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Matamoros, Marin Fatima. "Modélisation et optimisation des fours de cémentation gazeuse basse pression". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0288.
Pełny tekst źródłaThis PhD work deals with the development of an optimization methodology for low-pressure gas carburizing furnaces. The objective is to determine the optimal operating conditions allowing operators exposed to the toxic by-products generated (polycyclic aromatic hydrocarbons (PAHs) and soot in this case) to work in safer conditions. A first-principles model of the process based on mass balance equations as well as equations derived from a detailed kinetic mechanism of gas-phase acetylene pyrolysis is first developed. The kinetic model is then reduced in order to reduce the size of the differential system; then completed by a model of soot formation, a pyrolytic carbon formation reaction and heterogeneous phenomena occurring on the surface of the steel parts to be cemented which are described by means of Langmuir-Hinshelwood-Hougen-Watson model. Experiments conducted on a laboratory scale tubular reactor and a jet stirred reactor are carried out without steel parts. The results are then compared to the results of simulations of acetylene pyrolysis, soot and pyrolytic carbon formation in a plug flow reactor and in a perfectly stirred tank reactor. The results show the importance of the role played by the formation of pyrolytic carbon and soot on the formation of PAH. Experiments on an industrial low-pressure gas-carburizing furnace are conducted as well; they consist in the carburization of steel parts using an industrial "recipe", i.e. predetermined operating conditions obtained by trial-and-error basis in order to meet the desired carburizing depth. The experimental results are used to estimate the parameters of the heterogeneous surface reaction by assuming a complete model of low-pressure gas carburizing in a perfectly stirred tank reactor. The model is then used in the formulation of the dynamic constrained optimization problem which aims to minimize the production of toxic compounds while ensuring the industrial quality of the carburized steel parts. Optimal operating conditions allowing to obtain steel parts of the same quality as those obtained with the industrial recipe are then determined by solving the optimization problem and experiments using the new operating conditions are conducted in the industrial furnace. The results corroborate that the optimized recipe leads to steel parts of the same quality as the industrial recipe, while reducing the process toxicity
Wang, Danqi. "LOW-TEMPERATURE GAS-PHASE CARBURIZING AND NITRIDING OF 17-7 PH STAINLESS STEEL". Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1386165240.
Pełny tekst źródłaWeatherup, Clifford Robert. "New low pressure gas switches". Thesis, University of St Andrews, 1991. http://hdl.handle.net/10023/14040.
Pełny tekst źródłaАндріїшин, Mихайло Петрович, Костянтин Іванович Капітанчук, Назар Михайлович Андріїшин, Kostiantyn Kapitanchuk i Константин Иванович Капитанчук. "Natural gas turbine flow meters calibrations in low gas flow pressure situations". Thesis, Національний авіаційний університет, 2018. http://er.nau.edu.ua/handle/NAU/39801.
Pełny tekst źródłaУ статті визначено критерії калібрувань турбінних витратомірів природного газу. Запропоновано використовувати значення числа Рейнольдса як критерій, на який не впливає термодинамічні параметри та фізичні характеристики середовища, параметри турбінної решітки. модель і механічний стан витратоміра. Для експерименту використовували турбінний витратомір SM-RI-X-KG1000, DN200 з об'ємом потоку від 80 м3 / год до 1600 м3 / год, а тиск змінювався від 100 кПа до 700. Результати теоретичних розрахунків та даних експериментальних досліджень для числа Рейнольдса показано на графіку швидкості турбінного витратоміра на залежність від тиску. Встановлено, що витратомір, призначений для середовища низького тиску, повинен бути відкалібрований для фактичного діапазону тисків робочого середовища та значень температури
В статье определены критерии калибровок турбинных расходомеров природного газа. Предложено использовать значение числа Рейнольдса как критерий, на который не влияет термодинамические параметры и физические характеристики среды, параметры турбинной решетки. модель и механическое состояние расходомера. Для эксперимента использовали турбинный расходомер SM-RI-X-KG1000, DN200 с объемом потока от 80 м3 / ч до 1600 м3 / ч, а давление изменялось от 100 кПа до 700 Результаты теоретических расчетов и данных экспериментальных исследований для числа Рейнольдса показано на графике скорости турбинного расходомера в зависимости от давления. Установлено, что расходомер, предназначенный для среды низкого давления, должен быть откалиброван для фактического диапазона давлений рабочей среды и значений температуры
Yang, Suidong. "Diagnostics and modelling of an inductively coupled RF low-pressure low-temperature plasma". Thesis, n.p, 1998. http://oro.open.ac.uk/19841/.
