To see the other types of publications on this topic, follow the link: Monitoring of gas leakage.
Dissertations / Theses on the topic 'Monitoring of gas leakage'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Monitoring of gas leakage.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Mehra, Deepak. "Development of instrumentation for acoustic monitoring." Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=3083.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 2003.Title from document title page. Document formatted into pages; contains x, 61 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 59-61).
2
Palafox, Pepe. "Gas turbine tip leakage flow and heat transfer." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427699.
Full text
3
Ozmen, Teoman. "Gas Turbine Monitoring System." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607957/index.pdf.
Full textAbstract:
In this study, a new gas turbine monitoring system being able to carry out appropriate run process is set up for a gas turbine with 250 kW power rating and its accessories. The system with the mechanical and electrical connections of the required sub-parts is transformed to a kind of the test stand. Performance test result calculation method is described. In addition that, performance evaluation software being able to apply with the completion of the preliminary performance tests is developed for this gas turbine.
This system has infrastructure for the gas turbine sub-components performance and aerothermodynamics research. This system is also designed for aviation training facility as a training material for the gas turbine start and run demonstration. This system provides the preliminary gas turbine performance research requirements in the laboratory environment.
4
Matthiessen, Peter. "Rectal cancer surgery : Defunctioning stoma, anastomotic leakage and postoperative monitoring." Doctoral thesis, Linköping : Univ, 2006. http://www.bibl.liu.se/liupubl/disp/disp2006/med940s.pdf.
Full text
5
Xie, Song [Verfasser], and Ulrich [Akademischer Betreuer] Landgraf. "A gas monitoring chamber for ATLAS MDTs = Eine Gas Monitoring Chamber für ATLAS MDTs." Freiburg : Universität, 2011. http://d-nb.info/1123464561/34.
Full text
6
Popović, Ivan. "Aerothermal investigation of hub leakage flows in high-pressure turbines." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608563.
Full text
7
Joshi, Ameet Vijay. "Inverse problems in non-destructive evaluation of gas transmission pipelines using magnetic flux leakage." Diss., Connect to online resource - MSU authorized users, 2006.
Find full textAbstract:
Thesis (Ph. D.)--Michigan State University. Electrical and Computer Engineering Department, 2006.Title from PDF t.p. (viewed on June 19, 2009) Includes bibliographical references (p. 87-89). Also issued in print.
8
Fleischer, Stephen. "A study of gate-oxide leakage in MOS devices." Thesis, [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1364600X.
Full text
9
Kluka, James Anthony. "The design of low-leakage modular regenerators for gas-turbine engines." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/46564.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1995.Includes bibliographical references (p. [229]-231).
The design of a modular regenerator concept (patented by Wilson and MIT) for gas-turbine engines is investigated. Mechanical design analysis and theoretical performance calculations were made to show the concept's functionality and performance benefits over current regenerator designs. The modular regenerator concept consists of a ceramic-honeycomb matrix discretized into rectangular blocks, called modules. The modules are exposed to hot (turbine exhaust) and cold (compressor outlet) streams, then are periodically transported through linear passages from one stream to the other. Separating the matrix into modules reduces the transverse sealing lengths substantially. Furthermore, the range of gas-turbine applications increases with the modular concept since larger matrix face areas are possible. Module design is investigated which includes using current research results pertaining to manufacturing technology for rotary regenerators. Mechanical design analysis was made to investigate the possible module-movement schemes. Several regenerator configurations and orientations are introduced. One particular concept balances the pressure forces such that the power requirement for module movement is reduced substantially. Design drawings of a possible modular prototype showing the general configuration and mechanical layout accompany the analysis. A method for determining the regenerator size and measuring its fluid-mechanical and heat-transfer performance is given. An optimization study is made by analyzing the effects when several chosen design parameters are varied. Numerical results of a modular concept for a small gas-turbine engine (120 kW) are given. Seal leakage calculations were made for two modular concepts and compared to the leakage rates for two rotary concepts. The total seal-leakage rates for both modular cases were considerably less than the rotary concepts and can be reduced to well under one percent. In addition, techniques for further leakage reduction are given. Other design issues (to further prove the modular concept's feasibility) not covered in this study have been identified. Guidelines for investigating these issues are given.
by James Anthony Kluka.
S.M.
10
Knost, Daniel G. "Parametric Investigation of the Combustor-Turbine Interface Leakage Geometry." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29145.
Full textAbstract:
Engine development has been in the direction of increased turbine inlet
temperatures to improve efficiency and power output. Secondary flows develop
as a result of a near-wall pressure gradient in the stagnating flow approaching
the inlet nozzle guide vane as well as a strong cross-passage gradient within the
passage. These flow structures enhance heat transfer and convect hot core flow
gases onto component surfaces. In modern engines it has become critical to cool
component surfaces to extend part life.
Bypass leakage flow emerging from the slot between the combustor and
turbine endwalls can be utilized for cooling purposes if properly designed. This
study examines a three-dimensional slot geometry, scalloped to manipulated
leakage flow distribution. Statistical techniques are used to decouple the effects
of four geometric parameters and quantify the relative influence of each on
endwall cooling levels and near-wall total pressure losses. The slot geometry is
also optimized for robustness across a range of inlet conditions.
Average upstream distance to the slot is shown to dominate overall cooling
levels with nominal slot width gaining influence at higher leakage flow rates.
Scalloping amplitude is most influential to near-wall total pressure loss as formation
of the horseshoe vortex and cross flow within the passage are affected.
Scalloping phase alters local cooling levels as leakage injection is shifted laterally
across the endwall.Ph. D.
11
Zhang, Chen. "Piezoelectric-Based Gas Sensors for Harsh Environment Gas Component Monitoring." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1538769/.
Full textAbstract:
In this study, gas sensing systems that are based on piezoelectric smart material and structures are proposed, designed, developed, and tested, which are mainly aimed to address the temperature dependent CO2 gas sensing in a real environment. The state-of-the-art of gas sensing technologies are firstly reviewed and discussed for their pros and cons. The adsorption mechanisms including physisorption and chemisorption are subsequently investigated to characterize and provide solutions to various gas sensors. Particularly, a QCM based gas sensor and a C-axis inclined zigzag ZnO FBAR gas sensor are designed and analyzed for their performance on room temperature CO2 gas sensing, which fall into the scope of physisorption. In contrast, a Langasite (LGS) surface acoustic wave (SAW) based acetone vapor sensor is designed, developed, and tested, which is based on the chemisorption analysis of the LGS substrate. Moreover, solid state gas sensors are characterized and analyzed for chemisorption-based sensitive sensing thin film development, which can be further applied to piezoelectric-based gas sensors (i.e. Ca doped ZnO LGS SAW gas sensors) for performance enhanced CO2 gas sensing. Additionally, an innovative MEMS micro cantilever beam is proposed based on the LGS nanofabrication, which can be potentially applied for gas sensing, when combined with ZnO nanorods deposition. Principal component analysis (PCA) is employed for cross-sensitivity analysis, by which high temperature gas sensing in a real environment can be achieved. The proposed gas sensing systems are designated to work in a high temperature environment by taking advantage of the high temperature stability of the piezoelectric substrates.
12
Nwachukwu, Arthur Nwachukwu. "Improved ground-gas risk prediction using in-borehole gas monitoring." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/improved-groundgas-risk-prediction-using-inborehole-gas-monitoring(610a2b47-5fcd-483d-93d4-a193179d227b).html.
Full textAbstract:
Elevated concentrations of ground-gases (CH4 and CO2) and VOCs in contaminated soil and water around the world pose significant risk both to human health and the environment. There is, therefore, a requirement to monitor them for effective risk assessment and remediation. Current ground-gas monitoring is often ineffective for determining their representative concentrations and fluxes – the two most important parameters necessary for ground-gas risk assessment. These failures of current monitoring may arise from its low temporal resolution. The recent ability to monitor at high temporal resolution – using Gasclam - makes it possible to determine whether this is the case and whether high resolution monitoring can be more effective. CH4 and CO2 were monitored at several sites using Gasclam. This showed that in many cases concentrations were sufficiently variable that current sampling practices would be ineffective at detecting worst case concentrations. Furthermore, the time-series data produced by Gasclam allowed the predictive power of the established relationships between atmospheric pressure and gas concentration to be improved. The failures in the relationship could also be understood as hysteresis which gave an index of ground permeability and/or gas generation. These improvements in understanding could be used to improve the conceptual site models on which risk assessments are based. Similarly, high temporal resolution VOC measurement demonstrated the need for such measurement. The factors controlling VOC concentration were shown to be same to those controlling ground-gases; again this understanding of process would also improve the conceptual site model. A monitoring method that incorporated parallel non-specific real time measurement with a time integrated VOC measurement that identified specific VOC’s was tested. The method was an improvement on the separate methods as it could be used to reasonably infer the concentrations of specific VOC’s at high temporal resolution. The ability to monitor gas concentrations at high temporal resolution gave the potential for the rate of gas concentration recovery subsequent to purging of the borehole to be used as an index of gas flux. These tests proved to be practical, generally taking less than the time of a site visit, and reproducible. Variability in these recovery profiles was assessed at different sites, times and for different gases.
