Download or read book Gas Sensing in Industry by Tunable Diode Laser Spectroscopy TDLS written by Maximilian Lackner and published by . This book was released on 2008 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book State of the art Laser Gas Sensing Technologies written by Yufei Ma and published by MDPI. This book was released on 2020-03-05 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: Trace gas sensing technologies are widely used in many applications, such as environmental monitoring, life science, medical diagnostics, and planetary exploration. On the one hand, laser sources have developed greatly due to the rapid development of laser media and laser techniques in recent years. Some novel lasers such as solid-state, diode, and quantum cascade lasers have experienced significant progress. At present, laser wavelengths can cover the range from ultraviolet to terahertz, which could promote the development of laser gas sensing technologies significantly. On the other hand, some new gas sensing methods have appeared, such as photothermal spectroscopy and photoacoustic spectroscopy. Laser spectroscopy-based gas sensing techniques have the advantages of high sensitivity, non-invasiveness, and allowing in situ, real-time observation. Due to the rapid and recent developments in laser source as well as the great merits of laser spectroscopy-based gas sensing techniques, this book aims to provide an updated overview of the state-of-the-art laser gas sensing technologies.

Download or read book Advances in Tunable Diode Laser Spectroscopy for Aero Engine Research written by Thomas Benoy and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tunable diode laser spectroscopy (TDLS) is a widely used technique for the measurement of gas species and offers in-situ operation, accuracy and faster response time compared to other optical and non-optical gas sensing techniques.The work in this thesis focusses on the measurement of CO2 in the harsh environment of a gas turbine engine (GTE). The work is part of a much larger initiative called Fibre Laser Imaging of gas Turbine Exhaust Species (FLITES) aimed at obtaining concentration distributions of gas species such as CO2 and NO, unburnt hydrocarbons, and soot in a gas turbine exhaust plume using optical tomography. In the FLITES system, a thulium doped fibre amplifier (TDFA) is used to boost the optical power output from a 2 mW, 1997 nm, multi-quantum well distributed feedback (DFB-MQW) laser to feed 126 measurement channels arranged in dodecagon geometry for optical tomography. Hence, agile TDLS techniques need to be developed which can be scaled up to the multi-channel measurement system.Attributed by the interference from noise in the measurement environment of a GTE, phase sensitive detection using a lock-in amplifier (LIA) has to be employed where an additional current modulation is applied to the DFB laser, creating an instantaneous intensity modulated output and a delayed wavelength modulation (WM) output. This technique falls under a metrology branch known as wavelength modulation spectroscopy (WMS).The unknown measurement conditions expected in a GTE engine necessitates the use of calibration-free WMS techniques for the simultaneous measurement of gas concentration and temperature. Calibration-free techniques in WMS have been developed at the Centre for Microsystems and Photonics (CMP) of Strathclyde University. These are known as the phasor decomposition method (PDM) and the residual amplitude modulation (RAM) technique. They employ the signals obtained using the first harmonic demodulation of the WMS signals, followed by post processing to recover the gas absorption line shape. It was known in the CMP group that the accuracy of these techniques was limited by the variation in the laser modulation parameters such as the phase of the wavelength modulation relative to the intensity modulation (WM-IM phase lag) and the wavelength modulation amplitude across the laser current scan.The solutions to two problems are addressed in this thesis, viz. the implementation of correction procedures to account for the variation in the laser modulation parameters across the current scan and the need for a calibration-free technique for the measurement of CO2 in a GTE exhaust plume scalable to a multi-channel measurement system.Accurate measurements of the wavelength modulation parameters were made across the current scan and correction algorithms were implemented to compensate for its effects on the recovered gas absorption line shape.The gas spectral parameters were measured in the lab for the R48 absorption line of CO2 near 1997.2 nm at the higher temperatures (up to 500°C) expected in a GTE exhaust plume, using a heated gas cell. A Fourier expansion model was developed for the WMS signals which employ the measured laser modulation and gas spectral parameters. 1f normalised 2f WMS technique was chosen as the calibration-free measurement approach due to the advantages of cancellation of the transmission fluctuations as well as signal normalisation. The 2f/1f measurement technique was validated in the lab at higher temperatures for the simultaneous recovery of the CO2 concentration and temperature with an accuracy of 3.39 % and 3.72 %, respectively. Subsequently, field campaigns were conducted at the Rolls-Royce test facility at East Kilbride, yielding concentration and temperature values having good correlation to the engine operating conditions such as the throttle and core temperature.Multi-channel tomographic measurements were conducted on the test phantoms at INTA, Madrid, using TFLAS-WMS (tunable fibre laser absorption spectroscopy). Accurate concentration images could be recovered using tomographic reconstruction algorithms.

