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Author: Ian Schultz Publisher: ISBN: Category : Languages : en Pages :
Book Description
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.
Author: Ian Schultz Publisher: ISBN: Category : Languages : en Pages :
Book Description
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.
Author: James R. P. Bain Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
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.
Author: E. Roland Menzel Publisher: CRC Press ISBN: 9780824792657 Category : Science Languages : en Pages : 328
Book Description
This work describes experimental techniques using laser spectroscopy and presents specific practical applications for this technology in many fields, including physics, engineering, chemistry, medicine and bioscience. The general spectroscopic features of molecules are delineated; transition metal and rare earth complexes are examined; and transition selection rules are explained.
Author: Thomas Benoy Publisher: 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.
Author: Marwa El-Azazy Publisher: BoD – Books on Demand ISBN: 1789849683 Category : Science Languages : en Pages : 180
Book Description
Delving into Infrared Spectroscopy: Principles, Advances and Applications, and with basic knowledge of IR spectroscopy, will provide the reader with a synopsis of fundamentals and groundbreaking advances in the field. Readers will see a variety of MIR applications and difficulties encountered, especially in an industrial environment. Competency in FT-IR spectroscopy in biomedical research and early-stage diagnosis of obesity is shown. Challenges associated with VIS-NIR applications are shown through application of the technique in assessing quality parameters of fruits. Moreover, IR spectroscopic studies of radiation-stimulated processes, and the influence of using IR in developing an ideal catalyst and hence an efficient catalysis process, are discussed. The impact of coupling multivariate data analysis techniques to IR is shown in almost every chapter.
Author: Helmut H. Telle Publisher: CRC Press ISBN: 1466588233 Category : Science Languages : en Pages : 751
Book Description
"a very valuable book for graduate students and researchers in the field of Laser Spectroscopy, which I can fully recommend" —Wolfgang Demtröder, Kaiserslautern University of Technology How would it be possible to provide a coherent picture of this field given all the techniques available today? The authors have taken on this daunting task in this impressive, groundbreaking text. Readers will benefit from the broad overview of basic concepts, focusing on practical scientific and real-life applications of laser spectroscopic analysis and imaging. Chapters follow a consistent structure, beginning with a succinct summary of key principles and concepts, followed by an overview of applications, advantages and pitfalls, and finally a brief discussion of seminal advances and current developments. The examples used in this text span physics and chemistry to environmental science, biology, and medicine. Focuses on practical use in the laboratory and real-world applications Covers the basic concepts, common experimental setups Highlights advantages and caveats of the techniques Concludes each chapter with a snapshot of cutting-edge advances This book is appropriate for anyone in the physical sciences, biology, or medicine looking for an introduction to laser spectroscopic and imaging methodologies. Helmut H. Telle is a full professor at the Instituto Pluridisciplinar, Universidad Complutense de Madrid, Spain. Ángel González Ureña is head of the Department of Molecular Beams and Lasers, Instituto Pluridisciplinar, Universidad Complutense de Madrid, Spain.
Author: Christopher Lyle Strand Publisher: ISBN: Category : Languages : en Pages :
Book Description
The work presented herein describes several advances in the evolution of combustion diagnostics based upon the technique of tunable diode laser absorption spectroscopy (TDLAS). The primary focus of this work was to provide the theoretical and practical means to perform in-situ TDLAS measurements within the harsh flow environments of hypersonic impulse ground-test facilities. In addition to this primary focus, the development and application of this work led to a comprehensive analytical framework for wavelength-modulation spectroscopy and enhanced the understanding of the complex flow environments within hypersonic flow facilities and hypersonic combustion experiments. Hypersonics is the field of aeronautics concerned with flight speeds that are highly supersonic, typically on the order of Mach 5 and above. Presently, it is the domain of spacecraft during re-entry and a select cadre of rocket-powered and air-breathing test vehicles (e.g., North American X-15, NASA X-43, Boeing X-51, HyShot I-IV, HiFiRE 0-3, etc.). It is also a regime of grand aspirations, including routine inexpensive space access, rapid intercontinental transport, atmospheric entry on other planets, and numerous strategic military applications. The development of hypersonic technology is confounded by the immensity of the problem, especially the complexity of interacting physical phenomena and the shortcomings in the fundamental understanding thereof. Understanding of this complex regime and the development of technologies to utilize this regime for flight require a comprehensive scientific and engineering approach