13
Weisser, Karl. "Gas monitoring system using ultrasound sensors." Thesis, KTH, Mikrosystemteknik (Bytt namn 20121201), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91814.
Full textAbstract:
This thesis reports a collaboration between KTH Microsystem Technology Labs and Maquet critical care. Maquet is a company that produces medical ventilators and anesthesia machines. In an anesthesia machine it is important to monitor the anesthesia concentration that is delivered so that the delivered anesthesia concentration does not deviate from the desired concentration. Furthermore, in case of fail function there is a need to stop the delivery of anesthesia to the patient and flush the system. The anesthetic agent concentration is presently monitored with an infrared spectrometer. By using ultrasound technology it is possible to determine the volume concentration of a gas mixture by knowing the sound speed in the gases. Maquet has an ultrasound sensor that is developed to measure the oxygen concentration in air. This sensor was modified in order to measure nitrous oxide and anesthesia. The anesthesia concentration was measured by placing sensors upstream and downstream from the vaporizer. Using this ultrasound sensor system one can observe that the average discrepancy of the entire concentration range is ±0.84 % for Desflurane and 0.17 % for Isoflurane in relation to the infraredspectrometer sensor that is presently used in the anesthesia machine to monitor the anesthetic agent. Measurements show that the rise time of the ultrasound sensor varies when placing the sensor in different orientations with respect to the airway flow. It also show that by placing a flow restrictor that is used to force the airway flow in to the sensors measurement chamber reduces the rise time to a tenth of its previous value.
14
Valentine, Francisco L. "Effect of debris-induced lift-off on magnetic flux leakage inspection results." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1415.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains ix, 107 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references (p. 50-51).
15
Martínez, Lacasa Daniel. "Application of autonomous mobile platforms for environmental supervision and gas leakage localization." Doctoral thesis, Universitat de Lleida, 2017. http://hdl.handle.net/10803/400391.
Full textAbstract:
Aquesta tesi doctoral presenta la recerca realitzada en l’anàlisi i desenvolupament de procediments de supervisió ambiental mitjançant l’ús de plataformes robòtiques mòbils donant especial importància a la localització de fonts de gas tòxic volàtil. En aquesta tesi aquest tipus d’aplicacions es denominen com aplicacions d’Intel·ligència Ambiental (AmI) les quals pretenen automatitzar aquests processos de forma efectiva per la seva integració en entorns interiors de freqüent ús humà. En primer lloc es proposa la implementació d’un sistema de control d’alt nivell basat en una arquitectura multi-agent per la execució dels diferents serveis robòtics requerits. Seguidament es proposa la utilització d’un robot mòbil per la supervisió ambiental d’un entorn de treball d’interior per el manteniment de la confortabilitat i de condicions saludables. La segona part de la tesi adreça el problema de la localització de fonts de gas volàtil utilitzant robots mòbils. En aquesta secció es proposa una metodologia per la caracterització acurada d’àrees on es realitzaran els experiments de localització de fonts de gas i la realització d’una sèrie d’experiments en diferents àrees amb diferents configuracions.Esta tesis doctoral presenta la investigación realizada en el análisis y desarrollo de procedimientos de supervisión ambiental mediante el uso de plataformas robóticas móviles dando especial importancia a la localización de Fuentes de gas toxico volátil. En esta tesis este tipo de aplicaciones se denominan como aplicaciones de Inteligencia Ambiental (AmI) las cuales pretenden automatizar estos procesos de forma efectiva para su integración en entornos interiores de frecuente uso humano. En primer lugar se propone la implementación de un sistema de control e alto nivel basado en una arquitectura multi-agente para la ejecución de los diferentes servicios robóticos requeridos. A continuación se propone la utilización de un robot móvil para la supervisión ambiental de un entorno de trabajo de interior para el mantenimiento de la confortabilidad y de las condiciones saludables. La segunda parte de la tesis trata el problema de la localización de fuentes de gas volátil utilizando robots móviles. En esta sección se propone una metodología para la caracterización precisa de áreas donde se realizaran los experimentos de localización de fuentes de gas y la realización de una serie de experimentos en diferentes áreas bajo diferentes configuraciones.
This PhD thesis presents the performed research on the analysis and development of ambient supervision procedures by means of using robotic mobile platforms giving special importance to the localization of toxic volatile gas sources. In this thesis this kind of applications are denominated as Ambient Intelligence (AmI) applications which pretends to automatize this processes in an effective way for its integration in human-frequented indoor environments. In a first view, it is proposed the implementation of a high level control system based on a multi-agent architecture for the execution of the different required robot services. Next, it is proposed the use of a mobile robot for ambient supervision of an indoor workplace environment for the maintenance of comfortability and healthy conditions. The second part addresses the localization of toxic volatile gas sources by using mobile robots. In this section is proposed a methodology for an accurate characterization of the areas where the gas source localization experiments will be carried out. In addition, the realization of several experiments in different areas under different setups are presented.
16
Kerr, Bradley Gray. "Experimental and theoretical rotordynamic coefficients and leakage of straight smooth annular gas seals." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1518.
Full textAbstract:
Results are presented for experimental and theoretical rotordynamic coefficients
and leakage of straight smooth annular gas seals. Experimental rotordynamic
coefficients were measured and trends in changes of rotordynamic coefficients with
operating variables such as rotor speed, back-pressure, fluid preswirl, and seal clearance
are analyzed.
Experimental results show that cross-coupled stiffness coefficients are highly
influenced by fluid preswirl and only moderately influenced by other operating
parameters, whereas direct damping is nearly unaffected by changes in operating
parameters. Effective damping, a good indicator of stability, is highly affected by fluid
preswirl. Although rotordynamic coefficients of straight smooth annular gas seals are
assumed to be frequency independent, experimental results suggest a frequency
dependent nature at high back-pressures and high excitation frequencies.
Experimental results for rotordynamic coefficients and leakage are compared
with theoretical predictions of ISOTSEAL, an isothermal-flow, two-control-volume,
bulk-flow rotordynamic analysis program. All rotordynamic coefficients are underpredicted.
Direct stiffness is poorly predicted while cross-coupled stiffness and direct
damping are predicted reasonably well. Leakage is also consistently under-predicted.
Theory predicts a slight frequency dependent nature for a limited number of test
configurations.
17
Rhino, Kévins. "Caractérisation, quantification et modélisation des processus de transfert et des interactions CO₂-eau-roche en milieu poreux non saturé en contexte de forage lors d'un stockage géologique." Thesis, Bordeaux 3, 2017. http://www.theses.fr/2017BOR30040/document.
Full textAbstract:
Le stockage géologique du carbone est l’une des techniques les plus prometteuses pour réduire le taux de CO₂ dans l’atmosphère. La séquestration géologique possède la capacité et la longévité potentielles pour diminuer les émissions de CO₂ vers l’atmosphère. Dans le cadre d’injections à l’échelle industrielle, les réservoirs carbonatés peuvent faire partie des sites aptes à stocker du CO₂. Toutefois, ces injections à grandes profondeurs sont sujettes à des risques de fuites du piège géologique lui-même ou des infrastructures liés à l’exploitation du site de stockage. Ainsi, il existe principalement deux types de fuite : brutale et diffuse. Dans les deux cas, elles sont susceptibles d’entrainer des risques pour l’environnement et de mettre en danger les populations. Il est ainsi nécessaire de développer des outils capables de prévenir une fuite de CO₂ quel que soit son type. Par ailleurs, il est particulièrement indispensable de comprendre les mécanismes de transport réactif qui rentrent en jeu lors de l’arrivée de cette fuite en contexte de proche surface (zone vadose) et ainsi d’essayer d’étudier comment cette fuite peut s’amortir. Ces travaux de thèse traitent donc de la caractérisation, de la quantification et de la modélisation des processus de transferts et des interactions CO₂-H₂O-CaCO₃ dans la zone vadose en contexte de fuite à partir d’un puits de forage. Cette problématique a été d’abord abordée par une approche expérimentale sur un site pilote à Saint-Emilion. Puis, les interactions CO₂-H₂O-CaCO₃ ont été étudiées au travers d’une approche expérimentale à l’échelle de la carotte en laboratoire. L’approche expérimentale a conduit à la réalisation de deux fuites dans la zone vadose du site pilote : une fuite diffuse et une fuite ultra diffuse. Elles furent réalisées dans la continuité des expériences qui avaient déjà eu lieu auparavant. Une comparaison de l’ensemble des fuites a montré la nécessité d’utiliser des gaz nobles comme précurseurs de l’arrivée en surface du CO₂. Selon le type de fuite, l’hélium peut servir de précurseur temporel du CO₂, tandis que le krypton prévient de l’étendue du panache de gaz durant la fuite. Plus la pression d’injection du CO₂ est importante et plus le gaz migre par advection. Par ailleurs, une pression d’injection importante favorise l’existence de passage préférentiel dans la zone vadose. L’utilisation d’isotopes tels que ceux de l’hélium et du carbone permet de mettre en évidence la présence locale de phases aqueuses dans le massif et de déterminer l’origine biologique ou anthropique du CO₂. Les expériences à l’échelle de la carotte permettent d’estimer le pouvoir tampon des calcaires oligocènes en fonction du faciès de la roche. La perméabilité et la porosité de celle-ci conditionnent la dissolution des calcaires. De même, la réactivité des carbonates en contexte de fuite dépend du pH de la phase aqueuse, du débit qui traverse le réseau poreux, de la saturation en eau et des caractéristiques pétro-physiques des carbonatesCarbon storage is one of the most encouraging methods to decrease CO₂ concentration into the atmosphere. Carbon storage provides the longevity and the capacity needed to decrease CO₂ emissions toward the atmosphere. When dealing with storage on an industrial scale, carbonated reservoirs can be among the most suitable storage sites. However, these high depth injections are subject to leakage risks from the geologic trap itself or from the framework created by the establishment of the site. Two main types of leakage exist: brutal and diffusive leakage. In both cases, they are likely to endanger the environment and the population. Therefore, it is essential to develop tools that are able to anticipate any types of CO₂ leakage. Furthermore, it is also necessary to understand the reactive transport mechanism that take place when the leakage arrives in the shallow subsurface (vadose zone)and to see how the leakage can be buffered. This work deals with the characterization, the quantification and the modelling of transfer processes and CO₂-H₂O-CaCO₃ interactions into the vadose zone in a context of a leakage from a drilling well. This issue was first dealt through field experiment on the site of Saint Emilion. Then, the CO₂-H₂O-CaCO₃ interactions were studied through an experimental approach in laboratory. Two leakage experiments were performed on the site: a diffusive leakage and an ultra-diffusive leakage. They were performed as a sequel of former experiments carried on the pilot site. A comparison of all the leakage experiments revealed the necessity to use noble gases as precursor of the CO₂ arrival at the surface. Depending of the type of the leakage, helium can be a temporal precursor while krypton can anticipate the spread of the CO₂ gas plume. The higher the injection pressure, the more the gas migrates through advective flux. Moreover, a high injection pressure favors the existence of preferential paths in the vadose zone. The use of helium and carbon isotopes makes it possible to reveal the presence of a local aqueous phase within the porous media and to identify the origin of CO₂. The core scale experiments lead to the estimation of the buffering power of Oligocene limestone according to the rock facies. The permeability and the porosity influence the dissolution of the limestone. The reactivity of carbonates during a leakage depends on the pH of the aqueous phase, the flow rate that goes through the porous media, the water saturation and petrophysical characteristics of the carbonates
18
Shakmak, B. H. "Condition monitoring of water leakage detection in buried pipes using sensor fusion systems." Thesis, Nottingham Trent University, 2016. http://irep.ntu.ac.uk/id/eprint/31336/.
Full textAbstract:
Water is significantly lost within water networks in most countries with an estimates of 30% would be lost due to leaks in water pipelines. Water leaks are one of the major factors facing the world, from waste water for no appropriate reason other than a lack of sustainable management programmes. This research work will investigates several sensor techniques and image/signal processing methods to detect water leaks within buried pipeline system. A sensor fusion method for the detection of water leakage in pipes, which consists of two or more sensory systems, is proposed in this research work. The suggested sensor fusion system will investigate a combination of transient signals of several direct types, such as flow and pressure, and non-direct types such as acoustic signals and infrared images. The sensors will identify signals inside the pipeline system and will detect any acoustic or transient signals. This might happen as a result of a leakage while the thermal imager will look outside the pipeline system for any leakage signs. This is by way of detecting the contrast in temperature and humidity of the soil surrounding the leakage point. The data has been collected using software that can read and store the required signal data with the infrared image data as required. The collected data is subjected to processing using the Matlab software and based on the results a computer algorithm which has been developed to be used in detection, locating and identifying the leaks using artificial intelligence techniques. The methodology of this research work includes constructing a test rig of a pipeline equipped with necessary instrumentations for data acquiring purposes. As such, data acquisition device, pressure sensors, acoustic sensors, temperature sensors, infrared camera, normal visual camera and any other necessary equipment for water flow control. A series of experiments have been conducted with the test rig in the laboratory and a field experimental work has been conducted in Libya with the results having been highlighted within this report. The expected contribution to knowledge would include significant technical and theoretical aspects of the experimental work and analysis. The contribution includes the comparison between the high and low-resolution infrared cameras. Additionally, an application of a novel approach to using a combination of infrared technology and visual images with a sensory fusion system of acoustic emission and transient signal to detect water leaks in pipeline systems. The work requires building a test rig to develop the experimental work as well as carrying out field works. The contribution to knowledge also includes the developing of an artificial intelligence algorithm for detecting water leakage in pipelines, which would determine the best times of detection when estimating and quantifying the leakage amount.
19
Wang, Zan. "Characterization and Monitoring of Geochemical and Geophysical Effects of CO2 Leakage from Sequestration Reservoirs." Research Showcase @ CMU, 2015. http://repository.cmu.edu/dissertations/498.
Full textAbstract:
Geological carbon sequestration is considered a promising initial option to slow or reduce global atmospheric CO2 concentrations. To demonstrate that the implementation of carbon sequestration is safe and effective as a greenhouse gas control technology, characterization and monitoring of geochemical and geophysical effects of CO2 leakage from sequestration reservoirs is crucial. A multimodel predictive system (MMoPS) has been developed to predict CO2 solubility in brine more accurately, so that storage capacity and cost estimates could be improved. The CO2 leakage level is characterized through an assessment of the integrity and permeability of the caprock inferred from pressure measurements in the injection zone using a Bayesian approach. The detection power of pressure monitoring is evaluated using the expected distribution of pressure increases in the injection zone for permeable vs. impermeable caprock cases. The distributions of detection power using seismic travel time measurements at different CO2 leakage levels are obtained using a statistical analysis and test. The methodology and results in this work should improve our ability to understand the storage reservoir chemistry and the statistical performance of the sole pressure or seismic monitoring, which could be integrated into a monitoring network, combining multiple monitoring techniques for CO2 leakage detection.
20
Ranson, William Wayne. "Adiabatic Effectiveness Measurements of Leakage Flows along the Hub Region of Gas Turbine Engines." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/77017.
Full textAbstract:
To prevent melting of turbine blades, numerous cooling schemes have been developed to cool the blades using cooler air from the compressor. Unfortunately, the clearance gap between adjacent hub sections allows coolant to leak into the hub region. Coolant flow also leaks into the hub region through gaps between individual stages. The results of a combined experimental and computational study of cooling along the hub of a first stage turbine blade caused by leakage flows are discussed in detail. Additionally, this study examines a novel cooling feature, called a microcircuit, which combines internal convective cooling with external film cooling.
For the experimental investigation, scaled up blades were tested in a low speed wind tunnel. Adiabatic effectiveness measurements were made with infrared thermography of the entire hub region for a range of leakage flow conditions. For the computations, a commercially available computational fluid dynamics (CFD) code, FLUENT 6.0, was used to simulate the various flows.
Results show that featherseal leakage flows provide small cooling benefits to the hub. Increases in featherseal flow provide no additional cooling to the hub region. Unlike the featherseal, leakage flows from the front rim provide ample cooling to the hub region, especially the leading edge of the blade passage. None of the leakage flows provide significant cooling to the pressure side region of the hub or trailing edge suction side. With the addition of the hub microcircuits, there is improved hub cooling of the suction side of the blades. Though the coolant exit uniformity was low and affected by the featherseal flow, the microcircuits were shown to provide more cooling along the hub region. Good agreements were observed between the computational and experimental results, though computations over-predicted front rim cooling and microcircuit uniformity.Master of Science
21
Hills, M. "Solid state sensors for gas monitoring and control." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604069.