Download or read book Environmental Application of High Sensitive Gas Sensors with Tunable Diode Laser Absorption Spectroscopy written by Xiaojuan Cui and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the fact of global warming, air quality deterioration and health concern over the past few decades, great demands and tremendous efforts for new technology to detect hazard gases such as CH4, CO2, CO, H2S, and HONO have been performed. Tunable diode laser absorption spectroscopy (TDLAS) is a kind of technology with advantages of high sensitivity, high selectivity, and fast responsivity. It has been widely used in the applications of greenhouse gas measurements, industrial process control, combustion gas measurements, medicine, and so on. In this chapter, we will briefly summarize the most recent progress on TDLAS technology and present several kinds of gas sensors developed mainly by our group for various field applications. These could expand from energy, environment, and public safety to medical science.

Download or read book Use of Diffuse Reflections in Tunable Diode Laser Spectroscopy written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Tunable diode laser absorption spectroscopy (TDLAS) is an optical gas sensing technique in which the emission frequency of a laser diode is tuned over a gas absorption line of interest. A fraction of the radiation is absorbed by the sample gas and this can be determined from measurements of initial intensity and the intensity transmitted through the sample. The amount of light absorbed is related to the gas concentration. Additional modulation techniques combined with phase sensitive detection allow detection of very low gas concentrations (several parts per million). The advantages of using TDLAS for trace gas sensing include; fast response times, high sensitivity and high target gas selectivity. However, the sensitivity of many practical TDLAS systems is limited by the formation of unintentional Fabry-Perot interference fringes in the optical path between the source and detector. The spacing between the maxima of these fringes, in particular those generated in gas cells, can be in the same wavelength range as Doppler and pressure-broadened molecular line widths. This can lead to (1) interference fringe signals being mistaken for gas absorption lines leading to false concentration measurements or (2) distortion or complete obscuring of the shape and strength of the absorption line, such that the sensitivity of the instrument is ultimately limited by the fringes. The interference fringe signals are sensitive to thermal and mechanical instabilities and therefore can not be removed by simple subtraction techniques. Methods that have been proposed by previous workers to reduce the effects of interference fringes include careful alignment of optical components and/or mechanically jittering the offending components. In general the alignment of the optical components is critical. This often leads to complex and fragile designs with tight tolerances on optical component alignment, and can therefore be difficult and expensive to maintain in field instruments. This thesis pr.

Download or read book Wavelength Modulation Spectroscopy with Tunable Diode Lasers written by Kevin Duffin and published by . This book was released on 2007 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tunable diode laser spectroscopy (TDLS) has become the preferred option for industrial gas monitoring. TDLS with direct detection provides absolute measurement of a rotational / vibrational gas absorption line transmission function, facilitating the extraction of gas concentration (from line strength measurement). TDLS with wavelength modulation spectroscopy (WMS) enables AC detection of absorption line derivatives at frequencies where laser and 1/f noise is reduced. Coupled with lock-in detection, this provides a sensitivity improvement of up to 2 orders of magnitude. At fixed temperature and pressure, calibration to signals measured on a known gas composition has been used successfully to determine system scaling factors. However, demand has grown for gas monitoring in environments where the gas pressure is constantly varying and unknown. This introduces significant errors in the analysis as the primary system scaling factor is a function of linewidth, which is varying with the unknown pressure. Errors also arise from the inaccuracies in determining a number of instrument scaling factors, including the AM and FM characterisation of the laser. Pressure measurements may be made and the errors in concentration corrected, if the gas absorption linewidth can be accurately measured from the recovered signals and the instrument scaling factors can be accurately determined. However, the lack of accurate in-situ wavelength referencing schemes for use in the field, make linewidth measurement extremely difficult. Add to this the fact that conventional TDLS / WMS measurements are prone to systematic interference and the errors accumulated from inaccurate instrument scaling (noted above) and linewidth measurement, could determine a large final error on the derived concentration and / or pressure. This work reports the proposal, development and validation of both an in-fibre wavelength referencing scheme and a new technique for measuring the absolute absorption line transmission function using TDLS with WMS. Measuring the absolute absorption line transmission profile, as a function of the laser's wavelength scan across the absorption line, facilitates the extraction of the gas concentration and pressure via comparisons to theory (based on HITRAN data). Through novel signal processing techniques, the approach is free from systematic distortion and is absolute without the need for calibration. This new approach provides many of the benefits of TDLS / WMS, whilst offering the simplicity and accuracy of TDLS with direct detection. The promising results show that we have significantly advanced TDLS technology towards realising a stand-alone instrument for determining accurate gas composition measurements in harsh industrial environments.