including fundamental theory, computations, ground-testing, and flight testing. Due to the capacity of ground-test facilities to formulate tractable hypersonic experiments and, within those experiments, the capability of specialized diagnostics to extract critical information, ground-testing is the primary approach to cracking the multi-physics puzzle of hypersonic flight. Shock-tube-derived impulse flow facilities are a specific form of hypersonic ground-test facility and fill a critical niche within the field. These facilities are characterized by extremely short test times, often less than a few milliseconds, but excel at producing high-enthalpy flows with realistic flow chemistry. This capability is particularly valuable for the investigation of chemically reacting flows within air-breathing hypersonic vehicles such as the scramjet. Effective use of the short-duration test time is progressively being unlocked by the development of modern high-bandwidth instrumentation. Tunable diode laser absorption spectroscopy (TDLAS) offers the potential to provide quantitative measurement of numerous critical flow parameters within these facilities, including temperature, velocity, and species partial pressure. The violent flow environment of a flow model in an impulse ground-test facility creates a formidable challenge for the implementation of a TDLAS diagnostic. Impulse flow test times on the order of 1 ms necessitate exceptionally high measurement bandwidths to capture relevant transient phenomena. Harsh flow conditions introduce substantial measurement noise through mechanically- and density-gradient-induced beam-steering. Short optical paths within the model limit the magnitude of the optical absorption signal and the confined environment limits the resources available for required optical hardware. Further challenges are introduced through the requirements of generating an academically valuable dataset. Multiple simultaneous quantitative measurement parameters at numerous locations within the flow-field are often desirable in both reacting and non-reacting flows. To address the challenges of TDLAS sensing in impulse flow facilities, the efforts of this work include advances in both diagnostic methodology and optical hardware design. A new analytical framework has been developed for the technique of scanned-wavelength-modulation spectroscopy (scanned-WMS) to reject noise and achieve high-sensitivity while permitting the simultaneous measurement of temperature, partial pressure, and velocity. This new framework has enabled accurate measurements at unprecedented bandwidths in harsh flow environments. Integration of TDLAS optical components into flow models has led to novel approaches for harsh-environment optical alignment hardware, combining precision and sufficient robustness to survive repeated firings of an impulse facility. Furthermore, the intense beam-steering induced by facility vibrations and turbulent density gradients have motivated a comprehensive redesign of conventional beam collection approaches. TDLAS diagnostics leveraging these advances have been implemented in both the Stanford Expansion Tube Flow Facility for the purpose of facility characterization and in the HyShot II scramjet experiment at the High Enthalpy Shock Tunnel in Göttingen, Germany to investigate reacting and non-reacting scramjet flows. Results from each of these campaigns are presented as an illustration of the diagnostic capabilities developed in this work.
Author: Richard W. Solarz Publisher: Routledge ISBN: 1351435612 Category : Technology & Engineering Languages : en Pages : 712
Book Description
Bringing together scattered literature from a range of sources, Laser Spectroscopy and ItsApplications clearly elucidates the tools and concepts of this dynamic area, and providesextensive bibliographies for further study.Distinguished experts in their respective fields discuss resonance photoionization, laser absorption,laser-induced breakdown, photodissociation, Raman scattering, remote sensing,and laser-induced fluorescence. The book also incorporates an overview of the semiclassicaltheory of atomic and molecular spectra.Combining background at an intermediate level with an in-depth discussion of specifictechniques, Laser Spectroscopy and Its Applications is essential reading for laser and opticalscientists and engineers; analytical chemists; health physicists; researchers in optical,chemical, pharmaceutical, and metallurgical industries. It will also prove useful for upperlevelundergraduate and graduate students of laser spectroscopy and its applications, andin-house seminars and short courses offered by firms and professional societies.
Author: David L. Andrews Publisher: Springer Science & Business Media ISBN: 1461303370 Category : Science Languages : en Pages : 229
Book Description
Here is the first graduate-level textbook to offer an introduction to the field of laser spectroscopy. Chapters cover a broad range of topics in detail, emphasizing the theoretical and experimental aspects of the field. This much-needed text will allow students to explore current research and gain an understanding of the analytical and industrial applications of laser spectroscopy.
Author: Ian Schultz
Author: Ian Schultz
Author: James R. P. Bain
Author: E. Roland Menzel
Author: Thomas Benoy
Author: Marwa El-Azazy
Author: Helmut H. Telle
Author: Christopher Lyle Strand
Author: Richard W. Solarz
Author: David L. Andrews
Author: