This research is for the implementation of non-intrusive measurement techniques in the study of high temperature pipe flow. A low pressure, laboratory scale hybrid rocket motor simulator was built to achieve high temperatures with various gases. A quartz test section was designed, built, and implemented into the existing test setup to accommodate the laser beam of the existing Tunable Diode Laser Absorption Spectrometer (TDLAS) system which was designed to observe water vapor. A super-heated water vapor injector was designed to obtain the desired water vapor concentrations. Flow characteristics were simultaneously recorded using the existing TDLAS system and the DAQ system for temperatures for later comparison. A numerical study using a commercial CFD package was used to predict the flow characteristics at certain locations for experimental comparison. Based on this study, it is concluded that the TDLAS can be used to make real time temperature measurements of heated internal gas flows.

This research focuses on developing optical sensing systems for 2D and 3D spatial monitoring of temperature and concentration distribution profiles of complex or reacting gas flows. Non-invasive, species specific and sensitive nature of monitoring allows spatial information to be extracted from harsh environments with poor physical access, allowing validation of computational models or process monitoring. This is suitable for processes like combustion engines or sealed atmospheric cloud chambers. A novel line-of-sight (LOS) Tunable Diode Laser Absorption Spectroscopy(TDLAS) system using a preselected laser diode centred at 7212.88 cm-1 was first designed to monitor the change of relative humidity (water vapour concentration) during an expansion process within the Manchester Ice Cloud Chamber (MICC), operating from atmospheric pressure, down to 0.7 atm. The experimental results were validated with an Aerosol Cloud Precipitation Interaction Model (ACPIM) simulation, feasible for tomography applications. The MICC shares similar combustion monitoring challenges such as minimal optical access or reactive gas flows. The TDLAS system developed for the MICC was then used as a foundation design for a TDLAS tomography setup capable of conducting temporal two-dimensional (2D) and three-dimensional (3D) concentration and temperature imaging. This system uses the principle of two-line thermometry, centred within the near infrared (NIR) region of 7181.93cm-1 and 7179.8 cm-1. The laser was divided into 4 simultaneous parallel beams using a 1 × 4 fiber coupler (4 LOS). Using a motorised platform, the beams were projected at 0.5° interval, from 0° to 179° angle within 3.6 s, around the exhaust of two asymmetrical shaped flame burners. A total of 360 projection slices comprised of 1440 integrated absorbance data were used per tomogram reconstruction. By solving for the spatial distribution of temperature first, the concentration distribution of water vapour could be then calculated. Reconstruction algorithms (Filtered Back Projection, Fourier Slice Reconstruction and Direct Fourier Reconstruction (DFR)) were compared using a range of criteria. The DFR method was selected as the best method at 700 zero padding, with a spatial in-plane resolution of 1-2 lp/cm, pixel resolution of 128 by 128, thermocouple temperature validations of ±5°C and a relative mean error performance of 8.12%. The concentration could not be validated due to the lack of a mass spectrometer.3D volumetric monitoring results took 36 seconds to complete, and was constructed using 10 interpolated parallel, 1 cm height interval spaced tomograms. Independent vertical slices along the x-axis and y-axis could also be extracted. The temporal results were also successfully conducted and consisted of a quick succession of 16 experiments at a temporal resolution of 0.28 frames per second. A tomographic system that performs 3D and 2D temporal sensing was successfully developed and validated. Although 3D work was conducted using planar imaging or hyperspectral tomography, no work has been conducted so far using NIR TDLAS systems to date.

Lean, premixed combustion has enjoyed increased application due to the need to reduce pollutant emissions. Unfortunately, operating the flame at lean conditions increases susceptibility to thermoacoustic (TA) instability. Self-excited TA instabilities are a result of the coupling of the unsteady heat release rate of the flame with the acoustics of the combustion chamber. The result is large pressure oscillations that degrade performance and durability of combustion systems. Industry currently has no reliable tool to predict instabilities a priori. CFD simulations of full-scale, turbulent, reacting flows remain unrealizable. The work in this paper is part of a study that focuses on developing compact models of TA instabilities, i.e. acoustics and flame dynamics. Flame dynamics are defined as the response in heat release to acoustic perturbations. Models of flame dynamics can be coupled with models of combustor enclosure acoustics to predict TA instabilities. In addition, algorithms to actively control instabilities can be based on these compact models of flame dynamics and acoustics. The work outlined in this thesis aims at determining the flame dynamics model experimentally. Velocity perturbations are imparted on laminar and turbulent flames via a loudspeaker upstream of the flame. The response of the flame is observed through two measurements. Hydroxyl radical (OH*) chemiluminescence indicates the response in chemical reaction rate. Tunable Diode Laser Absorption Spectroscopy (TDLAS), centered over two water absorption features, allows a dynamic measurement of the product gas temperature. The response in product gas temperature directly relates to the enthalpy fluctuations that couple to the acoustics. Experimental frequency response functions of a laminar, flat-flame burner and a turbulent, swirl-stabilized combustor will be presented as well as empirical low-order models of flame dynamics. / Master of Science

<div>Laser-absorption spectroscopy (LAS) is widely used for providing non-intrusive and quantitative measurements of gas properties (such as temperature and absorbing species mole fraction) in combustion environments. However, challenges may arise from the line-of-sight nature of LAS diagnostics, which can limit their spatial resolution. Further, time-resolution of such techniques as scanned direct-absorption or wavelength-modulation spectroscopy is limited by the scanning speed of the laser and the optical bandwidth is often limited by a combination of a laser's intrinsic tunability and its scanning speed. The work presented in this dissertation investigated how recent advancements in mid-IR camera technology and lasers can be leveraged to expand the spatial, temporal, and spectral measurement capabilities of LAS diagnostics. Novel laser-absorption imaging and ultrafast laser-absorption spectroscopy diagnostics are presented in this dissertation. In addition, the high-pressure combustion chamber (HPCC) and high-pressure shock tube (HPST) were designed and built to enable the study of, among others, energetic material combustion, spectroscopy, non-equilibrium and chemistry using optical diagnostics.<br></div><div><br></div>

In the manufacturing process of float glass often atmospheric pressure chemical vapour deposition (APCVD) reactors are integrated on-line for the deposition of functional thin solid films. Such functional films have applications in architectural glass, flat panel displays and solar cells. As glass moves downstream in the process, the thin film is deposited at temperatures between 500 to 700°C. The high temperatures make it difficult to monitor the deposition process and thin film quality control is commonly done at the end of the line or at lower temperatures. A time delay therefore exists between the point of thin film deposition and subsequent quality control, which can lead to large quantities of defective product being produced before faults are detected. It is therefore desirable to monitor in the APCVD reactor for rapid feedback of unexpected deviations from desired process conditions, reaction progress and fault detection. High uniformity of film properties across the substrate are important, but APCVD reactors are often empirically designed and the detailed chemical reaction mechanism is unknown. This leads to inefficient gas flow patterns and precursor utilization as well as difficulties in the design of new reactors. The APCVD deposition of tin oxide from the mono-butyl-tin tri-chloride (MBTC) is an example of such a process. Optical monitoring instruments in-situ and in-line on the APCVD reactor provided rapid feedback about process stability and progress non-invasively. Near infrared diode laser absorption spectroscopy (NIR-LAS) monitored the concentration of the reaction species hydrogen chloride (HCl) in-situ and spatially in the coating zone. A mid-infrared grating absorption spectrometer (IR-GAS) with novel pyro-electric array detector monitored the concentration of precursor entering the coating system simultaneously. In combination these instruments provide the means for rapid process feedback. Fourier transform infrared absorption spectroscopy (FTIR) was used to investigate the unknown decomposition pathway of the precursor to find the yet unknown key tin radical that initiates film growth. Stable species forming during MBTC decomposition over a temperature range of 170 to 760°C were investigated but the tin intermediate remains unknown. Computational fluid dynamics (CFD) is routinely employed in research and industry for the numerical simulation of CVD processes in order to predict reactor flow patterns, deposition rates, chemical species distribution or temperature profiles. Two and three dimensional models with complex geometries and detailed reaction models exist. A three dimensional computational fluid dynamics (CFD) model of the used APCVD reactor was built using the Fluent CFD software. The numerical simulation included a chemical model that predicted qualitatively the chemical species distribution of hydrogen chloride in the gas phase. This was confirmed through comparison with NIR-LAS results. Design shortcomings due to inefficient flow patterns were also identified. In combination the optical tools developed provide the means for safe and efficient manufacturing of thin films in APCVD reactors. CFD simulations can be used to increase precursor utilization and film uniformity in the development of new reactor designs.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21756号 / 工博第4573号 / 新制||工||1713(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 蓮尾 昌裕, 教授 木村 健二, 教授 江利口 浩二 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Laser absorption spectroscopy has been a valuable technique for sensitive, non-intrusive, in-situ detection of gaseous and liquid phase target species. The infrared spectral region is specifically attractive as it provides opportunities for selective sensing of a multitude of species in various applications. This thesis explores techniques for interference-free sensing in the infrared region for environmental, combustion, and petrochemical applications. A mid-infrared laser-based sensor was designed to detect trace amounts of benzene using off-axis cavity-enhanced absorption spectroscopy and a multidimensional linear regression algorithm. This sensor achieved unprecedented detection limits, making it ideal for environmental and occupational pollution monitoring. Moreover, wavelength tuning and deep neural networks were employed to differentiate between the broadband similar-shaped absorbance spectra of benzene, toluene, ethylbenzene, and xylene isomers. Benzene sensing was enhanced by recent advancement in semiconductor laser technology, which enabled access to the long wavelength mid-infrared region through commercial distributed feedback quantum cascade lasers. The strongest benzene absorbance band in the infrared is near 14.84 μm, and thus was probed for sensitive benzene detection. Wavelength tuning with multidimensional linear regression were employed to selectively measure benzene, carbon dioxide, and acetylene. Cepstral analysis and wavelength tuning were used to develop a selective sensor for fugitive methane emissions. The sensor was proved to be insensitive to baseline laser intensity imperfections and spectral interference from other present species. In combustion studies, it is desirable to have a diagnostic technique that can detect multiple species simultaneously with high sensitivity, selectivity, and fast time response to validate and improve chemical kinetic mechanisms. A mid-infrared laser sensor was developed for selective and sensitive benzene, toluene, ethylbenzene, and xylenes detection in high-temperature shock tube experiments using deep neural networks. The laser was tuned near 3.3 μm, and an off-axis cavity-enhanced absorption spectroscopy setup was used to enable trace detection. Finally, a novel near-infrared laser-based sensor was developed for water-cut sensing in oil-water flow. The sensor was shown to be immune to the presence of salt and sand in the flow and to temperature variations over 25-60°C. This technique has significant advantages for well and reservoir management, where highly accurate water-cut measurements are required.

<p dir="ltr">This work presents the development and application of novel laser absorption spectroscopy sensors that were deployed to make high-rate (1-15 kHz) measurements of temperature, CO, NO, CO₂, and air-fuel ratio in internal combustion engine (ICE) systems. These sensors provided measurements with unprecedented time resolution in ICE exhaust that allowed for individual cylinder firing events to be detected which will greatly improve understanding of ICE systems and allow for emissions reduction strategies to be tested. </p>

No description available.

The nature of work conducted during the course of study towards a MSc degree focused on tunable diode laser absorption spectroscopy (TDLAS). This field involves the in-situ detection of gas constituents from low concentration samples. Specifically, I will focus on TDLAS systems utilizing practical optics, readymade electronics, and commercially available near infrared vertical cavity surface emitting lasers (VCSEL). In attempting to lower the minimum detectable concentrations of constituent gases, quantifying contributory noise sources is vital. Consequently, I seek to characterize principle noise sources of a prototypical TDLAS system in order to gain understanding of the limits that inhibit detection of trace gas concentrations. The noise sources which were focused on can be categorized as follows: source laser noise, optical noise, and detection noise. Through this work it was my goal to provide the means of achieving superior sensitivities.