Download or read book Green Electronics written by Cristian Ravariu and published by BoD – Books on Demand. This book was released on 2018-06-20 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Green Electronics book is intended to stimulate people's thinking toward the new concepts of an environment-friendly electronics - the main challenge in the future. The book offers multiple solutions to push the classical electronic industry toward green concepts, aided by nanotechnologies, with revolutionary features that provide low power consumption in electronics, use biomaterials for integrated structures, and include environmental monitoring tools. Based on organic semiconductors/insulators without toxic precursors, green electronic technologies launched promising devices like OLED, OTFT, or nano-core-shell transistors. The Green Electronics book successfully presents the recent directions collected worldwide and leaves free space for continuing year by year with new subtopics.

Download or read book Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Process Monitoring II written by Alan Fried and published by SPIE-International Society for Optical Engineering. This book was released on 1999 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Air Monitoring by Spectroscopic Techniques written by Markus W. Sigrist and published by John Wiley & Sons. This book was released on 1994-03-31 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt: Leading experts discuss the characteristics, advantages, limitations and future aspects of modern spectroscopic techniques for environmental analysis. Demonstrates how these methods can be applied to trace gas detection and assessment. Concentrates on the latest techniques--both laser and non-laser based--which offer advantages for air pollution and gas monitoring as opposed to more conventional methods. Numerous examples of applications illustrate the potential of the techniques backed up by cutting-edge information and representative data.

Download or read book Extended NIR Laser Diagnostics for Gas Sensing Applications written by Aamir Farooq and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of diagnostics based on laser-absorption spectroscopy for combustion applications has been an important and active field of research over the past two decades due to the advantages of this non-intrusive optical sensing technique compared to traditional sampling-based sensing methods. Tunable diode laser (TDL) sensors, in particular, have shown the ability to provide in situ, time-resolved, line-of-sight measurements of temperature, gas species concentration, velocity, density, mass flux, and pressure in a variety of combustion environments. This thesis explores three new areas of TDL research: (a) extended near-infrared (NIR) diagnostics, (b) sensing under high-pressures, and (c) applications to chemical kinetics. Water vapor (H2O) and carbon dioxide (CO2) are attractive sensing targets for hydrocarbon-fueled systems as they are primary combustion products and their concentrations can be interpretrated to indicate combustion progress and efficiency. Both these gases have absorption spectra in the infrared (IR) region. Most previous TDL absorption sensors were designed to exploit robust telecommunications diode lasers and optical fiber technology in the 1.3-1.6 [mu]m (NIR) wavelength region. Recent developments in semiconductor diode-laser technology have extended the range of continuous wave (CW) room-temperature single-mode diode lasers to 2.9 [mu]m, allowing access to stronger vibrational bands of H2O and CO2 in the extended-NIR region. The first combustion diagnostics in the extended-NIR wavelength were demonstrated as part of this thesis work. The sensors were designed by selecting optimal transitions and then measuring the pertinent spectroscopic parameters in controlled laboratory environements. These sensors were then tested in the combustion environments of a flat flame and shock tube to validate their performance. These new sensors provide enhanced sensitivity and improved accuracy compared to previous TDL diagnostics. As part of this work, a novel diagnostic based on wavelength modulation spectroscopy (WMS) of CO2 was developed to make precise measurements of temperature behind reflected shock waves. This temperature diagnostic achieved an unprecedented uncertainty of

