7103 research outputs found
Sort by
Investigation and model development of pressure relief valve leak tightness
No full textControlling and assessing the leak tightness of a Pressure Relief Valve (PRV) has been a challenge since the original design of the product. With more stringent demands from the nuclear power industry for leakproof PRV's, closer to the set-pressure, there has been a drive by both industry and academia for a better design method for many known metal-to-metal contacting seal/surface problems. This thesis attempts to understand the surface metrology characteristics which facilitate leakage, from which a numerical modelling tool is developed.Drawn from industry experience, it is found that the main surface finish contributing factor to leakage is form, rather than roughness. Industry experience combined with metrology measurements allowed investigating the effects of poli-lapping and improving the surface form for a new disc. This led to reducing the leakage rate proving, this to be the key influencing parameter on leakage. A numerical modelling tool is created taking into consideration the surface form, waviness and roughness. The numerical approach requires efficient coupling of a non-linear structural Finite Element Analysis (FEA) with a Computational Fluid Dynamic (CFD) solver. This allows the examination of the relationship between deformation of the contacting surfaces, based on the applied spring force, and the resultingmicro-flow of gas through any available gaps and the overall leakage to be found.;The API527 Seat Tightness methodology is followed to allow leakage rates to be measured and the computational model to be validated at a set-pressure of 0.5 MPa. It was found that the API527 standard falls short of being able to quantify leakage, rather it is understood to be an indicator of leakage. The FEA numerical model builds upon the current literature by using the sum surface technique, which is partially validated in this thesis. The CFD model is verified and validated using equations and experimental results found in the literature. There is confidence in the leakage results calculated via the CFD model up to 10MPa, after which no equations or experimental data exist in the literature which can be used for validation purposes against the CFD results. It is found by reducing the seat length to 0.5 mm and applying a force equivalent to 18.6 MPa, the contact between the metal surfaces reduced to 99.5% roughness contact. Another technique developed called the Surface Compliance Technique (SCT) showed that by applying 2.2x the spring force for a set-pressure of 18.6MPa, the gap spacing due to the form and waviness is plastically deformed, closing the gap spacing. A secondary factor known as valve swivel was also investigated finding that it has no effect on leakage. Also from the roughness numerical CFD model, the permeability coefficient is found. In addition, the numerical approach can potentially be applied to other metal-to-metal contacting surface components, such as flanges with metal gaskets, to help eliminate leakage.Controlling and assessing the leak tightness of a Pressure Relief Valve (PRV) has been a challenge since the original design of the product. With more stringent demands from the nuclear power industry for leakproof PRV's, closer to the set-pressure, there has been a drive by both industry and academia for a better design method for many known metal-to-metal contacting seal/surface problems. This thesis attempts to understand the surface metrology characteristics which facilitate leakage, from which a numerical modelling tool is developed.Drawn from industry experience, it is found that the main surface finish contributing factor to leakage is form, rather than roughness. Industry experience combined with metrology measurements allowed investigating the effects of poli-lapping and improving the surface form for a new disc. This led to reducing the leakage rate proving, this to be the key influencing parameter on leakage. A numerical modelling tool is created taking into consideration the surface form, waviness and roughness. The numerical approach requires efficient coupling of a non-linear structural Finite Element Analysis (FEA) with a Computational Fluid Dynamic (CFD) solver. This allows the examination of the relationship between deformation of the contacting surfaces, based on the applied spring force, and the resultingmicro-flow of gas through any available gaps and the overall leakage to be found.;The API527 Seat Tightness methodology is followed to allow leakage rates to be measured and the computational model to be validated at a set-pressure of 0.5 MPa. It was found that the API527 standard falls short of being able to quantify leakage, rather it is understood to be an indicator of leakage. The FEA numerical model builds upon the current literature by using the sum surface technique, which is partially validated in this thesis. The CFD model is verified and validated using equations and experimental results found in the literature. There is confidence in the leakage results calculated via the CFD model up to 10MPa, after which no equations or experimental data exist in the literature which can be used for validation purposes against the CFD results. It is found by reducing the seat length to 0.5 mm and applying a force equivalent to 18.6 MPa, the contact between the metal surfaces reduced to 99.5% roughness contact. Another technique developed called the Surface Compliance Technique (SCT) showed that by applying 2.2x the spring force for a set-pressure of 18.6MPa, the gap spacing due to the form and waviness is plastically deformed, closing the gap spacing. A secondary factor known as valve swivel was also investigated finding that it has no effect on leakage. Also from the roughness numerical CFD model, the permeability coefficient is found. In addition, the numerical approach can potentially be applied to other metal-to-metal contacting surface components, such as flanges with metal gaskets, to help eliminate leakage
