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Author: Rodrigo Sanchez-Gonzalez Publisher: ISBN: Category : Languages : en Pages :
Book Description
The study of high-speed flows represents a challenging problem in the fluid dynamics field due to the presence of chemical reactions and non-equilibrium effects. Hypersonic flights, where speeds reach Mach 5 and above, are particularly influenced by these effects, resulting in a direct impact on the flow and consequently on the aerodynamic performance of a vehicle traveling at these speeds. The study of hypersonic flow conditions requires the experimental capability of determining local temperatures, pressures and velocities using non-intrusive techniques. Furthermore, the simultaneous measurement of two or more variables in a complex flow boosts the amount of information that is obtained since valuable correlations can be established. This research includes the design, construction and characterization of a hypersonic flow apparatus explicitly intended as a tool for advanced laser diagnostics development. This apparatus is characterized by its pulsed operation mode that translates into a significant reduction in mass flow rates and can be operated for long periods at Mach numbers ranging from 2.8 to 6.2. The flow conditions during the uniform flow time interval of each pulse vary by less than 1%, generating a flow of sufficient quality for quantitative measurements. The development of a laser diagnostic technique, the VENOM technique, which is a non-intrusive method to provide simultaneous 2-D measurements of the mean and instantaneous fluctuations in two-component velocity and temperature is also presented. This technique represents the first single diagnostic capable of instantaneous two-component velocimetry and thermometry in a gaseous flow field by combining two Nitric Oxide Planar Laser Induced Fluorescence methods: two-component Molecular Tagging Velocimetry and two-line thermometry, employing the nascent NO(v"=1) arising from the NO2 photodissociation as a molecular tracer. The VENOM technique is expected to be not only applicable to cold high-speed flows, which is the focus of the present work, but also to combustion and other reactive or high-enthalpy flow fields.
Author: Rodrigo Sanchez-Gonzalez Publisher: ISBN: Category : Languages : en Pages :
Book Description
The study of high-speed flows represents a challenging problem in the fluid dynamics field due to the presence of chemical reactions and non-equilibrium effects. Hypersonic flights, where speeds reach Mach 5 and above, are particularly influenced by these effects, resulting in a direct impact on the flow and consequently on the aerodynamic performance of a vehicle traveling at these speeds. The study of hypersonic flow conditions requires the experimental capability of determining local temperatures, pressures and velocities using non-intrusive techniques. Furthermore, the simultaneous measurement of two or more variables in a complex flow boosts the amount of information that is obtained since valuable correlations can be established. This research includes the design, construction and characterization of a hypersonic flow apparatus explicitly intended as a tool for advanced laser diagnostics development. This apparatus is characterized by its pulsed operation mode that translates into a significant reduction in mass flow rates and can be operated for long periods at Mach numbers ranging from 2.8 to 6.2. The flow conditions during the uniform flow time interval of each pulse vary by less than 1%, generating a flow of sufficient quality for quantitative measurements. The development of a laser diagnostic technique, the VENOM technique, which is a non-intrusive method to provide simultaneous 2-D measurements of the mean and instantaneous fluctuations in two-component velocity and temperature is also presented. This technique represents the first single diagnostic capable of instantaneous two-component velocimetry and thermometry in a gaseous flow field by combining two Nitric Oxide Planar Laser Induced Fluorescence methods: two-component Molecular Tagging Velocimetry and two-line thermometry, employing the nascent NO(v"=1) arising from the NO2 photodissociation as a molecular tracer. The VENOM technique is expected to be not only applicable to cold high-speed flows, which is the focus of the present work, but also to combustion and other reactive or high-enthalpy flow fields.
Author: Publisher: ISBN: Category : Languages : en Pages : 36
Book Description
Progress is reported for the past year of an interdisciplinary program aimed at establishing advanced optical diagnostic techniques applicable to combustion gases and plasmas, with some emphasis on high speed flows. The primary flowfield parameters of interest are species concentrations (including electrons), temperature, mass density, pressure, and velocity, and quantities derivable from these parameters such as mass flow rate (from the product of density and velocity). The techniques under study are based on laser spectroscopy, particularly laser absorption and laser-induced fluorescence, with the latter capable of providing both single-point and multi-point (2-d and 3-d) measurements. Laser sources include tunable cw lasers (ring dye and semiconductor diode lasers) and tunable pulsed lasers (excimer-pumped dye and narrow-linewidth excimer). The cw lasers are spectrally narrow, allowing study of a new class of techniques based on spectral lineshapes and shifts, while the pulsed lasers provide intense bursts of photons needed for techniques based on light-scattering phenomena. Accomplishments of note include: the first optical measurement of mass flux in high speed air flows; the first applications of tunable semiconductor diode lasers to absorption and fluorescence measurements in high temperature plasmas and supersonic flows, and to the measurement of water vapor in high temperature combustion gases; the first application of the planar laser-induced fluorescence (PLIF) technique to nonequilibrium shock tunnel flows; and further advances in the development of shock tube diagnostics for rate constant measurements of elementary combustion reactions. Laser, Imaging, Combustion, Velocity, Pressure, Temperature, Fluorescence, Reacting, Flow, Plasma.
Author: Publisher: ISBN: Category : Languages : en Pages : 152
Book Description
We report the results of experimental and numerical investigations of fluid mechanics in reacting and high-speed nonreacting flows. For these experiments, the primary focus was on the development and application of advanced laser-based diagnostics for quantitative measurements of: (1) temperature (coherent anti-Stokes Raman spectroscopy of N2 and molecular filtered Rayleigh scattering) in reacting subsonic flows, (2) species concentration (OH, CH, NO, CO, and acetone laser-induced fluorescence) also in reacting subsonic flows, and (3) velocity (particle-imaging velocimetry and filtered Rayleigh scattering) in both subsonic and supersonic flows.
Author: D. F. Grosjean Publisher: ISBN: Category : Combustion Languages : en Pages :
Book Description
Experimental and numerical investigations on gas-turbine combustion processes and jet-fuel thermal stability were undertaken. Advanced laser-based diagnostic techniques were developed and applied to the experimental study of combustion processes (jet diffusion flames and research combustors) and jet-fuel thermal-stability processes (autoxidation, global chemistry, and fuel-additive effects). In addition, numerical computational fluid dynamics with chemistry (CFDC) models detailing both the fluid dynamics and chemistry were developed to simulate realistic environments. The development, calibration, and evaluation of the numerical models employing fundamental combustion and fuel experiments was the ultimate goal of this research program.
Author: D. F. Grosjean Publisher: ISBN: Category : Combustion Languages : en Pages : 0
Book Description
Experimental and numerical investigations on gas-turbine combustion processes and jet-fuel thermal stability were undertaken. Advanced laser-based diagnostic techniques were developed and applied to the experimental study of combustion processes (jet diffusion flames and research combustors) and jet-fuel thermal-stability processes (autoxidation, global chemistry, and fuel-additive effects). In addition, numerical computational fluid dynamics with chemistry (CFDC) models detailing both the fluid dynamics and chemistry were developed to simulate realistic environments. The development, calibration, and evaluation of the numerical models employing fundamental combustion and fuel experiments was the ultimate goal of this research program.
Author: Publisher: ISBN: Category : Languages : en Pages : 45
Book Description
This LDRD was a Sandia Fellowship that supported Andrea Hsu's PhD research at Texas A & M University and her work as a visitor at Sandia's Combustion Research Facility. The research project at Texas A & M University is concerned with the experimental characterization of hypersonic (Mach>5) flowfields using experimental diagnostics. This effort is part of a Multidisciplinary University Research Initiative (MURI) and is a collaboration between the Chemistry and Aerospace Engineering departments. Hypersonic flight conditions often lead to a non-thermochemical equilibrium (NTE) state of air, where the timescale of reaching a single (equilibrium) Boltzmann temperature is much longer than the timescale of the flow. Certain molecular modes, such as vibrational modes, may be much more excited than the translational or rotational modes of the molecule, leading to thermal-nonequilibrium. A nontrivial amount of energy is therefore contained within the vibrational mode, and this energy cascades into the flow as thermal energy, affecting flow properties through vibrational-vibrational (V-V) and vibrational-translational (V-T) energy exchanges between the flow species. The research is a fundamental experimental study of these NTE systems and involves the application of advanced laser and optical diagnostics towards hypersonic flowfields. The research is broken down into two main categories: the application and adaptation of existing laser and optical techniques towards characterization of NTE, and the development of new molecular tagging velocimetry techniques which have been demonstrated in an underexpanded jet flowfield, but may be extended towards a variety of flowfields. In addition, Andrea's work at Sandia National Labs involved the application of advanced laser diagnostics to flames and turbulent non-reacting jets. These studies included quench-free planar laser-induced fluorescence measurements of nitric oxide (NO) and mixture fraction measurements via Rayleigh scattering.
Author: Publisher: ISBN: Category : Aeronautics Languages : en Pages : 488
Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: Rodrigo Sanchez-Gonzalez
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