Pełny tekst źródłaParkinson, J. S. "Control system design for low pressure gas distribution networks". Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378367.
Pełny tekst źródłaIngram, S. G. "Investigations of low pressure RF discharges in argon". Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.480534.
Pełny tekst źródłaSchirlin, Julien T. "Targeting low vapour pressure compounds in gas-phase electron diffraction". Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/11377.
Pełny tekst źródłaCraig, G. "Thomson scattering measurements in low pressure inert and molecular gas plasmas". Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403450.
Pełny tekst źródłaMoss, Graham James. "A time-dependent collisional-radiative model of low pressure gas discharges". Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269399.
Pełny tekst źródłaJusto, Hernandez Ruiz. "Low differential pressure and multiphase flow measurements by means of differential pressure devices". Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/1077.
Pełny tekst źródłaMalmberg, Andreas. "The influence of carbonitriding on hardness, retained austenite and residual stress in 52100 steel". Thesis, KTH, Materialvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173804.
Pełny tekst źródłaJayasuriya, Jeevan. "Experimental Investigations of High Pressure Catalytic Combustion for Gas Turbine Applications". Doctoral thesis, KTH, Kraft- och värmeteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-134445.
Pełny tekst źródłaQC 20131125
O'Connor, Gavin Thomas. "Development of a low pressure-inductively coupled plasma-ion source for mass spectrometry". Thesis, University of Plymouth, 1998. http://hdl.handle.net/10026.1/1764.
Pełny tekst źródłaKalitan, Danielle Marie. "A Study of Syngas Oxidation at High Pressures and Low Temperatures". Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2422.
Pełny tekst źródłaPh.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering PhD
McCluney, Peter. "Development of a small natural gas fuelled two stroke cycle engine using low pressure injection". Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241433.
Pełny tekst źródłaLeimkuehler, Thomas O. "Investigation of low-pressure laser induced fluorescence for measuring temperature profiles in a rarefied gas /". free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9999301.
Pełny tekst źródłaHeath, Melissa. "Heat Transfer Regimes during Charging of Pressure Vessels with Compressed Gas at Low Reynolds Numbers". Thesis, Griffith University, 2018. http://hdl.handle.net/10072/378153.
Pełny tekst źródłaThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text
Vancko, Jr Robert M. "Effect of a drag reducing agent on pressure drop and flow regime transitions in multiphase horizontal low pressure pipelines". Ohio University / OhioLINK, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1184354301.
Pełny tekst źródłaMrosek, Matthias. "Model-based control of a turbocharged diesel engine with high- and low-pressure exhaust gas recirculation". Phd thesis, VDI Verlag, 2017. https://tuprints.ulb.tu-darmstadt.de/6960/1/Dissertation_Mrosek_TUprints.pdf.
Pełny tekst źródłaLe, Thi Kim Cuong. "Raman spectroscopy of soot produced in low pressure flames : ex situ Analyses and Online Gas Phase Studies". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS068/document.
