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Weldhagen, Gerhard Frederick. "Laboratory Detection and Gene Cassette Stability of the Novel Extended-Spectrum Beta-Lactamase, GES-2 from Pseudomonas aeruginosa." Thesis, University of Pretoria, 2004. http://hdl.handle.net/2263/29221.
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Extended-spectrum beta-lactamases (ESBLs) in Pseudomonas aeruginosa tend to be geographically scattered, such as GES-2, which partially compromises the efficacy of imipenem. The G170N mutation, ascribed to a CC to AA base pair substitution on positions 493-494 of the blaGES-2 coding region, distinguishes this ESBL from blaGES-1 and the blaIBC-type genes, making it an ideal target for developing a novel sequence-specific, peptide nucleic acid (PNA)-based, multiplex-PCR detection method. Utilizing two primer pairs in conjunction with a PNA probe, this novel method delivered accurate identification of blaGES-2 compared to standard PCR and gene sequencing techniques, when tested against one hundred (n = 100) P. aeruginosa clinical isolates as well as previously published, well-described control strains. This method has the potential to be used in large-scale, cost-effective screening programmes for specific or geographically restricted ESBLs. To date, in addition to being only described in South Africa, GES-2 is notoriously difficult to identify in P. aeruginosa, using standard methodology. A real-time PCR method using the LightCycler™ was compared to a two-step nested-PCR assay for the detection of blaGES and blaIBC genes from one hundred P. aeruginosa clinical isolates collected over a four-year period from two teaching hospitals in Pretoria, South Africa. Real-time PCR amplification was monitored through hybridisation of fluorescently labelled probes followed by melting curve analysis to detect the relevant G170N mutation occurring in the omega loop region of blaGES-2. Nested-PCR products were subjected to automated DNA sequencing and compared to melting point (Tm) analyses results obtained from the LightCycler assay. Real time and nested-PCR assays detected a blaIBC gene product from 83 and 88 clinical isolates respectively, with the LightCycler thus exhibiting a sensitivity of 94.3% compared to the nested-PCR assay. Comparison of Tm and gene sequencing data however revealed 100% specificity for sequence specific detection of blaGES-2 with the LightCycler. One clinical isolate was found to harbour a blaGES-1 gene, making this the first report of this specific ESBL from South Africa. Selective antibiotic pressure has recently been implicated as a possible driving force behind point mutations observed in blaGES–type genes. This part of the study subjected two well-characterized clinical isolates with class 1 integron-borne blaGES-type genes to five days incubation in the presence of sub-inhibitory concentrations of 15 different antibiotics, including beta-lactams, aminoglycosides and quinolones. Restriction enzyme analysis and DNA sequencing of blaGES-1, blaGES-2 and their immediate upstream genetic environments failed to demonstrate any changes compared to non-exposed controls. Short-term exposure to a sub-inhibitory level of a single antimicrobial agent is thus unlikely to select significant mutations in these beta-lactamase genes or their regulatory mechanisms.Thesis (PhD (Medical Microbiology))--University of Pretoria, 2006.
Medical Microbiology
unrestricted
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Ruiz, Leonardo Guizilini Plazas [UNESP]. "Resistência aos beta-lactâmicos e detecção dos genes blashv, blatem, blactx-m e blages em Enterobacteriaceae isoladas de efluentes hospitar e comunitário em um município do noroeste paulista." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/94851.
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ruiz_lgp_me_sjrp.pdf: 1611382 bytes, checksum: e9dd037c5c8d3c485f14ae8a1628ab2e (MD5)As Enterobacteriaceae constituem um importante grupo de patógenos humanos, causadores de infecções hospitalares e comunitárias. Nestas bactérias, a produção de beta-lactamases de espectro estendido (ESBL) é um dos principais mecanismos de resistência aos antibióticos, e responsável pela falha da terapia antimicrobiana. Enterobactérias resistentes a antibióticos são encontradas em águas superficiais e apresentam alta prevalência em águas servidas, inclusive pós-tratamento. Esta realidade caracteriza-se como um importante problema de saúde pública, pois estes ambientes atuam como reservatórios de patógenos humanos e de genes de resistência que se disseminam horizontalmente. Crescentes evidências mostram a relação entre a disseminação ambiental de bactérias resistentes e genes de resistência e a evolução da resistência em bactérias de importância clínica. Este estudo investigou a diversidade de enterobactérias produtoras de ESBL e a presença dos genes blaSHV, blaTEM, blaCTX-M e blaGES em amostras de água coletadas de efluentes hospitalar e comunitário em um município localizado na região noroeste do estado de São Paulo. Genes de resistência foram detectados em várias espécies de Enterobacteriaceae apresentando resistência a diversas classes de antimicrobianos. Estes dados indicam a necessidade de adoção de medidas para o controle da disseminação de bactérias resistentes a antimicrobianos e seus genes no meio ambiente.
The Enterobacteriaceae constitutes an important group of human patogens, causing of hospital and communitarian infections. In these bacteria, the production of extended spectrum beta-lactamases (ESBL) is one of the main mechanisms of resistance the antibiotics, responsible for the imperfection of the therapy against infections for gram-negative bacilli. Enterobacteria resistant the antibiotics are found in superficial waters and present high prevalence in served waters, also post-cure. This reality is characterized as an important problem of public health, therefore these environments act as reservoirs of human patogens and genes of resistance that if spread through horizontal transmission. Increasing evidences show the relation between the ambient dissemination of resistant bacteria and genes of resistance and the evolution of the resistance in bacteria of clinical importance. This study it investigated the diversity of producing Enterobacteria of ESBL and the presence of the genes blaSHV, blaTEM, blaCTX-M and blaGES in water samples collected in the system of sewers in a city located in the region the northwest of the state of São Paulo. The respective genes of resistance had been detected in several strains producing of ESBL presenting profile of multiple resistant to the diverse antimicrobials groups, suggesting the necessity of the surveillance and the adoption of measures for the control of the dissemination of the genes of resistance in the environment.
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Ruiz, Leonardo Guizilini Plazas. ""Resistência aos beta-lactâmicos e detecção dos genes blashv, blatem, blactx-m e blages em Enterobacteriaceae isoladas de efluentes hospitar e comunitário em um município do noroeste paulista" /." São José do Rio Preto : [s.n.], 2010. http://hdl.handle.net/11449/94851.
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Orientador: Mara Corrêa Lelles NogueiraBanca: Doroti de Oliveira Garcia
Banca: Fátima Pereira de Souza
Resumo: As Enterobacteriaceae constituem um importante grupo de patógenos humanos, causadores de infecções hospitalares e comunitárias. Nestas bactérias, a produção de beta-lactamases de espectro estendido (ESBL) é um dos principais mecanismos de resistência aos antibióticos, e responsável pela falha da terapia antimicrobiana. Enterobactérias resistentes a antibióticos são encontradas em águas superficiais e apresentam alta prevalência em águas servidas, inclusive pós-tratamento. Esta realidade caracteriza-se como um importante problema de saúde pública, pois estes ambientes atuam como reservatórios de patógenos humanos e de genes de resistência que se disseminam horizontalmente. Crescentes evidências mostram a relação entre a disseminação ambiental de bactérias resistentes e genes de resistência e a evolução da resistência em bactérias de importância clínica. Este estudo investigou a diversidade de enterobactérias produtoras de ESBL e a presença dos genes blaSHV, blaTEM, blaCTX-M e blaGES em amostras de água coletadas de efluentes hospitalar e comunitário em um município localizado na região noroeste do estado de São Paulo. Genes de resistência foram detectados em várias espécies de Enterobacteriaceae apresentando resistência a diversas classes de antimicrobianos. Estes dados indicam a necessidade de adoção de medidas para o controle da disseminação de bactérias resistentes a antimicrobianos e seus genes no meio ambiente.
Abstract: The Enterobacteriaceae constitutes an important group of human patogens, causing of hospital and communitarian infections. In these bacteria, the production of extended spectrum beta-lactamases (ESBL) is one of the main mechanisms of resistance the antibiotics, responsible for the imperfection of the therapy against infections for gram-negative bacilli. Enterobacteria resistant the antibiotics are found in superficial waters and present high prevalence in served waters, also post-cure. This reality is characterized as an important problem of public health, therefore these environments act as reservoirs of human patogens and genes of resistance that if spread through horizontal transmission. Increasing evidences show the relation between the ambient dissemination of resistant bacteria and genes of resistance and the evolution of the resistance in bacteria of clinical importance. This study it investigated the diversity of producing Enterobacteria of ESBL and the presence of the genes blaSHV, blaTEM, blaCTX-M and blaGES in water samples collected in the system of sewers in a city located in the region the northwest of the state of São Paulo. The respective genes of resistance had been detected in several strains producing of ESBL presenting profile of multiple resistant to the diverse antimicrobials groups, suggesting the necessity of the surveillance and the adoption of measures for the control of the dissemination of the genes of resistance in the environment.
Mestre
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Braga, Jisbaque Melo. "Prevalência e sensibilidade antimicrobiana de escherichia coli e klebsiella pneumoniae isoladas de infecções nosocomiais no hospital regional norte em sobral/ce e detecção genética de blatem, blashv blactx-m e blages em espécimes produtores de betalactamase de espectro estendido (esbl)." reponame:Repositório Institucional da UFC, 2016. http://www.repositorio.ufc.br/handle/riufc/22878.
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BRAGA, J.M. Prevalência e sensibilidade antimicrobiana de escherichia coli e
klebsiella pneumoniae isoladas de infecções nosocomiais no hospital
regional norte em sobral/ce e detecção genética de blatem, blashv
blactx-m e blages em espécimes produtores de betalactamase de
espectro estendido (esbl). 2016. 101f. Dissertação (Mestrado em Ciências da Saúde) – Campus de Sobral, Universidade Federal do Ceará, Sobral, 2016.Submitted by Mestrado Ciências da Saúde (ppgcsufcsobral@gmail.com) on 2017-05-25T14:15:01Z No. of bitstreams: 1 2016_dis_jmbraga.pdf: 4368780 bytes, checksum: f1881d9ef6d76e8cb665b910b9dcd076 (MD5)
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Escherichia coli and Klebsiella pneumoniae are Gram-negative bacilli account for a significant portion of infections in hospitals. Its importance has increased due to increased production of beta-lactamases of extended spectrum (ESBL). These enzymes are produced by some Gram negative bacilli and mediate resistance to beta-lactams, such as cephalosporins and aztreonam. In these pathogens, the majority of the ESBL identified are TEM, SHV and CTX-M types. This study aimed to analyze the prevalence and antimicrobial susceptibility of E. coli and K. pneumoniae isolated from nosocomial infections in North Regional Hospital in Sobral/CE, Brazil, from March 2015 to March 2016, and to detect blaTEM, blaSHV, blaCTX-M, blaKPC, blaVIM and blaGES genes of isolates which exhibited ESBL phenotype. A total of 245 isolates (132 E. coli and 113 K. pneumoniae) were analyzed. Of these, 145 (59.1%) had ESBL phenotype and 44 were characterized genetically by presence of blaTEM, blaSHV, blaCTX-M, blaKPC, blaVIM and blaGES genes. The rates of E.coli and Klebsiella pneumoniae ESBL producers were 49.2% and 70.8%, respectively. This research revealed that ESBL-producing E. coli strains were more sensitive to meropenem (100%), amikacin (96.9%), colistin (90.8%) and tigecycline (90.8%), and more resistant to ampicillin (100%), ceftriaxone (100%) and cefepime (96.9%). On the other hand, K. pneumoniae ESBL producers were more sensitive to colistin (100%), amikacin (96.2%) and meropenem (93.7%), and more resistant to ceftriaxone (100%), ceftazidime (100%), cefepime (98.7%) and ampicillin (98.7%). The blaCTX-M gene was detected in 14 (31.8%) isolates, blaTEM and blaSHV genes were detected both in 3 specimens (6.8%), the blaGES gene was detected in only one isolate (2.2%), while blaKPC and blaVIM genes were not detected. Our findings show high levels of resistance to beta-lactam antibiotics, as well as increasing linear trend for ESBL production by the studied species. The gene with the highest detection rates among the isolates was blaCTX-M gene, which is certainly the most important ESBL gene today. We detected one strain of Klebsiella pneumoniae harboring blaGES and blaCTX-M genes, being of our knowledge the first report in Brazil, which demonstrates the great potential for worldwide spread of resistance genes between Gram-negative bacillus.
Escherichia coli e Klebsiella pneumoniae são bacilos Gram-negativos responsáveis por uma parcela significante de infecções em ambiente hospitalar. Sua importância aumentou devido ao surgimento de espécimes produtoras de betalactamases de espectro estendido (ESBL). Essas enzimas são produzidas por alguns bacilos Gram-negativos e conferem resistência aos betalactâmicos, como cefalosporinas e aztreonam. Nesses patógenos, a maioria das ESBL identificadas é do tipo TEM, SHV e CTX-M. Este estudo teve como objetivo analisar a prevalência e a sensibilidade antimicrobiana de E.coli e K. pneumoniae isoladas de infecções nosocomiais do Hospital Regional Norte, Sobral/CE, Brasil no período de março de 2015 a março de 2016, assim como realizar a detecção dos genes blaTEM, blaSHV, blaCTX-M, blaKPC, blaVIM e blaGES nos isolados que exibiram fenótipo ESBL. No total, 245 isolados (132 E. coli e 113 K. pneumoniae) foram analisados. Destes, 145 (59,1%) apresentaram fenótipo ESBL e 44 foram caracterizados geneticamente quanto à detecção dos genes blaTEM, blaSHV, blaCTX-M, blaKPC, blaVIM e blaGES. As taxas de produção de ESBL por E.coli e K. pneumoniae foram 49,2% e 70,8%, respectivamente. Essa pesquisa revelou que E.coli produtoras de ESBL foram mais sensíveis ao meropenem (100%), amicacina (96,9%), colistina (90,8%) e tigeciclina (90,8%), e mais resistentes à ampicilina (100%), ceftriaxona (100%) e cefepima (96,9%). Já K. pneumoniae produtoras de ESBL foram mais sensíveis à colistina (100%), amicacina (96,2%) e meropenem (93,7%), e mais resistentes à ceftriaxona (100%), ceftazidima (100%), cefepima (98,7%) e ampicilina (98,7%). O gene blaCTX-M foi detectado em 12 (27,2%) isolados, os genes blaTEM e blaSHV foram detectados em 3 espécimes cada um (6,8%), o gene blaGES foi detectado em apenas um isolado (2,2%), enquanto os genes blaKPC e blaVIM não foram detectados. Nossos achados revelam altos índices de resistência aos betalactâmicos, assim como tendência linear crescente para produção de ESBL pelas espécies estudadas. O gene com maiores taxas de detecção entre os isolados foi o gene blaCTX-M que, certamente, é o gene ESBL mais importante clinicamente na atualidade. Nós detectamos um isolado de Klebsiella pneumoniae contendo o gene blaGES e blaCTX-M, sendo do nosso conhecimento o primeiro relato no Brasil, o que demonstra o grande potencial de disseminação mundial de genes de resistência entre bacilos Gram-negativos.
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Blagoev, Blagoy [Verfasser]. "Arbeitszeitregime im Lock-in? : Eine pfadtheoretische Untersuchung der Persistenz überlanger Arbeitszeiten in einem Beratungsunternehmen / Blagoy Blagoev." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1099282845/34.
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Hettasch, Georg. "Optimization of fir-tree-type turbine blade roots using photoelasticity." Thesis, Stellenbosch : University of Stellenbosch, 1992. http://hdl.handle.net/10019.1/993.
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Thesis (MEng.)-- University of Stellenbosch, 1992.
140 leaves on single pages, preliminary pages i-xi and numbered pages 1-113. Includes bibliography. Digitized at 600 dpi grayscale to pdf format (OCR),using an Bizhub 250 Konica Minolta Scanner and at 300 dpi grayscale to pdf format (OCR), using a Hp Scanjet 8250 Scanner.Thesis (MEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 1992
ENGLISH ABSTRACT: The large variety of turbo-machinery blade root geometries in use in industry prompted the question if a optimum geometry could be found. An optimum blade root was defined as a root with a practical geometry which, when loaded, returns the minimum fillet stress concentration factor. A literature survey on the subject provided guidelines but very little real data to work from. An initial optimization was carried out using a formula developed by Heywood to determine loaded projection fillet stresses. The method was found to produce unsatisfactory results, prompting a photoelastic investigation. This experimental optimization was conducted in two stages. A single tang defined load stage and a single tang in-rotor stage which modeled the practical situation. The defined load stage was undertaken in three phases. The first phase was a preliminary investigation, the second phase was a parameter optimization and the third phase was a geometric optimization based on a material utilization optimization. This material optimization approach produced good results. From these experiments a practical optimum geometry was defined. A mathematical model which predicts the fillet stress concentration factor for a given root geometry is presented. The effect of expanding the single tang optimum to a three tang root was examined.
AFRIKAANSE OPSOMMING: Die groot verskeidenheid lemwortelgeometrieë wat in turbomasjiene gebruik word het die vraag na 'n optimum geometrie laat ontstaan. Vir hierdie ondersoek is 'n optimum geometrie gedefineer as 'n praktiese geometrie wat, as dit belas word, die mimimum vloeistukspanningskonsentrasiefaktor laat ontstaan. 'n Literatuur studie het riglyne aan die navorsing gegee maar het wynig spesifieke en bruikbare data opgelewer. Die eerste optimering is met die Heywood formule, wat vloeistukspannings in belaste projeksies bepaal, aangepak. Die metode het nie bevredigende resultate opgelewer nie. 'n Fotoelastiese ondersoek het die basis vir verdere optimeering gevorm. Hierdie eksperimentele optimering is in twee stappe onderneem. 'n Enkelhaak gedefineerde lasgedeelte en 'n enkelhaak in-rotor gedeelte het die praktiese situasie gemodeleer. Die gedefineerde lasgedeelte is in drie fases opgedeel. Die eerste fase was n voorlopige ondersoek. Die tweede fase was 'n parameter optimering. 'n Geometrie optimering gebasseer op 'n materiaal benuttings minimering het die derde fase uitgemaak. Die materiaal optimerings benadering het goeie resultate opgelewer. Vanuit hierdie eksperimente is 'n optimum praktiese geometrie bepaal. 'n Wiskundige model is ontwikkel, wat die vloeistukspanningskonsentrasiefaktor vir 'n gegewe wortelgeometrie voorspel. Die resultaat van 'n geometriese uitbreiding van die enkelhaaklemwortel na 'n driehaaklemwortel op die spanningsverdeling is ondersoek.
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Bose, Anushika. "Birds & Blades." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22458.
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Kollisionen von Vögeln mit Windturbinen haben sich zu einer bedenklichen Quelle für die Gefährdung besonders von Populationen seltenerer Vogelarten entwickelt. Allerdings wird im Allgemeinen auch bestätigt, dass die Nutzung der Windenergie unverzichtbar ist. Das Hauptziel dieser Arbeit war es, die Relevanz der Wechselwirkungen zu verstehen, die zwischen technischen Infrastrukturen und den von Kollisionen betroffenen Vogelarten auf der Landschaftsebene stattfinden. Da sowohl von der Landschaft beeinflusst werden. Unter Nutzung der durch gezielte Nachsuche gefundenen Opfer der am häufigsten von Kollisionen betroffenen Artengruppen paradoxerweise as als Proxy für das Vorkommen von Arten, und Durch die Anwendung verschiedener Techniken zur Modellierung der Artenverbreitung (SDMs) die “kollisionsempfindliche Nische “für jede der Vogelgruppen beschrieben. Obwohl die vorhergesagten Gebiete mit potenziellen Kollisionsrisiko insgesamt nur kleine, aber stark verteilt im ungefährdes Bundeslandes hatten. Greifvögel mit die breiteste Nische, die zudem signifikante Überlappungen mit den kollisionsempfindlichen Nischen der anderen Gruppen aufwies. Die niedrig bewerteten Gebiete weiter differenziert, die als tatsächliche „Bereiche ohne Risiko“ interpretiert wurden, für weitere geplante Winkraftanlagen. Zusätzlich die jeweiligen Potentiale und Gefärdungen für Kollisionen auf der Basis der regionalen Dichteverteilungen der Arten in Brandenburg mit Ensemble-Methoden von Boosted Regression Trees wird ebenfalls bewertet. Zusammenfassend, diese Analysen paradigmatisch, sowohl die Gebiete als auch die Entfernungen zu den Grenzlinien der verschiedenen Landnutzungsformen ein höheres Risiko für die Kollision von Individuen der untersuchten Arten mit Windkraftanlagen ergibt ermitteln . Dieser Ansatz kann es möglich machen, zukünftige Windparkerweiterungen in der Landschaft im die möglichst kollisionsfreie und naturverträglicheStandorte in der Landschaft.Although, it is well recognized that harnessing wind energy is highly indispensable, but collisions of birds at wind turbines has also developed simultaneously, concerning multiple bird species. With wind being strongly affected by the landscape and the behaviour of birds also being strongly influenced by the landscape, the main objective of the thesis was to understand the relevance of interactions between wind energy infrastructures and bird species from an ecological perspective of the landscape. Utilizing the carcass collision datasets of the frequently-hit bird-groups paradoxically as proxies for species presence, collision sensitive ecological distances to different land-use types were ascertained, by employing multiple techniques of species distribution modelling (SDMs), to delineate their respective collision sensitive niche employing the capabilities of machine learning algorithms. The predicted areas were specialized and highly dispersed across the federal state, with raptors showing the broadest niche and significant overlaps with the other groups. Based on estimated collision probabilities of the assessed areas (between 0 and 1), further segregations differentiated only those areas with negligible collision probabilities, <0.05, which were interpreted as the actual "no risk areas, suggesting any further planned additions of wind turbines to be suitably positioned only in these “safer” areas. Additionally, these collision probabilities were translated to strike susceptibilities, by relating them to the regional density distributions of the species as well. Summarizing, these analyses paradigmatically ascertained collision risk areas, and especially the collision sensitive distances from different land-use types to these areas, enabling the accurate guidance of future wind farm expansions in the landscape. Ultimately, formulating novel wind turbine allocation strategies to minimize avian collisions, making them as compatible as possible.
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Drude, Matthias, and Else Lasker-Schüler. "Mein blaues Klavier: (1986)." Matthias Drude, 2018. https://slub.qucosa.de/id/qucosa%3A17093.
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Birgmark, Anja. "Wear of Coater Blades." Thesis, Karlstads universitet, Fakulteten för teknik- och naturvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-27183.
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Medd, Adam Jon. "Inverse design of turbomachinery blades." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0010/MQ34391.pdf.
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Ireland, Peter. "Internal cooling of turbine blades." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235870.
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Purvis, Richard. "Rotor blades and ground effect." Thesis, University College London (University of London), 2002. https://ueaeprints.uea.ac.uk/20790/.
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This thesis uses numerical, asymptotic and flow structural techniques to examine various aspects of rotor blade flows and ground effect. It explores two- and three-dimensional flows, generally concentrating upon regimes that have a degree of relevance to typical rotor blade flows. Chapter 2 considers, as a first step towards understanding a general rotor blade system in ground effect, a finite rotating disc near horizontal ground. More specifically, it concentrates on determining the layer shape beyond the disc rim that, due to the presence of the ground, cannot remain flat without violating a pressure condition across it. Chapter 3 examines the flow past many blades in ground effect using both a numerical approach and considering various limits of interest to illuminate some of the important features such as enhanced lift and sheltering effects. Chapter 4 then extends this by exploring the many blade limit, whereby the flow develops a periodic structure once sufficiently many blades have been passed. We then move on to three-dimensional configurations. Chapter 5 takes the previous work further by considering the interactive case that arises after a very large number of blades have been passed, generating a pressure-displacement interaction in the boundary layer. We examine the case of three-dimensional blades, considering the full triple deck problem and then the short blade limit, investigating the flow structure for this physically relevant case. Chapter 6 considers the flow past a three-dimensional hump on a blade of a rotor, examining the flow structure and solution and tentatively using this to propose a description of the flow past the trailing corner of a typical rotor blade. Finally Chapter 7 returns to ground effect, exploring the flow past a single, three-dimensional blade near the ground. It uses a compact difference technique to examine the flow solution for a particular blade shape and investigates the idea of change-over points, where the effective leading edge becomes a trailing edge switching the boundary conditions, these points being generally unknown in advance
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Bose, Anushika [Verfasser]. "Birds & Blades / Anushika Bose." Berlin : Humboldt-Universität zu Berlin, 2021. http://d-nb.info/1229435301/34.
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Pursell, Mark Edward. "Two Blades Come Together: Stories." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3932.