Full textAbstract:
A probe for the continuous on-line measurement of hydrogen dissolved in liquid aluminium has been developed using the perovskite proton conductor CaZrO3-In, in conjunction with a Zr,ZrH2 solid state reference. The probe has been designed to an industrial prototype standard, and measurements were in good agreement with established (but cumbersome) hydrogen measurement methods such as the AISCAN analyser, LECO analysis, and the Straube-Pfeiffer technique. The electrolytic domain of CaZrO3-In has been investigated using a novel double-cell arrangement to simultaneously fix the chemical potential of both hydrogen and oxygen at the electrodes of a pellet of the electrolyte. As predicted from the defect equilibria, the electrolyte makes the transition from the hydrogen ion conduction domain to the oxygen ion domain under conditions of low oxygen partial pressure and high hydrogen partial pressure. The pO2 corresponding to the Zr,ZrO2 equilibrium is low enough to locate CaZrO3-In in the oxygen ion conduction domain. Sodium b-alumina was employed to measure the pO2 developed under operating conditions at the sensor reference electrode by a sample zirconium containing dissolved oxygen. This was found to be many orders of magnitude higher than the pO2 corresponding to the Zr,ZrO2 equilibrium, and was five magnitude higher than the pO2 marking the H+/O2- conduction domain boundary for CaZrO3-In, suggesting that Zr, ZrH2 may be suitable as a reference material. Hydrogen sensors manufactured using CaZrO3-In as the solid electrolyte and a Zr,ZrH2 solid state reference were found to provide stable, reproducible emfs at constant temperature and pH2, and showed full Nernstian response following a change in pH2 at the measuring electrode. The recently developed Current Reversal Mode can accurately determine the emf of a solid electrolyte sensor, and also provides additional information in the form of the sensor resistance. A detailed study has identified how the CRM parameters should be selected in order to make accurate measurements. The sensor resistance measurement was used to improve measurement accuracy and stability of an internally heated yttria stabilised zirconia oxygen sensor. When applied to a commercially available probe for measuring hydrogen dissolved in liquid aluminium it was found that erroneous emf readings, measured after prolonged use in the melt, were accompanied by a corresponding increase in the sensor resistance, opening up the possibility of using CRM as an on-line diagnostic tool.
22
Ratcliff, Paul Ronald. "Background rejection in gas detectors." Thesis, University of Leicester, 1988. http://hdl.handle.net/2381/35768.
Full textAbstract:
Investigations have been made on the minimisation of the background count rate detected in proportional counters, while maximising the signal detection efficiency. Two methods of background rejection have been developed, based on the time profile of the shaped detector pulses and on the lateral extent of the induced charge distribution on the cathode. Both these systems have proved highly efficient, and the former has been applied to a multiwire proportional chamber designed as a monitor for plutonium lung contamination, an application where high efficiency detection is critical. This instrument, which incorporates full six-sided "massless" guard cells, and utilises real-time data acquisition and handling by microcomputer, has been developed, optimised, and assessed as a possible competitor to the phoswich detectors in use at present and the solid state detectors under development. Results indicate that the counter is likely to offer no more than a marginal improvement in sensitivity, insufficient to justify its increased compexity and higher costs.
23
Xu, Jinming. "Effects of operating damage of labyrinth seal on seal leakage and wheelspace hot gas ingress." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5867.
Full textAbstract:
The labyrinth seal is widely used in turbomachinery to minimize or control
leakage between areas of different pressure. The present investigation numerically
explored the effect of damage and wear of the labyrinth seal on the turbomachinery
flow and temperature fields. Specifically, this work investigated: (1) the effect of rubgroove
downstream wall angle on seal leakage, (2) the effect of tooth bending damage
on the leakage, (3) the effect of tooth "ÃÂÃÂmushrooming"ÃÂÃÂ damage on seal leakage, and (4)
the effect of rub-groove axial position and wall angle on gas turbine ingress heating.
To facilitate grid generation, an unstructured grid generator named OpenCFD was
also developed. The grid generator is written in C++ and generates hybrid grids
consisting primarily of Cartesian cells.
This investigation of labyrinth seal damage and wear was conducted using the
Reynolds averaged Navier-Stokes equations (RANS) to simulate the flows. The high-
Reynolds k - Model and the standard wall function were used to model the turbulence.
STAR-CD was used to solve the equations, and the grids were generated using
the new code OpenCFD.
It was found that the damage and wear of the labyrinth seal have a significant
effect on the leakage and temperature field, as well as on the flow pattern. The
leakage increases significantly faster than the operating clearance increase from the
wear. Further, the specific seal configuration resulting from the damage and wear was found to be important. For example, for pure-bending cases, it was found that the
bending curvature and the percentage of tooth length that is bent are important, and
that the mushroom radius and tooth bending are important for the mushrooming
damage cases. When an abradable labyrinth seal was applied to a very large gas
turbine wheelspace cavity, it was found that the rub-groove axial position, and to
a smaller degree, rub-groove wall angle, alter the magnitude and distribution of the
fluid temperature.
24
Dagson, Josef, and Källström Samuel Nissilä. "Air Leakage Diagnosis in Heavy Duty Truck Engines with EGR and VGT." Thesis, Linköpings universitet, Fordonssystem, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-88183.
Full textAbstract:
Scania CV AB is a leading company within development and production of buses, trucks as well as industrial and marine engines. New environmental and safety legislations continuously demand higher quality from the products. An upcoming European legislation, Euro 6, implies that gas leakages from truck engines should be detected while driving. If the source of the leakage is not only detected, but also isolated, that is separated from other faults, the adjustments in the workshop goes faster since there is no need for leakage localisation. A faster reparation increases the up-time, i.e. the amount of time that the truck can be used. This master thesis work uses current methods developed at Scania for residual generation to perform model-based leakage diagnosis. In this work, measurements are gathered for dierent sensor faults and two leakages. The measurements are used to evaluate the actual performance of the resulting diagnosis system. The result, based on the residuals generated by the method, shows that leakages on the boost-side and the exhaust-side can be detected, and isolated from faults in the pressure sensors on the boost-side and the exhaust-side. The isolation of these four faults is considered the hardest to achieve among sensor faults and leakages why the full isolation performance is promising. Further measurements are needed to determine the full isolation performance of the diagnosis system. The resulting system is reasoned to be suitable for execution in real time on-board the truck.Scania CV AB är en ledande koncern inom utveckling och produktion av bussar, lastbilar samt industri- och marinmotorer. Nya lagkrav för miljö och säkerhet ställer ständigt högre krav på de tillverkade produkterna. Ett nära förestående lagkrav för lastbilar, Euro 6, innebär att gasläckage från motorn ska detekteras under körning. Om läckaget förutom att detekteras också kan isoleras, det vill säga särskiljas från andra fel, går reparationen i verkstaden snabbare då man slipper lokalisera läckaget. En snabbare reparation ökar up-time, det vill säga tiden som lastbilen kan användas på åkeriet. I detta exjobb används befintliga metoder för residualgenerering framtagna på Scania för att åstadkomma modelbaserad läckagediagnos. Arbetet tar även fram mätdata för olika givarfel samt för två läckage i motorn. Denna mätdata används för att utvärdera det erhållna diagnossystemets faktiska prestanda. Resultatet, som bygger på residualerna som metoden genererat, visar att läckage går att detektera, och att läckagen går att isolera från fel på tryckgivarsensorer på laddluftssidan och avgassidan. Denna isolering anses vara den svåraste att uppnå av alla sensorfel samt läckage varvid övrig isoleringsprestande verkar lovande. Däremot behövs mer mätdata för att säkert kunna fastställa övrig isoleringsprestanda. Diagnosmetoden lämpar sig troligen för exekvering i realtid ombord på lastbilen.
25
Sivret, Eric Claude Civil & Environmental Engineering Faculty of Engineering UNSW. "Off-gas Nitrous Oxide monitoring for nitrification aeration control." Publisher:University of New South Wales. Civil & Environmental Engineering, 2009. http://handle.unsw.edu.au/1959.4/43702.