Pełny tekst źródłaEvery year, an amount of 107 tons of soot is produced on the world scale. Soot, as part of atmospheric black carbon, has serious impacts on climate change and human health. The impacts depend on many factors including adsorbed compounds, aging and mixing processes. Therefore in order to reduce the soot amount, besides considering these mentioned factors, the study of formation kinetics, structure and optical properties is also essential. There are several methods applied in soot investigations. Raman spectroscopy plays a particular role as it is a powerful tool for structural investigation of the carbon-based materials because it is sensitive to molecular structures. In this work, differential Raman cross sections of soot and some other carbonaceous particles were measured to progress toward quantitative Raman spectroscopy. Soot particles produced by premixed ethylene flames at a low pressure were investigated by ex-situ Raman measurement on deposited films and in-situ(online) Raman measurement in the gas phase. Combination of the Raman spectroscopy of soot sampled on substrates with infrared and optical spectroscopy and transmission electron microscopy allowed progressing on the interpretation of soot Raman spectra. The online gas phase measurements provided a novel view on soot birth and structures in low pressure flames with, for instance, the detection of a large amount of sp hybrized carbon atoms during nascent soot growth. These studies pave the way to soot detection and analysis directly and quantitatively in the atmosphere
Zhang, Kaiyi. "CO2 Minimum Miscibility Pressure and Recovery Mechanisms in Heterogeneous Low Permeability Reservoirs". Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/93728.
Pełny tekst źródłaMaster of Science
The new technologies to recover unconventional resources in oil and gas industry, such as fracturing and horizontal drilling, boosted the production of shale gas and tight oil in 21st century and contributed to the North America oil and gas production. Although the new technologies and strong demand spiked the production of tight oil resources, there are still unknowns of oil and gas flow mechanisms in tight rock reservoirs. As we know, the oil and gas resources are stored in the pores of reservoir formation rock. During production process, the oil and gas are pushed into production wells by formation pressure. However, the pore radius of shale rock is extremely small (around nanometers), which reduces the flow rate of oil and gas and raises capillary pressure in pores. The high capillary pressure will alter the oil and gas phase behavior and it may influence the value of minimum miscibility pressure (MMP), which is an important design parameter for CO2 injection (an important technology to raise production). To investigate this influence, we changed classical model with considering capillary pressure and this modified model is implemented in different methods to calculate MMP. The results show that CO2 -MMP in shale reservoirs are affected by capillary pressure and the results from different methods match well. Moreover, in tight rock reservoirs, the heterogeneous pore size distribution, such as fractures in reservoirs, may affect the flow of oil and gas and MMP value. So, this work also investigates the effect of pore size heterogeneity on oil and gas flow mechanisms. According to the simulation results, compositional gradient forms in heterogeneous nanopores of tight reservoirs and this gradient will cause diffusion which will dominate the other fluid flow mechanisms. Therefore, we always need to consider molecular diffusion in the simulation model for shale reservoirs.
Cheng, An-jen Tzeng Y. "Cold cathodes for application in poor vacuum and low pressure gas environments carbon nanotubes versus zinc oxide nanoneedles /". Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/master's/CHENG_AN-JEN_7.pdf.
Pełny tekst źródłaBolduc, Mathieu. "Deposition of Commercially Pure Titanium Powder Using Low Pressure Cold Spray and Pulsed Gas Dynamic Spray for Aerospace Repairs". Thesis, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24249.
Pełny tekst źródłaMoore, Myles Thomas. "An Integrative Geochemical Technique to Determine the Source and Timing of Natural Gas Formation in Gas Hydrates". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1577959057433697.
Pełny tekst źródłaLui, Samson Sze-Sang. "A Data Acquisition System Experiment for Gas Temperature and Pressure Measurements on a Liquid-Nitrogen-Powered Vehicle". Thesis, University of North Texas, 1998. https://digital.library.unt.edu/ark:/67531/metadc278790/.
Pełny tekst źródłaPelletier, Jean-Louis. "Development of Ti-6Al-4V Coating onto Ti-6Al-4V Substrate Using Low Pressure Cold Spray and Pulse Gas Dynamic Spray". Thesis, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24239.
Pełny tekst źródłaCotton, Dominique. "Etude de formation d'hémicarbure de tantale (Ta2C) par l'intermédiaire d'un procédé de cémentation sous pression réduite". Thesis, Dijon, 2015. http://www.theses.fr/2015DIJOS010/document.
