Near-Infrared Diode Laser Absorption Diagnostic for Temperature and Water Vapor in a Scramjet Combustor (Postprint). PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages : 13
Book Description
Tunable diode laser absorption measurements of gas temperature and water concentration were made at the exit of a model scramjet combustor fueled on JP-7. Multiplexed, fiber-coupled, near-infrared distributed feedback lasers were used to probe three water vapor absorption features in the 1.34 to 1.47 mum spectral region (2v1 and v1 + v3 overtone bands). Ratio thermometry was performed using direct absorption wavelength scans of isolated features at a 4-kHz repetition rate, as well as 2f wavelength modulation scans at a 2-kHz scan rate. Large signal-to-noise ratios demonstrate the ability of the optimally engineered optical hardware to reject beam steering and vibration noise. Successful measurements were made at full combustion conditions for a variety of fuel/air equivalence ratios and at eight vertical positions in the duct to investigate spatial uniformity. The use of three water vapor absorption features allowed for preliminary estimates of temperature distributions along the line of sight. The improved signal quality afforded by 2f measurements, in the case of weak absorption, demonstrates the utility of a scanned wavelength modulation strategy.
Author: Publisher: ISBN: Category : Languages : en Pages : 13
Book Description
Tunable diode laser absorption measurements of gas temperature and water concentration were made at the exit of a model scramjet combustor fueled on JP-7. Multiplexed, fiber-coupled, near-infrared distributed feedback lasers were used to probe three water vapor absorption features in the 1.34 to 1.47 mum spectral region (2v1 and v1 + v3 overtone bands). Ratio thermometry was performed using direct absorption wavelength scans of isolated features at a 4-kHz repetition rate, as well as 2f wavelength modulation scans at a 2-kHz scan rate. Large signal-to-noise ratios demonstrate the ability of the optimally engineered optical hardware to reject beam steering and vibration noise. Successful measurements were made at full combustion conditions for a variety of fuel/air equivalence ratios and at eight vertical positions in the duct to investigate spatial uniformity. The use of three water vapor absorption features allowed for preliminary estimates of temperature distributions along the line of sight. The improved signal quality afforded by 2f measurements, in the case of weak absorption, demonstrates the utility of a scanned wavelength modulation strategy.
Author: Publisher: ISBN: Category : Languages : en Pages : 20
Book Description
Two laser-based measurement techniques are implemented in a direct-connect hydrocarbon-fueled scramjet combustor. Planar laser-induced fluorescence (PLIF) of the OH radical is used to examine the flame structure within the combustor. Tunable diode laser-based absorption spectroscopy (TDLAS) is used to measure water vapor concentration and static temperature near the combustor exit. Combined with conventional measurements and Reynolds-averaged CFD simulations, these optical diagnostic techniques significantly enhance the information that is obtained from the scramjet combustor. Wall pressure data show the combustor to be operating in dual-mode with two regions of elevated pressure corresponding to the primary and secondary flameholding zones. The OH radical is well-distributed across the combustor with high OH concentrations occurring along the body, side, and cowl walls. TDLAS measurements indicate non-uniform body-to-cowl profiles in both temperature and water concentration. Near-wall regions are found to be the hottest while the core region is cooler.
Author: Tudor Ioan Palaghita Publisher: ISBN: 9780549008804 Category : Languages : en Pages : 143
Book Description
This thesis describes the development of a sensing technique for temperature nonuniformity along the line of sight through combustion exhaust. Tunable diode laser absorption spectroscopy is used to measure three absorption lines and compute a variable to characterize the level of temperature nonuniformity along the laser path.
Author: Ali Javan Publisher: ISBN: Category : Languages : en Pages : 39
Book Description
The purpose of this work was to develop a highly stable spin flip Raman laser that could be tuned through the 5 micron region in order to study water vapor absorption lines. The pressure broadening coefficients for various buffer gases when added to water was measured with this system. A general technique was devised to measure the shape of absorption lines well out onto the wings to determine if there were any deviation from a Lorentzian lineshape. In addition, theoretical work was done on the interaction of a radiation field with molecules undergoing a collision. A formulation was developed and used to treat the case of a collision between two noble gases.
Author: Publisher: ISBN: Category : Languages : en Pages : 36
Book Description
Progress is reported for the past year of an interdisciplinary program aimed at establishing advanced optical diagnostic techniques applicable to combustion gases and plasmas, with some emphasis on high speed flows. The primary flowfield parameters of interest are species concentrations (including electrons), temperature, mass density, pressure, and velocity, and quantities derivable from these parameters such as mass flow rate (from the product of density and velocity). The techniques under study are based on laser spectroscopy, particularly laser absorption and laser-induced fluorescence, with the latter capable of providing both single-point and multi-point (2-d and 3-d) measurements. Laser sources include tunable cw lasers (ring dye and semiconductor diode lasers) and tunable pulsed lasers (excimer-pumped dye and narrow-linewidth excimer). The cw lasers are spectrally narrow, allowing study of a new class of techniques based on spectral lineshapes and shifts, while the pulsed lasers provide intense bursts of photons needed for techniques based on light-scattering phenomena. Accomplishments of note include: the first optical measurement of mass flux in high speed air flows; the first applications of tunable semiconductor diode lasers to absorption and fluorescence measurements in high temperature plasmas and supersonic flows, and to the measurement of water vapor in high temperature combustion gases; the first application of the planar laser-induced fluorescence (PLIF) technique to nonequilibrium shock tunnel flows; and further advances in the development of shock tube diagnostics for rate constant measurements of elementary combustion reactions. Laser, Imaging, Combustion, Velocity, Pressure, Temperature, Fluorescence, Reacting, Flow, Plasma.
Author: Wen Yu Peng Publisher: ISBN: Category : Languages : en Pages :
Book Description
Detonation-driven combustors have received considerable research interest over the past several decades due to their theoretical thermodynamic advantages over conventional deflagration-driven combustion devices used in propulsion and power generation systems. The rotating detonation engine (RDE) architecture, in particular, has been identified as a promising path for achieving these thermodynamic advantages in practice due to their simple hardware geometries, lack of moving parts, ability to be continuously fed with propellants, and high operating frequencies. Central to increasing the technological readiness of RDEs is the development of robust, time-resolved sensors for in situ measurements of temperature and combustion products within the detonation chamber to validate computational models and guide practical design efforts. The work presented in this dissertation details the development, validation, and demonstration of a novel laser-absorption spectroscopy (LAS) sensor platform capable of performing time-resolved and simultaneous measurements of temperature, H2O, CO2, and CO concentrations within the annular gap of RDE test articles at the Naval Postgraduate School (NPS) in Monterey, CA. Despite the highly confined geometries (with path lengths on the order of 1 cm) and intense thermodynamic conditions (temperatures and pressures ranging from 700-2000 K and 2-8 atm, respectively) in the RDE test apparatus, the sensor achieved high-precision measurements of the target quantities through the use of four lasers probing strong mid-infrared absorption transitions near 2482, 2551, 4182, and 4854 nm and the implementation of wavelength-modulation spectroscopy (WMS), a LAS sensing technique capable of correcting for or rejecting many of the signal distortion sources commonly encountered in the harsh RDE detonation environment. The reported measurement rate of 44 kilosamples per second was sufficient to resolve intra-detonation cycle dynamics within the RDE. Additionally, to minimize perturbations to the combustion environment and to limit the hardware modifications needed for optical access into the RDE detonation chamber, the single-ended LAS sensing strategy--where the laser light was delivered into and collected from the detonation chamber through a single optical port--was used.
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Author: Jonathan Teng-Chieh Liu
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Author: Mark E. Newfield
Author: Tudor Ioan Palaghita
Author: Ali Javan
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Author: Wen Yu Peng
Author: Avishek Guha