Full textAbstract:
Effective control of nitrification processes employed at municipal wastewater treatment plants is essential for maintaining process reliability and minimizing environmental impacts and operating costs. While a range of process control strategies are available, they share a dependence on invasive liquid phase monitoring and are based on a periphery understanding of the metabolic status of the processes being controlled. Utilization of off-gas nitrous oxide (N2O) monitoring as a real-time indicator of the process metabolic status is a novel process control concept with the potential to address these concerns. This thesis details the development and evaluation of an off-gas N2O stress response based control technique. Examination of the stress response relationship demonstrated that it met the majority of the criteria of interest for process control. A simple feedback aeration control strategy was developed and evaluated through process simulation to determine the feasibility of implementation, cost effectiveness and associated environmental benefits. The off-gas N2O based control strategy provided better matching between aeration supply and metabolic demand, allowing the process to be maintained at the desired operating setpoints and avert nitrification failure. Performance was demonstrated to be similar to dissolved oxygen based feedback aeration control, although slightly more efficient at reduced dissolved oxygen concentrations. A technical, economic and environmental evaluation indicated that aeration control based on non-invasive off-gas N2O monitoring is technically feasible and has the potential to offer significant environmental and economic benefits including reductions in operating costs and process capital investment, as well as improved effluent compliance and reductions in emissions of gaseous pollutants including greenhouse gases. Overall, while off-gas N2O monitoring based aeration control techniques have the potential to provide significant economic and environmental benefits, a number of research questions remain to be answered. Future work in the form of long-term field trials is required to address these issues and allow quantification of economic and environmental benefits.
26
Kim, Man-Keun. "Economic investigation of discount factors for agricultural greenhouse gas emission offsets." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/2187.
Full textAbstract:
This dissertation analyzes the basis for and magnitudes of discount factors based on the characteristics of greenhouse gas emission (GHGE) offsets that are applied to the GHGE reduction projects, concentrating on agricultural projects. Theoretical approaches to discount factors, estimation and incorporation of discount factors procedures are developed. Discount factors would be imposed by credit purchasers due to noncompliance with regulatory program of the credits with GHG program including consideration of shortfall penalties and limited durations. Discount factors are proposed for (i) additionality, (ii) leakage, (iii) permanence, and (iv) uncertainty. Additionality arise when the region where an AO project is being proposed would have substantial adoption of the AO practice in the absence of GHG programs (business as usual GHGE offset). Leakage arises when the effect of a program is offset by an induced increase in economic activity and accompanying emissions elsewhere. The leakage effect depends on demand and supply elasticities. Permanence reflects the saturation and volatility characteristics of carbon sequestration. Carbon is stored in a volatile form and can be released quickly to the atmosphere when an AO practice is discontinued. The permanence discount depends on the project design including practice continuation after the program and the dynamic rate of offset. Also, consideration of multiple offsets is important. Uncertainty arises due to the stochastic nature of project quantity. The uncertainty discount tends to be smaller the larger the size of the offset contract due to aggregation over space and time. The magnitude of these discounts is investigated in Southeast Texas rice discontinuation study. The additionality and the leakage discounts are found to play an important role in case of rice lands conversion to other crops but less so for pasture conversions and yet less for forest conversions. The permanence discount is important when converting to other crops and short rotation forestry. When all discounts are considered, rice lands conversion to forest yields claimable credits amounting to 52.8% ~ 77.5% of the total offset. When converting rice lands to pasture, the claimable credits 45.1% ~ 64.2%, while a conversion of rice lands to other crops yields claimable credits 38.9% ~ 40.4%.
27
Seifert, Brent Alan. "Measurements versus predictions for rotordynamic coefficients and leakage rates for a novel hole-pattern gas seal." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4782.
Full textAbstract:
Results are presented for measured and predicted rotordynamic coefficients and
leakage for hole-pattern seals with a hole depth that varies axially along the seal.
Testing was done to discover how pressure ratio, inlet preswirl, and rotor speed affect
the sealsâ rotordynamic characteristics and leakage. The results were compared to a
constant hole depth hole-pattern seal.
Experimental results show that the sealsâ rotordynamic characteristics are not
strongly influenced by pressure ratio.
There were three preswirl conditions tested, each separated by a 6.9 bar (100
psi) difference in inlet pressure. Therefore, normalized preswirl results were compared.
The normalized results indicate that introducing inlet fluid preswirl affects the crosscoupled
stiffness and effective damping coefficients. Inlet preswirl increases the
magnitude of cross-coupled stiffness. Effective damping decreases with inlet preswirl,
as well as the effective damping cross-over frequency increasing. These results
indicate that swirl brakes would be of great value.
Rotor speed had a significant effect on the cross-coupled coefficients; both
increased with speed.
Experimental results were compared to results for a constant hole depth holepattern
seal. The variable hole-depth seal has higher direct damping. The crosscoupled
stiffness and cross-coupled damping coefficients were very similar. The direct
stiffness was always lower at lower frequencies and higher at higher frequencies for the
variable hole depth hole-pattern seal. This was also the case for effective stiffness.
The effective damping of the variable hole-depth seal was not only larger than for the constant hole depth seal, it also had a drastically lower cross-over frequency. The
difference in cross-over frequency was 40 percent on average.
Experimental results for rotordynamic characteristics and leakage were
compared to theoretical predictions by ISOTSEAL 2, a modified version of ISOTSEAL.
Both cross-coupled stiffness and damping are reasonably predicted. Direct damping is
always under-predicted. ISOTSEAL 2 does a poor job of predicting direct stiffness.
Direct stiffness is over-predicted at lower frequencies and under-predicted at higher
frequencies. This is also the case for effective stiffness. ISOTSEAL 2 under-predicts
the direct damping, but does an excellent job of predicting the direct damping crossover
frequency. Seal leakage is well predicted by ISOTSEAL 2.
28
Basirat, Farzad. "Process Models for CO2 Migration and Leakage : Gas Transport, Pore-Scale Displacement and Effects of Impurities." Doctoral thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-315490.
Full textAbstract:
Geological Carbon Storage (GCS) is considered as one of the key techniques to reduce the rate of atmospheric emissions of CO2 and thereby to contribute to controlling the global warming. A successful application of a GCS project requires the capability of the formation to trap CO2 for a long term. In this context, processes related to CO2 trapping and also possible leakage of CO2 to the near surface environment need to be understood. The overall aim of this thesis is to understand the flow and transport of CO2 through porous media in the context of geological storage of CO2. The entire range of scales, including the pore scale, the laboratory scale, the field experiment scale and the industrial scale of CO2 injection operation are addressed, and some of the key processes investigated by means of experiments and modeling. First, a numerical model and laboratory experimental setup were developed to investigate the CO2 gas flow, mimicking the system in the near-surface conditions in case a leak from the storage formation should occur. The system specifically addressed the coupled flow and mass transport of gaseous CO2 both in the porous domain as well as the free flow domain above it. The comparison of experiments and modelling results showed a very good agreement indicating that the model developed can be applied to evaluate monitoring and surface detection of potential CO2 leakage. Second, the field scale CO2 injection test carried out in a shallow aquifer in Maguelone, France was analyzed and modeled. The results showed that Monte Carlo simulations accounting for the heterogeneity effects of the permeability field did capture the key observations of the monitoring data, while a homogeneous model could not represent them. Third, a numerical model based on phase-field method was developed and model simulations carried out addressing the effect of wettability on CO2-brine displacement at the pore-scale. The results show that strongly water-wet reservoirs provide a better potential for the dissolution trapping, due to the increase of interface between CO2 and brine with very low contact angles. The results further showed that strong water-wet conditions also imply a strong capillary effect, which is important for residual trapping of CO2. Finally, numerical model development and model simulations were carried out to address the large scale geological storage of CO2 in the presence of impurity gases in the CO2 rich phase. The results showed that impurity gases N2 and CH4 affected the spatial distribution of the gas (the supercritical CO2 rich phase), and a larger volume of reservoir is needed in comparison to the pure CO2 injection scenario. In addition, the solubility trapping significantly increased in the presence of N2 and CH4.
29
Wingbrant, Helena. "Studies of MISiC-FET sensors for car exhaust gas monitoring." Doctoral thesis, Linköpings universitet, Tillämpad Fysik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-4674.
