Author: Avishek GuhaPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Tomographic Imaging of Combustion Zones Using Tunable Diode Laser Absorption Spectroscopy (TDLAS)
Author: Avishek GuhaTomographic Laser Absorption Imaging of Combustion Gases in the Mid-wave Infrared
Author: Chuyu WeiPublisher:
ISBN:
Category :
Languages : en
Pages : 180
Book Description
This dissertation describes advancements in mid-infrared laser absorption tomography for spatio-temporal measurements of thermochemistry in reacting flows relevant to combustion systems. Tunable laser absorption spectroscopy is combined with tomographic reconstruction techniques to resolve small diameter (
Measurements of Combustion Gases Using Tunable Diode Laser Absorption Spectroscopy
Author: Reynolds Reed SkaggsPublisher:
ISBN:
Category :
Languages : en
Pages : 554
Book Description
Absorption Spectroscopy of Combustion Gases Using a Tunable Diode Laser
Author: Patricia Kuntz FalconePublisher:
ISBN:
Category : Absorption spectra
Languages : en
Pages : 209
Book Description
Combustion Gas Measurements Using Tunable Laser Absorption Spectroscopy
Author: R. K. HansonPublisher:
ISBN:
Category :
Languages : en
Pages : 9
Book Description
Applications of tunable infrared diode lasers for combustion gas measurements are described. The diode laser serves as a source of narrow-linewidth infrared radiation whose wavelength can be rapidly modulated to perform fast, high-resolution absorption spectroscopy. Measurements of fully resolved vibration-rotation lines in the fundamental band of CO are used to infer temperature, CO species concentrations and CO collisions halfwidths in the post-flame gases of a flat flame burner. The feasibility of diode laser measurements in fluctuating and particle-laden combustion flows is also demonstrated. (Author).
Advances in Tunable Diode Laser Spectroscopy for Aero Engine Research
Author: Thomas BenoyPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
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.
Novel Diode Laser Absorption Techniques for Combustion Diagnostics
Author: Gordon S. HumphriesPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
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.
Application of Tunable Diode Laser Absorption Spectroscopy to Environmental and Combustion Chemistry
Author: Deborah Ann HillComparison of Near and Mid-Infrared Tunable Diode Laser Absorption Spectroscopy for the Analysis of Combustion Gases
Author: J. H. MillerTunable Diode Laser Absorption Probe Techniques for Species Measurements in Combustion Gases
Author: Susan Marie SchoenungPublisher:
ISBN:
Category : Carbon monoxide
Languages : en
Pages : 234
Book Description