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 2017 with total page 530 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 Near Infrared Tunable Diode Laser Spectroscopy for Aero Engine Related Applications written by James R. P. Bain and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tunable diode laser spectroscopy is a widely used technique for recovering quantitative gas information in a range of industrial applications. Established methods often use readily available, robust and low cost optoelectronic hardware in the near-infrared, with output wavelengths that coincide with the absorption spectra of several important gas species of interest, providing a versatile platform for gas analysis instrumentation. In this work the challenges associated with the recovery of gas information from harsh detection environments, particularly for aero engine diagnostics, are considered. For stand-alone instrumentation, calibration-free direct absorption measurements are highly advantageous yet calibrated techniques employing wavelength modulation spectroscopy are often favoured due to their significantly higher sensitivities. Recent developments have enabled calibration-free line shape recovery using lock-in amplifier detection of the residual amplitude modulation in wavelength modulated signals. These techniques have significant potential in harsh environments, but the overall sensitivity is limited by distortions to the recovered line shapes at high modulation amplitudes and by large background signals that saturate the detection electronics. In this thesis, solutions to these two problems are proposed, investigated and validated. A correction function is derived that is able to account for line shape distortions at arbitrarily high modulation indices. Application of the function depends upon knowledge of the experimental modulation index and two methods for extracting this information directly from the experimental signals are described. The full correction procedure has been experimentally validated. An investigation was made into the use of autobalanced photoreceivers, typically used for common mode noise cancellation, for direct absorption measurements and in a different configuration for nulling of the residual amplitude modulation (RAM) in wavelength modulation spectroscopy. Initial measurements suggest that removal of the background RAM can increase the lock-in detection sensitivity by over an order of magnitude. In addition an external amplitude modulator has been iv shown to be an effective method for producing sensitive absorption signals that are free of distortions, recoverable at frequencies that are outside the bandwidth of most environmental noise sources. A temperature sensor based on ratio thermometry of ambient water vapour absorption was designed and evaluated. The sensor is intended to provide accurate intake gas temperature information during aero engine ground testing when misting conditions prevent standard thermocouples from providing reliable data. Direct detection and second harmonic wavelength modulation spectroscopy experiments were undertaken in an environmental chamber, over the range 273-313K, to test the potential accuracy of the proposed system. Using a second harmonic peak height method, temperature information based on a calibration was able to recover temperature measurements with precision of ±0.4K however the overall accuracy suffered from a problematic calibration drift. Three engine test campaigns are described in which a range of recovery methods and potential optical system layouts are evaluated for the purposes of intake and exhaust mounted test bed sensor systems. The effects of extreme noise conditions were observed on a variety of measurements and favourable detection and modulation options were identified for the purpose of planning proposed future engine tests. Exhaust plume measurements of high temperature water vapour on the Rolls-Royce Environmentally Friendly Engine demonstrator established the viability of temperature and concentration measurements up to 850K.

Download or read book Advances in Optical Diagnostics Based on Tunable Diode Laser Spectroscopy written by Toni Laurila and published by . This book was released on 2005 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Tunable Diode Laser Spectroscopy Using Residual Amplitude Modulation Techniques written by Keith Ruxton and published by . This book was released on 2010 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Practical Applications of Laser Absorption Spectroscopy for Aeroengine Testing written by Ian Schultz and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Reliable air-breathing hypersonic propulsion systems offer the potential to revolutionize aircraft performance in a variety of high-speed aerospace applications through substantial efficiency gains and hardware cost savings. Supersonic combustion ramjet (scramjet) engines are one such device that promise propulsion capabilities up to about Mach 10. However, before these devices are ever practically realized, considerable technical challenges must be overcome in combustor-inlet interaction, fuel-air mixing, and coupled turbulent flow/combustion modeling. The growing power of computational tools have accelerated the pace of solving these problems, but the accuracy of computational approaches can only be validated by rigorous experimental testing. Thus, there is a need for both facilities capable of creating conditions experienced during hypersonic flight, as well as diagnostics that can characterize the operation of those facilities and provide experimental data for the validation of computational models. Optical diagnostics such as laser absorption spectroscopy are capable of providing non-intrusive, in situ measurements of important flow-field parameters such as temperature, velocity, species concentrations, which makes them an invaluable resource to hypersonic aeroengine researchers. Absorption spectroscopy, in particular, has benefited from recent advances in laser and optics technology, allowing access to a variety of wavelengths corresponding to absorption transitions of important combustion species such as O2, H2O, and CO2. Moreover, these sensors only require compact, low-power laser sources and light can be delivered via fiber-optics, which enables the sensor to more easily integrate with test facility hardware. As a result, laser absorption spectroscopy has become a workhorse in experimental scramjet research, and has been applied in test facilities around the world. Building upon this prior work, here the design and results of several different spectroscopic sensors for facility characterization and distinct scramjet operation modes are presented. Both hydrogen-fueled and hydrocarbon-fueled scramjets are investigated in a variety of geometric configurations. These results comprise the largest data set of laser absorption spectroscopy measurements within scramjet combustors published to date, and are a valuable resource for computational researchers who wish to compare their models with experimental data. A primary drawback of laser absorption spectroscopy is that some techniques are sensitive to nonuniformity along the measurement line-of-sight. In highly three-dimensional flows such as within a scramjet combustor, this can prove to be a considerable hindrance. However, in the work here particular care has been taken to account for nonuniformity along the measurement path, and new techniques, including a new approach to wavelength-modulation spectroscopy data reduction, have been developed and applied to provide quantitatively accurate path-integrated measurements in the presence of nonuniformities. Additionally, novel applications of laser absorption spectroscopy are presented, including the use of absorption data to place an upper bound on the cavity residence time within a scramjet combustor, and a new sensor design for measuring air temperature in high-enthalpy facilities by tracking the formation of nitric oxide.