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This collection of seven short stories details the emotional triumphs and complications of characters whose lives are altered by issues of sexuality and disconnection. An adolescent girl feels her father slipping away from her and, in turn, willfully destroys the imaginary world of the boy she babysits; a speech therapist struggles to make headway with a young patient while finding himself unable to communicate with his ex-lover; a gay poet cheats on his boyfriend in a desperate attempt to fuel his failing art. The dramatis personae of Two Blades Come Together is comprised of individuals who struggle towards grace and happiness but are thwarted by their inability to fit neatly into the lives of those they love. Several of the stories approach these issues through the framework of contemporary myth, exploring how fairy tales and the supernatural act upon the characters' relationships and the way they perceive their situations. The heroines of "Proof of Snow" and "The Pill Woman" are both affected by the unseen; one suffers under the strange influence of her brother even after his death, while the other must make a decision to uphold her fairy-tale world or dismantle it. In these stories, the tangibility of the supernatural is elusive and unproven, but the altered perceptions of the protagonists and their actions because of it are extremely real, with extremely real consequences. The collection also explores and tests the boundaries between poetry and fiction, pushing always towards language that is aesthetic and musical while not sacrificing the momentum and architecture of prose. Two Blades Come Together incorporates linguistic ideas from poets as varied as contemporary surrealists Laura Kasischke and Mary Ruefle to the grounded wryness of Tony Hoagland and Lynda Hull, weaving poetic language with narrative, hybridizing the qualities of fiction and poetry in an attempt to create a unique, musical vision of short fiction that is both functional and artful.M.F.A.
Department of English
Arts and Humanities
Creative Writing MFA
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Dong, Yuan. "Boundary layers on compressor blades." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278266.
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Hart, M. "Boundary layers on turbine blades." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305764.
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Moore, Timothy David. "Automated inspection of turbine blades." Thesis, University of Manchester, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.762419.
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Kee, Kim Chung. "Particle impacts on impeller blades." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624407.
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Zimmer, Aline Katharina. "Investigation of the impact of turbine blade geometry on near-field microwave blade tip time of arrival measurements." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26558.
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Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Jagoda, Jechiel; Committee Co-Chair: Jacobs, Laurence; Committee Member: Seitzman, Jerry. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Gase, Zachary M. "Below-Rated Control of Swept-Blade Wind Turbines." Scholarly Commons, 2016. https://scholarlycommons.pacific.edu/uop_etds/225.
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Modelling studies have shown that 1.5 and 3.0 MW wind turbines with blade sweep have an increased annual energy production (AEP) of approximately 5% when compared to straight-blade wind turbines. The objective of the research was to further increase below-rated, variable speed, power capture when using swept-blades. When operating in the variable speed region, the turbine’s torque is proportional to the square of the generator speed, and k is the proportionality constant (T = kΩ 2 ). Initial studies indicated that the value of k needed to be lowered from the original value to increase AEP. This proved to be slightly beneficial for the 3.0 MW turbine but not for the 1.5 MW turbine. The optimal tip speed ratio was too high for both turbines and limited the ability to increase AEP. Original swept-blade chords were designed to fit a linear pattern for manufacturing purposes, but it is believed this is no longer a necessary constraint. The blades were redesigned to have a non-linear chord distribution, which is based on the Betz optimal design method, and the resultant increase in solidity proved to be the solution for slowing down the blades’ rotational speed. The change in chord design proved to be beneficial for both 1.5 and 3.0 MW wind turbines and had immediate, measurable increases to AEP. An effort to further increase AEP was then conducted by using an alternative torque-speed controller, which used a different equation to relate speed and torque. This method only resulted in an increase of AEP for the 1.5 MW turbine. In conclusion, the highest recorded AEP increases from straight-blade values were 6.9% and 8.9% for the 1.5 and 3.0 MW turbines, respectively. The 1.5 MW turbine benefited from the custom controller and redesigned chords, whereas the 3.0 MW turbine only benefited from redesigned chords.
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Höyland, Jörg. "Challenges for large wind turbine blades." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13545.
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With global climate problems receiving increasingly international political attention,most European nations are looking for sources of renewable energy. Wind turbines area promising source of renewable energy and their numbers have steadily increasedsince the introduction of the modern wind turbine in the 1970s. The largest units todayhave a rated power of 7 MW and blades ranging up to 62.5 m in length. Offshore windturbines have access to stronger winds with less turbulence, thereby increasing theenergy output of each unit. Offshore turbines will also have a lesser environmentalimpact than onshore turbines. It is believed that the development of offshore wind turbineswill encourage the development of even longer blades. The main spar geometry of a 100 m wind turbine blade was established in order to evaluatehow the use of carbon and glass fiber composites would affect the design. A hybridsolution using UD carbon fiber for global stiffness and ±45° glass fiber plies for bucklingresistance was also developed. The ultimate loads were calculated for blades with pitchcontrol and blades experiencing failure of pitch control during the 1-year and 50-yearextreme gust. The DNV-OS-J102 standard for wind turbines was used in the calculationof safety factors for both loads and material strength criteria. The distribution of ±45°anti-buckling plies by buckling analysis is extremely time consuming and therefore aprogram for automatic ply distribution was developed. The Matlab program interactedwith the FEM software Abaqus, defining input files and extracting results, and proved tobe highly efficient. The results from the FEM analyses were combined with a simple costmodel in order to evaluate both the weight and cost of the different spar solutions. Important weight reductions can be obtained by optimizing the performance of the composite laminate in the spar. Several sub-models of the 100 m spar were created withthe aim of optimizing the spar’s buckling performance. The angle and distribution ofboth the ±45° and UD plies were systematically altered in order to increase the bucklingload. The introduction of ply homogenization and core material in the flange was alsoevaluated and yielded the largest increases of buckling load. The results from the optimizedsub-models were implemented in a 100 m spar and found to decrease theamount of ±45° plies by 50 %. A 6 m scaled main spar of glass fiber composite was produced by resin infusion. Thespar was tested in a 4-point bending test and designed to fail by buckling of the topflange. In order to control the location of the buckling failure, an artificial imperfectionwas introduced in the middle of the top flange during manufacturing. The imperfectionis representative for imperfections found during manufacturing of wind turbine spars. Inaddition to measuring force and global deflection, 25 strain gages were installed tomonitor the spar. Finally, a FEM analysis of the 6 m spar was developed and correlated with the experimentalresults. By implementing the imperfection in the compression spar and the useof non-linear analysis, the strain patterns from the test results were successfully reproduced
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Marinus, Benoît. "Multidisciplinary optimization of aircraft propeller blades." Phd thesis, Ecole Centrale de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00692363.
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Open rotors are known to have significant advantages in terms of propulsive efficiency. These advantages translate directly in reduced fuel burn so that they nowadays benefit from a surge of interest. At the same time, recent advances in numerical simulations make the application of multidisciplinary optimization for the demanding design of transonic propeller blades, an affordable option. Therefore, an optimization method in which the performance objectives of aerodynamics, aeroacoustics and aeroelasticity compete against each other, is developed and applied for the design of high-speed single-rotation propellers. The optimization is based on Multi-Objective Differential Evolution (MODE).This technique is a particular kind of evolutionary algorithm that mimics the natural evolution of populations by relying on the selection, recombination and eventually mutation of blade designs, each of them being represented by a vector of design variables (e.g. chord width, tip sweep, etc). MODE has the advantage of dealing concurrently with all the objectives in the selection of potentially promising designs among a population. In order to keep the computational cost within reasonable margins, the assessment of the performance of proposed designs is done in a two-level approach. A metamodel provides performance estimates for each proposed design at extremely low computational effort while high-fidelity analysis codes provide accurate performance values on some promising designs at much higher cost. To safeguard the accuracy of the estimates, the metamodel is initially trained on a population that is specifically assembled for that purpose. The training is repeated from time to time with the high-fidelity performance values of promising designs. Different high-fidelity tools have been developed and used for the assessment of performance.The CFD-tool performs steady RANS simulations of a single blade passage of the isolated propeller in free air under zero angle of attack. These simulations provide the aerodynamic performance values. The full propeller is modelled thanks to cyclic boundary conditions. The k - ε turbulence model is used in combination with wall treatment. Adiabatic no-slip wall conditions are imposed on the spinner and blade surfaces whereas the test-section radial boundary is reproducing the effects of a pressure far-field. This approach has proven its robustness and, above all, its accuracy as satisfactory agreement with experimental results has been found for different operating conditions over a wide range of blade shapes, as well as sufficient grid independency. In the post-processing of the aerodynamic results, the Sound Pressure Level (SPL)is computed for tonal noise at various observer locations by the aeroacoustic solver(CHA). Formulation 1A from Farassat is used for this purpose. This formulation is related to the inhomogeneous wave equation derived from Lighthill's acoustic analogy by Ffowcs Williams and Hawkings (FW-H). It benefits from the partial decoupling of the acoustic and aerodynamic aspects and is particularly suited to compute the noise from propellers. The thickness noise and loading noise are expressed by separate equations in the time-domain whereas the quadrupole source term is dropped from the original FW-H equation. The blade surface is chosen as integration surface and a newly developed truncation technique is applied to circumvent the mathematical singularity arising when parts of the blade reach sonic conditions in terms of kinematics with respect to the observer. This approach delivers accurate values at acceptable computational cost. Besides, CSM-computations make use of a finite elements solver to compute the total mass of the blade as well as the stresses resulting from the centrifugal and aerodynamic forces. Considering the numerous possibilities to tailor the blade structure so that it properly takes on the stresses, only a simplified blade model is implemented. [...]
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Fulton, Mark V. "Stability of elastically tailored rotor blades." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/12248.
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Rogalsky, Timothy P. "Aerodynamic shape optimization of fan blades." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ35083.pdf.
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Nowak, William J. "Fatigue stress analysis of turbine blades /." Online version of thesis, 2007. http://hdl.handle.net/1850/5467.
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He, Li. "Unsteady flows around oscillating turbomachinery blades." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385407.
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Hamakhan, Idres Azzat. "Design of high efficiency turbomachinery blades." Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/618.
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Burman, Jörgen. "Design optimisation of aeroengine compressor blades." Licentiate thesis, Luleå, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25824.
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Optimisation of multistage axial compressors is a time-demanding challenge in large need of effective methods. Traditionally, the design has been based on "trial-and-error" procedures, which count on the skills and experience of the designer to suggest redesigns that are likely to yield improvements. While design by "trial-and-error" usually yield acceptable solutions, automatic shape optimisation will assist in finding the optimal design and shorten the design cycle. This thesis considers issues that have to be solved before automatic shape optimisation of compressor blades can be performed, as well as a demonstration of the developed methods suitability for optimising 2D compressor blades. In paper A the geometry parameterisation of compressor blades is studied. Non-Uniform Rational B-Splines (NURBS) are used for the basic geometry description. The profile shape is then described in terms of traditional parameters, e.g. throat and maximum thickness, and an optimisation algorithm is used to adjust the NURBS parameters until the requested values of the traditional parameters are obtained. In paper B the presence of numerical noise in the objective function is investigated. The occurrence of numerical noise is related to the discretisation of the partial differential equations describing the flow. The truncation error in the flow equations together with the discontinuous change in the grid as the geometry is modified will produce a small amplitude "wave-pattern" imposed on the objective function. Two optimisation techniques, a response surface model and a gradient based method, are used to study how the solution is affected by the numerical noise when minimising the pressure drop in an axisymmetric contraction. In paper C the geometry definition using implicit design variables (paper A) is combined with a response surface model (paper B) to optimise the performance of a 2D compressor blade for a jet engine. The results show that the geometry modification strategy using implicit design variables can be used for optimisation. However, more experience is necessary before a definite conclusion can be drawn to claim that using these design parameters are superior to using the control points of the NURBS.Godkänd; 2001; 20070314 (ysko)
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Bolger, John Jude. "Three dimensional design of compressor blades." Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/251477.
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Pearce, Robert. "Internal cooling for HP turbine blades." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:832038c9-e934-413d-bbb5-336ab4775055.
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Modern gas turbine engines run at extremely high temperatures which require the high pressure turbine blades to be extensively cooled in order to reach life requirements. This must be done using the minimum amount of coolant in order to reduce the negative impacts on the cycle efficiency. In the design process the cooling configuration and stress distribution must be carefully considered before verification of the design is conducted. Improvements to all three of these blade design areas are presented in this thesis which investigates internal cooling systems in the form of ribbed, radial passages and leading edge impingement systems. The effect of rotation on the heat transfer distribution in ribbed radial passages is investigated. An engine representative triple-pass serpentine passage, typical of a gas turbine mid-chord HP blade passage, is simulated using common industrial RANS CFD methodology with the results compared to those from the RHTR, a rotating experimental facility. The simulations are found to perform well under stationary conditions with the rotational cases proving more challenging. Further study and simulations of radial passages are undertaken in order to understand the salient flow and heat transfer features found, namely the inlet velocity profile and rib orientation relative to the mainstream flow. A consistent rib direction gives improved heat transfer characteristics whilst careful design of inlet conditions could give an optimised heat transfer distribution. The effect of rotation on the heat transfer distribution in leading edge impingement systems is investigated. As for the radial passages, RANS CFD simulations are compared and validated against experimental data from a rotating heat transfer rig. The simulations provide accurate average heat transfer levels under stationary and rotating conditions. The full target surface heat transfer in an engine realistic leading edge impingement system is investigated. Experimental data is compared to RANS CFD simulations. Experimental results are in line with previous studies and the simulations provide reasonable heat transfer predictions. A new method of combined thermal and mechanical analysis is presented and validated for a leading edge impingement system. Conjugate CFD simulations are used to provide a metal temperature distribution for a mechanical analysis. The effect of changes to the geometry and temperature profile on stress levels are studied and methods to improve blade stress levels are presented. The thermal FEA model is used to quantify the effect of HTC alterations on different surfaces within a leading edge impingement system, in terms of both temperature and stress distributions. These are then used to provide improved target HTC distributions in order to increase blade life. A new method using Gaussian process regression for thermal matching is presented and validated for a leading edge impingement case. A simplified model is matched to a full conjugate CFD solution to test the method's quality and reliability. It is then applied to two real engine blades and matched to data from thermal paint tests. The matches obtained are very close, well within experimental accuracy levels, and offer consistency and speed improvements over current methodologies.
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Ricquemaque, Lore. "FEM model of impacts on blades." Thesis, KTH, Kraft- och värmeteknologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185693.
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In-service support engineers often have to answer derogations requests regarding impacts on compressor blades. The stress concentration factor is a physical quantity helping them to take the decisions : it is a measure of the local increase of the stress due to the impact. Several techniques already exist to derive it like Petersons' abaci giving it regarding the geometrical parameters of the impact. They are user friendly but conservative in practice. The most accurate method is zoom-calculation : a Finite Element Model is created to precisely measure the stress concentration factor. This effective approach is however very time-consuming. In between, Snecma engineers developed a few years ago a law on the form of abaci derived from a zoom-calculation results database. The main purpose of this thesis is to create laws regarding new geometrical parameters and increase the size of the database following on from the work already carried out. FEM models depending on various parameters are thus created to derive stress concentration factors. A deep difference from what has been done before rests on the method : a calculation chain is developed to get results on different sets of impact parameters. It enables to easily and quickly update the mesh on the models and thus to consider numerous defect geometries. The final results of the study are a set of abaci giving the stress concentration factor due to the impact regarding its geometrical parameters.
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Dias, Bruno Ricardo Barros. "Adaptive gurney flap for rotor blades." Master's thesis, Universidade da Beira Interior, 2013. http://hdl.handle.net/10400.6/1976.
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Desde muito tempo vários esforços tem sido feitos de maneira a optimizar o rotor dos helicópteros com o objectivo de reduzir a emissão de poluentes. Durante vários anos foram feitas várias optimizações estrutrais na pá do rotor.
Estudos recentes numéricos e experimentais mostram que para melhor a performance do rotor várias considerações aerodinâmicas têm que ser levadas em conta.
O principal objectivo deste trabalho é estudar e optimizar um mecanismo preliminar constituído por um flap dinâmico que consiga controlar a camada limite na pá. O flap escolhido foi o Gurney Flap, desenvolvido nos anos 70 por um piloto de automóveis com o intuito de provocar uma downforce de maneira a melhorar o desempenho do automovél. A razão desta escolha deve-se por
o flap ter uma superfície relativamente pequena com baixas forças de inércia permitindo baixos consumos de energia e sem adicionar extra carga para na pá. A utilização deste flap demonstrou
o aumento as propriedades aerodinâmicas de pá, portanto, reduzindo o consumo de combustÃvel.
Para este estudos várias análises estruturais foram realizadas usando softwares comerciais entre eles; análises cináticas, de maneira a estudar o deslocamento, velocidade e aceleraçao do mecanismo e também do sistema de actuação; análises dinâmica, possibilitando o calculo de tensões e deformações do sistema sujeito a várias cargas de inécia e por fim uma análise modal, bastante importante devido ao mecanismo estar sujeito a uma frequência de actuação.
