Download or read book Laser induced Fluorescence Diagnostics Using a Two line Excitation Method written by Michael S. Smith and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tracer based Planar Laser induced Fluorescence Diagnostics written by Brian Ho-yin Cheung and published by Stanford University. This book was released on 2011 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two advances to tracer-based planar laser-induced fluorescence (PLIF) diagnostics are presented in this work. The first improvement is the development of a 3-pentanone fluorescence quantum yield (FQY) database and model for a wide range of conditions in support of quantitative PLIF diagnostics. In addition, this work presents a sensitive, time-resolved tracer-based PLIF diagnostic, accomplished by using a continuous-wave (CW) laser with the high-FQY tracer toluene. Because of its ease of use and desirable photophysical properties, PLIF diagnostics using 3-pentanone as a tracer are common, particularly for internal combustion engine (ICE) diagnostics. Thus, there is a need for 3-pentanone FQY measurements and modeling over a wide range of temperatures, pressures, and excitation wavelengths. For insight into the collisionless process in the FQY model, measurements were made in 3-pentanone vapor at low-pressures across a range of temperatures using a flowing cell. Laser excitation with 248, 266, 277, 308 nm wavelengths were utilized, and Rayleigh scattering of the laser beam was used to calibrate the optical efficiency of the collection optics and detector. This low-pressure data allows calculation of the 3-pentanone fluorescence rate and non-radiative de-excitation rate in the fluorescence model. The vibrational relaxation cascade parameter for 3-pentanone collisions was also determined. Measurements of 3-pentanone FQY were also made over a range of temperatures and pressures relevant to diagnostic applications, and, in particular, combined high-temperature and high-pressure conditions applicable to internal combustion engines (ICE). These data were collected in a custom-built optical cell capable of simultaneous high-pressure and high-temperature conditions. The behavior of the FQY in nitrogen for temperatures up to 745 K and in air up to 570 K was examined for pressures from 1 to 25 bar. These data were used to further optimize the parameters in the FQY model representing collisional processes. The large quantity of data with 308 nm excitation allowed optimization of the nitrogen quenching rate, and data in air were used to optimize the oxygen quenching rate. These data were also used to optimize the vibrational relaxation parameters for nitrogen and oxygen. The model with the updated parameters is consistent with the data collected in the current work, as well as with fluorescence measurements made in optical ICEs up to 1100 K and 28 bar. Another area of tracer-based PLIF diagnostics development is time-resolved imaging. Because PLIF diagnostics are often performed using pulsed lasers, the time resolution of measurements is limited to the pulse rate of laser. Use of a high-powered visible laser with an off-the-shelf cavity frequency doubler is shown to produce a moderate-power CW beam in the ultraviolet wavelength regime. Application of this CW source to excite toluene, a high-FQY tracer, yields a sensitive, time-resolved tracer-based PLIF diagnostic. Fluctuation detection limits for tracer mole fraction were investigated by applying the diagnostic to an atmospheric temperature and pressure nitrogen jet seeded with 4% toluene, and detection limits of better than 1% of the maximum toluene mole fraction were achieved for detection of fluorescence signal at a point, along a line, and over a plane. The diagnostic was also demonstrated on a turbulent jet for line and planar detection and demonstrated the potential for toluene time-resolved PLIF diagnostics with CW lasers.

