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 Development and Application of Tracer based Planar Laser induced Fluorescence Imaging Diagnostics for HCCI Engines written by Jordan Andrew Snyder and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Homogeneous charge compression ignition (HCCI) is an emerging engine strategy that can provide both high efficiency and low emissions, particularly in terms of NOx and soot. An important challenge of HCCI is the inherent narrow load range, bounded by combustion instability and misfires at low-load, and high pressure rise- rate (PRR) at high-load. In response, researchers have devised a number of strategies to expand the limits of HCCI operation. Negative valve overlap (NVO) with pilot injection can extend the low-load gasoline HCCI operating limit by increasing sensible energy during main compression through hot residual gas retention. Chemical effects due to reformation of the pilot injection may further impact combustion. Similarly, the high-load limit can be extended by increasing naturally occurring thermal stratification (TS) of the in- cylinder charge. These non-uniformities result in sequential auto-ignition that can effectively lower the PRR and thus expand the high-load limit. While demonstrations of these strategies have been successful and multiple engine studies have been completed, further characterization of key processes such as residual gas mixing and TS development is needed. This motivates the development of quantitative imaging diagnostics to improve the understanding of these complicated processes. In this study, tracer-based planar laser-induced fluorescence (PLIF) diagnostics for temperature and composition have been refined and optimized for application in HCCI engines at both load extremes. Acetone and 3-pentanone (both ketones) have been selected as seeded PLIF tracers as they provide good overall sensitivity and performance. Single-line and two-line diagnostic variations have been investigated, with an emphasis on optimizing overall diagnostic performance through excitation wavelength selection. Based on a detailed uncertainty analysis excitation wavelengths of 277 nm and 308 nm were selected for subsequent studies. Resulting single-shot temperature precisions were typically on the order 4 K and 12 K for the single-line and two-line techniques respectively. The corresponding mole fraction precision for the two-line technique was typically 4-5%. These results are consistent with the uncertainty analysis and demonstrate the utility of the optimization. HCCI studies were performed in two optically accessible engines, each configured for a specific load extreme. Residual mixing for low-load HCCI operation with NVO was first studied using the two-line technique to provide the simultaneous temperature and composition distribution. These measurements indicated rapid mixing of retained residuals during gas exchange and early compression, reaching a steady-state value midway through compression. Temperature stratification gradually increased throughout the remainder of compression while compositional stratification effectively remained constant. Variation of operating parameters such as main and NVO injection timing exhibited minimal differences in thermal or compositional stratification during main compression. Measurement during NVO recompression and re-expansion were also acquired to assess the in-cylinder temperatures stratification prior to chemical reaction and gas exchange. Next the development of thermal stratification for high-load HCCI with conventional valve timing was investigated using the single-line technique. These studies indicated a progressive increase in TS during compression, reaching a maximum standard deviation of 10 K at top dead center. Comparison of results for motored and fired operation exhibited similar trends. This finding indicates that the mechanism producing the TS is the same for both cases, although some differences in magnitude can occur. A subsequent parametric study proved that these differences can be attributed to the impact of both incomplete fuel mixing and cylinder-wall temperature variation, depending on the type of engine operation (DI skipfiring or premixed continuous firing). All measurements demonstrate the feasibility of quantitative tracer-based PLIF diagnostics in harsh engine environments and provide useful information for future HCCI engine development.
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 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 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 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 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 Springer Handbook of Experimental Fluid Mechanics written by Cameron Tropea and published by Springer Science & Business Media. This book was released on 2007-10-09 with total page 1570 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accompanying DVD-ROM contains ... "all chapters of the Springer Handbook."--Page 3 of cover.
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 Laser Diagnostics for High Pressure Combustion written by David Escofet-Martin and published by . This book was released on 2017 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laser diagnostics have been a staple for experimental combustion research as a modern tool to evaluate high temperature reacting flow environments and to contribute to the fundamental knowledge needed for improving our current combustion systems in a non-intrusive way; they also represent an essential tool for validating computational models. High pressure diagnostics are of particular importance due to the fact that the majority of practical combustion systems operate at high pressure, involving increased challenges in the measurements. The current work examines a variety of linear and non-linear light/matter interaction processes (Raman, fluorescence, and coherent anti-Stokes Raman spectroscopy or CARS) with the goal of measuring the temperature, pressure, and spatial distribution of important reacting flow species. The specific techniques involving OH planar laser induced fluorescence (PLIF), two-line OH PLIF thermometry, two-photon CO PLIF, nanosecond vibrational CARS and hybrid femtosecond/picosecond rotational CARS are all demonstrated at atmospheric pressure using a non-premixed coflow impinging jet as a study flame and examined in detail under high pressure conditions (up to 12 bar) as a coflow flame and in a calibration high pressure vessel; the implications of pressure are discussed in detail in the linear and non-linear techniques. The high pressure experimental data set shows soot laser induced incandescence (LII) as a source of interference for high pressure LIF in non-premixed flames, good agreement with 3 different chemical mechanisms, in particular at high pressure, between an OpenFOAM simulated fluorescence and the experimental pressure dependent data regarding both the spatial distribution of the OH molecule and the overall number of $OH$ molecules interacting with the excitation source. Chirp is identified as a critical parameter when using a second harmonic bandwidth compressor in the hybrid fs/ps CARS configuration, and the chirped CARS signal depends strongly on probe delay in N2 experiments. High quality high pressure data can be achieved once chirp influence has been quantified accurately. Together the combination of diagnostics studied provide insights into high pressure laser diagnostics challenges beyond what is currently available.
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1993 with total page 354 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 Technology and its Applications written by Yufei Ma and published by BoD – Books on Demand. This book was released on 2019-01-03 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: The laser has become more and more important in scientific research and industrial applications. Now, the laser wavelength can cover the range from ultraviolet to terahertz and output laser performance has significantly progressed in recent years. This book is focused on the advanced diode laser, fiber laser, and their applications in laser ablation, laser-introduced fluorescence, and laser treatment. The advantages of laser technology are shown comprehensively.