Depois de conduzidas estas análises foi possivél optimizar o peso da desenho inicial em cerca de 50% respeitando todos os requerimentos impostos e as características do material. Foram estudados dois tipos de sistema de de actuação deixando em aberto a escolha do actuador.Various efforts have been made in order to optimize the helicopter rotor with the objective to reduce the emission of pollutants. For several years many studies have conducted to a structural optimization of rotor blade. Recent experimental and numerical studies show that for the best performance of the rotor several aerodynamic considerations must be taken into account. The main objective of this work is to study and optimize a preliminary mechanism consisting in a dynamic flap that can control the boundary layer on the blade. The chosen flap was a Gurney flap which was developed in the 70’s by a race driver in order to cause a downforce improving the performance of the race cars. The reason for this choice is due to the flap having a relatively small surface with low inertial forces allowing low energy consumption and without adding extra load to the blade. The use of this flap has demonstrated to increase the aerodynamics properties of blade therefore reducing the fuel consumption. For this study a number of structural analyses were performed using commercial software between them: kinematics analysis in order to study the displacement, velocity and acceleration of the mechanism and also the actuation system; dynamic analysis , enabling the calculation of stress and strain of the system subjected to various inertial loads, and finally, a modal analysis, very important due to the mechanism being subject to a high frequency of actuation. After these analyses was possible to optimize the design of the mass in about 50% respecting all the requirements imposed and the characteristics of the material. There are two types of actuation system, while leaving open the choice of the actuator.
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Li, Leihong. "Structural design of composite rotor blades with consideration of manufacturability, durability, and manufacturing uncertainties." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24757.
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Thesis (Ph.D.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Hodges, Dewey H.; Committee Member: Bauchau, Olivier A.; Committee Member: Johnson, Ellis; Committee Member: Makeev, Andrew; Committee Member: Volovoi, Vitali V.
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Raubenheimer, Gert. "Vibration excitation of axial compressor rotor blades." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17987.
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Thesis (MScEng)--Stellenbosch University, 2011.ENGLISH ABSTRACT: Turbomachines are exposed to several environmental factors which may cause failure of components. One of these factors, high cycle fatigue, is often caused by blade utter. This thesis forms part of a project of the European Seventh Framework Programme (FP7), called project Future. Project Future is doing theoretical and experimental investigation into the occurrence of utter in turbomachinery. The objective of this thesis was to evaluate the effectiveness of a gas injection system as a means of exciting vibrations on the rst stage rotor blades of a compressor. Unsteady simulations of the excitation velocity perturbations were performed in the Computational Fluid Dynamics (CFD) software, Numeca FINE/Turbo. Experimental testing on the in-house Rofanco compressor test bench, using one prototype of the 15 injector system, provided data that was used to implement boundary conditions and to verify certain aspects of the unsteady simulation results. The simulation results revealed the following: the injector bypass frequency was so dominant that the excitation frequency was hardly detectable in the majority of cases. Furthermore, several secondary frequencies were consistently present. The injector bypass frequency, as well as the secondary frequencies, occurred as a result of the convolution of Fast Fourier Transforms. While the injector bypass frequencies can theoretically be eliminated, it will not be possible to eliminate the secondary frequencies from the blade response. In conclusion, according to the CFD results, it will not be possible to excite a single excitation frequency by making use of a nite number of gas injector vibration exciters.
AFRIKAANSE OPSOMMING: Turbomasjiene word onderwerp aan verskeie omgewingsfaktore wat falings van komponente kan veroorsaak. Een van hierdie faktore, naamlik hoëfrekwensie vermoeidheid, word onder andere veroorsaak deur lem adder. Hierdie tesis is deel van 'n projek in die Sewende Europese Raamwerk Program (European Seventh Framework Programme - FP7), projek Future. Projek Future doen teoretiese en eksperimentele ondersoek na die voorkoms van lemfl adder in turbomasjienerie. Die doelwit van hierdie tesis was om die effektiwiteit van 'n gasinspuiter vibrasie-opwekkingstelsel te evalueer, deur gebruik te maak van onbestendige simulasie in die berekenings vloei-meganika sagtewarepakket, Numeca FINE/Turbo. Eksperimentele toetswerk op die plaaslike Rofanco kompressortoetsbank, met 'n prototipe van die 15 inspuiter stelsel, het inligting verskaf wat gebruik is om die inlaattoestande te spesi seer en simulasieresultate te korreleer. Die simulasieresultate het getoon dat die frekwensie waarteen 'n lem by die inspuiters verbybeweeg, so prominent is, dat dit in die meerderheid van gevalle baie meer prominent is as die opwekkingsfrekwensie. Verder was daar ook deurgaans 'n aantal sekondêre frekwensies teenwoordig. Die teenwoordigheid van die inspuiter verbybeweeg frekwensie en die sekondêre frekwensies is die resultaat van die konvolusie van Vinnige Fourier Transforme. Alhoewel dit in teorie moontlik sal wees om die inspuiter verbybeweeg frekwensie te elimineer, is dit onmoontlik om die sekondêre frekwensies uit die lem vibrasie te elimineer. Ter opsomming, volgens die berekenings vloei-meganika resultate, is dit nie moontlik om met 'n stelsel van 'n eindige aantal inspuiters, 'n enkele vibrasie frekwensie op te wek nie.
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Turnock, Wingyan Wong. "Impact response of composite helicopter rotor blades." Thesis, Cranfield University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422188.
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Khan, Fahd. "Investigating into advanced coatings for bandsaw blades." Thesis, Northumbria University, 2011. http://nrl.northumbria.ac.uk/36301/.
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Bandsawing is an important metal cutting operation carried out in a variety of industries in order to remove raw material for secondary operations. Due to its continuous cutting action, bandsawing has over taken other cutting processes such as power hack sawing and circular sawing. Bandsawing operation offers numerous advantages such as high cutting rate, low kerf loss, longer tool life and high automation possibilities, due to its efficient and continuous cutting action. It is costly and time-consuming to test the wear of the full bandsaw products on a full-scale bandsaw machine. In order to overcome this, a single tooth test rig has been developed at Northumbria University, which utilizes a single bandsaw tooth instead of the complete bandsaw loop. Previous research has utilized this test rig for evaluating bi-metal saws while machining steels. Development of new, wear resistant and difficult-to-cut materials such as titanium alloys (e.g. Ti-17) imposes greater demands on bandsawing operations. Traditionally, high speed steels and cemented carbides have been employed to cut/machine these materials. The main disadvantage of high speed steel cutting tools is that it undergoes severe plastic deformation when cutting at temperatures above 600oC. Tungsten carbide cutting tools have proven their supremacy in almost all the machining processes and interrupted cutting of these difficult-to-cut titanium alloys. One of the challenges in design of cemented tungsten carbide tools is the optimization of toughness and wear resistance. This has led to the development of coated carbide tools, which accounts for the major portion of all commercial metal cutting inserts sold worldwide. This current research has furthered the use of single tooth test rig, by using un-coated and coated tungsten carbide tipped bandsaw blades while machining high performance titanium alloys (Ti-17). The purpose is to evaluate and assess the performance of un-coated and coated carbide bandsaw teeth and ascertain wear mechanisms and modes of single bandsaw tooth, in a way that is representative of full product testing. Two different coatings (AlTiN and TiAlSiN) were chosen to be deposited using arc evaporation PVD technique. These coatings were selected due to their properties in terms of wear resistance and structure: TiAlSiN is nano-structured, while AlTiN is conventional in terms of its grain size. These coatings were characterized using various techniques, such as electron microscopy and nano-indentation. Cutting tests were carried out using un-coated and coated carbide bandsaw teeth. Adhesive wear and diffusion wear were identified as the wear mechanisms, while flank wear and chipping were confirmed as the principal wear modes for the un-coated carbide bandsaw teeth. Cutting forces were found to be less while machining Ti-17 alloy using coated teeth as compared to the forces obtained while machining with un-coated teeth. Less material was found to be adhering to the coated teeth as compared to un-coated teeth. Finite element analyses (FEA) were carried out on interaction of the cutting tool and the workpiece to determine the stress concentration during the cutting process. It was found that the increase in the honing lengths on the carbide teeth reduced the stresses and moved the maximum stress from the edge of the rake face to the honed edge.
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Dow, Eric Alexander. "Robust design and tolerancing of compressor blades." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97351.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 147-152).