Pełny tekst źródłaTantalum is a very dense metal (d = 16.6) and has a very high melting temperature of 2996°C. This material is particularly required for crucibles used for pyrochemical applications. Early studies show that a carburizing treatment enhances corrosion resistance from liquid metals. Indeed, the intergranular attack of tantalum is stopped by Ta2C precipitates, which occupy the grain boundary regions. The production of the carbon saturated tantalum with Ta2C precipitates requires a good understanding of tantalum carburizing.A carburizing treatment on tantalum sample causes the emergence of a TaC layer on surface and Ta2C layer just below. A reduction of carbon flow has enabled the study of the first steps of tantalum carbides formation. This specific condition of carburizing leads to an epitaxic growth of carbide layers on tantalum substrate. EBSD analysis highlights the crystallographic relations between each phase.Tantalum carbide layers are highly carbon concentrated. So the growth of carbide layers has to be controlled during the carburizing treatment. Several parameters may affect carbide layers growth : process parameters (time and temperature of carburizing treatment) and external parameters such as the reactive surface of the samples. The influence of these parameters on tantalum carbide growth kinetics has been studied. In addition, the diffusion of carbon in tantalum has been modeled with CASTEM© software. Experimental data are used to compute parameters of the model, such as carbon diffusion coefficient in tantalum.Other microstructures than TaC can be obtained on surface by applying an annealing treatment after carburizing. With this treatment, the carbon contained on surface diffuses to the bulk of the metal. Annealing treatment parameters have been determined to get on surface TaC, or Ta2C, or carbon saturated tantalum with Ta2C precipitates
Beule, Caroline de [Verfasser], i Gerhard [Akademischer Betreuer] Wurm. "Lifting grains from a dust bed by interaction with optical radiation and gas at low ambient pressure / Caroline de Beule. Betreuer: Gerhard Wurm". Duisburg, 2016. http://d-nb.info/1090785550/34.
Pełny tekst źródłaRobin, Frisk. "Distortion Analysis of Low Pressure Carburized Components : A heat treatment distortion comparison of transmission gear components for truck and automobile". Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-193539.
Pełny tekst źródłaMrosek, Matthias Patrick Alexander [Verfasser], Rolf [Akademischer Betreuer] Isermann i Ulrich [Akademischer Betreuer] Konigorski. "Model-based control of a turbocharged diesel engine with high- and low-pressure exhaust gas recirculation / Matthias Patrick Alexander Mrosek ; Rolf Isermann, Ulrich Konigorski". Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2017. http://d-nb.info/1145141935/34.
Pełny tekst źródłaSimiema, de Freitas Barbosa Gustavo [Verfasser], Bernd [Akademischer Betreuer] Mayer, Bernd [Gutachter] Mayer i Jürgen [Gutachter] Meichsner. "Construction and Evaluation of Gas Feed-in System, Electrodes and Gas Exhaustion System applied to Low Pressure Plasma Coating Processes / Gustavo Simiema de Freitas Barbosa ; Gutachter: Bernd Mayer, Jürgen Meichsner ; Betreuer: Bernd Mayer". Bremen : Staats- und Universitätsbibliothek Bremen, 2018. http://d-nb.info/1165772302/34.
Pełny tekst źródłaLoukota, Martin. "Návrh dvoutlakého vertikálního kotle na odpadní teplo za plynovou turbínou na zemní plyn". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-319280.
Pełny tekst źródłaBongers, Marian David Verfasser], Astrid [Akademischer Betreuer] Pundt, Astrid [Gutachter] Pundt, Michael [Gutachter] Seibt, Hans Christian [Gutachter] Hofsäss, Reiner [Gutachter] [Kirchheim, Vasily [Gutachter] Moshnyaga i Martin [Gutachter] Wenderoth. "In situ studies on palladium/rutile titanium dioxide exposed to low pressure hydrogen gas environments / Marian David Bongers ; Gutachter: Astrid Pundt, Michael Seibt, Hans Christian Hofsäss, Reiner Kirchheim, Vasily Moshnyaga, Martin Wenderoth ; Betreuer: Astrid Pundt". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://d-nb.info/1171521464/34.