Full textAbstract:
The increasing size of the car fleet makes it important to find ways of lowering the amounts of pollutants from each individual diesel or gasoline engine to almost zero levels. The pollutants from these engines predominantly originate from emissions at cold start, in the case when gasoline is utilized, and high NOx emissions and particulates from diesel engines. The cold start emissions from gasoline vehicles are primarily due to a high light-off time for the catalytic converter. Another reason is the inability to quickly heat the sensor used for controlling the air-to-fuel ratio in the exhausts, also called the lambda value, which is required to be in a particular range for the catalytic converter to work properly. This problem may be solved utilizing another, more robust sensor for this purpose. One way of treating the high NOx levels from diesel engines is to introduce ammonia in the exhausts and let it react with the NOx in a special catalytic converter to form nitrogen gas and water, which is called SCR (selective catalytic reduction). However, in order to make this system reduce NOx efficiently enough for meeting future legislations, closed loop control is required. To realize this type of system an NOx or ammonia sensor is needed. This thesis presents the efforts made to test the SiC-based field effect sensor device both as a cold start lambda sensor for gasoline engines and as an NH3 sensor for SCR systems in diesel engines. The MISiC (metal insulator silicon carbide) lambda sensor has proven to be both sensitive and selective to lambda, and its properties have been studied in lambda stairs both in gasoline engine exhausts and in the laboratory. There is, however, a small cross-sensitivity to CO. The influence of metal gate restructuring on the linearity of the sensor has also been investigated. The metal tends to form islands by time, which decreases the catalytic activity and thereby gives the sensor, which is binary when fresh, a linear behavior. Successful attempts to prevent the restructuring through depositing a protective layer of insulator on top of the metal were made. The influence of increasing the catalytic activity in the measurement cell was also studied. It was concluded that the location of the binary switch point of MISiC lambda sensors could be moved towards the stoichiometric value if the consumption of gases in the measurement cell was increased. The MISiC NH3 sensor for SCR systems has been shown to be highly sensitive to ammonia both in laboratory and diesel engine measurements. The influence of other diesel exhaust gas components, such as NOx, water or N2O has been found to be low. In order to make the ammonia sensor more long-term stable experiments on samples with different types of co-sputtered Pt or Ir/SiO2 gas-sensitive layers were performed. These samples turned out to be sensitive to NH3 even though they were dense and NH3 detection normally requires porous films. The speed of response for both sensor types has been found to be fast enough for closed loop control in each application.On the day of the ublic defence of the doctoral thesis, the status of article IV was: accepted, article V was: submitted and article VII was: manuscript.
30
Honegger, Ueli. "Gas turbine combustion modeling for a Parametric Emissions Monitoring System." Thesis, Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/371.
Full text
31
Wingbrant, Helena. "Studies on MISiC-FET sensors for car exhaust gas monitoring /." Linköping : Univ, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-4674.
Full text
32
Pike, Andrew Charles. "Design of chemoresistive silicon sensors for application in gas monitoring." Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/36261/.
Full textAbstract:
The growing concerns over our exposure to hazardous substances have been addressed by stringent legislation to ensure air quality. A wide variety of applications have therefore arisen which require the reliable detection of hazardous gases. Hence, the motivation behind the research presented in this thesis was the aim of developing a portable gas monitor to detect nitrogen dioxide, carbon monoxide and volatile organic compounds (e.g. benzene, toluene). The need to improve gas sensor technology for suitability to this demanding application has been identified. Thus, the objectives were to develop a number of ultra-low power devices consisting of an array of chemoresistive gas sensors for incorporation into an intelligent sensor system. The operation of these sensors relies on the measurement of a change in resistance of a gas-sensitive material when exposed to specific gases. Silicon technology has been employed in order to obtain reproducible, miniaturised sensors with a low unit cost. Furthermore, chemoresistors employing metal oxide semiconductor (MOS), metal-substituted phthalocyanine (XPc) and conducting polymer (CP) materials have been used because of their sensitivity to the gases of interest. Common problems associated with these materials are poor specificity to a target gas and poor stability. However, the approach to minimising these problems was to design arrays of cross-sensitive chemoresistors for use in a microprocessor-based intelligent sensor system. The microprocessor applies a pattern recognition algorithm to the sensor outputs to extract the required information. This thesis describes the design, fabrication and characterisation of these sensor arrays. MOS and XPc materials have shown an optimum performance at elevated temperatures. Micromachining techniques have therefore been employed to integrate resistance heaters in a micro-hotplate structure, which can allow temperatures of 600°C to be attained in —15 ms with a typical power consumption of —150 mW/sensor. A pulsed mode of operation should provide average power consumptions of less than 1 mW. A low power consumption is critical for a portable batterypowered instrument. The design, modelling and characterisation of the micro-hotplate structures have also been described. The design and development of a novel automated gas sensor test system was also fundamental to this research, in order to accurately characterise sensor responses and to validate theoretical models. The research objectives have been fulfilled in that a number of sensor array devices have been produced, which are suitable for a portable intelligent instrument. The different designs and materials are compatible for integration into a hybrid sensor. The advancements achieved in sensor technology provide a foundation for future research into the production of a portable intelligent sensor system.
33
Köpke, Uwe Gerhard. "Condition monitoring of buried gas pipes using a vibrating PIG." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259460.
Full text
34
Day, Jonathan Christopher. "Numerical simulation of a microfabricated gas preconcentrator for environmental monitoring." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3290.
Full textAbstract:
Thesis (M.S.) -- University of Maryland, College Park, 2005.Thesis research directed by: Dept. of Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
35
Lee, Y. H. "Gas turbine engine health monitoring by fault pattern matching method." Thesis, Cranfield University, 1998. http://dspace.lib.cranfield.ac.uk/handle/1826/10714.
Full textAbstract:
The
gas turbine engine has a wide range of applications, these include industrial and
aerospace applications on locomotive, ferry, compressor and power generation, and
the most popular application will be for the air transportation. The application for air
transportation including military and commercial aircraft is highly sensitive to safety
concerns. The engine health monitoring system plays a major role for addressing this
concern, a good engine monitoring system will not only to provide immediate and
correct information to the engine user but also provide useful information for
managing the maintenance activities. Without a reliable performance diagnosis
module involved, there will be not possible to build a good health monitoring system.
There are many methodologies had been proposed and studied during past three
decades, and yet still struggling to search for some good techniques to handle
instrumentation errors. In order to develop a reliable engine performance diagnosis
technique, a fully understanding and proper handling of the instrumentation is
essential.
A engine performance fault pattern matching method has been proposed and
developed in this study, two fault libraries contains a complete defined set of 51963
faults was created by using a newly serviced fighter engine component data. This
pattern matching system had been verified by different approaches, such as compares
with linear and nonlinear diagnosis results and compares with performance sensitivity
analysis results by using LTF program engine data. The outcomes from the
verications indicate an encouraging result for further exploring this method.
In
conclusion, this research has not only propose a feasible performance diagnosis
techniques, but also developed and verified through different kind of approaches for
this techniques. In addition to that, by proper manipulating the created fault library, a
possible new tool for analyzing the application of instruments' implementation was
discovered. The author believes there will be more to study by using this created fault
pattern library. For instance, this fault pattern library can be treated as a very good
initial training sets for neural networking to develop a neural diagnosis technique.
This study has put a new milestone for further exploring gas turbine diagnosis
technique by using fault pattern related methods.
36
Lynch, Stephen P. "Endwall Heat Transfer and Shear Stress for a Nozzle Guide Vane with Fillets and a Leakage Interface." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31912.
Full textAbstract:
Increasing the combustion temperatures in a gas turbine engine to achieve higher efficiency and power output also results in high heat loads to turbine components downstream of the combustor. The challenge of adequately cooling the nozzle guide vane directly downstream of the combustor is compounded by a complex vortical secondary flow at the junction of the endwall and the airfoil. This flow tends to increase local heat transfer rates and sweep coolant away from component surfaces, as well as decrease the turbine aerodynamic efficiency. Past research has shown that a large fillet at the endwall-airfoil junction can reduce or eliminate the secondary flow. Also, leakage flow from the interface gap between the combustor and the turbine can provide some cooling to the endwall. This study examines the individual and combined effects of a large fillet and realistic combustor-turbine interface gap leakage flow for a nozzle guide vane. The first study focuses on the effect of leakage flow from the interface gap on the endwall upstream of the vane. The second study addresses the influence of large fillets at the endwall-airfoil junction, with and without upstream leakage flow. Both studies were performed in a large low-speed wind tunnel with the same vane geometry. Endwall shear stress measurements were obtained for various endwall-airfoil junction geometries without upstream leakage flow. Endwall heat transfer and cooling effectiveness were measured for various leakage flow rates and leakage gap widths, with a variety of endwall-airfoil junction geometries.
Results from these studies indicate that the secondary flow has a large influence on the coverage area of the leakage coolant. Increased leakage flow rates resulted in better cooling effectiveness and coverage, but also higher heat transfer rates. The two fillet geometries tested affected coolant coverage by displacing coolant around the base of the fillet, which could result in undesirably high gradients in endwall temperature. The addition of a large fillet to the endwall-airfoil junction, however, reduced heat transfer, even when upstream leakage flow was present.
Master of Science
37
Meyer, Eric Todd. "Evaluation of exhaust flowrate measurement techniques for a mobile emissions monitoring system." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1855.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains xii, 89 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 67-68).
38
Addali, Abdulmajid. "Monitoring Gas Void Fraction In Two-Phase Flow With Acoustic Emission." Thesis, Cranfield University, 2010. http://hdl.handle.net/1826/4475.
Full textAbstract:
The two-phase gas/liquid flow phenomenon can be encountered over a range of gas and liquid flow rates in the chemical engineering industry, particularly in oil and gas production transportation pipelines. Monitoring and measurement of their characteristics, such as the gas void fraction, are necessary to minimise the disruption of downstream process facilities. Thus, over the last decade, the investigation, development and use of multiphase flow metering system have been a major focus for the industry worldwide. However, these meters suffer from several limitations in some flow conditions such as Slug flow regime.
This research presents experimental results correlating Acoustic Emission measurements with Gas Void Fraction (GVF) in a two-phase air / water flow. A unique experimental facility was modified to accommodate an investigation into the applicability of the Acoustic Emission (AE) technology in monitoring two-phase gas\liquid flow. The testing facility allowed for investigations over a range of superficial liquid velocities (0.3 to 2.0 ms-1) and superficial gas velocities (0.2 to 1.4 ms-1). The influence of several variables such as temperature, viscosity and surface roughness were also investigated. Measurements of AE for varying gas void fractions were compared to conductive probe measurements and results showed a direct correlation between the AE energy and the gas void fraction.
It is concluded that the GVF can be determined by measurement of Acoustic Emission and this forms the major contribution of this thesis.
39
Davison, Craig Robin. "Model based prognostic health monitoring techniques for small gas turbine engines." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0009/MQ52890.pdf.
Full text
40
Falahat, Reza. "Quantitative monitoring of gas injection, exsolution and dissolution using 4D seismic." Thesis, Heriot-Watt University, 2012. http://hdl.handle.net/10399/2559.
Full textAbstract:
The main concern in the monitoring of gas injection, exsolution and dissolution is the exact spatial distribution of the gas volumes in the subsurface. In principle, this concern is addressed by the use of 4D seismic data. However, it is recognised that the seismic response still largely provides a qualitative estimate of the moved subsurface fluids; exact quantitative evaluation of fluid distributions and associated saturations remains a challenge still to be solved. It is widely believed that a few percent of gas makes the pore fluid mixture very compressible, so that it cannot be distinguished from a more complete gas saturation using seismic techniques. However, because of the fact that a gas distribution viewed at the reservoir scale is distinctly different from that observed at the laboratory scale, conclusions from laboratory measurements may not, in fact, be wholly applicable. Indeed, it is found in this study that the main factor controlling the seismic response is gas thickness, whilst gas saturation per se remains approximately constant. Modelling studies show that, for thin reservoirs (less than tuning thickness), both timeshift and amplitude change attributes have a linear trend with gas volume. In theory, this conclusion does not apply to thick reservoirs, as the amplitude change then becomes non-linear. However, because thick reservoirs are normally combinations of intra reservoir sand and shale, it is anticipated that a linear amplitude response can still be expected in most reservoirs. Reservoir heterogeneity is observed to affect these results by less than 2%. In the modeling, a spurious deviation from linearity is evident with increasing simulation model cell size (especially the vertical dimension). The understanding above is applied to both timeshift and amplitude change attributes in a North Sea gas injection field. Here, seismic scale calibration coefficients are obtained by a volumetric method which aims to calculate gas volume maps using the 4D seismic attributes. The work reveals that the results from the two mapped attributes appear reasonably close but still have regions of disparity. Synthetic data based on the reservoir model and further analysis of the observed data have been able to replicate some of these differences and identify them as due to inter-layer wave interferences and 4D noise. Similar findings to the above also apply to gas exsolution, in which gas migrates after arriving at the critical gas saturation, and establishes two specific gas saturations in the ii reservoir: maximum gas saturation within the gas cap and critical or minimum gas saturation within the oil leg. On the other hand, for the reverse process, in which reservoir pressure builds up, it is noted that it is not only the fluid type that impacts the gas when it goes back into solution, but also other reservoir properties such as relative permeability curves, transmissibility, Kv/Kh, and the injection/production plan. The laboratory-proposed equations for calculation of solution gas oil ratio (Rs) and pressure dependency of the fluid and rock are found to be not directly valid in cases in which the reservoir pressure drops below the bubble point pressure. In this situation, gas evolves, migrates and alters the pressure dependency of the saturated rock and solution gas oil ratio. A compositional change of the gas and oil is found to occur with pressure drop. However, it is observed to have a negligible impact on the seismic domain. Finally, importance is drawn to the role of engineering principles when interpreting dynamic reservoir changes from 4D seismic data. In particular, it is found that, in clastic reservoirs, the principal parameters controlling mapped 4D signatures are not the pressure and saturation changes per se, but these changes scaled by the corresponding thickness (or pore volume) of the reservoir volume that these effects occupy. This understanding is validated both with numerical modelling and analytic calculation. This provides a basis for a linear equation that can readily and accurately be used to invert for pressure and saturation changes. The observed seismic data are then inverted for pressure and saturation changes using the principles above. The results show that the simulator does appear to predict the inverted seismic observations fairly accurately. However, there are also some noticeable differences which require some specific updates to the transmissibility multipliers (and hence barriers) and the net-to-gross distribution in the simulation model. This project reveals the ability of 4D seismic to quantitatively monitor the gas injection and exsolution, and highlights the fact that laboratory measures are not directly applicable at the reservoir scale. It can be concluded that the impact of the reservoir scale phenomena needs to be taken into account during time-lapse seismic interpretations.
41
Williams, D. "Exhaust gas ionization sensors for spark ignition engine control and monitoring." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371264.
Full text
42
McIntyre, Andrew D. "A study of NOâ†x monitoring using membrane amperometric gas sensors." Thesis, University of Strathclyde, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249766.
Full text
43
Davis, Nicholas Mark. "Mid-infrared spectroscopic instrumentation for airborne monitoring of atmospheric gas species." Thesis, Cranfield University, 2018. http://dspace.lib.cranfield.ac.uk/handle/1826/13506.
Full textAbstract:
Methane is a colourless, odourless gas that can be found extensively in nature. The average global concentration of methane is currently approximately 1.8ppm, the highest concentration for over 800,000 years. Although this concentration is signi cantly lower than that of CO2 (391ppm), methane has a global warming potential up to 34 times greater over a hundred year period. As a result, trace detection of atmospheric methane has gained increased attention as a form of environmental protection. The purpose of this thesis is to undertake investigations into the development of instrumentation to make observations of background levels of atmospheric methane. Newly available wavelength sources along with alternative gas cells are investigated for potential use in this instrument. Laboratory analysis of a new external cavity Bragg-stabilised laser (ECBSL) operating at 1651nm was performed, with comparisons made against against a bre-coupled distributed feedback (DFB) laser diode. The ECBSL showed promise for use in the detection of methane in the laboratory, with a limit of detection of 8ppm using a 25cm pathlength single-pass gas cell being comparable to that of the DFB laser diode. Issues with alignment stability were however observed with this laser, limiting the measurements that could be made and restricting its use outside of laboratory conditions, with utilisation on light aircraft deemed to be impossible in its current con guration. Investigations were then performed into the performance of a newly available interband cascade laser (ICL), with emission at 3311nm. A full characterisation of the ICL was performed, alongside measurements of methane using both a 25cm pathlength single-pass cell and an integrating sphere with e ective pathlength of 54.5cm, with single-point limits of detection of 2.2ppm and 1.0ppm being determined respectively. A combination of an Allan variance and absorption line- tting techniques were utilised to improve the limit of detection using the integrating sphere, resulting in a 0.3ppm limit of detection for a 25 second average. The design and development of instrumentation to perform measurements of background concentrations of atmospheric methane utilising the combination of ICL and integrating sphere is then described. The reasoning behind the selection of components and progression of the instrument design is described. Once assembled, laboratory testing of the instrument showed a single-point limit of detection of 1.6ppm, higher than that seen with the previous set-up, however this was still below the background methane concentration. An initial shakedow flight was carried out once the instrument had been certi ed and installed in the aircraft. Due to failures of two electrical components, further flight testing was postponed until improvements to component isolation have been made. This flight demonstrated, however, that the instrument has the potential to provide measurements of atmospheric methane, as the majority of components operated as expected, including both the laser and the cell optics.
44
Dowker, Kenneth Paul. "Long period fibre grating as gas sensor for environmental pollution monitoring." Thesis, Sheffield Hallam University, 2003. http://shura.shu.ac.uk/19578/.
Full textAbstract:
The principle objective of the work presented in this thesis is to investigate and demonstrate the possibility of utilising the inherent properties of long-period gratings (LPGs) to detect the existence and concentration of a given gas in the region immediately surrounding the fibre cladding. The principle and the viability of using LPGs for sensor applications is supported by the preliminary results reported here. However, the sensitivity of the sensor requires further improvement before it can in any way challenge the existing sensors in this field. The operational characteristics and limitations of existing optical sensors are reviewed and the advantages of a LPG based optical sensor highlighted. Thorough explanations of the theory and principles of light propagation, mode formation, and mode coupling in optical fibres are presented. Computer simulations predicting the optical effects due to changes in ambient indices from theoretical conditions are successfully derived, confirming the results obtained by experimental investigation. Various established coating methods are investigated and utilised in the application of optically sensitive compounds adsorbed onto the cladding with different levels of success, the poly-electrolyte self assembly (PESA) and evaporation methods proving most suitable. A novel method of monitoring the build up of PESA layers in-situ using surface plasmon resonance (SPR) methods is introduced. The coating chemicals used in this investigation showed some optical sensitivity at the optimum wavelengths used in optical fibres to the various gases being monitored, in most cases causing a detectable change in the optical characteristics of the modes in the LPG.This study has shown the possibility of using a suitably prepared LPG as a gas sensor. The LPG is coated with a chemical whose refractive index is changed by absorption of a given gas and thus the change in the coupling wavelengths being caused by the existence of the gas. Maximum shifts in coupling wavelength of +/-1.5 nm for relatively high gas concentrations are observed. The possibility of using a coating material which absorbs water, or surrounding the LPG with a suitable liquid is also demonstrated, the refractive index of the coating or liquid and thus the coupling wavelength shift being affected by the reaction of the gas. The possibility of using a single temperature immune LPG for ambient index sensing by observing different coupling wavelengths in the same grating is also reported.
45
Badmaarag, Ulzii-Orshikh. "Optical Chemical Sensing Device for In-situ Non-Invasive Gas Monitoring." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1583155117533193.
Full text
46
Maolod, Rizgar Rassul. "The use of microseismic monitoring as a guide for gas production." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15676/.
Full textAbstract:
Numerical modelling makes it possible to consider studying microseismic events resulted from hydraulic fracturing through a synthetic model, too give us rational understandings for generation of the events and the efficiency of the fracturing process itself. The research presented in this thesis uses Discrete Element Method (DEM) approach to simulate the acoustic emissions within rock samples in order to achieve the computational modelling of the micro seismic events during hydraulic fracturing process. In terms of its relation to the fracture properties and its uses in determining the successfulness of the fracturing operation. (DEM), is used in three dimensions to create model to simulate the acoustic emission from a rock sample under stress and from an injection tests on two rock sample too. The model modifies a method that was originally developed before. The developed model was validated by comparing with the results from an experiment on Springwell sandstone under a triaxial stresses. In addition, comparison with two injection tests was performed. The program is further improved using a novel changing combination factor of event to enhance the modelling results, and to expand the application of the microseismic monitoring. The developed model offers control on the number of seismic events and the statistical distribution of the events. In addition, the source of the event predictions were similar to the real one which can lead to realistic prediction regarding the type of fracture. Furthermore, it was possible to extend the program application to predict the pore collapse sources of the acoustic emissions and the aperture of the resulted fractures. In addition, the model can predict the aperture of the fractures and the expected permeability of the fractured model. The validated model could therefore help to assess the effectiveness of a hydraulic fracturing project.
47
Pandoščák, Michal. "Monitoring a analýza uživatelů systémem DLP." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2011. http://www.nusl.cz/ntk/nusl-236966.
Full textAbstract:
The purpose of this masters thesis is to study issues of monitoring and analysis of users using DLP (Data Loss Prevention) system, the definition of internal and external attacks, the description of the main parts of the DLP system, managing of politic, monitoring user activities and classifying the data content. This paper explains the difference between contextual and content analysis and describes their techniques. It shows the fundamentals of network and endpoint monitoring and describes the process and users activities which may cause a data leakage. Lastly, we have developed endpoint protection agent who serves to the monitoring activities at a terminal station.
48
Sousa, Elisangela Orlandi de. "Detecção de vazamentos em tubulações atraves de metodo acustico e da analise de transientes de pressão." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266157.
Full textAbstract:
Orientador: Sandra Lucia da CruzDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-08T04:57:11Z (GMT). No. of bitstreams: 1 Sousa_ElisangelaOrlandide_M.pdf: 2598884 bytes, checksum: 7421959dcef02a5096290563b5f4500e (MD5) Previous issue date: 2007
Resumo: Redes de tubulação são sistemas complexos de dutos utilizados no transporte de fluidos a longas distâncias. Um pequeno vazamento em uma tubulação pode provocar grandes perdas de produtos e sérios danos ao meio ambiente até serem detectados. Com o propósito de prevenir vazamentos em tubulações, várias técnicas são relatadas na literatura. Este trabalho descreve o desenvolvimento e teste de uma técnica de detecção de vazamento de gás em tubulação baseada no método acústico e na análise de transientes de pressão gerados a partir do vazamento. Transientes de pressão e o ruído sonoro gerado pelo vazamento foram detectados e analisados em uma tubulação operando sem e com escoamento contínuo de gás (ar) em várias condições de operação. O trabalho experimental utilizou um vazo de pressão de 34,5 litros e uma tubulação com 60 m de comprimento e ½¿ de diâmetro. A pressão de operação variou de 2 a 7 kgf/cm2. Vazamentos de várias magnitudes foram simulados através de um orifício localizado na tubulação cujo diâmetro variou entre 0,4 mm a 5 mm. O microfone e o transdutor de pressão foram instalados no vaso de pressão ou na tubulação para detectar a ocorrência de vazamento, ambos conectados a um computador PC através de um conversor ADA. O sinal gerado pelo microfone foi amplificado e passou por um banco de filtros passa faixa sendo transformado em três sinais com amplitudes independentes, cada uma com uma faixa de freqüência específica de 1kHz, 5kHz e 9kHz. O programa de aquisição de dados foi escrito em linguagem C para ler e processar os dados. Os resultados experimentais mostraram que é possível detectar vazamentos em tubulações através do método acústico. A análise dos sinais de amplitude para freqüências diferentes mostrou que o ruído sonoro gerado pelo vazamento depende da magnitude do vazamento e da pressão na tubulação. Em todos os experimentos a ocorrência de vazamento foi prontamente detectada pelo microfone enquanto as mudanças nos perfis de transientes de pressão não eram sempre significativas para detectar o vazamento
Abstract: Pipeline networks are complex systems of ducts used in the fluid transportation through long distances. Even small leaks in a pipeline can lead to great losses of product and serious damages to the environment before it could be detected. With the purpose of preventing leakage in pipelines, various techniques have been reported in the literature. This work describes the development and test of a gas leak detection technique in pipelines based on an acoustic method and on the analysis of pressure transients generated by the leak. Pressure transients and the noise generated by leakage have been detected and analysed in a pipeline operating with and without continuous flow of gas (air) under various operation conditions. The experimental setup made use of a 34,5 liters pressure vessel and a 60 m long, ½¿ in diameter pipeline. The operational pressure varied from 2 to 7 kgf/cm². Leakages of various magnitudes were simulated through an orifice located in pipeline whose diameter varied from 0,4 mm to 5,0 mm. A microphone and a pressure transducer were installed either in the pressure vessel or in the pipeline to detect leak occurrence, both being connected to a PC computer through an ADA converter. The signal generated by the microphone was amplified and also passed through a bank of band pass filters being transformed into three signals with independent amplitude, each one with a band of specific frequency of 1 kHz, 5 kHz and 9 kHz. The data acquisition software was written in C language to read and process all data. The experimental results showed that it is possible to detect leaks in pipelines based on acoustic method. The analysis of the signal amplitude for different frequencies showed that the noise signal generated by leakage depend on both leak magnitude and pressure in the pipeline. In all experiments leak occurrence was readily detected by the microphone while the changes in pressure transient profiles were not always significant to detect the leak
Mestrado
Sistemas de Processos Quimicos e Informatica
Mestre em Engenharia Química
49
Van, Der Velde Alvarez Daniel Eduardo. "Test versus predictions for rotordynamic and leakage characteristics of a convergent-tapered, honeycomb-stator/smooth-rotor annular gas seal." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1156.
Full text
50
Wu, Bingbing. "Ensuring Respiratory Protection through Respirator Fit Testing and Real-Time Monitoring." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535374058309808.
Full text