Three-dimensional visualisation and quantitative characterisation of fossil fuel flames using tomography and digital imaging techniques

This thesis describes the design, implementation and experimental evaluation of a prototype instrumentation system for the three-dimensional (3-D) visualisation and quantitative characterisation of fossil fuel flames. A review of methodologies and technologies for the 3-D visualisation and characterisation of combustion flames is given, together with a discussion of main difficulties and technical requirements in their applications. A strategy incorporating optical sensing, digital image processing and tomographic reconstruction techniques is proposed. The strategy was directed towards the reconstruction of 3-D models of a flame and the subsequent quantification of its 3-D geometric, luminous and fluid dynamic parameters. Based on this strategy, a flame imaging system employing three identical synchronised RG B cameras has been developed. The three cameras, placed equidistantly and equiangular on a semicircle around the flame, captured six simultaneous images of the flame from six different directions. Dedicated computing algorithms, based on image processing and tomographic reconstruction techniques have been developed to reconstruct the 3-D models of a flame. A set of geometric, luminous and fluid dynamic parameters, including surface area, volume, length, circularity, luminosity and temperature are determined from the 3-D models generated. Systematic design and experimental evaluation of the system on a gas-fired combustion rig are reported. The accuracy, resolution and validation of the system were also evaluated using purpose-designed templates including a high precision laboratory ruler, a colour flat panel and a tungsten lamp. The results obtained from the experimental evaluation are presented and the relationship between the measured parameters and the corresponding operational conditions are quantified. Preliminary investigations were conducted on a coal-fired industry-scale combustion test facility. The multi-camera system was reconfigured to use only one camera due to the restrictions at the site facility. Therefore the property of rotational symmetry of the flame had to be assumed. Under such limited conditions, the imaging system proved to provide a good reconstruction of the internal structures and luminosity variations inside the This thesis describes the design, implementation and experimental evaluation of a prototype instrumentation system for the three-dimensional (3-D) visualisation and quantitative characterisation of fossil fuel flames. A review of methodologies and technologies for the 3-D visualisation and characterisation of combustion flames is given, together with a discussion of main difficulties and technical requirements in their applications. A strategy incorporating optical sensing, digital image processing and tomographic reconstruction techniques is proposed. The strategy was directed towards the reconstruction of 3-D models of a flame and the subsequent quantification of its 3-D geometric, luminous and fluid dynamic parameters. Based on this strategy, a flame imaging system employing three identical synchronised RG B cameras has been developed. The three cameras, placed equidistantly and equiangular on a semicircle around the flame, captured six simultaneous images of the flame from six different directions. Dedicated computing algorithms, based on image processing and tomographic reconstruction techniques have been developed to reconstruct the 3-D models of a flame. A set of geometric, luminous and fluid dynamic parameters, including surface area, volume, length, circularity, luminosity and temperature are determined from the 3-D models generated. Systematic design and experimental evaluation of the system on a gas-fired combustion rig are reported. The accuracy, resolution and validation of the system were also evaluated using purpose-designed templates including a high precision laboratory ruler, a colour flat panel and a tungsten lamp. The results obtained from the experimental evaluation are presented and the relationship between the measured parameters and the corresponding operational conditions are quantified. Preliminary investigations were conducted on a coal-fired industry-scale combustion test facility. The multi-camera system was reconfigured to use only one camera due to the restrictions at the site facility. Therefore the property of rotational symmetry of the flame had to be assumed. Under such limited conditions, the imaging system proved to provide a good reconstruction of the internal structures and luminosity variations inside the This thesis describes the design, implementation and experimental evaluation of a prototype instrumentation system for the three-dimensional (3-D) visualisation and quantitative characterisation of fossil fuel flames. A review of methodologies and technologies for the 3-D visualisation and characterisation of combustion flames is given, together with a discussion of main difficulties and technical requirements in their applications. A strategy incorporating optical sensing, digital image processing and tomographic reconstruction techniques is proposed. The strategy was directed towards the reconstruction of 3-D models of a flame and the subsequent quantification of its 3-D geometric, luminous and fluid dynamic parameters. Based on this strategy, a flame imaging system employing three identical synchronised RG B cameras has been developed. The three cameras, placed equidistantly and equiangular on a semicircle around the flame, captured six simultaneous images of the flame from six different directions. Dedicated computing algorithms, based on image processing and tomographic reconstruction techniques have been developed to reconstruct the 3-D models of a flame. A set of geometric, luminous and fluid dynamic parameters, including surface area, volume, length, circularity, luminosity and temperature are determined from the 3-D models generated. Systematic design and experimental evaluation of the system on a gas-fired combustion rig are reported. The accuracy, resolution and validation of the system were also evaluated using purpose-designed templates including a high precision laboratory ruler, a colour flat panel and a tungsten lamp. The results obtained from the experimental evaluation are presented and the relationship between the measured parameters and the corresponding operational conditions are quantified. Preliminary investigations were conducted on a coal-fired industry-scale combustion test facility. The multi-camera system was reconfigured to use only one camera due to the restrictions at the site facility. Therefore the property of rotational symmetry of the flame had to be assumed. Under such limited conditions, the imaging system proved to provide a good reconstruction of the internal structures and luminosity variations inside the flame. Suggestions for future development of the technology are also reported