Slowly varying pipe flow of thixotropic fluids
Get PDFIn this thesis we study lubrication flows of thixotropic and antithixotropic fluids in two flow problems: unsteady flow in a slowly varying 3D pipe, and oscillating flow in a uniform cylindrical pipe. We consider two fluid models which exhibit interesting non-Newtonian behaviour: the viscous Moore-Mewis-Wagner (MMW)model, and the viscoplastic Houška model.In Chapters 2-6 we study unsteady thixotropic flow in a slowly varying pipe, in a particular regime in which the thixotropic effects are considered 'weak', with the aim of determining whether we may describe generally the qualitative behaviour of thixotropic fluids in such flows. Previous work by Pritchard et al. [Journalof Non-Newtonian Fluid Mechanics, 238: 140-157, 2016] in the related problem of steady 2D channel flow suggests that such a description may be available.After obtaining the governing equations for this problem, we perform a detailed analysis of the flow for the MMW and Houška models, and determine all of the possible behaviours of these models. This analysis shows that the results and physical interpretations of Pritchard et al. are insightful but not complete. We also study the application of an off-the-shelf finite element program to determine the suitability of such programs for studying slowly varying thixotropic flows.In Chapter 7 we study the similar but simpler problem of unsteady thixotropic pipe flow driven by an oscillating pressure gradient. This problem is simpler than the problem considered in Chapters 2-6, which allows us to explore a wider range of thixotropic behaviours, in which the thixotropic effects range from 'weak' to'strong'. We are able to describe the full range of thixotropic behaviour using a combination of analytical and numerical methods.In this thesis we study lubrication flows of thixotropic and antithixotropic fluids in two flow problems: unsteady flow in a slowly varying 3D pipe, and oscillating flow in a uniform cylindrical pipe. We consider two fluid models which exhibit interesting non-Newtonian behaviour: the viscous Moore-Mewis-Wagner (MMW)model, and the viscoplastic Houška model.In Chapters 2-6 we study unsteady thixotropic flow in a slowly varying pipe, in a particular regime in which the thixotropic effects are considered 'weak', with the aim of determining whether we may describe generally the qualitative behaviour of thixotropic fluids in such flows. Previous work by Pritchard et al. [Journalof Non-Newtonian Fluid Mechanics, 238: 140-157, 2016] in the related problem of steady 2D channel flow suggests that such a description may be available.After obtaining the governing equations for this problem, we perform a detailed analysis of the flow for the MMW and Houška models, and determine all of the possible behaviours of these models. This analysis shows that the results and physical interpretations of Pritchard et al. are insightful but not complete. We also study the application of an off-the-shelf finite element program to determine the suitability of such programs for studying slowly varying thixotropic flows.In Chapter 7 we study the similar but simpler problem of unsteady thixotropic pipe flow driven by an oscillating pressure gradient. This problem is simpler than the problem considered in Chapters 2-6, which allows us to explore a wider range of thixotropic behaviours, in which the thixotropic effects range from 'weak' to'strong'. We are able to describe the full range of thixotropic behaviour using a combination of analytical and numerical methods
Inhibition of the DHHC superfamily : development of chemical tools
Get PDFAcylation, the attachment of fatty acids onto cysteine residues, is a major post-translational modification of cellular proteins, catalysed by the DHHC superfamily. The actions of acylation impact on a number of important physiological processes, and defects in these processes have been linked to a range of diseases and disorders. A major effort has been invested in identifying the substrates that DHHC enzymes are active against, however, there is still a lack of understanding of the specific substrate profiles of individual enzymes and how DHHC-substrate specificity is achieved. To begin to assess the downstream effects of palmitoylation by this enzyme superfamily, and in turn assess the possibility of targeting palmitoylation and interrogating its therapeutic potential, chemical tools are required. The University of Strathclyde has established a partnership with Ono Pharmaceuticals, in Japan, and Professor Luke Chamberlain from the Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS). The overall objective from this partnership is to provide chemical probes to elucidate DHHC fatty acid selectivity and DHHC-substrate specificity profiles, and to prepare selective inhibitors for members of the DHHC superfamily. The first short-term aim of the project was to establish selectivity between two DHHC enzymes, DHHC3 and DHHC7, and to develop selective inhibitors of S-acylation. In order to bring this project forward, six series of compounds have been synthesised, and tested within a cell-based assay. Two 'hit' compounds have been identified as 'semi-pan' inhibitors of S-acylation by the DHHC superfamily. The second part of the project was to develop a tool compound capable of elucidating DHHC-substrate profiles. One such compound was proposed and synthetic routes towards it are under development. The final aim of the project was to provide inhibitors of DHHC2. Three series of compounds have been targeted, synthesised and tested within