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Author: Leyen S. Chang
Publisher:
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Languages : en
Pages :
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Mass flux is one of the most critical parameters in the calculation of engine thrust and assessment of aeroengine performance. Conventional mass-flux measurements are facilitated with invasive temperature and pressure probes which tend to disturb the flow, generate shock structures, have limited lifetimes, and require frequent maintenance. In response, there is a growing opportunity for tunable diode laser (TDL) diagnostics, which can be deployed noninvasively with fast time response and high accuracy. The focus of this work is the development of a TDL mass-flux sensor based on water vapor absorption for deployment in a combustion-driven Mach 2.7 wind tunnel at NASA Langley. The 1f-normalized wavelength-modulation spectroscopy with second harmonic detection (WMS-2f/1f) technique was employed for its unique noise-rejection capability and increase in signal-to-noise ratio; this method was used to measure velocity with improved precision while simultaneously determining temperature. Density was inferred from an independent pressure measurement and the ideal gas law. The sensor temperature measurements were validated against thermocouple readings in a heated cell at Stanford to within 1%. Measurements of velocity were made in a low-speed wind tunnel with accuracy within 0.5m/s of a pitot probe reading; a reduction of 50% in the standard deviation of the velocity measurement was also observed by using optimized WMS-2f/1f. In addition, the influence of flow nonuniformity on line-of-sight (LOS) measurements is investigated by simulating path-integrated lineshapes from computational fluid dynamics (CFD) solutions. The results are quantified in order to develop a correction to the path-integrated measurements obtained in this work. The capstone mass-flux measurements were performed in the NASA Langley Direct-Connect Supersonic Combustion Test Facility isolator. Temporally resolved velocity data was corrected according to the nonuniformity analysis of path-integrated lineshapes, bringing the sensor velocity measurement within 0.25% of the value predicted by the facility code (4m/s in a 1630m/s flow). Temperature measurements were made with high precision (10K standard deviation in a 990K flow), and agreement with the predicted value was also within 1%. Mass-flux measurements had similar precision (standard deviation less than 1% of full scale) and accuracy (within 1% of predicted value). Finally, spatially resolved velocity and mass-flux data taken along both the height and width of the isolator were found to be in close agreement with the CFD solution. These results show that TDL mass-flux sensing based on WMS-2f/1f can produce temporally and spatially resolved measurements with high precision and accuracy in a supersonic flow, thus demonstrating the sensor's potential for future deployment in unknown mass-capture environments such as inlet models and flight tests.
Author: Leyen S. Chang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Mass flux is one of the most critical parameters in the calculation of engine thrust and assessment of aeroengine performance. Conventional mass-flux measurements are facilitated with invasive temperature and pressure probes which tend to disturb the flow, generate shock structures, have limited lifetimes, and require frequent maintenance. In response, there is a growing opportunity for tunable diode laser (TDL) diagnostics, which can be deployed noninvasively with fast time response and high accuracy. The focus of this work is the development of a TDL mass-flux sensor based on water vapor absorption for deployment in a combustion-driven Mach 2.7 wind tunnel at NASA Langley. The 1f-normalized wavelength-modulation spectroscopy with second harmonic detection (WMS-2f/1f) technique was employed for its unique noise-rejection capability and increase in signal-to-noise ratio; this method was used to measure velocity with improved precision while simultaneously determining temperature. Density was inferred from an independent pressure measurement and the ideal gas law. The sensor temperature measurements were validated against thermocouple readings in a heated cell at Stanford to within 1%. Measurements of velocity were made in a low-speed wind tunnel with accuracy within 0.5m/s of a pitot probe reading; a reduction of 50% in the standard deviation of the velocity measurement was also observed by using optimized WMS-2f/1f. In addition, the influence of flow nonuniformity on line-of-sight (LOS) measurements is investigated by simulating path-integrated lineshapes from computational fluid dynamics (CFD) solutions. The results are quantified in order to develop a correction to the path-integrated measurements obtained in this work. The capstone mass-flux measurements were performed in the NASA Langley Direct-Connect Supersonic Combustion Test Facility isolator. Temporally resolved velocity data was corrected according to the nonuniformity analysis of path-integrated lineshapes, bringing the sensor velocity measurement within 0.25% of the value predicted by the facility code (4m/s in a 1630m/s flow). Temperature measurements were made with high precision (10K standard deviation in a 990K flow), and agreement with the predicted value was also within 1%. Mass-flux measurements had similar precision (standard deviation less than 1% of full scale) and accuracy (within 1% of predicted value). Finally, spatially resolved velocity and mass-flux data taken along both the height and width of the isolator were found to be in close agreement with the CFD solution. These results show that TDL mass-flux sensing based on WMS-2f/1f can produce temporally and spatially resolved measurements with high precision and accuracy in a supersonic flow, thus demonstrating the sensor's potential for future deployment in unknown mass-capture environments such as inlet models and flight tests.
Author: Yufei Ma
Publisher: MDPI
ISBN: 3039283987
Category : Technology & Engineering
Languages : en
Pages : 278
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Book Description
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.
Author: Alan Fried
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 370
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Author: Ivanka Stanimirović
Publisher: BoD – Books on Demand
ISBN: 1789235022
Category : Technology & Engineering
Languages : en
Pages : 100
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Book Description
Temperature is the most often-measured environmental quantity and scientists are continuously improving ways of sensing it. To present their work in the field of temperature sensing, researchers from distant parts of the world have joined their efforts and contributed their ideas according to their interest and engagement. Their articles will give you the opportunity to understand concepts and uses of fiber-optic sensing technology. The optical fiber Mach-Zehnder interferometer for temperature sensing is presented, as well as the optical fiber-distributed temperature sensor and fiber Bragg grating-based sensor. You can learn about tunable diode laser absorption spectroscopy and its various industrial applications. Last but not least, cutting temperature measurements during the machining of aluminum alloys provides us with an insight into the correlation between cutting conditions, mechanical strength of the aluminum alloy, and the cutting temperature measured using the tool-workpiece thermocouple system. The editors hope that the presented contributions will allow both professionals and readers not involved in the immediate field to understand and enjoy the topic.
Author: Thomas Benoy
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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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.
Author: Keith Martin Wilson
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
Publisher:
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Category : Aeronautics
Languages : en
Pages : 880
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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.
Author:
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Category :
Languages : en
Pages : 5
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Line-locked near-IR diode lasers and a simple retroreflector/telescope system were used for remote sensing of atmospheric constituents over long atmospheric paths. The experimental configuration used in preliminary measurements of atmospheric water vapor and oxygen with AlGaAs diode lasers is presented. A prototype field sensor system currently under development shares the same basic configuration but incorporates interchangeable AlGaAs and InGaAsP diode-laser modules for monitoring a variety of atmospheric gases.
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Languages : en
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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.
Author: Xing Chao
Publisher:
ISBN:
Category :
Languages : en
Pages :
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In situ sensors based on laser absorption spectroscopy are developed to monitor key species in combustion exhaust gases. Direct absorption (DA) and wavelength-modulation-spectroscopy (WMS) strategies are investigated for extended near-infrared and mid-infrared laser devices to detect target species in harsh environments at combustion exhaust temperatures in the presence of high moisture level and heavy particulate loading. A real time, in situ sensor for carbon monoxide (CO) was developed using DFB diode lasers near 2.3 æm, with selected transitions (R(10) near 4297.7 cm-1, R(11) near 4300.7 cm-1) in the first overtone band of CO. The sensor was studied in the controlled laboratory environments of a heated cell and a combustion exhaust rig. High temperature water vapor absorption spectra were first measured, and shown to produce