Pełny tekst źródłaNgeleka, Tholakele Prisca. "Sulphur dioxide capture under fluidized bed combustion conditions / Tholakele Prisca Ngeleka". Thesis, North-West University, 2005. http://hdl.handle.net/10394/1416.
Pełny tekst źródłaThesis (M.Sc. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2006.
Ngeleka, Tholakele Prisca. "An investigation into the feasibility of applying the watergas shift process to increase hydrogen production rate of the hybrid sulphur process / T.P. Ngeleka". Thesis, North-West University, 2008. http://hdl.handle.net/10394/4108.
Pełny tekst źródłaThesis (M.Sc. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2009.
Malbois, Pierre. "Analyse expérimentale par diagnostics lasers du mélange kérosène/air et de la combustion swirlée pauvre prémélangée, haute-pression issue d’un injecteur Low-NOx". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMIR25/document.
Pełny tekst źródłaAeronautical engine manufacturers are banking on the development of innovative fuel injection systems to reduce fuel consumption and pollutant emissions. The aim of the thesis is to contribute to the experimental investigation of a "Lean Premixed" injector by developing laser diagnostics coupling approaches based on Mie scattering and fluorescent emission of tracers. Measurements are performed at high pressure on the HERON combustion test bench. An innovative approach with fluorescence imaging of kerosene has resulted in the quantification of the kerosene/air mixture. The flame structure was analyzed simultaneously by OH-PLIF and velocity PIV measurements were performed to complete this analysis. A preliminary development of CO-PLIF was also conducted. The numerous measurements provided a detailed analysis of the mechanisms of flame/spray/aerodynamic interactions during a swirl-stabilized kerosene/air combustion at high pressure
Filoušová, Natálie. "Parní turbína v paroplynovém cyklu". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318750.
Pełny tekst źródłaBiggs, Timothy James. "Studies of crystalline organic molecular materials under extreme conditions". Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:51dae806-2954-4ea7-a3cb-1980ecb53e98.
Pełny tekst źródłaFletcher, Nathan James. "Design and Implementation of Periodic Unsteadiness Generator for Turbine Secondary Flow Studies". Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1560810428267352.
Pełny tekst źródłaFernandes, Hipolito Ana Isabel. "Étude des phénomènes de transport dans un réacteur catalytique pilote de type filaire". Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10285/document.
Pełny tekst źródłaSmall size fixed-bed reactors are a common choice for testing industrial supported catalyst under industrial operating conditions. The most common criterion for reactor’s scale-down is based on the conservation of the liquid hourly space velocity which leads to a very low fluid flow velocity at the laboratory scale. Under these conditions, the external mass transfer flux can become the limiting step of the process. In this context, a new reactor geometry was proposed to intensify mass and heat transfers and to increase fluid flow velocities: the single pellet string reactor. This reactor is composed of a tube with an internal diameter close to that of the catalyst particles and with a high length over diameter ratio. The main goal of this thesis is to characterise the hydrodynamic and external mass transfer performances of this new reactor in order to define its application domain. In two-phase gas-liquid flow, the reactor flow is plug flow and the liquid hold-up values are high, which insures a complete wetting of the catalyst particles. The mass transfer coefficients were quantified and the measured rates are much higher than those observed in conventional pilot fixed-bed reactors, which can be explained by the increased local liquid velocities and by the modified Taylor flow regime. Catalytic tests with a very fast model reaction revealed that the external mass transfer performances of the single pellet string reactor are close to those measured in a stirred tank reactor equipped with a catalytic basket. In conclusion, the single pellet string reactor represents a new and efficient alternative to fixed-bed pilot reactors to study shaped catalysts
TERNER, MATHIEU. "Innovative materials for high temperature structural applications: 3rd Generation γ-TiAl fabricated by Electron Beam Melting". Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2527509.