an in vitro assay. One hit compound has been identified as a potential cysteine selective warhead and an SAR has been carried out.Acylation, the attachment of fatty acids onto cysteine residues, is a major post-translational modification of cellular proteins, catalysed by the DHHC superfamily. The actions of acylation impact on a number of important physiological processes, and defects in these processes have been linked to a range of diseases and disorders. A major effort has been invested in identifying the substrates that DHHC enzymes are active against, however, there is still a lack of understanding of the specific substrate profiles of individual enzymes and how DHHC-substrate specificity is achieved. To begin to assess the downstream effects of palmitoylation by this enzyme superfamily, and in turn assess the possibility of targeting palmitoylation and interrogating its therapeutic potential, chemical tools are required. The University of Strathclyde has established a partnership with Ono Pharmaceuticals, in Japan, and Professor Luke Chamberlain from the Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS). The overall objective from this partnership is to provide chemical probes to elucidate DHHC fatty acid selectivity and DHHC-substrate specificity profiles, and to prepare selective inhibitors for members of the DHHC superfamily. The first short-term aim of the project was to establish selectivity between two DHHC enzymes, DHHC3 and DHHC7, and to develop selective inhibitors of S-acylation. In order to bring this project forward, six series of compounds have been synthesised, and tested within a cell-based assay. Two 'hit' compounds have been identified as 'semi-pan' inhibitors of S-acylation by the DHHC superfamily. The second part of the project was to develop a tool compound capable of elucidating DHHC-substrate profiles. One such compound was proposed and synthetic routes towards it are under development. The final aim of the project was to provide inhibitors of DHHC2. Three series of compounds have been targeted, synthesised and tested within an in vitro assay. One hit compound has been identified as a potential cysteine selective warhead and an SAR has been carried out
Novel camel milk-derived proteins and their application in the management of acne vulgaris
Get PDFAcne vulgaris, caused by the bacterium P. acnes, is the most common cutaneous disorder in adolescents. Acne is not a life-threatening condition, however, it has significant psychological and physical effects on patients. P. acnes is capable of causing remarkable inflammatory responses. Topical therapy is advisable in acne treatment in mild to moderate acne conditions. Recently, available treatments for acne are mostly based on antibiotics and retinoids. The use of antibiotics has the limitations of developing bacterial resistance, while retinoids are highly teratogenic. The bacterial resistance and teratogenicity of isotretinoin led scientists to search for more potent and safer therapeutic options. Camel milk has been used in the preparation of pharmaceutical and cosmetic compositions such as anti-acne products. It was found that camel milk composition is closer to the human milk. Passive immunity is provided to new-borns by Immunoglobulins present in colostrum until its own immune system matures. The concentration in colostrum of specific antibodies against pathogens can be raised by immunizing a mammal with these pathogens or their antigens. Immunized milk products are preparations made of such hyper-immune antibodies enriched from it. Camel milk and milk-derived products have a growing potential therapeutic value. The objective of this research is to evaluate the antimicrobial and anti-inflammatory effects of immunized camel milk whey and its components against P. acnes and to develop a formula that harnesses all its beneficial properties. P. acnes was heat-killed in culture to obtain their outer membrane proteins (OMPs). The OMPs were mapped and quantified using SDS-PAGE and Bradford Assay, respectively. OMPs were used to prepare a vaccination injected into female lactating camels in timely manner. The immunized camel milk was collected then pasteurized, delipidized, de-caseinated, and freeze-dried to obtain the whey into powder form. The anti-P.acnes antibodies in the immunized camel whey were separated using Protein G and Protein A Chromatography and quantified by SDS-PAGE and ELISA, respectively. Then, the antimicrobial peptides (AMPs) including PGRPs and Lactoferrin were isolated by Heparin Affinity Chromatography, and mapped by SDS-PAGE. The antimicrobial and anti-inflammatory activity of the immunized camel whey and its constituents against P. acnes was evaluated in vitro. In vivo activity was also evaluated using rabbit ear model. After the activity of the immunized camel whey was confirmed, four topical formulae were developed and their composition and preparation protocol were patented. The findings of this research imply that the constituents of immunized camel milk whey (i.e. polyclonal anti-P. acnes antibodies, peptidoglycan recognition proteins (PGRPs), and lactoferrin) possess significant antimicrobial and anti-inflammatory activity against P. acnes, 90% and 70%, respectively. Topical formulae including; facial wash, serum, cream and gel enriched with 3% to 5% of immunized camel milk whey were developed and their activity against P. acnes was evaluated. Immunized camel milk whey that has been developed in this research exerts significant antimicrobial and anti-inflammatory activity against P. acnes and the unique composition formulated has been patented. Furthermore, the stability of the topical cream was validated to show that the antibodies in the cream formula retained around 75% of their activity.Acne vulgaris, caused by the bacterium P. acnes, is