Download or read book Development of a Direct Low Pressure Laser induced Fluorescence Measurement Technique for NO2 Ambient Measurements and Urban NOx Chemistry written by Linda Acha George and published by . This book was released on 1991 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Acid Precipitation written by and published by . This book was released on 1992-07 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development of an Atmospheric Pressure Laser Induced Fluorimeter AP LIF for NO2 and Application of AP LIF for Study of Heterogeneous NO2 Chemistry written by Jeremy Parra and published by . This book was released on 2012 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrogen dioxide (NO2) is a pollutant of interest for study both because of its controlling role in the oxidant capacity of the atmosphere and the health risks it poses. Concerns about the health effects of NO2 and its role in forming deleterious atmospheric species have made it desirable to have low-cost, sensitive ambient measurements of NO2. A continuous-wave laser-diode laser-induced fluorescence (LIF) system for NO2 was developed here which operates at ambient pressure, thereby eliminating the need for an expensive pumping system. The current prototype system has achieved sensitivity several orders of magnitude beyond previous efforts at ambient pressure (limit of detection of 2 ppb, 60 s averaging time). Ambient measurements of NO2 were made in Portland, Oregon using both the standard NO2 chemiluminescence method and the LIF instrument and showed good agreement (r2 = 0.92). In addition, investigations into surface mediated chemistry involving oxides of nitrogen (namely, NO2) have stimulated new inquiry into potential heterogeneous sources of NO2 as well as challenged the stability of permanent sinks for NO2. The possibility that surface mediated chemistry plays a significant role in NOy chemistry in urban air has for the past few decades received considerable attention. The AP-LIF NO2 instrument is uniquely suited to measure surface chemistry under near ambient conditions. The so called 'renoxification' reaction of gaseous NO with surface bound HNO3 yielding NO2 (2HNO3(surface) + NO--> 3NO2 +H2O(surface)) was suggested as a potentially important source of NO2 which also degraded the stability of nitric acid as a sink of active oxides of nitrogen. Yet, there is disagreement in the literature as to the importance of this reaction. The disagreement stems from differing measurements of the rate for the renoxification reaction. Because there are differences in experimental setups no one research group has studied the renoxification reaction under ambient conditions, i.e., at moderate concentrations of NOy and in a static cell held at 1 atm. In this work, the production of NO2 was measured using a novel AP-LIF. This setup made it possible to measure the rate of production of NO2 due to the heterogeneous reaction of NO with HNO3 under ambient conditions. Under these conditions it was found that renoxification due to gas-phase NO on surface HNO3 is not a significant source of NO2. However, this study did show the importance of water vapor in the renoxification of surface HNO3.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 1991 with total page 660 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 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 Investigation of Low pressure Laser Induced Fluorescence for Measuring Temperature Profiles in a Rarefied Gas written by Thomas Orville Leimkuehler and published by . This book was released on 2000 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a rarefied gas, heat transfer in the transition regime (i.e., Knudsen number range of 0.1 to 10) is affected by molecular as well as gas-surface interactions. Theoretical results for the heat transfer can be obtained through computational solutions of the Boltzmann equation and appropriate intermolecular and gas-surface interaction models. As with all computational and phenomenological models, experimental verification is required. In this work, a low-pressure laser induced fluorescence (LIF) technique is investigated for measuring temperature profiles between parallel flat plates, and the results are compared to theoretical predictions. Iodine vapor is used as the gas medium due to its attractive spectral properties. Two surfaces of a closed, short cylindrical iodine cell are employed as a parallel flat plate geometry and are maintained at different temperatures. Cold and hot plate temperature combinations of (1) 20°C and 70°C, respectively, and (2) 20°C and 115°C, respectively, were used. Calibration measurements were performed at uniform temperatures of 45°C and 70°C, Solid iodine stem temperatures of 0°C and -20°C, corresponding to pressures of 30 mtorr and 3 mtorr, respectively, and Knudsen numbers of 0.05 and 0.5, respectively, were investigated. The data shows the expected trends, indicating observable temperature jumps at the surfaces and matching well with the theoretical predictions in the bulk gas. Deviations from the theory were largest near the surface, possibly a result of the limitations of the theoretical models for this particular experimental case. In addition, problems stemming from fluctuations of the chamber pressure as well as attenuation of the excitation laser beam affected collection of definitive temperature profile measurements. However, much progress with the low-pressure LIF technique has been made, and the technique continues to look promising for obtaining accurate and reliable temperature profile measurements in the transition regime.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1980 with total page 1280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book ACS Directory of Graduate Research 1993 written by American Chemical Society. Committee on Professional Training and published by . This book was released on 1993 with total page 1700 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies of Atomic Nitrogen in Low Pressure Discharges by Two Photon Laser Induced Fluorescence written by Steven Frank Adams and published by . This book was released on 1999-07-01 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of diagnostic experiments have been compiled to investigate rf and microwave discharges in N2, such as those used for plasma processing of electronic materials. To develop a picture, as complete as possible, of the discharge chemistry, several reactive intermediates, e.g. N, N2(A), N2(B) and N2(C), were monitored. An alternative two-photon laser induced fluorescence (TALIF) scheme for detection of atomic nitrogen has been characterized and used to monitor and evaluate various atomic nitrogen sources. Photodissociation of N2O and subsequent detection of N atom photofragments by TALIF was also performed using the 207 NM laser pulse. From measurements within the pulsed rf discharge, a kinetic model was developed which predicted absolute concentrations of various discharge species. The behavior of several discharge species were also monitored in the N2 microwave discharge and compared to the model for the addition of small amounts of H2 and NH3. Atomic nitrogen destruction by surface and volume reaction was investigated by temporal N atom decay within a pulsed rf discharge. The volume loss rate of atomic nitrogen was also quantified to be substantially increased with the addition of as little as 0.1% O2 in an N2 rf discharge.
Download or read book Laser Induced Fluorescence Measurements and Modeling of Nitric Oxide in High Pressure Premixed Flames written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-25 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laser-induced fluorescence (LIF) has been applied to the quantitative measurement of nitric oxide (NO) in premixed, laminar, high-pressure flames. Their chemistry was also studied using three current kinetics schemes to determine the predictive capabilities of each mechanism with respect to NO concentrations. The flames studied were low-temperature (1600 less than T less than 1850K) C2H6/O2/N2 and C2H6/O2/N2 flames, and high temperature (2100 less than T less than 2300K) C2H6/O2/N2 flames. Laser-saturated fluorescence (LSF) was initially used to measure the NO concentrations. However, while the excitation transition was well saturated at atmospheric pressure, the fluorescence behavior was basically linear with respect to laser power at pressures above 6 atm. Measurements and calculations demonstrated that the fluorescence quenching rate variation is negligible for LIF measurements of NO at a given pressure. Therefore, linear LIF was used to perform quantitative measurements of NO concentration in these high-pressure flames. The transportability of a calibration factor from one set of flame conditions to another also was investigated by considering changes in the absorption and quenching environment for different flame conditions. The feasibility of performing LIF measurements of (NO) in turbulent flames was studied; the single-shot detection limit was determined to be 2 ppm. Reisel, John R. and Laurendeau, Normand M. Unspecified Center NASA-CR-195404, E-9248, NAS 1.26:195404 NAG3-1038; RTOP 537-02-20...
Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2726 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Collaborative Test of the Chemiluminescent Method for Measurement of No2 in Ambient Air written by Paul C. Constant (Jr.) and published by . This book was released on 1975 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NO2 based Laser induced Fluorescence LIF Technique to Measure Cold flow Mixing written by A. Gulati 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 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:
Download or read book Laser induced Fluorescence Measurements of Radicals in Low pressure Flames to Optimize Combustion Chemistry written by Jay B. Jeffries and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optical Measurements of Fluctuating Temperatures in a Supersonic Turbulent Flow Using One and Two photon Laser induced Fluorescence written by and published by . This book was released on 1984 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Organic Peroxy Radicals written by P. D. Lightfoot and published by . This book was released on 1992 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
