Laser Diagnostics - Science topic

This work presents an experimental investigation of solid fuel combustion in a laminar flow reactor with high-speed laser diagnostics. The main focus lays on the development of image evaluation approaches for accurate determination of single-particle ignition based on optical measurement data. Homogeneous ignition of individual bituminous coal part...

The combustor and turbine inlet pressures of modern aviation and power-generation gas turbine engines can vary between 30 and 50 bar. Innovative diagnostic methods are needed to understand the complex thermo-physical processes taking place under these conditions. Non-intrusive, spatially, and temporally resolved optical and laser diagnostic methods...

Spontaneous Raman scattering is a conventional in-situ laser-diagnostic method that has been widely used for measurements of temperature and major species. However, utilization of Raman scattering in sooting flames suffers from strong interference including laser-induced fluorescence, laser-induced incandescence, and flame luminosity, which has bee...

Electron powder bed fusion (E-PBF) is an additive manufacturing technology used to produce parts layer-wise for advanced aerospace, biomedical, and other applications. Precise control over the energy transferred to the powder by the electron beam is key to further process improvements. Here, we used tunable diode laser absorption spectroscopy to ch...

The prospects of healthcare systems and their results may be influenced by nanotechnology. Researchers have recently become very interested in gold nanoparticles (AuNPs) because of their superior physiochemical characteristics. AuNPs exhibit size-and shape-dependent optical and electronic properties and are noncorroding, biocompatible, and amenable...

The recent progress in high-speed ( ≥ 100 k H z ) laser diagnostics for hypersonic flows is reviewed. Owing to the ultrahigh flow speed, a laser frequency of 100 kHz or higher is required for hypersonic diagnostics. Here, two main laser diagnostic techniques are discussed: focused laser differential interferometry (FLDI) and pulse-burst laser-based...

Up to date, the soot evolution process during hydrocarbon combustion is not fully understood. This fact basically derives from the simultaneous interplay of numerous chemical reactions linked to rapid changes, complex physical processes such as heat and mass transfer or agglomeration, and a required size of observation in the nanometric down to the...

Laser-induced damage (LID) on high-power laser facilities is one of the limiting factors for the increase in power and energy. Inertial confinement fusion (ICF) facilities such as Laser Mégajoule or the National Ignition Facility use spectral broadening of the laser pulse that may induce power modulations because of frequency modulation to amplitud...

High-power lasers can generate energetic particle beams and astrophysically relevant pressure and temperature states in the high-energy-density (HED) regime. Recently-commissioned high-repetition-rate (HRR) laser drivers are capable of producing these conditions at rates exceeding 1 Hz. However, experimental output from these systems is often limit...

The paper describes a method of laser correction of geometric errors for CNC-controlled multi-axis equipment – CMMs and machine-tools. The method utilizes Kalman’s concept of “control and observation”. A multi-function laser interferometer is suitable to be used as an “observer” for digital production, and a CNC-programs postprocessor, introduced b...

Explosive blasts, used in a variety of engineering applications, have coupled multiphase dynamics, and require high-fidelity spatiotemporally resolved measurements to understand and accurately predict key design parameters. This study evaluates burst-mode laser-based particle-field visualization and particle image velocimetry (PIV) for planar measu...

Characterization of soot agglomerates often relies on the angular distribution of their light scattering cross-section, C, that is based on the structure factor exponent, Ds, and asymmetry parameter, g, and depend on agglomerate mobility, dm, and constituent primary particle, dp, size distributions. Here, discrete element modeling is interfaced wit...

Laser diagnostics techniques are widely used in experimental fluid mechanics. By far the most widely used systems for getting spatial velocity fields and turbulence data are laser Doppler anemometers (LDA). Further, in the cases of two-phase flows phase Doppler analysers (PDA) are typically chosen to measure the size and velocity of the droplets or...

Turbulent premixed flames subjected to extreme levels of turbulence exhibit reaction zone broadening and thinning. Instantaneous flame structures visualized using advanced laser diagnostic methods have shown significantly different behaviours of flame/turbulence interaction in jet flames stabilized on burners of different sizes. This paper aims to...

A dual color, frequency and pulse duration agile laser system, capable of delivering laser pulses in arbitrary temporal profiles with ∼ 1 ns to ∼ 1 µs pulse duration, chirping rates of ∼27 MHz/ns with an achievable chirping range of several GHz across the pulse duration, and with energies ranging from a few nJ to hundreds of mJ per pulse has been d...