the most common cutaneous disorder in adolescents. Acne is not a life-threatening condition, however, it has significant psychological and physical effects on patients. P. acnes is capable of causing remarkable inflammatory responses. Topical therapy is advisable in acne treatment in mild to moderate acne conditions. Recently, available treatments for acne are mostly based on antibiotics and retinoids. The use of antibiotics has the limitations of developing bacterial resistance, while retinoids are highly teratogenic. The bacterial resistance and teratogenicity of isotretinoin led scientists to search for more potent and safer therapeutic options. Camel milk has been used in the preparation of pharmaceutical and cosmetic compositions such as anti-acne products. It was found that camel milk composition is closer to the human milk. Passive immunity is provided to new-borns by Immunoglobulins present in colostrum until its own immune system matures. The concentration in colostrum of specific antibodies against pathogens can be raised by immunizing a mammal with these pathogens or their antigens. Immunized milk products are preparations made of such hyper-immune antibodies enriched from it. Camel milk and milk-derived products have a growing potential therapeutic value. The objective of this research is to evaluate the antimicrobial and anti-inflammatory effects of immunized camel milk whey and its components against P. acnes and to develop a formula that harnesses all its beneficial properties. P. acnes was heat-killed in culture to obtain their outer membrane proteins (OMPs). The OMPs were mapped and quantified using SDS-PAGE and Bradford Assay, respectively. OMPs were used to prepare a vaccination injected into female lactating camels in timely manner. The immunized camel milk was collected then pasteurized, delipidized, de-caseinated, and freeze-dried to obtain the whey into powder form. The anti-P.acnes antibodies in the immunized camel whey were separated using Protein G and Protein A Chromatography and quantified by SDS-PAGE and ELISA, respectively. Then, the antimicrobial peptides (AMPs) including PGRPs and Lactoferrin were isolated by Heparin Affinity Chromatography, and mapped by SDS-PAGE. The antimicrobial and anti-inflammatory activity of the immunized camel whey and its constituents against P. acnes was evaluated in vitro. In vivo activity was also evaluated using rabbit ear model. After the activity of the immunized camel whey was confirmed, four topical formulae were developed and their composition and preparation protocol were patented. The findings of this research imply that the constituents of immunized camel milk whey (i.e. polyclonal anti-P. acnes antibodies, peptidoglycan recognition proteins (PGRPs), and lactoferrin) possess significant antimicrobial and anti-inflammatory activity against P. acnes, 90% and 70%, respectively. Topical formulae including; facial wash, serum, cream and gel enriched with 3% to 5% of immunized camel milk whey were developed and their activity against P. acnes was evaluated. Immunized camel milk whey that has been developed in this research exerts significant antimicrobial and anti-inflammatory activity against P. acnes and the unique composition formulated has been patented. Furthermore, the stability of the topical cream was validated to show that the antibodies in the cream formula retained around 75% of their activity
Development of a guided wave EMAT online inspection system for Al/Al-Sn/Al/steel and CuSn/steel bimetal strip bond quality control used in the automotive industry
Get PDFCold roll bonded (CRB) Al/Al-Sn/Al/steel and sintered CuSnNi/steel bimetal strips are used in the automotive industry for the manufacture of engine bearings, bushes and thrust washers. Any defects such as delamination or porosity that occur in bimetal strips during manufacturing can cause problems at downstream production steps and if they remain undetected, could result in components failing in the field, which is a significant business risk.;One way to reduce this business risk is to install a final inspection system on a continuous production line as the strip passes a fixed inspection point. In process control this could alert the operators to reject defective material and correct process parameters when the defect occurs. As this system requires 100% volumetric inspection, installing it has its challenges due to the harsh manufacturing environment in which the strip moves at up to 20 m/min in the processing lines at room temperature.;A literature review and feasibility study on different non-destructive testing (NDT) techniques to inspect bond quality of CRBed Al/Al-Sn/Al/steel bimetal strips was conducted to assess technologies that could be developed for serial inspection. Guided waves generated using Electromagnetic Acoustic Transducers (EMATs) was identified as best suited for this application. Since this technology was not available off-the-shelf, significant research and experimental work was carried out to develop an automated prototype system.;The system was successfully installed at a strip processing line and demonstrated the online bond inspection capability for Al/Al-Sn/Al/steel and CuSnNi/steel bimetal strips, which is the main achievement of this EngD project. For CuSnNi/steel strips, causes of defects and preventative control measures were studied and examined. Industrialisation of the inspection system will significantly reduce the company business risk and improve bond quality of bimetal strips.Cold roll bonded (CRB) Al/Al-Sn/Al/steel and sintered CuSnNi/steel bimetal strips are used in the automotive industry for the manufacture of engine bearings, bushes and thrust washers. Any defects such as delamination or porosity that occur in bimetal strips during manufacturing can cause problems