Pełny tekst źródłaGicquel, Alix. "Etude des processus catalytiques heterogenes dans les milieux plasmas basse pression hors-equilibre". Paris 6, 1987. http://www.theses.fr/1987PA066396.
Pełny tekst źródłaTobek, Miroslav. "Řešení dopravy v centru Havlíčkova Brodu". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225922.
Pełny tekst źródłaMallardeau, Catherine. "L'hydrogène atomique polarisé : interaction avec les films d'Helium : expérience de compression". Paris 6, 1986. http://www.theses.fr/1986PA066186.
Pełny tekst źródłaQuichaud, Viviane. "Etude des processus elementaires : de synthese de la molecule no, en post-decharge en ecoulement, de collisions titane-gaz rares, titane-molecules, par perturbation laser resolue en temps". Paris 6, 1987. http://www.theses.fr/1987PA066135.
Pełny tekst źródłaHsu, Shuo-Han, i 徐碩韓. "Study on Low-temperature Carburizing of Austenitic Stainless Steel by the Gas Carburizing Method". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/11375772547653487334.
Pełny tekst źródła國立臺灣大學
機械工程學研究所
100
Austenitic stainless steel is an alloy steel containing large amounts of nickel, chromium and other alloying elements. The surface will form a thin layer of Cr2O3 passive film, which is resistant to corrosion, so that this type of stainless steel can be applied in petroleum engineering, chemical engineering, medical equipment, and the food industry etc. However, this stainless steel will easily be scratched due to its low hardness; therefore in the application of mechanical parts, its wear resistance often fails to meet the requirements of the users. Carburization is one of the surface hardening techniques commonly used in industries, but the traditional high temperature carburization (800℃~1100℃) will lead to the precipitation of chromium carbides (Cr7C3) onto the grain boundaries, which will significantly reduce the corrosion resistance of the stainless steel. To prevent the precipitation of the chromium carbides, this research focuses on utilizing a carburization technique with long duration at low temperature, lower than or at 520°C, to increase the surface hardness of the stainless steel. At low temperatures, substitutive chromium atoms are not easy to move, but interstitial carbon atoms can move more easily. Therefore, carbon atoms can dissolve into the stainless steel, which can increase its surface hardness and wear resistance. In addition, the chromium atoms within the stainless steel cannot precipitate to form carbides; therefore, preventing from the decreasing of the corrosion resistance of the stainless steel. This research utilizes the mixture of nitrogen and methanol dissociation gas to carburize the surface of the stainless steel. Before the carburization process, the passive film on the surface of the stainless steel should be removed through the so-called activation treatment. This research uses a pre-oxidation process with hydrochloric acid vapor to replace the conventional activation treatment, so that the former can save more time than the latter. Within ten minutes, the passive film will be completely removed, and then the stainless steel can be carburized. After the stainless steel is pre-oxidized by the hydrochloric acid vapor under appropriate conditions, and then carburized at a low temperature, the effects of the carburization on the stainless steel are evaluated from the microstructure, hardness distribution, wear resistance and corrosion resistance of the carburized layer.The results are as follow: 1. The carburized layer created at a carburizing temperature of 470°C mainly consists of a super saturated solid solution of carbon atoms and only a minute amount of carbide; On the contrary, the carburized layer created at a carburizing temperature of 520°C is a mixture which consists of a super saturated solid solution and a noticeable amount of carbides. 2. Major carbides generated from AISI 304 in the carburized layer are Cr7C3. In addition to Cr7C3, another type of carbide generated from AISI 316 is Mo2C. 3. When comparing the carburizing rate and the carburized layer’s thickness of both stainless steels, AISI 316 is better than AISI 304, overall. 4. When the stainless steel is carburized at low temperatures, the deterioration of its corrosion resistance is not significant. The carburizing of AISI 304, on the contrary, will increase the corrosion resistance to the hydrochloric acid. When closely observing the effect of carburizing temperature on the corrosion resistance, the higher carburizing temperature of 520°C produces more carbides, which results in poor corrosion resistance. As opposed to a lower carburizing temperature of 470°C, less carbides are produced, resulting in better corrosion resistance. 5. When the low temperature carburized specimen is compared with the raw one, its wear resistance is improved significantly. The main reason is due to a large amount of compressive stress generated on the surface of the carburized specimen because of the super saturation of carbon atoms, therefore resulting in significant improvement in surface hardness and wear resistance.