Variations in the geometry of compressor blades can be introduced by variability in the manufacturing process or by in-service erosion. Recent research efforts have focused on characterizing the impacts of this geometric variability on turbomachinery performance and designing blade geometries whose performance is robust to this variability. Relatively little work has been done to specify the appropriate level of variability by designing the manufacturing tolerances. This thesis presents new approaches for optimizing tolerances that can be applied to compliment existing geometry optimization techniques. Building upon previous research, a Gaussian random field model of manufacturing variability is developed and used to estimate the statistical performance impacts of geometric variability on compressor blade performance. Flow mechanisms that deteriorate the mean performance in the presence of geometric variability are analyzed for design and off-design conditions. A probabilistic, gradient-based optimization framework is presented and applied to optimize the tolerances of compressor blades, as well as to optimize the tolerances and blade geometry simultaneously. The effectiveness of simultaneous optimization of the geometry and manufacturing tolerances is compared to a sequential procedure where the nominal blade geometry is optimized first, followed by the tolerances. Single-point optimization, where the performance at a single flow incidence is optimized, is found to produce geometries that are not robust to manufacturing variations. Adopting a multi-point design strategy results in blades that are robust to both variations in the geometry and incidence, allowing a sequential design strategy to be used.
by Eric Alexander Dow.
Ph. D.
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Gubran, Ahmed. "Vibration diagnosis of blades of rotating machines." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/vibration-diagnosis-of-blades-of-rotating-machines(40f1d466-b393-42f6-a65a-e16801f06920).html.
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Rotating blades are considered to be the one of the most common cause of failures in rotating machinery. Blade failure modes normally occur as a result of cracks due to unexpected operating conditions, which are normally caused by accidents of foreign objects damage, high cycle fatigue, blade rubbing, blade root looseness, and degradation from erosion and corrosion. Thus, detection of blade faults has an important role in reducing blade related failures and allowing repairs to be scheduled for the machinery. This in turn will lead to reduction in maintenance costs and thus raise productivity and safety aspects of operation. To maintain vital components of rotating machines, such as blades, shafts, bearings and gear boxes, at optimal levels, detection of failures in such components is important, because this will prevent any serious damage that could affect performance. This research study involves laboratory tests on a small rig with a bladed disc rotor that applied vibration measurements and analysis for blade fault detection. Three measurements: shaft torsional vibration, on-bearing vibration (OBV) and on-casing vibration (OCV), are used. A small test rig of a single stage bladed disc holding 8-blades was designed and manufactured, to carry out this research study to assess the usefulness and capability of each vibration technique in detection of incipient defects within machine blades. A series of tests was conducted on a test rig for three different cases of blade health conditions: (a) healthy blade(s) with mistuned effects, (b) blade root looseness and (c) cracks in a blade on two different blade sizes (long and short blades) in order to discover changes in blades' dynamic behaviour during the machine running-up operation. The data were collected using the three measurements during machine run-up and then recorded. The measured vibration data were analysed by computing the blades' resonance at different engine orders (EOs) related to the blade(s) resonance frequencies and their higher harmonics, to understand the blade(s) dynamics behaviour for the cases of healthy and faulty blade(s). Data have been further processed using a polar plot presentation method which provides clear results that can be used for monitoring blade integrity. To validate the obtained experimental results, a simplified mathematical model was also developed. Finally, a comparative study between three methods was undertaken to understand the relative advantages and limitations in the blade heath monitoring.
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Kumar, Apurva. "Robust design methodologies : application to compressor blades." Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/72037/.
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Compressor blades are subtle aerodynamic shapes designed after years of research and insight. They inevitably show deviations from their desired shapes due to manufacturing errors, erosion or foreign object damage. In the present study we focus on seeking compressor blade geometries, that are robust in performance in the presence of geometric uncertainty. Sophisticated tools for representing and propagating uncertainty are employed. Novel method for modeling eroded blade geometry and simulating manufacturing variations with process capability data are presented. These are combined with an automatic meshing routine and a high fidelity viscous flow solver for performance analysis. A combination of Design of Experiment techniques and Gaussian Process emulators are employed to develop efficient surrogate models for uncertainty analysis and exploring the design space. Efficient multiobjective optimization based robust design methodologies are presented. The robust design methods in conjunction with the surrogate model are used to seek blades that have less variation in performance in the presence of erosion and manufacturing variations. Main effects and sensitivity analysis are also performed to understand the effect of each noise variable on the performance. The performance of the robust blades obtained are compared to that of deterministic optimal blades in the presence of the uncertainties. The robust optimal blades exhibit considerably less variability and mean shift in performance as compared to the optimal blades. Finally, a probabilistic framework is developed to deal with randomness in objectives during multiobjective optimization and is applied in conjunction with Gaussian Process emulators for robust design.
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Valero, Ricart Omar Ruben. "Multidisciplinary concurrent optimization of gas turbine blades." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:b89d8f80-9134-4856-8223-5f55967c0bde.
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This thesis presents the study and development of optimization methods that can perform concurrent aerodynamic-aeroelastic blade optimization in a multi-bladerow environment, and for realistic turbomachinery blade geometries. The Nonlinear Harmonic Phase Solution Method has been chosen as the flow solution method of this work because of its capability to calculate the aeroelasticity features of interest (blade flutter) and the main flow aerodynamic performance in steady flow timescales. The first optimization method that is shown is a more generic non-gradient method with an improved version of a quadratic Response Surface Model. The new Re-Scaled Response Surface Model has shown marked convergence and performance improvements against traditional surrogate models. However, the computational cost of this method for cases with a large number of design variables limits its real applications. A gradient-based adjoint method is presented next as a cost-independent alternative that can accomplish efficient multi-bladerow optimization for a large number of variables within the current levels of computational power. The continuous adjoint system has been developed based on the same methodology as the flow solution method and it shows a more consistent relation between the flow field and its corresponding adjoint field, in agreement with the "anti-physics" information path. An adjoint interface treatment has been developed as an extension of the flow harmonic interface treatment. This unique treatment allows capture of the damping sensitivities of the vibrating blade to shape changes in adjacent rows. The application of this method to the design optimization of compressor and turbine stages has shown its capability to perform efficient multicomponent and multi-disciplinary design optimization of turbomachinery blades.
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Taylor, John. "The dynamics and stresses of bandsaw blades." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26333.
Full textAbstract:
This study investigates the stresses and dynamics of stationary, idling and cutting bandsaw blades.
A method of obtaining an estimate of the stresses in an idling bandsaw blade is presented. The estimate is determined by measuring the stresses that occur when the blade vibrates in its lowest fundamental modes and assuming that the idling behaviour can be represented by a summation of these modes. The natural frequencies of the bandsaw blade have been measured for various operating conditions and the measured results are compared to existing analytical predictions. A modification to the analysis of torsional motion is presented that accounts for the internal stress distribution existing in the blade due to the roll tensioning that such blades receive.
The displacements and frequency spectra of the bandsaw blade during the cutting process are obtained. The displacements are compared to the surface of the cut lumber, and the frequency spectra are compared to the dynamic response characteristics of the idling blade.
The results of this study will be of interest to those wishing to improve their understanding of the stresses and dynamics associated with idling and cutting bandsaw blades and desiring more accurate predictions of blade natural frequencies.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Ahuja, Anil. "Random vibrations of mistuned periodic structures." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-11012008-063055/.
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Ozbay, Serkan. "Extension-Twist Coupling Optimization in Composite Rotor Blades." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/10422.
Full textAbstract:
For optimal rotor performance in a tiltrotor aircraft the difference in the inflow and the rotor speeds between the hover and cruise flight modes suggests different blade twist and chord distributions. The blade twist rates in current tiltrotor applications are defined based upon a compromise between the figure of merit in hover and propeller efficiency in airplane mode. However, when each operation mode is considered separately the optimum blade distributions are found to be considerably different.
Passive blade twist control, which uses the inherent variation in centrifugal forces on a rotor blade to achieve optimum blade twist distributions in each flight mode through the use of extension-twist coupled composite rotor blades, has been considered for performance improvement of tiltrotor aircraft over the last two decades. The challenge for this concept is to achieve the desired twisting deformations in the rotor blade without altering the aeroelastic characteristics of the vehicle. A concept referred to as the sliding mass concept is proposed in this work in order to increase the twist change with rotor speed for a closed-cell composite rotor blade cross-section to practical levels for performance improvement in a tiltrotor aircraft. The concept is based on load path changes for the centrifugal forces by utilizing non-structural masses readily available on a conventional blade, such as the leading edge balancing mass.
A multilevel optimization technique based on the simulated annealing method is applied to improve the performance of the XV15 tiltrotor aircraft. A cross-sectional analysis tool, VABS together with a multibody dynamics code, DYMORE are integrated into the optimization process. The optimization results revealed significant improvements in the power requirement in hover while preserving cruise efficiency. It is also shown that about 21% of the improvement is provided through the sliding mass concept pointing to the additional flexibility the concept provides for tailoring of the structure without any additional weight penalty on the system.