at downstream production steps and if they remain undetected, could result in components failing in the field, which is a significant business risk.;One way to reduce this business risk is to install a final inspection system on a continuous production line as the strip passes a fixed inspection point. In process control this could alert the operators to reject defective material and correct process parameters when the defect occurs. As this system requires 100% volumetric inspection, installing it has its challenges due to the harsh manufacturing environment in which the strip moves at up to 20 m/min in the processing lines at room temperature.;A literature review and feasibility study on different non-destructive testing (NDT) techniques to inspect bond quality of CRBed Al/Al-Sn/Al/steel bimetal strips was conducted to assess technologies that could be developed for serial inspection. Guided waves generated using Electromagnetic Acoustic Transducers (EMATs) was identified as best suited for this application. Since this technology was not available off-the-shelf, significant research and experimental work was carried out to develop an automated prototype system.;The system was successfully installed at a strip processing line and demonstrated the online bond inspection capability for Al/Al-Sn/Al/steel and CuSnNi/steel bimetal strips, which is the main achievement of this EngD project. For CuSnNi/steel strips, causes of defects and preventative control measures were studied and examined. Industrialisation of the inspection system will significantly reduce the company business risk and improve bond quality of bimetal strips
Children referred for additional support for literacy difficulties : their views of being included
Get PDFThe Education (Additional Support for Learning) (Scotland) Act 2004, as amended, provides the human rights-based legal framework which underpins the system for identifying and supporting the additional support need of any pupil in Scotland. The Supporting Children's Learning Code of Practice (2017) details the duties on education authorities and other relevant agencies to support learning. In response to these legislative and practice frameworks, Scottish schools operate a staged intervention model (levels 1- 4/ stage 1- 4) for identifying and supporting young people with additional support needs in schools.;However, despite these positive legislative and policy frameworks, the system does not always operate successfully to deliver the rights and entitlements of young people, in schools pupils with literacy difficulties continue to experience challenges in school, and a particularly difficult time appears to be at Stage 1 and 2 as the process begins.;The theoretical context for this research is the capability approach of Amarya Sen (1979). The purpose of this research is to document and explore differing pupil experiences of, and perspectives on, the support processes during Stage 1 and Stage 2 intervention in one Scottish secondary school. Using semi structured interviews and visual data techniques (pictures and photographs) the experiences and opinions of the young people were gathered.;This research finds that the pupils did not have a depth of knowledge of the staged intervention system and did not feel involved or listened to throughout their experience. The perception of the literacy difficulties and challenges in learning framed the learner identity, and challenges continued despite staged intervention support.;It concludes that pupil voice is potentially a strong change-agent and that insights gathered from the pupil perspective offer an important source of data that could prompt professional reflection on the support processes adopted in schools.The Education (Additional Support for Learning) (Scotland) Act 2004, as amended, provides the human rights-based legal framework which underpins the system for identifying and supporting the additional support need of any pupil in Scotland. The Supporting Children's Learning Code of Practice (2017) details the duties on education authorities and other relevant agencies to support learning. In response to these legislative and practice frameworks, Scottish schools operate a staged intervention model (levels 1- 4/ stage 1- 4) for identifying and supporting young people with additional support needs in schools.;However, despite these positive legislative and policy frameworks, the system does not always operate successfully to deliver the rights and entitlements of young people, in schools pupils with literacy difficulties continue to experience challenges in school, and a particularly difficult time appears to be at Stage 1 and 2 as the process begins.;The theoretical context for this research is the capability approach of Amarya Sen (1979). The purpose of this research is to document and explore differing pupil experiences of, and perspectives on, the support processes during Stage 1 and Stage 2 intervention in one Scottish secondary school. Using semi structured interviews and visual data techniques (pictures and photographs) the experiences and opinions of the young people were gathered.;This research finds that the pupils did not have a depth of knowledge of the staged intervention system and did not feel involved or listened to throughout their experience. The perception of the literacy difficulties and challenges in learning framed the learner identity, and challenges continued despite staged intervention support.;It concludes that pupil voice is potentially a strong change-agent and that insights gathered from the pupil perspective offer an important source of data that could prompt professional reflection on the support processes adopted in schools
Heterogenous integration of diamond with non-native substrates
Get PDFStrathclyde theses - ask staff. Thesis no. : T15227This thesis addresses the challenges with utilising diamond for integrated optical devices; a platform where its impressive material properties can be exploited. The major objective was to develop a process by which diamond could be heterogeneously integrated with non-native device platforms, to overcome its limited geometry. A process was developed for fabrication, handling, and hybrid integration of ultra thin diamond membranes. Plasma-etch chemistries were developed, that enabled such processing, and provided sub-nm r.m.s. roughness.Two sets of monolithic diamond structures were fabricated and transfer printed with a thickness down to ~10 nm. For thickness characterisation, diamond platelets, finding a low local-variation across typical device geometries. Diamond resonator devices were also fabricated and when integrated with SOI waveguides they showed high Q-factors as large as 1.8 x 10⁵. Thermo-optic tuning of these devices by > 450 pm at low mW powers was demonstrated, which has great significance to all integrated optical fields where resonant frequency of a cavity is important. The techniques developed are independent of integration platforms and are of wide reaching relevance to the optics community.This thesis addresses the challenges with utilising diamond for integrated optical devices; a platform where its impressive material properties can be exploited. The major objective was to develop a process by which diamond could be heterogeneously integrated with non-native device platforms, to overcome its limited geometry. A process was developed for fabrication, handling, and hybrid integration of ultra thin diamond membranes. Plasma-etch chemistries were developed, that enabled such processing, and provided sub-nm r.m.s. roughness.Two sets of monolithic diamond structures were fabricated and transfer printed with a thickness down to ~10 nm. For thickness characterisation, diamond platelets, finding a low local-variation across typical device geometries. Diamond resonator devices were also fabricated and when integrated with SOI waveguides they showed high Q-factors as large as 1.8 x 10⁵. Thermo-optic tuning of these devices by > 450 pm at low mW powers was demonstrated, which has great significance to all integrated optical fields where resonant frequency of a cavity is important. The techniques developed are independent of integration platforms and are of wide reaching relevance to the optics community
Integrated CFD modelling for nozzle design for fog generation
Get PDFPreviously held under moratorium from 22nd August 2019 until 22nd August 2023.Sprays, as dynamic droplet/particle clouds of functional substances, are widely used in industry, agriculture, and our daily lives. Sprays are different depending on the situations in which they are used and are characterized by pattern, capacity, impact, angle and drop size. Each application has its own requirements for spray characteristics and these requirements are demanding continuing development of atomization systems. Improvement of spraying systems which use a nozzle to convert bulk liquid into dispersed droplets requires knowledge of the atomization process. Although great effort has been dedicated to study, describe, and predict spray generation, flow evolution from continuous stream to separated droplets is still beyond full understanding. What is more, internal nozzle flow and initial breakup that decide the characteristics of far-field spray take place inside enclosed injector, this makes it challenging for non-invasive measurement. At the beginning of this study, available nozzle designs and their performances, and commonly used approaches for modelling fluid flows were reviewed. It is emphasised that there is currently a lack of detailed design principles for sprays with a fine droplet and high flow rate, this type has a great potential for wide application. However, this remains a challenge for advanced nozzle design. To overcome difficulties in the nozzle design, a development workflow is planned in detail. Requirement-oriented nozzle optimization and an integrated CFD model establishment are two closely related components in this study. Numerical results help the justification and dimension selection for nozzle design while physical tests on the nozzle help to validate the CFD model. Architecture for integrated CFD modelling is discussed including the steps for bridging the knowledge gap between different numerical theories. CFD-aided advanced nozzle design and optimization actions are conducted. With parametric modelling a large number of nozzle dimensions can be tested numerically, this largely reduces the development cycle and cost compared to real part fabrication and physical testing. The first detailed design of a nozzle is achieved based on the results from CFD modelling. The designed nozzle was fabricated and then tested in a fog dynamic lab. The results of flow rates, spray angles, and droplet sizes were recorded. These results are used to validate the proposed integrated CFD model. Design of the nozzle was improved by requirement-driven optimization. Virtual testing based on valid integrated CFD modelling is used to study the optimized nozzle design. As an important achievement of this study, a multi-fluid fogging nozzle was designed. Numerical evaluation using integrated CFD modelling shown that the nozzle could generate sprays with flow rate up to 0.53 / and droplets ranging mostly from 2 to 5 . The designed nozzle was manufactured and tested in laboratory in Spain. Data obtained from experiments successfully validates the performance predicted by simulations. Being capable to generate spray with high flow rate and fine droplets, this multi-fluid nozzle design shows its strong potential for fogging applications such as firefighting, pest management, and dust suppression.Sprays, as dynamic droplet/particle clouds of functional substances, are widely used in industry, agriculture, and our daily lives. Sprays are different depending on the situations in which they are used and are characterized by pattern, capacity, impact, angle and drop size. Each application has its own requirements for spray characteristics and these requirements are demanding continuing development of atomization systems. Improvement of spraying systems which use a nozzle to convert bulk liquid into dispersed droplets requires knowledge of the atomization process. Although great effort has been dedicated to study, describe, and predict spray generation, flow evolution from continuous stream to separated droplets is still beyond full understanding. What is more, internal nozzle flow and initial breakup that decide the characteristics of far-field spray take place inside enclosed injector, this makes it challenging for non-invasive measurement. At the beginning of this study, available nozzle designs and their performances, and commonly used approaches for modelling fluid flows were reviewed. It is emphasised that there is currently a lack of detailed design principles for sprays with a fine droplet and high flow rate, this type has a great potential for wide application. However, this remains a challenge for advanced nozzle design. To overcome difficulties in the nozzle design, a development workflow is planned in detail. Requirement-oriented nozzle optimization and an integrated CFD model establishment are two closely related components in this study. Numerical results help the justification and dimension selection for nozzle design while physical tests on the nozzle help to validate the CFD model. Architecture for integrated CFD modelling is discussed including the steps for bridging the knowledge gap between different numerical theories. CFD-aided advanced nozzle design and optimization actions are conducted. With parametric modelling a large number of nozzle dimensions can be tested numerically, this largely reduces the development cycle and cost compared to real part fabrication and physical testing. The first detailed design of a nozzle is achieved based on the results from CFD modelling. The designed nozzle was fabricated and then tested in a fog dynamic lab. The results of flow rates, spray angles, and droplet sizes were recorded. These results are used to validate the proposed integrated CFD model. Design of the nozzle was improved by requirement-driven optimization. Virtual testing based on valid integrated CFD modelling is used to study the optimized nozzle design. As an important achievement of this study, a multi-fluid fogging nozzle was designed. Numerical evaluation using integrated CFD modelling shown that the nozzle could generate sprays with flow rate up to 0.53 / and droplets ranging mostly from 2 to 5 . The designed nozzle was manufactured and tested in laboratory in Spain. Data obtained from experiments successfully validates the performance predicted by simulations. Being capable to generate spray with high flow rate and fine droplets, this multi-fluid nozzle design shows its strong potential for fogging applications such as firefighting, pest management, and dust suppression
Voltage-based backup protection and protection performance analysis using wide-area PMU data
No full textThis dissertation describes a system that analyses and summarises the operation of protection and provides backup protection functionality, using only voltage data from PMUs and wide-area communications infrastructure. The ability to rapidly identify the presence of faults, their locations and the presence of protection/circuit breaker failures, solely from voltage measurements, is the overarching contribution from this work. The scheme can operate in addition to existing backup schemes to provide a further, or alternative, relatively inexpensive, effective, simple, fast, wide-area backup protection to improve the resilience of power systems. Methods of power system model simplification for different types of fault have also been developed for establishing the capabilities and voltage thresholds of the scheme, and this simplification method is also claimed as a contribution arising from the work. It is shown how the system can operate for a wide range of fault levels, types and resistances { thereby addressing one of the key challenges for protection associated with concerns over protection in the context of reducing and more variable fault levels in future power systems.To validate the developed scheme, case studies assessing scheme performance in several scenarios are presented. Variations of fault resistance, time of fault occurrence, fault location, and fault levels are simulated in Matlab (Simscape Power Systems) using the well-established and accepted IEEE 14-bus network.Hardware in the loop tests are also conducted using an RTDS and actual PMU devices to test and validate the performance of the scheme and to demonstrate its ability to operate using actual hardware and in real time. Applicability of the developed system to large-scale power networks is also demonstrated. It is shown that the scheme is suited to interconnected power systems, and can operate with both reduced fault levels and for different types of faults with high resistances.Future work and suggestions for extensions to the developed system are also presented.This dissertation describes a system that analyses and summarises the operation of protection and provides backup protection functionality, using only voltage data from PMUs and wide-area communications infrastructure. The ability to rapidly identify the presence of faults, their locations and the presence of protection/circuit breaker failures, solely from voltage measurements, is the overarching contribution