Download or read book Advances in Laser Spectroscopy written by F. T. Arecchi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Download or read book Industrial Applications of Tunable Diode Laser Absorption Spectroscopy written by Zhenzhen Wang and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Tunable diode laser absorption spectroscopy (TDLAS) utilizes the absorption phenomena to measure the temperature and species concentration. The main features of the TDLAS technique are its fast response and high sensitivity. Extensive research has been performed on the utilization of diode laser absorption spectroscopy for the system monitoring and its control. The TDLAS technique gives self-calibrations to reduce the noise such as particles and dusts because the laser wavelength is rapidly modulated at kHz rates. In addition, two dimensional (2D) temperature and concentration distributions can be obtained by combining computed tomography (CT) with TDLAS. The TDLAS applications have been extensively studied with great progress. This chapter largely focuses on the engineering fields, especially the practical industrial applications.

Download or read book Advances in Spectroscopy for Lasers and Sensing written by Baldassare Di Bartolo and published by Springer Science & Business Media. This book was released on 2006-07-21 with total page 574 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents the Proceedings of "New Development in Optics and Related Fields," held in Italy in June, 2005. This meeting was organized by the International School of Atomic and Molecular Spectroscopy of the "Ettore Majorana" Center for Scientific Culture. The purpose of this Institute was to provide a comprehensive and coherent treatment of the new techniques and contemporary developments in optics and related fields.

Download or read book Tunable Diode Laser Spectroscopy written by J. A. Deeny and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Program Solicitation written by and published by . This book was released on 1995 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Special Issue tunable Diode Laser Spectroscopy written by Markus Werner Sigrist and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tunable Diode Laser Development and Spectroscopy Applications written by Wayne Lo and published by . This book was released on 1983 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book NASA Technical Memorandum written by and published by . This book was released on 1990 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Novel Diode Laser Absorption Techniques for Combustion Diagnostics written by Gordon S. Humphries and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In-situ optical techniques offer one of the most attractive options for measuring species concentration and spatial distribution profiles in reacting environments, such as flames. The generally non-intrusive nature and spatial resolution of these techniques are now preferred over on extractive sampling, followed by analysis using techniques such as gas chromatography. In this thesis two laser absorption measurement techniques are applied to measure the soot distribution, and acetylene concentration profiles in a flat-flame burner. The in-situ measurement of the distribution of particulate matter in flames is a key step in understanding the mechanism of its formation. Most in-situ measurement systems for this purpose are based on laser induced incandescence where particles are heated using high power laser sources and the increased incandescence emission of the soot particles is detected. However as the soot cools by heat transfer to the surrounding gas, following laser heating, the pressure of the gas is increased creating an acoustic effect. Photoacoustic detection has been applied to quantify low concentrations of particulate matter in ambient air but there have been few applications of photoacoustic detection to the in-situ measurement of particulate matter formation in combustion processes. A novel simple approach using a modulated continuous wave diode laser is presented in this thesis. The measurements taken using this new technique are compared to measurements of the visible emission from the flame, and previous soot distribution measurements using laser induced incandescence. Absorption spectroscopy using near-infrared tunable diode lasers has been applied to measure species in several harsh environments such as aero-engine exhaust plumes, flames, and other industrial processes. Simple single pass absorption techniques are not always suitable for this purpose due to the low absorption of the target species, either due to low concentration or weak absorption line-strength at high temperatures. One method to increase the sensitivity of such techniques is by using cavity enhanced methods which increase the effective path length of the laser through the absorbing medium. One such cavity enhanced method is Cavity Ring-Down Spectroscopy (CRDS). CRDS uses a cavity constructed of highly reflecting mirrors, laser light is then coupled into this cavity and absorption measurements can be evaluated from the decay rate of light from the cavity. The design and, novel application of continuous wave CRDS to measure the concentration profile of acetylene in the flat-flame burner is presented. Difficulties in deriving an absolute acetylene concentration from the measured ringdown times were encountered due to the large number of interfering features. Serveral fitting and extraction techniques are applied and compared to attempt to overcome these difficulties.

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 Laser and Fiber Optic Gas Absorption Spectroscopy written by George Stewart and published by Cambridge University Press. This book was released on 2021-04-08 with total page 275 pages. Available in PDF, EPUB and Kindle. Book excerpt: A rigorous account of the physics and engineering of diode and fibre laser gas sensor design, with key applications.