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Pawar, Prashant M. "Structural Health Monitoring Of Composite Helicopter Rotor Blades." Thesis, Indian Institute of Science, 2006. http://hdl.handle.net/2005/273.
Full textAbstract:
Helicopter rotor system operates in a highly dynamic and unsteady aerodynamic environment leading to severe vibratory loads on the rotor system. Repeated exposure to these severe loading conditions can induce damage in the composite rotor blade which may lead to a catastrophic failure. Therefore, an interest in the structural health monitoring (SHM) of the composite rotor blades has grown markedly in recent years. Two important issues are addressed in this thesis; (1) structural modeling and aeroelastic analysis of the damaged rotor blade and (2) development of a model based rotor health monitoring system. The effect of matrix cracking, the first failure mode in composites, is studied in detail for a circular section beam, box-beam and two-cell airfoil section beam. Later, the effects of further progressive damages such as debonding/delamination and fiber breakage are considered for a two-cell airfoil section beam representing a stiff-inplane helicopter rotor blade. It is found that the stiffness decreases rapidly in the initial phase of matrix cracking but becomes almost constant later as matrix crack saturation is reached. Due to matrix cracking, the bending and torsion stiffness losses at the point of matrix crack saturation are about 6-12 percent and about 25-30 percent, respectively. Due to debonding/delamination, the bending and torsion stiffness losses are about 6-8 percent and about 40-45 percent after matrix crack saturation, respectively. The stiffness loss due to fiber breakage is very rapid and leads to the final failure of the blade. An aeroelastic analysis is performed for the damaged composite rotor in forward flight and the numerically simulated results are used to develop an online health monitoring system. For fault detection, the variations in rotating frequencies, tip bending and torsion response, blade root loads and strains along the blade due to damage are investigated. It is found that peak-to-peak values of blade response and loads provide a good global damage indicator and result in considerable data reduction. Also, the shear strain is a useful indicator to predict local damage. The structural health monitoring system is developed using the physics based models to detect and locate damage from simulated noisy rotor system data. A genetic fuzzy system (GFS) developed for solving the inverse problem of detecting damage from noise contaminated measurements by hybridizing the best features of fuzzy logic and genetic algorithms. Using the changes in structural measurements between the damaged and undamaged blade, a fuzzy system is generated and the rule-base and membership functions optimized by genetic algorithm. The GFS is demonstrated using frequency and mode shape based measurements for various beam type structures such as uniform cantilever beam, tapered beam and non-rotating helicopter blade. The GFS is further demonstrated for predicting the internal state of the composite structures using an example of a composite hollow circular beam with matrix cracking damage mode. Finally, the GFS is applied for online SHM of a rotor in forward flight. It is found that the GFS shows excellent robustness with noisy data, missing measurements and degrades gradually in the presence of faulty sensors/measurements. Furthermore, the GFS can be developed in an automated manner resulting in an optimal solution to the inverse problem of SHM. Finally, the stiffness degradation of the composite rotor blade is correlated to the life consumption of the rotor blade and issues related to damage prognosis are addressed.
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Husain, Al-taie Arkan Khilkhal. "Experimental Study of Radiation From Coated Turbine blades." Thesis, Cranfield University, 1990. http://dspace.lib.cranfield.ac.uk/handle/1826/4553.
Full textAbstract:
The specific power (or specific thrust) of modern gas
turbines is much influenced by the gas temperature at turbine
inlet. Even with the use of the best superalloy available and the
most advanced cooling configurations, there are competitive
pressures to operate engines at even higher gas temperatures.
Ceramic coatings operate as thermal barriers and can allow
the gas temperature to be increased by 50 to 220 K over the
operating gas temperature for an uncoated turbine .
It is important that the surface temperature of the blade
be determined as accurately as possible. Large uncertainties as
to the surface temperature require significant margins for safe
operation .
Blade surface temperatures can be determined with an
accuracy of 10 K using radiation pyrometry and about"30 to 40 K
by calculating the blade temperature based on---gas temperature
measurement of the exhaust gas plane. This'- makes pyrometry an
attractive option for advanced high temperature gas turbines .
However, there is little experience in measuring surface
temperatures of blades coated with ceramic coatings. There is
evidence that the. radiation signal picked up by the pyrometer
will not only depend on the surface temperature but also on a
number of optical properties of the coating. Important among
these are the emissivity of the coating and whether the coating
is translucent. Parameters affecting this are the coating
material, coating surface finish, coating thickness and whether
or not a bond coat is used .
This work explores these variables in a rig that simulates
the conditions within a turbine stage of a gas turbine engine. In
which six thermal barrier coating systems were tested. These
systems are of current interest to gas turbine manufacturers and
users. They include the latest advances in coating technology.
Four stabilized zirconia systems and two alumina based systems
were tested.
It was found experimentally that the surface emissivity of
these coating systems was invariant over the range 873 to 1023 K
surface temperature. It was found that the use of different
stabilizers did not affect the surface spectral emissivity.
In further experiments six turbine wheels were coated with
these systems and tested at turbine entry temperatures of 973,
1073, and 1173 K. It was found that the blade surface temperature
was function of the coating material, coating thickness and
turbine entry temperature. The blade surface temperature was also
function of the blade height being maximum at the blade tip and
minimum at the blade root .
It was found that the C-YPSZ was better insulator than the
rest of the systems. Whilst the blades coated with zirconia
based systems suffered minor loss near the edges, the two alumina
based systems were lost from more than a blade during the test.
This coating loss was picked up by. the pyrometer .
Analysis shows that the measured blade surface temperature
was within 10 K of that calculated. The use of 0.3 mm of C-YPSZ
on air cooled turbine blades caused 250 K surface temperature
increase and 270 K metal temperature decrease for turbine entry
temperature of 1673 K. The metal temperature reduction was as
high as 310 K for coating thickness of 0.5 mm.
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Nichols, James Franklin. "Two-dimensional analysis of turbine blades and nozzles." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17673.
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Hultman, Hugo. "Validation of Forced Response Methods for Turbine Blades." Thesis, KTH, Kraft- och värmeteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172144.
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Khan, Sameer. "Probalistic Stress Rupture Life Analysis of Turbine Blades." Honors in the Major Thesis, University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/970.
Full textAbstract:
This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Mechanical Engineering
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Wylie, Dave. "Factoring Blades and Versors in Euclidean Clifford Algebras." Thesis, Southern Illinois University at Edwardsville, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1564083.
Full textAbstract:
This thesis examines different methods of factoring elements of Clifford Algebras, specifically, Cℓn,0. Blades are factored using Fontijne's algorithm and other techniques. Versors are factored using Perwass's algorithm. Writing an element as a sum of blades, which are then factored, can make it more efficient to store or transmit that element. To evaluate the usefulness of expressing a given element of Cℓ n,0 this way, the number of scalars required to express that element is compared between factored and expanded forms.
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Moffatt, Stuart. "Forced response prediction for industrial gas turbine blades." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2692/.
Full textAbstract:
A highly efficient aeromechanical forced response system is developed for predicting resonant forced vibration of turbomachinery blades with the capabilities of fully 3-D non-linear unsteady aerodynamics, 3-D finite element modal analysis and blade root friction modelling. The complete analysis is performed in the frequency domain using the non linear harmonic method, giving reliable predictions in a fast turnaround time. A robust CFD-FE mesh interface has been produced to cope with differences in mesh geometries, and high mode shape gradients. A new energy method is presented, offering an alternative to the modal equation, providing forced response solutions using arbitrary mode shape scales. The system is demonstrated with detailed a study of the NASA Rotor 67 aero engine fan rotor. Validation of the forced response system is carried out by comparing predicted resonant responses with test data for a 3-stage transonic Siemens industrial compressor. Two fully-coupled forced response methods were developed to simultaneously solve the flow and structural equations within the fluid solver. A novel closed-loop resonance tracking scheme was implemented to overcome the resonant frequency shift in the coupled solutions caused by an added mass effect. An investigation into flow-structure coupling effects shows that the decoupled method can accurately predict resonant vibration with a single solution at the blade natural frequency. Blade root-slot friction damping is predicted using a modal frequency-domain approach by applying linearised contact properties to a finite element model, deriving contact Droperties from an advanced semi-analytical microslip model. An assessment of Coulomb and microslip approaches shows that only the microslip model is suitable for predicting root friction damping.