermore, for 5 accelerated burning-rate modifiers, all of them showed the same positive catalytic reactions for the thermal decomposition of AP, and for another 5 inhibited burning-rate modifiers, the (NH2)2CO had same inhibited effect, but others had positive catalytic effect. Finally, the thermal analysis of mixtures were carried out. The results of analysis showed that aluminum powder acted as an important role with regard to the inhibition of burning rate for propellants.
47
Herrera, Gomez Lady Carolina. "Experiments for the Measurement of LNG Mass Burning Rates". Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9368.
Testo completoAbstract (sommario):
Liquefied Natural Gas (LNG) is a commonly used flammable fuel that has safety concerns associated with vapor dispersion and radiation emitted from pool fires. The main objective of this effort is to advance the knowledge of pool fires and to expand the data that is commonly used to validate semi-empirical models. This includes evaluation of the methods that are utilized to obtain experimental values of mass burning rates, which are used in models where semi-empirical correlations cannot be applied.
A total of three small-size experiments designed to study the radiative characteristics of LNG pool fires were carried out at Texas A & M University's Brayton Fire Training Field (BFTF). This set of experiments was designed to study how the heat feedback from the fire to the pool surface is subsequently distributed through the liquid volume and the validity of different methods for measuring burning rates. In this work, a number of semi-empirical correlations were used to predict the characteristics of the flame and examine the predictive accuracy of these correlations when compared to the values obtained experimentally. In addition, the heat transferred from the energy received at the pool's surface to the surroundings was investigated. Finally, the parameters that influenced the measurement of radiative head feedback to the liquid pool were analyzed to investigate potential causes of calibration drift in the instrumentation.
The results of this work provided information regarding the validity of certain techniques for the measurement of mass burning rates and the use of correlations to predict the characteristics of an LNG pool fire on a small-scale. The findings from this work indicate that the energy received at the liquid surface was used entirely for evaporation and no indications of transmission to the surroundings were observed. Lastly, it was found that during the experiments, the sink temperature of the sensor was not constant, and therefore, the readings of the radiative heat were unreliable. This was due to the insufficient cooling effect of the water circulated. It was later shown in the laboratory that through a series of qualitative tests, a change of 20°C in the cooling water resulted in a calibration drift.
48
Hwang, Junny Tye, e 黃俊傑. "The optimization of the burning rarte of premixed flame". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/93303625216757956025.
Testo completo
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Mowery, Jessica Rae. "Insect succession on decomposing remains: the effects of burning". Thesis, 2018. https://hdl.handle.net/2144/33043.
Testo completoAbstract (sommario):
This experiment was designed to examine the effects of burning pig (Sus scrofa) remains on insect succession. Remains can be found burnt in a range of natural disasters including earthquakes, motor vehicle accidents, house fires, and brush fires. In homicides, more often than not, remains may be burnt to try and disguise the crime or destroy evidence. There has been little research conducted on the rate of insect succession at different levels of burning. This study will help to build upon the hypothesis that diverse levels of burning will each affect insect succession differently. The experiments took place in May 2017, and was repeated in August 2017. There were a total of three pigs used during this study, which were divided into quarters. Two quarters were used to represent each treatment level. One treatment remained unburnt and was used as a control in each experiment. The quarters were burnt at the research site in Holliston, MA. The Crow-Glassman Scale (CGS) was used to burn one treatment to level 2 and one treatment to level 3-4. They were then placed on site, no closer than five meters apart, surrounded by modified lobster cages and allowed to decompose. Notes, photographs, and insect collections took place every 2 hours on day 2 and twice a day for days 2 through 7. A final collection was then made on day 10 after the majority of tissue and insects were no longer present. The amount of insect activity was documented, photographs were taken, and samples were both preserved and reared through to adults. It was hypothesized that there was a correlation between insect activity and the level of burning. This was found to be true based on the results of this study, and with further research, will have the potential to aid in the determination of the post mortem interval (PMI) when burnt remains are found at the scene.
50
Loesel, Sitar Janet V. "Turbulent burning rates of near-flammability-limit H2-air-steam mixtures". 1995. http://hdl.handle.net/1993/18967.
Testo completo