Download or read book Diode Laser Measurement of H2O CO2 and Temperature in Gas Turbine Exhaust Through the Application of Wavelength Modulation Spectroscopy written by Marco E. Leon and published by . This book was released on 2007 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tunable Diode Laser Absorption Spectroscopy (TDLAS) provides an accurate, fast, and non-intrusive solution for species and temperature measurement. The application of this technology to measure temperature, H2O, and CO2 content from an industrial gas turbine has been demonstrated by this research. The multi-gas sensor system, consisting of inexpensive commercially available tunable diode lasers used in the telecommunications industry, uses Wavelength Modulation Spectroscopy (WMS) to quantify path-averaged temperature and concentrations. H2O and CO2 spectroscopic information was first gathered in the laboratory and then the system was packaged for field use. The work culminated in an eight-day test in April 2006 where actual stationary gas turbine emissions data were captured. The results demonstrate the capability for measurement of temperature, H2O, and CO2 in an industrial environment using two tunable diode lasers.

Download or read book Final Report ADVANCED LASER BASED SENSORS FOR INDUSTRIAL PROCESS CONTROL written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this work is to capture the potential of real-time monitoring and overcome the challenges of harsh industrial environments, Los Gatos Research (LGR) is fabricating, deploying, and commercializing advanced laser-based gas sensors for process control monitoring in industrial furnaces (e.g. electric arc furnaces). These sensors can achieve improvements in process control, leading to enhanced productivity, improved product quality, and reduced energy consumption and emissions. The first sensor will utilize both mid-infrared and near-infrared lasers to make rapid in-situ measurements of industrial gases and associated temperatures in the furnace off-gas. The second sensor will make extractive measurements of process gases. During the course of this DOE project, Los Gatos Research (LGR) fabricated, tested, and deployed both in-situ tunable diode laser absorption spectrometry (TDLAS) analyzers and extractive Off-Axis Integrated Cavity Output Spectroscopy (Off-Axis ICOS) analyzers.