Download or read book Strategies for Planar Laser induced Fluorescence Thermometry in Shock Tube Flows written by Ji Hyung Yoo and published by Stanford University. This book was released on 2011 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis was motivated by the need to better understand the temperature distribution in shock tube flows, especially in the near-wall flow regions. Two main ideas in planar laser-induced fluorescence (PLIF) diagnostics are explored in this thesis. The first topic is the development of a single-shot PLIF diagnostic technique for quantitative temperature distribution measurement in shock tube flow fields. PLIF is a non-intrusive, laser-based diagnostic technique capable of instantaneously imaging key flow features, such as temperature, pressure, density, and species concentration, by measuring fluorescence signal intensity from laser-excited tracer species. This study performed a comprehensive comparison of florescence tracers and excitation wavelengths to determine the optimal combination for PLIF imaging in shock tube flow applications. Excitation of toluene at 248nm wavelength was determined to be the optimal strategy due to the resulting high temperature sensitivity and fluorescence signal level, compared to other ketone and aromatic tracers at other excitation wavelengths. Sub-atmospheric toluene fluorescence yield data was measured to augment the existing photophysical data necessary for this diagnostic technique. In addition, a new imaging test section was built to allow PLIF imaging in all regions of the shock tube test section, including immediately adjacent to the side and end walls. The signal-to-noise (SNR) and spatial resolution of the PLIF images were optimized using statistical analysis. Temperature field measurements were made with the PLIF diagnostic technique across normal incident and reflected shocks in the shock tube core flow. The resulting images show uniform spatial distribution, and good agreement with conditions calculated from the normal shock jump equations. Temperature measurement uncertainty is about 3.6% at 800K. The diagnostic was also applied to image flow over a wedge. The resulting images capture all the flow features predicted by numerical simulations. The second topic is the development of a quantitative near-wall diagnostic using tracer-based PLIF imaging. Side wall thermal boundary layers and end wall thermal layers are imaged to study the temperature distribution present under constant pressure conditions. The diagnostic technique validated in the shock tube core flow region was further optimized to improve near-wall image quality. The optimization process considered various wall materials, laser sheet orientations, camera collection angles, and optical components to find the configuration that provides the best images. The resulting images have increased resolution (15[Mu]m) and are able to resolve very thin non-uniform near-wall temperature layers (down to 60[Mu]m from the surface). The temperature field and thickness measurements of near-wall shock tube flows under various shock conditions and test gases showed good agreement with boundary layer theory. To conclude this thesis, new applications and future improvements to the developed PLIF diagnostic technique are discussed. These suggested refinements can provide an even more robust and versatile PLIF imaging technique capable of measuring a wider range of flow conditions near walls.

Download or read book Tracer based Planar Laser induced Fluorescence Diagnostics written by Brian Ho-yin Cheung and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Two advances to tracer-based planar laser-induced fluorescence (PLIF) diagnostics are presented in this work. The first improvement is the development of a 3-pentanone fluorescence quantum yield (FQY) database and model for a wide range of conditions in support of quantitative PLIF diagnostics. In addition, this work presents a sensitive, time-resolved tracer-based PLIF diagnostic, accomplished by using a continuous-wave (CW) laser with the high-FQY tracer toluene. Because of its ease of use and desirable photophysical properties, PLIF diagnostics using 3-pentanone as a tracer are common, particularly for internal combustion engine (ICE) diagnostics. Thus, there is a need for 3-pentanone FQY measurements and modeling over a wide range of temperatures, pressures, and excitation wavelengths. For insight into the collisionless process in the FQY model, measurements were made in 3-pentanone vapor at low-pressures across a range of temperatures using a flowing cell. Laser excitation with 248, 266, 277, 308 nm wavelengths were utilized, and Rayleigh scattering of the laser beam was used to calibrate the optical efficiency of the collection optics and detector. This low-pressure data allows calculation of the 3-pentanone fluorescence rate and non-radiative de-excitation rate in the fluorescence model. The vibrational relaxation cascade parameter for 3-pentanone collisions was also determined. Measurements of 3-pentanone FQY were also made over a range of temperatures and pressures relevant to diagnostic applications, and, in particular, combined high-temperature and high-pressure conditions applicable to internal combustion engines (ICE). These data were collected in a custom-built optical cell capable of simultaneous high-pressure and high-temperature conditions. The behavior of the FQY in nitrogen for temperatures up to 745 K and in air up to 570 K was examined for pressures from 1 to 25 bar. These data were used to further optimize the parameters in the FQY model representing collisional processes. The large quantity of data with 308 nm excitation allowed optimization of the nitrogen quenching rate, and data in air were used to optimize the oxygen quenching rate. These data were also used to optimize the vibrational relaxation parameters for nitrogen and oxygen. The model with the updated parameters is consistent with the data collected in the current work, as well as with fluorescence measurements made in optical ICEs up to 1100 K and 28 bar. Another area of tracer-based PLIF diagnostics development is time-resolved imaging. Because PLIF diagnostics are often performed using pulsed lasers, the time resolution of measurements is limited to the pulse rate of laser. Use of a high-powered visible laser with an off-the-shelf cavity frequency doubler is shown to produce a moderate-power CW beam in the ultraviolet wavelength regime. Application of this CW source to excite toluene, a high-FQY tracer, yields a sensitive, time-resolved tracer-based PLIF diagnostic. Fluctuation detection limits for tracer mole fraction were investigated by applying the diagnostic to an atmospheric temperature and pressure nitrogen jet seeded with 4% toluene, and detection limits of better than 1% of the maximum toluene mole fraction were achieved for detection of fluorescence signal at a point, along a line, and over a plane. The diagnostic was also demonstrated on a turbulent jet for line and planar detection and demonstrated the potential for toluene time-resolved PLIF diagnostics with CW lasers.

Download or read book Optical and Laser Diagnostics written by C Arcoumanis and published by CRC Press. This book was released on 2016-04-19 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the automotive industry to blood flow monitoring, optical techniques and laser diagnostics are becoming integral parts in engineering and medical instrumentation. Written by leading global experts from industry, academic groups, and laboratories, this volume provides an international perspective on both existing applications and leading-edge r

Download or read book Development of a Diagonal Excitation observation Diagnostic Technique for Planar Laser induced Fluorescence of the Methyne Radical in Diesel Engines written by Mark P. Musculus and published by . This book was released on 1998 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fluorescence Diagnostics in Two step Laser Excitation of High J Atoms written by and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Using a pair of lasers near 6000 A, the J = 6 ground state is excited to a J = 6 intermediate level and then to a J = 5 upper state. Non-resonant fluorescences from both excited states are separately detected. Results of a set of model calculations are tabulated. Level 3 average populations are always very small, since the system decays rapidly into inaccessible metastable states. This means that chemistry experiments are difficult. The differences between parallel and perpendicular polarization are modest. The fluorescence dips converge to a value near 50%. The level 3 populations do not approach a common value. This means that the most reliable experimental measurement does not determine the level populations. The most striking changes appear in the last two, most exact, models. The difference between the models is that one includes, for the first time, the linear frequency chirp produced by the fanlike spread of the focussed laser beams. This seemingly innocuous change halves the population left in the ground state. It appears that analogues of adiabatic passage and adiabatic rapid passage respectively are being observed.

Download or read book Laser induced Fluorescence for Medical Diagnostics written by Stefan Andersson-Engels and published by . This book was released on 1989 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aspects of Laser Induced Fluorescence Employing Pulsed and Modulated Excitation written by Wilhelmus M. J. Ruyten and published by . This book was released on 1989 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Excitation Anisotropy in Laser induced fluorescence Spectroscopy written by A. Hirabayashi and published by . This book was released on 1986 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development and Optimisation of Two line Planar Laser Induced Fluorescence Technique for Combustion Measurements written by Mohammadreza Anbari Attar and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This study has focused on development, optimisation and implementation of the 2-line Planar Laser Induced Fluorescence (2-line PLIF) technique for combustion measurements on a single cylinder optical Gasoline Direct Injection (GDI) engine with both Spark Ignition (SI) and Controlled Auto Ignition (CAI) combustion operations. The CAI combustion was achieved by employing Negative Valve Overlap (NVO). Two excitation wavelengths at 308 nm (directly from a XeCl laser) and 277 nm (via Raman shifting a KrF laser output at 248 nm) were exploited for the measurements. A calibration curve of fluorescence signal intensity ratio of the two laser beams as a function of temperature was obtained by conducting a series of static tests on a specially designed Constant Volume Chamber (CVC). The developed technique was validated by measurements of in-cylinder charge temperature during the compression stroke for both motoring and firing cycles and comparing the PLIF values with the temperature values calculated from in-cylinder pressure data assuming a polytropic compression. Following the validation measurements, the technique was applied to study of fuel spray characteristics and simultaneous measurements of in-cylinder charge temperature and mole fraction of Exhaust Gas Residuals (EGR). Further optimisation of the thermometry technique by enhancing the fluorescence Signal to Noise Ratio (SNR) and improving both the temporal and spatial resolutions as well as measurements precision provided the opportunity to apply the technique to other combustion measurements. The thesis presents the first application of the 2-line PLIF diagnostic in study of direct injection charge cooling effects and study of flame thermal stratification in IC engines.