from this work. The scheme can operate in addition to existing backup schemes to provide a further, or alternative, relatively inexpensive, effective, simple, fast, wide-area backup protection to improve the resilience of power systems. Methods of power system model simplification for different types of fault have also been developed for establishing the capabilities and voltage thresholds of the scheme, and this simplification method is also claimed as a contribution arising from the work. It is shown how the system can operate for a wide range of fault levels, types and resistances { thereby addressing one of the key challenges for protection associated with concerns over protection in the context of reducing and more variable fault levels in future power systems.To validate the developed scheme, case studies assessing scheme performance in several scenarios are presented. Variations of fault resistance, time of fault occurrence, fault location, and fault levels are simulated in Matlab (Simscape Power Systems) using the well-established and accepted IEEE 14-bus network.Hardware in the loop tests are also conducted using an RTDS and actual PMU devices to test and validate the performance of the scheme and to demonstrate its ability to operate using actual hardware and in real time. Applicability of the developed system to large-scale power networks is also demonstrated. It is shown that the scheme is suited to interconnected power systems, and can operate with both reduced fault levels and for different types of faults with high resistances.Future work and suggestions for extensions to the developed system are also presented
Experimental and modelling study on the release of potassium during biomass combustion
Get PDFUnderstanding the release mechanism of potassium (K) is crucial in tackling alkali metal-induced ash problems during the combustion process of biomass. This thesis focuses onenhancing the knowledge on the release mechanism of potassium experimentally anddeveloping a model to predict the release profiles of potassium compounds from biomass.In the beginning, the thesis investigated the thermal characteristics of biomass and itsmajor chemical components in a thermogravimetric analyser (TGA). According to thetests, the thermal conversion process of natural biomass and be predicted through theanalyses of artificial biomass, which is the mixture of major chemical components. Theresults illustrate the feasibility to use major chemical components as initial inputs in thebiomass combustion model. Biomass combustion experiments were then performed in ahigh-temperature furnace-balance system (FBS). The results revealed that the finaltemperature affects the K transition the most. Over 60% of the initial K was lost as thefinal temperature increased from 30℃ to 1000℃. The heating rate affects the K transitionduring combustion by influencing the devolatilisation of volatile matter related K and thestructural changes of particles. The higher the heating rate, the more release of K. Thedeveloped kinetically controlled model was validated and used to estimate the release ofdifferent K compounds under different scenarios. The results indicate that KCl is themajor compound released at the early stage of combustion, followed by KOH and K₂SO₄.Analysing the reaction path of K reveals that KO and KO₂ are the most criticalintermediate species during combustion. The initial concentration of Cl significantlyaffects the release of major species: KCl, KOH, HCl and K₂SO₄; while the initialconcentration of S can affect the release of KOH and K₂SO₄ at high temperatures. Theexistence of O₂ in the system favours the formation of KO and KO₂, and thus to controlthe release of major K species.Understanding the release mechanism of potassium (K) is crucial in tackling alkali metal-induced ash problems during the combustion process of biomass. This thesis focuses onenhancing the knowledge on the release mechanism of potassium experimentally anddeveloping a model to predict the release profiles of potassium compounds from biomass.In the beginning, the thesis investigated the thermal characteristics of biomass and itsmajor chemical components in a thermogravimetric analyser (TGA). According to thetests, the thermal conversion process of natural biomass and be predicted through theanalyses of artificial biomass, which is the mixture of major chemical components. Theresults illustrate the feasibility to use major chemical components as initial inputs in thebiomass combustion model. Biomass combustion experiments were then performed in ahigh-temperature furnace-balance system (FBS). The results revealed that the finaltemperature affects the K transition the most. Over 60% of the initial K was lost as thefinal temperature increased from 30℃ to 1000℃. The heating rate affects the K transitionduring combustion by influencing the devolatilisation of volatile matter related K and thestructural changes of particles. The higher the heating rate, the more release of K. Thedeveloped kinetically controlled model was validated and used to estimate the release ofdifferent K compounds under different scenarios. The results indicate that KCl is themajor compound released at the early stage of combustion, followed by KOH and K₂SO₄.Analysing the reaction path of K reveals that KO and KO₂ are the most criticalintermediate species during combustion. The initial concentration of Cl significantlyaffects the release of major species: KCl, KOH, HCl and K₂SO₄; while the initialconcentration of S can affect the release of KOH and K₂SO₄ at high temperatures. Theexistence of O₂ in the system favours the formation of KO and KO₂, and thus to controlthe release of major K species
Access Repository Dashboard
Do you manage STAX (Strathclyde Repository)? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!