Tinashe, Sanyangare Edwin. "Conceptual design of a low pressure cold gas dynamic spray (LPCGDS) system". Thesis, 2010. http://hdl.handle.net/10539/8398.
Pełny tekst źródła(7038164), Gayathri Shivkumar. "Coupled plasma, fluid and thermal modeling of low-pressure and microscale gas discharges". Thesis, 2019.
Znajdź pełny tekst źródłaLarge scale and cost-efficient synthesis of carbon nanostructured materials has garnered tremendous interest over the last decade owing to their plethora of engineering and bio-science applications. One promising method is roll-to-roll radio frequency chemical vapor deposition and this work presents a computational investigation of the capacitively coupled radio frequency plasma in such a system. The system operates at moderate pressures (less than 30 mbar) with an 80 kHz square wave voltage input. The computational model aids the understanding of plasma properties and α-γ transition parameters which strongly influence the nanostructure deposition characteristics in the system. One dimensional argon and hydrogen plasma models are developed to characterize the effects of input voltage, gas pressure, frequency, and waveform on the plasma properties. A hybrid mode which displays the characteristics of both α and γ discharges is found to exist for the low cycle frequency 80 kHz square wave voltage input due to the high frequency harmonics associated with a square waveform. The threshold voltage at which the transition between the different regimes occurs is higher for hydrogen than for argon owing to its diatomic nature. Collision radiative modeling is performed to predict the argon emission intensity in the discharge gap. The results are found to lie within 16% of the optical emission spectroscopy measurements with better agreement at the center of the discharge, where the measurement uncertainty is low and the emission by ions is not significant. A quasi-zero dimensional steady state chemistry model which uses the hydrogen plasma properties as inputs predicts high concentrations of C2H, C2H2, C2H3+, C2H4+ and C2H6+ during carbon nanostructure deposition.
Carbon nanostructures are popularly used as field emitters. Field emission based microplasma actuators generate highly non-neutral surface discharges that can be used to heat, pump, and mix the flow through microchannels and offer an innovative solution to the problems associated with microcombustion. They provide a constant source of heat to counter the large heat loss through the combustor surface, they aid in flow transport at low Reynolds numbers without the use of moving parts, and they provide a constant supply of radicals to promote chain branching reactions. This work presents two actuator concepts for the generation of field emission microplasma, one with offset electrodes and the other with planar electrodes. They operate at input voltages in the 275 to 325 V range at a frequency of 1 GHz which is found to be the most suitable value for flow enhancement. The momentum and energy imparted by the charged particles to the neutrals as modeled by 2D Particle-In-Cell with Monte Carlo Collisions (PIC/MCC) are applied to actuate flow in microchannels using 2D Computational Fluid Dynamics modeling. The planar electrode configuration is found to be more suitable for the purpose of heating, igniting and mixing the flow, as well as improving its residence time through a 10 mm long microcombustor. The combustion of hydrogen and air with the help of 4 such actuators, each with a power consumption of 47.5 mW/cm, generates power with an efficiency of 28.8%. Coating the electrode surface with carbon nanostructures improves the combustion efficiency by a factor of 2.5 and reduces the input voltage by a factor of 6.5. Such microcombustors can be applied to all battery based systems requiring micropower generation with the ultimate goal of “generating power on a chip'”.
Amato, Giorgio. "Design Solutions for Reducing Losses in Aeronautical Low-Pressure Turbines". Doctoral thesis, 2021. http://hdl.handle.net/2158/1235154.
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