Download or read book Laser Induced Fluorescence and Ionization Techniques for Combustion Diagnostics written by BE. Forch and published by . This book was released on 1990 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Light atomic species such as oxygen atoms (O) and hydrogen atoms (H) are fundamentally important in a wide variety of combustion-related phenomena such as flame ignition, propagation, extinction and in chemical flame reactions. Furthermore, they are difficult to detect by conventional laser based optical methods (laser induced fluorescence) in combustion environments because the necessary resonance excitation wavelengths fall far into the vacuum ultraviolet (vuv) and the requisite tunable laser sources are not generally available. However, recent developments in nonlinear spectroscopic techniques such as multiphoton induced emission (MPE) and multiphoton ionization (MPI) have made direct detection of these light atoms possible. We have utilized a number of laser multiphoton excitation schemes for their detection using tunable lasers in the 190 to 400 nm range. Similar diagnostic techniques were attempted for the detection of carbon (C) and nitrogen (N) atoms in flames. The effects of laser induced photochemical pertubations on species detection in flames were also investigated. These nonlinear spectroscopic techniques have been demonstrated to be very useful in combustion studies but special care needs to be taken with respect to possible perturbations that may result from the use of short-wavelength lasers.

Download or read book Demonstration of the Feasibility of Laser Induced Fluorescence for Arc Jet Flow Diagnostics written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laser Induced Fluorescence (LIF) studies are carried out on nitric oxide and oxygen molecules in the arc jet flows at the NASA Johnson Space Center Reentry Testing Facility. Measurements are taken in the free stream and from a blunt body shock layer. Tests are performed under different flow conditions to determine the feasibility and sensitivity of the LIF technique for various species. This is developed as a part of high enthalpy flow diagnostics and will be useful to elucidate the rotational and vibrational temperatures. Adequate sensitivity for the detection of O(2) and NO is demonstrated. Proposed improvements of the existing system are presented. Arepalli, Sivaram Unspecified Center NAS9-17900...

Download or read book Strategies for Planar Laser induced Fluorescence Thermometry in Shock Tube Flows written by Ji Hyung Yoo and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis was motivated by the need to better understand the temperature distribution in shock tube flows, especially in the near-wall flow regions. Two main ideas in planar laser-induced fluorescence (PLIF) diagnostics are explored in this thesis. The first topic is the development of a single-shot PLIF diagnostic technique for quantitative temperature distribution measurement in shock tube flow fields. PLIF is a non-intrusive, laser-based diagnostic technique capable of instantaneously imaging key flow features, such as temperature, pressure, density, and species concentration, by measuring fluorescence signal intensity from laser-excited tracer species. This study performed a comprehensive comparison of florescence tracers and excitation wavelengths to determine the optimal combination for PLIF imaging in shock tube flow applications. Excitation of toluene at 248nm wavelength was determined to be the optimal strategy due to the resulting high temperature sensitivity and fluorescence signal level, compared to other ketone and aromatic tracers at other excitation wavelengths. Sub-atmospheric toluene fluorescence yield data was measured to augment the existing photophysical data necessary for this diagnostic technique. In addition, a new imaging test section was built to allow PLIF imaging in all regions of the shock tube test section, including immediately adjacent to the side and end walls. The signal-to-noise (SNR) and spatial resolution of the PLIF images were optimized using statistical analysis. Temperature field measurements were made with the PLIF diagnostic technique across normal incident and reflected shocks in the shock tube core flow. The resulting images show uniform spatial distribution, and good agreement with conditions calculated from the normal shock jump equations. Temperature measurement uncertainty is about 3.6% at 800K. The diagnostic was also applied to image flow over a wedge. The resulting images capture all the flow features predicted by numerical simulations. The second topic is the development of a quantitative near-wall diagnostic using tracer-based PLIF imaging. Side wall thermal boundary layers and end wall thermal layers are imaged to study the temperature distribution present under constant pressure conditions. The diagnostic technique validated in the shock tube core flow region was further optimized to improve near-wall image quality. The optimization process considered various wall materials, laser sheet orientations, camera collection angles, and optical components to find the configuration that provides the best images. The resulting images have increased resolution (15[Mu]m) and are able to resolve very thin non-uniform near-wall temperature layers (down to 60[Mu]m from the surface). The temperature field and thickness measurements of near-wall shock tube flows under various shock conditions and test gases showed good agreement with boundary layer theory. To conclude this thesis, new applications and future improvements to the developed PLIF diagnostic technique are discussed. These suggested refinements can provide an even more robust and versatile PLIF imaging technique capable of measuring a wider range of flow conditions near walls.

Download or read book The Application of Laser Induced Fluorescence as a Plasma Diagnostic Technique written by Susan Hilary Law and published by . This book was released on 1986 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser induced Fluorescence Diagnostics for Xenon Hall Thrusters written by R. J. Cedolin and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laser Techniques in Luminescence Spectroscopy written by Tuan Vo-Dinh and published by ASTM International. This book was released on 1990 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: