Encontros e imaginações compartilhadas: lições sobre o que pode o queer*

AIAA Journal, 2003

Applied Optics, 2006

Pure rotational coherent anti-Stokes Raman spectroscopy was used for the simultaneous determination of temperature and exhaust-gas recirculation in a homogeneous charge-compression ignition engine. Measurements were performed in a production-line four-cylinder gasoline engine operated with standard gasoline fuel through small optical line-of-sight accesses. The homogenization process of fresh intake air with recirculated exhaust gas was observed during the compression stroke, and the effect of charge temperature on combustion timing is shown. Single-pulse coherent anti-Stokes Raman spectroscopy spectra could not only be taken in the compression stroke but also during the gas-exchange cycle and after combustion. Consequently, the used method has been shown to be suitable for the investigation of two of the key parameters for self-ignition, namely temperature and charge composition.

29th Aerospace Sciences Meeting, 1991

A coherent anti-Stokes Raman scattering (CARS) system has been hardened for use in a NASA Langley supersonic combustion test cell.

36th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2000

engine propellent injector

Combustion and Flame

Dual-pump coherent anti-Stokes Raman spectroscopy (CARS) was used to measure the mole fractions of major species as well as the rotational and vibrational temperatures of N 2 in a hydrogen fueled dual-mode scramjet flowpath operated in the "ram" mode. Developments in CARS methods and uncertainties are described, including a detailed analysis of the effects of spatial averaging. Mean and standard deviation of the turbulent fluctuations of temperature and mole fractions at multiple planes in the flow path and scatter plots of vibrational and rotational temperature are presented. The flame is stabilized downstream of the ramp and grows under the influence of turbulence and rollup of the counterrotating vortex pair formed at the ramp; combustion continues in accelerating flow approaching the end of the measurement domain. Thermal non-equilibrium is observed in the mixing of air with the H 2 jet close to the injector.

Combustion and Flame, 2008

Dual-broadband rotational coherent anti-Stokes Raman spectroscopy (DB-RCARS) has been investigated for thermometry under high-pressure and high-temperature conditions, in the product gas of fuel-lean hydrocarbon flames up to 1 MPa. Initial calibration measurements made in nitrogen, oxygen, and air, at pressures up to 1.55 MPa and temperatures up to 1800 K, showed good agreement between experimental and theoretical spectra. In the highpressure flames, high-quality single-shot spectra were recorded in which nitrogen lines dominated, and peaks from CO 2 and O 2 were also visible. A spectral model including the species N 2 , CO 2 , and O 2 , as well as the best available Raman linewidth models for flame thermometry, were used to evaluate the experimental spectra. Experimental problems as well as considerations related to the spectral evaluation are discussed. This work demonstrates the significant potential of DB-RCARS thermometry for applications in high-pressure and high-temperature environments.

Applied Optics, 2005

An optimal system for temperature measurements by coherent anti-Stokes Raman spectroscopy (CARS) in turbulent flames and flows is presented. In addition to a single-mode pump laser and a modeless dye laser, an echelle spectrometer with a cross disperser is used. This system permits simultaneous measurement of the N 2 CARS spectrum and the broadband dye laser profile. A procedure is developed to use software to transform this profile into the excitation profile by which the spectrum is referenced. Simultaneous shot-to-shot referencing is compared to sequential averaged referencing for data obtained in flat flames and in room air. At flame temperatures, the resultant 1.5% imprecision is limited by flame fluctuations, indicating that the system may have a single-shot imprecision below 1%. At room temperature, the 3.8% single-shot imprecision is of the same order as the best values reported for dualbroadband pure-rotational CARS. Using the unique shot-to-shot excitation profiles, simultaneous referencing eliminates systematic errors. At 2000 and 300 K, the 95% confidence intervals are estimated to be Ϯ20 and Ϯ10 K, respectively.

Experimental Thermal and Fluid Science, 2018

A gas turbine model combustor for swirling spray flames has been operated at atmospheric pressure with n-hexane, n-dodecane and kerosene Jet A-1. Temperature measurements were performed using single-shot broadband shifted vibrational coherent anti-Stokes Raman spectroscopy (SV-CARS). Series of 1200 single-shot measurements were performed at different radial and vertical locations in the flames from which the temperature distributions were deduced. In regions with high droplet load a significant number of CARS spectra were discarded due to large signal background from laser-induced breakdown effects. Results from the flames burning different fuels were compared and revealed considerable differences in the temperature profiles. The temperature measurements are part of a comprehensive research program that aims at the design of alternative fuels for aero engines and stationary gas turbines. In addition to the experimental characterization of the spray flames, the datasets are used for the validation and improvement of computational models.

Comptes Rendus Physique, 2004

This article reviews the study of Raman line shapes of molecular species involved in reactive media, such flames or engines, at high temperature and high pressure. This study is of interest from a fundamental as well as from a practical point of view with regards to the CARS temperature diagnostic of GH 2 -LOX combustion systems. We will particularly draw attention to recent investigations by means of Stimulated Raman Spectroscopy (SRS) in H 2 -H 2 O mixtures at temperature up to 1800 K. Whereas H 2 -X systems usually exhibit large inhomogeneous effects, due to the speed dependence of the collisional parameters, the absence of such apparent inhomogeneous signatures in the H 2 -H 2 O system allowed us to model the broadening coefficients with simple polynomial laws. These laws permit extrapolations with a narrow confidence interval, as required for temperature measurements. The applications of these results to the temperature diagnostic on the small-scale facility MASCOTTE at ONERA will be described. To cite this article: F. Chaussard et al., C. R. Physique 5 (2004).  2004 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Experiments in Fluids, 2021

Prediction of flow-field properties in supersonic jets using computational fluid dynamics (CFD) code predictions has become routine; however, obtaining accurate solutions becomes more challenging when there is a significant temperature difference between the jet core and the ambient air and/or compressibility effects are significant. Benchmark sets of flow field property data are required in order to assess current CFD capabilities and develop better modeling approaches for these turbulent flow fields where accurate calculation of temperatures and turbulent heat flux is important. Particle Image Velocimetry, spontaneous rotational Raman scattering spectroscopy, and Background-Oriented Schlieren (BOS) have been previously used to acquire measurements of the mean and root-mean-square (rms) velocities, the mean and rms gas temperatures, and density gradients in subsonic jet flows and film cooling flows. In this work, the ability to measure density is added to the list of measurands available using the acquired Raman spectra. The suite of measurement techniques are now applied to supersonic jet flows. The computation of the local gas pressure in the potential core of an over-expanded jet is demonstrated using the Raman measured gas temperature and density. Additionally, a unique density feature in temperature matched, perfectly expanded jet flow shear layers identified using BOS was verified using the Raman measurement technique. These non-intrusive flow measurements are compared against RANS predictions of the supersonic jet flow properties as a means of assessing their prediction accuracy.

45th AIAA Aerospace Sciences Meeting and Exhibit, 2007

This paper describes the development of an experiment to acquire data for developing and validating computational fluid dynamics (CFD) models for turbulence in supersonic combusting flows. The intent is that the flow field would be simple yet relevant to flows within hypersonic air-breathing engine combustors undergoing testing in vitiated-air ground-testing facilities. Specifically, it describes development of laboratory-scale hardware to produce a supersonic combusting coaxial jet, discusses design calculations, operability and types of flames observed. These flames are studied using the dual-pump coherent anti-Stokes Raman spectroscopy (CARS)-interferometric Rayleigh scattering (IRS) technique. This technique simultaneously and instantaneously measures temperature, composition, and velocity in the flow, from which many of the important turbulence statistics can be found. Some preliminary CARS data are presented. I. Nomenclature Variables: ER = Equivalence ratio H = Convective heat transfer coefficient M = Mach number at nozzle exit M c = Convective Mach number M enthalpy = Flight Mach number with the same enthalpy q w = Surface heat flux r = Radial distance T = Nozzle exit static temperature T wall = Burner interior wall temperature

Combustion and Flame, 1997

Temperature fluctuations have been measured in a turbulent, natural gas-fueled, piloted jet diffusion flame with a fuel jet exit Reynolds number of 9700, using broadband Coherent Anti-Stokes Raman Spectroscopy (CARS) nitrogen thermometry with a best spatial resolution of 0.9 mm. Radial profiles of mean temperature and root mean square (rms) temperature fluctuations have been acquired and temperature probability density functions (pdfs) have been constructed for streamwise distances in the range 4.2 < x/d < 66.7.

47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition, 2009

This paper presents simultaneous measurements at multiple points of two orthogonal components of flow velocity using a single-shot interferometric Rayleigh scattering (IRS) technique. The measurements are performed on a large-scale Mach 1.6 (Mach 5.5 enthalpy) H 2-air combustion jet during the 2007 test campaign in the Direct Connect Supersonic Combustion Test facility at NASA Langley Research Center. The measurements are performed simultaneously with CARS (Coherent Anti-stokes Raman Spectroscopy) using a combined CARS-IRS instrument with a common path 9-nanosecond pulsed, injectionseeded, 532-nm Nd:YAG laser probe pulse. The paper summarizes the measurements of velocities along the core of the vitiated air flow as well as two radial profiles. The average velocity measurement near the centerline at the closest point from the nozzle exit compares favorably with the CFD calculations using the VULCAN code. Further downstream, the measured axial velocity shows overall higher values than predicted with a trend of convergence at further distances. Larger discrepancies are shown in the radial profiles.

A basic experiment was conducted at the outlet of the Mascotte test facility of Onera. This combustion chamber has been initially developed to study elementary processes involved in high pressure cryogenic propellant combustion. The facility is fed with liquid oxygen and gaseous hydrogen and ends with a Mach 2 nozzle. Downstream from the nozzle, the reactive flowfield expands into the air environment, leading to the generation of multiple Mach disks along the centerline of the flowfield and post-combustion zones generated from mixing processes between ambient air and the reactive flowfield. Several spatially and time-resolved non-intrusive optical diagnostics were applied to characterize the supersonic rocket engine plume along a distance of 600 mm from the nozzle exit. Two stagnation pressures of 10 and 20 bar were tested in order to modify the jet exit pressure to ambient flow pressure ratio. Planar Laser-Induced Fluorescence (PLIF) on the OH radical and spontaneous emission of the OH * exited radical, allowed to study the structure of the flowfield whereas the temperature flowfield has been investigated by use of the H 2 coherent anti-Stokes Raman scattering (CARS) technique. Averaged and instantaneous images acquired with short exposure times (0.5 to 3 µs) by the use of OH * emission allow a well-description of the structure and the location of the Mach disks. By contrast, quantitative instantaneous OH-PLIF allows to deduce the location and the turbulent structure of the post-combustion zones. Theses images, obtained by exciting the weak Q P21 (5) OH-rotational transition provide also quantitative data and they may be used to estimate the local reaction rate. Quantitative temperature measurements based on coherent anti-Stokes Raman scattering from H 2 give additional clues on the thermodynamical behavior of the flow. Finally, a comparison between the data measured and numerical predictions obtained with a Navier-Stokes solver including a chemistry model is presented for the two cases studied.