Download or read book Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Process Monitoring II written by Alan Fried and published by SPIE-International Society for Optical Engineering. This book was released on 1999 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Trace Gas Monitoring by Open path Tunable Diode Laser Absorption Spectrometer OP TDLAS written by University of Victoria (B.C.). Centre for Earth and Ocean Research and published by . This book was released on 1996* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Utilization of Multiple Harmonics of Wavelength Modulation Absorption Spectroscopy for Practical Gas Sensing written by Kai Sun and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: To meet more rigorous criteria for environmental-unfriendly emissions and to increase energy efficiency, in-situ real-time sensors are needed to optimize the performance of next-generation energy systems. The emergence of high-quality (narrow linewidth, fast tuning capability) tunable diode lasers (TDLs) has enabled the use of wavelength modulation spectroscopy (WMS) for harsh industrial applications. Compared to conventional direct absorption measurements, WMS has the advantage of 10-100 times better detection sensitivity, avoids the need to obtain a zero-absorption baseline, and provides much better isolation from the beam steering, non-absorption transmission loss (e.g., light scattering) or mechanical vibrations. Many models have been developed to interpret the measured WMS signal into absolute absorption. However, most of these models are limited to specific applications by a wide variety of assumptions and approximation most of which deal with the simultaneous intensity and wavelength modulation of injection-current-modulated diode lasers. In this dissertation, two generalized approaches to analyze the WMS absorption signal were developed that account for non-ideal simultaneous intensity modulation of laser output when injection current variation is used for wavelength modulation. The first approach is ideal for wavelength-fixed WMS (the laser mean wavelength is fixed) analysis and the second approach is ideal for wavelength-scanned (the laser mean wavelength is scanned) WMS analysis, and both of them can be used for arbitrary modulation depth, or laser architectures even when severe non-linear intensity modulation occurs simultaneously with wavelength modulation. These new interpretations of WMS absorption signals provide the potential for extended and improved use of WMS for practical gas sensing in a much wider array of applications. The first approach built on earlier work in our laboratory. The analysis of calibration-free, 1f-normalized, WMS-2f absorption signals was extended to higher harmonics (for example 3f, 4f ...) using traditional Fourier analysis. The new approach and procedure developed also accounts for non-ideal wavelength-tuning of the injection-current tuned laser as well as etalon interference from the optical components in the laser line-of-sight (LOS). This approach was validated using measurements of the CO transition of R (11) in the 1st overtone band near 2.3æm in a laboratory cell at room temperature for a range of CO mole fractions (0.21-2.8%) and pressures (5-20atm). For high-pressure gas sensing, wavelength modulation spectroscopy with higher-order harmonic detection (WMS-nf, n> 2) was found to have less influence from the WMS background signals when the selected modulation depth was near the optimal modulation depth for the WMS-2f signal. This WMS approach was then used for measurements in a pilot-scale entrained-flow coal gasifier at the University of Utah. Even though the particulate scattering reduced the laser transmission as much as 99.997%, and pressure broadening at the 18atm (~250psig) operating pressure blended the absorption transitions, successful in-situ rapid-time-resolved 1f-normalized WMS-2f absorption measurements for gas temperature and H2O mole fraction were made. Based on lessons learned during the gasifier measurements at Utah and a desire to eventually develop real-time sensors for long-term monitoring, a second approach for WMS analysis was developed that differs from previous WMS analysis strategies in two significant ways: (1) the measured laser intensity without absorption is used to simulate the transmitted laser intensity with absorption and (2) digital lock-in and low-pass filter software is used to expand both simulated and measured transmitted laser intensities into harmonics of the modulation frequency, WMS-nf (n=1,2,3 ...), avoiding the need for an analytic model of intensity modulation or Fourier expansion of the simulated WMS harmonics. The new method was demonstrated and validated with WMS of H2O dilute in air (1atm, 296K, near 1392nm). WMS-nf harmonics for n=1 to 6 are extracted and the simulations and measurements are found in good agreement for the entire WMS lineshape. This new analysis scheme was applied to monitor the synthesis gas output from an engineering-scale transport reactor coal gasifier at the National Carbon Capture Center. There the pressures ranged up to 15 atm (~220psig) and temperatures up to 650K. Continuous monitoring of moisture level in the gasifier output with 2s time resolution was performed by the TDL sensor for more than 500 hours, including the periods of burner ignition, combustion heating with a propane flame, coal combustion, coal gasification, and reactor shut-down via coal-feed termination. In addition, a novel and rapid approach to determine the collisional linewidth via the WMS signals at different harmonics at the modulation frequency is presented. The peak values of the WMS-nf absorption spectrum near the transition line center are used to infer the absorption lineshape, which is exploited here to extract collision-broadening halfwidth from the ratio of WMS-4f/WMS-2f (or other even harmonics) signals when the mean laser wavelength is tuned to line center. Measurement of the absorption linewidth enables quantitative WMS measurements without the need for a collision-broadening database. Alternatively, when collision-broadened spectral data are available, a WMS-based pressure sensor can be realized, and a demonstration using the 4fpeak/2fpeak ratio gives less than 0.7% difference for the pressure for cell measurements from 100 torr to 753 torr. These new WMS analysis schemes have been validated in near commercial environments and illustrate the potential of their use to develop practical TDL sensors for a wide variety of industrial applications.

Download or read book Tunable Diode Laser Spectroscopy Lidar and DIAL Techniques for Environmental and Industrial Measurements written by Alan Fried and published by . This book was released on 1994 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book ICOL 2019 written by Kehar Singh and published by Springer Nature. This book was released on 2021-03-01 with total page 908 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents peer-reviewed articles from the International Conference on Optics and Electro-optics, ICOL-2019, held at Dehradun in India. It brings together leading researchers and professionals in the field of optics/optical engineering/optical materials and provides a platform to present and establish collaborations in this important area, with the theme “Trends in Electro-optics Instrumentation for Strategic Applications”. Topics covered but not limited to are Optical Engineering, Optical Thin Films, Optical Materials, IR Sensors, Image Processing & Systems, Photonic Band Gap Materials, Adaptive Optics, Optical Image Processing & Holography, Lasers, Fiber Lasers & its Applications, Diffractive Optics, Innovative packaging of Optical Systems, Nanophotonics Devices and Applications, Optical Interferometry & Metrology, Terahertz, Millimeter Wave & Microwave Photonics, Fiber, Integrated & Nonlinear Optics and Optics and Electro-optics for Strategic Applications.