An Optical Machine Vision System for Applications in Cytopathology

This paper discusses a new approach to the processes of object detection, recognition and classification in a digital image focusing on problem in Cytopathology. A unique self learning procedure is presented in order to incorporate expert knowledge. The classification method is based on the application of a set of features which includes fractal parameters such as the Lacunarity and Fourier dimension. Thus, the approach includes the characterisation of an object in terms of its fractal properties and texture characteristics. The principal issues associated with object recognition are presented which include the basic model and segmentation algorithms. The self-learning procedure for designing a decision making engine using fuzzy logic and membership function theory is also presented and a novel technique for the creation and extraction of information from a membership function considered. The methods discussed and the algorithms developed have a range of applications and in this work, we focus the engineering of a system for automating a Papanicolaou screening test

A real-time multi-sensor 3D surface shape measurement system using fringe analysis

This thesis presents a state-of-the-art multi-sensor, 3D surface shape measurement system that is based upon fringe projection/analysis and which operates at speeds approaching real-time. The research programme was carried out as part of MEGURATH (www.megurath.org), a collaborative research project with the aim of improving the treatment of cancer by radiotherapy. The aim of this research programme was to develop a real-time, multi-sensor 3D surface shape measurement system that is based on fringe analysis, which provides the flexibility to choose from amongst several different fringe profilometry methods and to manipulate their settings interactively. The system has been designed specifically to measure dynamic 3D human body surface shape and to act as an enabling technology for the purpose of performing Metrology Guided Radiotherapy (MGRT). However, the system has a wide variety of other potential applications, including 3D modelling and visualisation, verbatim replication, reverse engineering and industrial inspection. It can also be used as a rapid prototyping tool for algorithm development and testing, within the field of fringe pattern profilometry. The system that has been developed provides single, or multi-sensor, measurement modes that are adaptable to the specific requirements of a desired application. The multi-sensor mode can be useful for covering a larger measurement area, by providing a multi-viewpoint measurement. The overall measurement accuracy of the system is better than O.5mm, with measurement speeds of up to 3 million XYZ points/second using the single-sensor mode and rising to up to 4.6 million XYZ points/second when measuring in parallel using the three sensor multi-sensor mode. In addition the system provides a wide-ranging catalogue of fringe profilometry methods and techniques, that enables the reconstruction of 3D information through an interactive user selection of 183 possible different paths of main combinations. The research aspects behind the development of the system are presented in this thesis, along with the author's contribution to this field of research, which has included the provision of a comprehensive framework for producing such a novel optical profilometry system, and the specific techniques that were developed to fulfil the aims of this research programme. This mainly included the following advanced methods: a transversal calibration method for the optical system, an adaptive filtering technique for the Fourier Transform Profilometry (FTP) method, and a method to synthetically restore the locations of the triangulation spots. Similarly, potential applications for the system have been presented and feasibility and accuracy analyses have been conducted, presenting both qualitative and quantitative measurement results. To this end, the high robustness levels exhibited by the system have been demonstrated (in terms of adaptability, accuracy and measurement capability) by performing extensive real experiments and laboratory testing. Finally, a number of potential future system developments are described, with the intention of further extending the system capabilities

Finite-Rate Chemistry Effects in Turbulent Premixed Combustion

In recent times significant public attention has been drawn to the topic of combustion. This has been due to the fact that combustion is the underlying mechanism of several key challenges to modern society: climate change, energy security (finite reserves of fossil fuels) and air pollution. The further development of combustion science is undoubtedly necessary to find improved solutions to manage these combustion science related challenges in the near and long term future. Combustion is essentially an exothermic process, this exothermicity or heat release essentially occurs at small scales, by small scales it meant these scales are small relative to the fluid length scales, for example heat release layer thicknesses in flames are typically much less than the fluid integral length scales. As heat release occurs at small scales this means that in turbulent combustion the small scales of the turbulence (which can be of the order of the heat release layer thickness) can possibly interact and influence the heat release and thus chemistry of the flame reaction zone. Premixed combustion is a combustion mode where the fuel and oxidiser are completely premixed prior to the flame reaction zone, this mode of combustion has been shown to be a promising method to maximise combustion efficiency and minimise pollutant formation. The continued and further application of premixed combustion to practical applications is limited by the current understanding of turbulent premixed combustion, these limitations in understanding are linked to the specific flame phenomena that can significantly influence premixed combustion in a combustion device, examples of such phenomena are: flame flashback, flame extinction and fuel consumption rate – all phenomena that are influenced by the interaction of the small scales of turbulence and chemistry. It is the study and investigation of the interaction of turbulence and chemistry at the small scales (termed finite-rate chemistry) in turbulent premixed flames that is the aim of this thesis which is titled “Finite-rate chemistry effects in turbulent premixed combustion”. Two very closely related experimental burner geometries have been developed in this thesis: the Piloted Premixed Jet Burner (PPJB) and the Premixed Jet Burner (PJB). Both feature an axisymmetric geometry and exhibit a parabolic like flow field. The PPJB and PJB feature a small 4mm diameter central jet from which a high velocity lean-premixed methane-air mixture issues. Surrounding the central jet in the PPJB is a 23.5mm diameter pilot of stoichiometric methane-air products, the major difference between the PPJB and the PJB is that the PJB does not feature a stoichiometric pilot. The pilot in the PPJB provides a rich source of combustion intermediates and enthalpy which promotes initial ignition of the central jet mixture. Surrounding both the central jet and pilot is a large diameter hot coflow of combustion products. It is possible to set the temperature of the hot coflow to the adiabatic flame temperature of the central jet mixture to simulate straining and mixing against and with combustion products without introducing complexities such as quenching and dilution from cold air. By parametrically increasing the central jet velocity in the PPJB it is possible to show that there is a transition from a thin conical flame brush to a flame that exhibits extinction and re-ignition effects. The flames that exhibit extinction and re-ignition effects have a luminous region near the jet exit termed the initial ignition region. This is followed by a region of reduced luminosity further downstream termed the extinction region. Further downstream the flame luminosity increases this region is termed the re-ignition region. For the flames that exhibit extinction and re-ignition it is proposed that intense turbulent mixing and high scalar dissipation rates drives the initial extinction process after the influence of the pilot has ceased (x/D>10). Re-ignition is proposed to occur downstream where turbulent mixing and scalar dissipation rates have decreased allowing robust combustion to continue. As the PJB does not feature a pilot, the flame stabilisation structure is quite different to the PPJB. The flame structure in the PJB is essentially a lifted purely premixed flame, which is an experimental configuration that is also quite unique. A suite of laser diagnostic measurements has been parametrically applied to flames in the PPJB and PJB. Laser Doppler Velocimetry (LDV) has been utilised to measure the mean and fluctuating radial and axial components of velocity at a point, with relevant time and length scale information being extracted from these measurements. One of the most interesting results from the LDV measurements is that in the PPJB the pilot delays the generation of high turbulence intensities, for flames that exhibit extinction the rapid increase of turbulence intensity after the pilot corresponds to the start of the extinction region. Using the LDV derived turbulence characteristics and laminar flame properties and plotting these flames on a traditional turbulent regime diagram indicates that all of the flames examined should fall in the so call distributed reaction regime. Planar imaging experiments have been conducted for flames using the PPJB and PJB to investigate the spatial structure of the temperature and selected minor species fields. Results from two different simultaneous 2D Rayleigh and OH PLIF experiments and a simultaneous 2D Rayleigh, OH PLIF and CH2O PLIF experiment are reported. For all of the flames examined in the PPJB and PJB a general trend of decreasing conditional mean temperature gradient with increasing turbulence intensity is observed. This indicates that a trend of so called flame front thickening with increased turbulence levels occurs for the flames examined. It is proposed that the mechanism for this flame front thickening is due to eddies penetrating and embedding in the instantaneous flame front. In the extinction region it is found that the OH concentration is significantly reduced compared to the initial ignition region. In the re-ignition region it is found that the OH level increases again indicating that an increase in the local reaction rate is occurring. In laminar premixed flames CH2O occurs in a thin layer in the reaction zone, it is found for all of the flames examined that the CH2O layer is significantly thicker than the laminar flame. For the high velocity flames beyond x/D=15, CH2O no longer exist in a distinct layer but rather in a near uniform field for the intermediate temperature regions. Examination of the product of CH2O and OH reveals that the heat release in the initial ignition region is high and rapidly decreases in the extinction region, an increase in the heat release further downstream is observed corresponding to the re-ignition region. This finding corresponds well with the initial hypothesis of an extinction region followed by a re-ignition region that was based on the mean chemiluminescence images. Detailed simultaneous measurement of major and minor species has been conducted using the line Raman-Rayleigh-LIF technique with CO LIF and crossed plane-OH PLIF at Sandia National Laboratories. By measuring all major species it is also possible to define a mixture fraction for all three streams of the PPJB. Using these three mixture fractions it was found that the influence of the pilot in the PPJB decays very rapidly for all but the lowest velocity flames. It was also found that for the high velocity flames exhibiting extinction, a significant proportion of the coflow fluid is entrained into the central jet combustion process at both the extinction region and re-ignition regions. The product of CO and OH conditional on temperature is shown to be proportion to the net production rate of CO2 for certain temperature ranges. By examining the product of CO and OH the hypothesis of an initial ignition region followed by an extinction region then a re-ignition region for certain PPJB flames has been further validated complementing the [CH2O][OH] imaging results. Numerical modelling results using the transported composition probability density function (TPDF) method coupled to a conventional Reynolds averaged Naiver Stokes (RANS) solver are shown in this thesis to successfully predict the occurrence of finite-rate chemistry effects for the PM1 PPJB flame series. To calculate the scalar variance and the degree of finite-rate chemistry effects correctly, it is found that a value of the mixing constant ( ) of approximately 8.0 is required. This value of is much larger than the standard excepted range of 1.5-2.3 for that has been established for non-premixed combustion. By examining the results of the RANS turbulence model in a non-reacting variable density jet, it is shown that the primary limitation of the predictive capability of the TPDF-RANS method is the RANS turbulence model when applied to variable density flows

Automatic Construction of Immobilisation Masks for use in Radiotherapy Treatment of Head-and-Neck Cancer

Current clinical practice for immobilisation for patients undergoing brain or head and neck radiotherapy is normally achieved using Perspex or thermoplastic shells that are moulded to patient anatomy during a visit to the mould room. The shells are “made to measure” and the methods currently employed to make them require patients to visit the mould room. The mould room visit can be depressing and some patients find this process particularly unpleasant. In some cases, as treatment progresses, the tumour may shrink and therefore there may be a need for a further mould room visits. With modern manufacturing and rapid prototyping comes the possibility of determining the shape of the shells from the CT-scan of the patient directly, alleviating the need for making physical moulds from the patients’ head. However, extracting such a surface model remains a challenge and is the focus of this thesis. The aim of the work in this thesis is to develop an automatic pipeline capable of creating physical models of immobilisation shells directly from CT scans. The work includes an investigation of a number of image segmentation techniques to segment the skin/air interface from CT images. To enable the developed pipeline to be quantitatively evaluated we compared the 3D model generated from the CT data to ground truth obtained by 3D laser scans of masks produced by the mould room in the frame of a clinical trial. This involved automatically removing image artefacts due to fixations from CT imagery, automatic alignment (registration) between two meshes, measuring the degree of similarity between two 3D volumes, and automatic approach to evaluate the accuracy of segmentation. This thesis has raised and addressed many challenges within this pipeline. We have examined and evaluated each stage of the pipeline separately. The outcomes of the pipeline as a whole are currently being evaluated by a clinical trial (IRAS ID:209119, REC Ref.:16/YH/0485). Early results from the trial indicate that the approach is viable

Radio-Frequency Optically Pumped Magnetometers for Eddy Current Measurements

Radio-frequency optically pumped magnetometers (RF OPMs) are capable of measuring oscillating magnetic fields with high sensitivity in the fT/sqrt(Hz) range. Two types of RF OPMs are presented in this thesis. The first is a portable, orientation-based RF OPM with 600 fT/sqrt(Hz) sensitivity at 10 kHz in unshielded conditions, a new benchmark for a portable unshielded RF OPM, and 200 fT/sqrt(Hz) sensitivity at 10 kHz in shielded conditions, close to the spin projection noise limit. Eddy current measurements were performed with this OPM to remotely detect aluminium disks with diameters as small as 1.5 cm at distances of ~25 cm from both the excitation coil and the OPM, demonstrating the possibility of using OPMs for remote sensing. Off-axis measurements were performed with this OPM to illustrate how the OPM readout can be interpreted for remote sensing. All aspects of the theory, experimental setup and results relevant for this orientation-based RF OPM and eddy current measurements are presented in this thesis. The second OPM presented is a table-top alignment-based RF OPM in shielded conditions using a buffer gas cell. The benefit of alignment-based magnetometers over orientation-based RF OPMs is that they require only one laser beam, making them compact and robust. Until now, the alignment-based magnetometer had only been used with hand-blown paraffin-coated cells, but not with buffer gas cells that can be produced on a mass scale using microfabrication techniques. We present here an alignment-based magnetometer using a buffer gas cell (Cs and N2). This one-beam RF OPM with a buffer gas cell obtained a sensitivity of 325 fT/sqrt(Hz) with an 800 Hz bandwidth to 10 kHz oscillating magnetic fields and is calculated to be close to the spin projection noise limit. The non-linear Zeeman splitting is observed with both the buffer gas cell and a paraffin-coated cell. These results open up the possibility for commercialisation and further miniaturisation of RF OPMs. We derive a set of equations for the off-axis detection of electrically conductive spheres for the arbitrary positioning of the sphere and magnetometer. The equations are interpreted with a focus on predicting the expected signals for the imaging of the electrical conductivity of the human heart using RF OPMs to potentially help diagnose atrial fibrillation more effectively in the future. The optimal setups are discussed. Details on how to design compact, low-noise balanced photodetectors are discussed. Several printed circuit board designs are presented and tested. The performance of the balanced photodetector exceeds that of a commercial balanced photodetector at low frequencies, being shot noise limited for powers as low as 3 uW at frequencies of 3 kHz

Moving experience: an investigation of embodied knowledge and technology for reading flow in improvisation

A thesis submitted to the University of Bedfordshire in partial fulfilment of the requirements for the degree of Doctor of PhilosophyThe thesis is concerned with the exploration of the notion of ‘flow’ from both a psychological and dance analysis perspective in order to extend the meaning of flow and move beyond a partiality of understanding. The main aim of the thesis recognises the need to understand, identify and interpret an analysis of the moments of flow perceivable in a dancer’s body during improvisatory practice, through technologically innovative means. The research is undertaken via both philosophical and practical enquiry. It addresses phenomenology in order to resolve the mind/body debate and is applied to research in flow in psychology by Mihalyi Csikszentmihalyi, and flow in movement analysis by Rudolf Laban and Warren Lamb. The significance of this endeavour can be seen in the reconsideration of the relation between mind and body, and art and science which informs the methodology for the research (Part One). The three main outcomes of the research are related to each of the three subsequent parts. The first research outcome is the articulation of a transdisciplinary approach to understanding flow and was developed by expanding on the current definitions of flow through an innovative transdisciplinary methodology (Part Two). Research outcome two addresses the intersubjective nature of flow, which was identified within improvisation. From this two methods were constructed for the collection and interpretation of the experience of the dancer. Firstly, through reflective practice as defined by Donald Schön. And secondly, an argument was provided for the use of motion capture as an embodied tool which extends the dancers embodied cognitive capabilities in the moment of improvisation (Part Three). The final research outcome was thus theorised that such embodied empathic intersubjectivity does not require a direct identification of the other’s body but could be achieved through technologically mediated objects in the world (Part Four). Subsequently, the findings from the research could support further research within a number of fields including dance education, dance practice and dance therapy, psychology, neuroscience, gaming and interactive arts

Radio-Frequency Optically Pumped Magnetometers for Eddy Current Measurements

Radio-frequency optically pumped magnetometers (RF OPMs) are capable of measuring oscillating magnetic fields with high sensitivity in the fT/sqrt(Hz) range. Two types of RF OPMs are presented in this thesis. The first is a portable, orientation-based RF OPM with 600 fT/sqrt(Hz) sensitivity at 10 kHz in unshielded conditions, a new benchmark for a portable unshielded RF OPM, and 200 fT/sqrt(Hz) sensitivity at 10 kHz in shielded conditions, close to the spin projection noise limit. Eddy current measurements were performed with this OPM to remotely detect aluminium disks with diameters as small as 1.5 cm at distances of ~25 cm from both the excitation coil and the OPM, demonstrating the possibility of using OPMs for remote sensing. Off-axis measurements were performed with this OPM to illustrate how the OPM readout can be interpreted for remote sensing. All aspects of the theory, experimental setup and results relevant for this orientation-based RF OPM and eddy current measurements are presented in this thesis. The second OPM presented is a table-top alignment-based RF OPM in shielded conditions using a buffer gas cell. The benefit of alignment-based magnetometers over orientation-based RF OPMs is that they require only one laser beam, making them compact and robust. Until now, the alignment-based magnetometer had only been used with hand-blown paraffin-coated cells, but not with buffer gas cells that can be produced on a mass scale using microfabrication techniques. We present here an alignment-based magnetometer using a buffer gas cell (Cs and N2). This one-beam RF OPM with a buffer gas cell obtained a sensitivity of 325 fT/sqrt(Hz) with an 800 Hz bandwidth to 10 kHz oscillating magnetic fields and is calculated to be close to the spin projection noise limit. The non-linear Zeeman splitting is observed with both the buffer gas cell and a paraffin-coated cell. These results open up the possibility for commercialisation and further miniaturisation of RF OPMs. We derive a set of equations for the off-axis detection of electrically conductive spheres for the arbitrary positioning of the sphere and magnetometer. The equations are interpreted with a focus on predicting the expected signals for the imaging of the electrical conductivity of the human heart using RF OPMs to potentially help diagnose atrial fibrillation more effectively in the future. The optimal setups are discussed. Details on how to design compact, low-noise balanced photodetectors are discussed. Several printed circuit board designs are presented and tested. The performance of the balanced photodetector exceeds that of a commercial balanced photodetector at low frequencies, being shot noise limited for powers as low as 3 uW at frequencies of 3 kHz