Combustion measurements using laser diagnostics are vital for experimentally revealing both qualitative and quantitative flame characteristics. This paper focuses on the application of the quantitative OH laser-induced fluorescence (OH-LIF) method for high-pressure and high-temperature flames. Under high-pressure conditions, the intense OH chemilum...

This paper presents a joint numerical and experimental study of the ignition process and flame structures in a gasoline partially premixed combustion (PPC) engine. The numerical simulation is based on a five-dimension Flamelet-Generated Manifold (5D-FGM) tabulation approach and large eddy simulation (LES). The spray and combustion process in an opt...

Physics of supercritical fluids is extremely complex and not yet fully understood. The importance of the presented investigations into the physics of supercritical fluids is twofold. First, the presented approach links the microscopic dynamics and macroscopic thermodynamics of supercritical fluids. Second, free falling droplets in a near to supercr...

The PANDORA (Plasmas for Astrophysics Nuclear Decays Observation and Radiation for Archaeometry) experiment aims to study the β-decay process inside a dense plasma mimicking stellar conditions. An electron cyclotron resonance plasma trap will be built at INFN-LNS in Catania, Italy, for the generation of the desired conditions in the laboratory. Thi...

A dual color, frequency and pulse duration agile laser system, capable of delivering laser pulses in arbitrary temporal profiles with ~1 ns to ~1 us pulse duration, chirping rates of ~27 MHz/ns with an achievable chirping range of several GHz across the pulse duration, and with energies ranging from a few nJ to hundreds of mJ per pulse has been dev...

The soot volume fraction, fv, measured by Santoro and coworkers in an ethylene diffusion flame by light extinction has become a standard for validation of models for soot formation and growth. This fv, however, has been obtained assuming soot spheres of constant refractive index. As a result, when compared to that measured by microscopy and thermoc...

We report on an optical investigation of the pyrolysis and photolysis of trimethylindium (TMIn) as a typical metalorganic precursor for functional nanowire growth, aiming at an in-depth understanding of the governing chemistry and optimization of aerosol-based (aerotaxy) and epitaxial growth processes. A flow reactor with special consideration give...

In order to reach the highest intensities, modern laser systems use adaptive optics to control their beam quality. Ideally, the focal spot is optimized after the compression stage of the system in order to avoid spatio-temporal couplings. This also requires a wavefront sensor after the compressor, which should be able to measure the wavefront on-sh...

We present the first Thomson scattering measurements of electron density and temperature in the Large Plasma Device (LAPD), a 22 m long magnetized linear plasma device at the University of California Los Angeles (UCLA). The diagnostic spectrally resolves the Doppler shift imparted on light from a frequency-doubled Nd:YAG laser when scattered by pla...

Strong field QED is an active research frontier. The investigation of fundamental phenomena such as pair creation, photon-photon and photon-electron interactions in the nonlinear QED regime are a formidable challenge both experimentally and theoretically. Several experiments around the world are being planned or in preparation to probe this strong...

As combustion technologies advance and traditional design boundaries are pushed, new ranges of conditions and new phenomena become relevant. Notably, advanced combustion engine technologies such as homogeneous charge compression ignition (HCCI) rely on low-temperature oxidation chemistry, also referred to as negative temperature coefficient (NTC) c...

We analyze the structure of methane–air and methane–hydrogen–air flames stabilized over the porous plate burner, using the method of laser-induced fluorescence. The simultaneous measurement of OH radical distribution and temperature is made under the equivalent conditions of reaction of two mixtures in terms of consumption of oxygen. We demonstrate...

Computational simulations have the potential to provide low-cost, low-risk insights into wildland fire structure and dynamics. Simulation accuracy is limited, however, by the difficulty of modeling physical processes that span a wide range of spatial scales. These processes include heat transfer via radiation and turbulent advection, as well as bot...

Jet fuels with various properties are desirable for different operational or environmental advantages, necessitating fuel-flexible technology. For example, JP-5 (A-3) and alternative jet-fuels with high flash points are favored for safe handling and other advantages. The study investigates the effects of fuel properties on the near-field spray char...

The optimization of non-premixed rotating detonation combustors (RDCs) requires improved understanding of the coupled effects of reactant stratification, fluid property gradients, and complex shock-wave interactions on the detonation wave structure within annular geometries. In the current work, simultaneous orthogonal views of chemiluminescence an...

Ammonia is considered as one of the most promising alternative fuels due to its carbon neutrality and the existing infrastructure for its mass production and delivery. However, burning neat ammonia has the issue of poor flame stability and high NO x emissions, making co-firing ammonia with conventional fuel a more feasible approach. The present wor...

Spectral-broadening of the APOLLON PW-class laser pulses using a thin-film compression technique within the long-focal-area interaction chamber of the APOLLON laser facility is reported, demonstrating the delivery of the full energy pulse to the target interaction area. The laser pulse at 7 J passing through large aperture, thin glass wafers is spe...

View Video Presentation: https://doi.org/10.2514/6.2022-1602.vid A new hypervelocity expansion tunnel (HXT) was recently brought to operational status at Texas A&M University. This facility allows for replication of true flight temperature, pressure, and velocity over a large portion of many hypersonic flight trajectories. The advantage of an expan...

View Video Presentation: https://doi.org/10.2514/6.2022-1525.vid The development of laser diagnostic methods based on Optical Parametric Oscillators (OPOs) has enabled high speed non-intrusive measurements of velocity, temperature and species composition in unsteady hypersonic flows at repetition rates exceeding dye laser performance. Here, we repo...

Strong field QED is an active research frontier. The investigation of fundamental phenomena such as pair creation, photon-photon and photon-electron interactions in the nonlinear QED regime are a formidable challenge -- both experimentally and theoretically. Several experiments around the world are being planned or in preparation to probe this stro...

The thesis work concerns development and application of four versatile nonlinear optical techniques, based on exploiting ultrashort laser pulses, for diagnostic purposes in gases and flames. The four techniques, all laser-based, are two-photon laser-induced fluorescence (TPLIF), hybrid femtosecond/nanosecond (fs/ns) rotational coherent anti-Stokes...

In this work, we present rigorous calibration and assessment of a surface ionization detector (SID) for alkali monitoring in industrial process gases and compare it to an in situ laser diagnostic method called collinear photofragmentation and atomic absorption spectroscopy (CPFAAS). The side-by-side comparison of the time-resolved alkali concentrat...

This study experimentally and numerically investigates the freezing characteristics and fluid dynamics of millimetre-sized sessile water droplets submerged in silicone oil at sub-zero temperatures under free convection. Individual water droplets were cooled to sub-zero temperatures (260-270 K) via interfacial heat transfer between the two liquid ph...

The article is devoted to the analysis of a diffusion combustion of a composite fuel (formed by an addition of non-oxidized aluminum (Al) nanoparticles (NP’s) to n-decane) with oxygen. The process of obtaining Al NP’s consisted of a laser fragmentation of initially large commercially produced NP’s (so called “Alex” with mean diameter is about 450 n...

We present ultrabroadband two-beam femtosecond/picosecond coherent Raman spectroscopy on the ro- vibrational spectra of CO2 and O2 , applied for multispecies thermometry and relative concentration measurements in a standard laminar premixed hydrocarbon flame. The experimental system employs fs-laser-induced filamentation to generate the compressed...

In this work, wavelengths were determined for the robust and simultaneous measurement of film thickness, urea concentration and fluid temperature. Film parameters such as film thickness, film temperature and the composition of the film are typically dynamically and interdependently changing. To gain knowledge of these quantities, a measurement meth...

Experimental determination of test gas caloric quantities in high-enthalpy ground testing is impeded by excessive pressure and temperature levels as well as minimum test timescales of short-duration facilities. Yet, accurate knowledge of test gas conditions and stagnation enthalpy prior to nozzle expansion is crucial for a valid comparison of exper...

The paper describes the development of the optically accessible test loop designed to conduct an experimental study of supercritical water with advanced optical laser diagnostics. The open-loop test rig has been designed for a water flow rate up to 25 g/s with maximum operating pressure and temperature of 300 bar and 500˚C, respectively. The test s...

This paper describes the generic design philosophy of optically accessible high-pressure model gas turbine combustors developed to perform combustion study with laser diagnostics at realistic conditions. A versatile combustor rig recently designed in the present work for maximum operating pressure and mass flow rate of 15 bar and 1 kg/s, respective...

In this work, an experimental investigation of AdBlue film formation in a generic selective catalytic reduction (SCR) exhaust gas test bench is presented. AdBlue is injected into a generic SCR test bench resulting in liquid film formation on the lower wall of the channel. The thickness of this liquid film is measured using a film thickness sensor b...

Stratified swirled flame is widely used in gas turbines and aero engines to achieve low emissions. However, the limitation of implementing laser diagnostic in real combustors acquires more accurate measurements of field information in the flame, especially the unsteady heat release, which relates to a lot of important phenomena, such as combustion...

Laser diagnostic techniques have evolved as a pioneering tool for understanding the combustion and fluid dynamics in internal combustion (IC) engines. These are non-intrusive techniques, which provide fundamental insights about the in-cylinder processes such as spray characteristics, fuel-air mixing, combustion, pollutant formation, etc. without af...

The effect of hydrogen ( $$\mathrm {H}_{\mathrm {2}}$$ H 2 ) enrichment on the flame-holding characteristics of two natural gas jet flames in crossflow is investigated here, experimentally. The flame and flowfield measurements are analyzed using simultaneously acquired high-speed (10 kHz) stereoscopic particle image velocimetry, planar laser-induce...

Pre-filming air-blast nozzles are a reliable atomizer type to inject fuel into the turbine combustion chamber due to their fine drop generation governed by the turbulent airstream. The complexity of the internal geometry and the large number of parameters affecting the nozzle performance have made this type of nozzles of prime interest for numerous...

Data are presented from experiments of flow boiling in a horizontal pipe. Specifically, refrigerant R245fa was evaporated in a 12.6 mm stainless steel pipe to which a uniform heat flux of up to 38 kW/m2 was applied. The bespoke facility operated at mass fluxes in the range 30–700 kg/m2.s and a saturation pressure of 1.7 bar. Flow patterns were iden...

The ignition and volatile combustion of single coal particles were investigated under laminar conditions. Relevant physico-chemical processes were analyzed under conventional and oxy-fuel atmospheres with varying O2 contents in experiments and simulations. An optically accessible laminar flow reactor with well-defined boundary conditions measured w...

Introduction: Semiconductor nanoplatelets (NPLs) are promising materials for nonlinear optical microscopy since they feature good two-photon absorption (TPA) properties, narrow photoluminescence spectra and high quantum yields of luminescence. Nevertheless, the use of semiconductor NPLs is inevitably connected with concerns about heavy metal ion t...

The presence of pulse front tilt (PFT), caused by angular dispersion (AD) in femtosecond laser pulses, could degrade the performance of the laser system and/or impact the experimental yields. We present a single-shot diagnostic capable of measuring the AD in the x–y plane by adopting an intensity mask. It can be applied to stretched pulses, making...

Mixing processes between main flow and effusion cooling air are investigated in an effusion cooled, swirl-stabilized pressurized single sector gas turbine combustor using advanced laser diagnostics. Quantitative planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) and planar laser-induced fluorescence of nitric oxide, seeded to the e...

The present study focuses on the application of a picosecond (ps) two-photon absorption laser-induced fluorescence (TALIF) technique in krypton (Kr) at variable pressure (0.1–10 mbar). The laser intensity (I, units W cm⁻²) is tuned between 1 and 480 MW cm⁻², and the depletion of the density of the Kr 5p′[3/2]2 fluorescing state through photoionizat...

Swirl-stabilized, turbulent, non-premixed ethylene–air flames at atmospheric pressure with downstream radially-injected dilution air were investigated from the perspective of soot emissions. The velocity and location of the dilution air jets were systematically varied while the global equivalence ratio was kept constant at 0.3. The employed laser d...

This study focuses on the characterisation of downwards annular gas-liquid (air-water) flows, by employing a combination of advanced laser-based and capacitance-based measurement methods. A variant of laser-induced fluorescence (LIF), referred to as structured-planar laser-induced fluorescence (S-PLIF), eliminates biases commonly encountered during...

This paper presents a comparison of experimental and numerical results for a series of turbulent reacting jets where silica nanoparticles are formed and grow due to surface growth and agglomeration. We use large-eddy simulation coupled with a multiple mapping conditioning approach for the solution of the transport equation for the joint probability...

The aim of this work is to investigate the effects of customized electrodes on the electron heating dynamics of the COST-Jet. The COST-Jet is operated with an applied sinusoidal alternating voltage of 13.56 MHz. With the help of phase resolved optical emission spectroscopy (PROES), the electron heating dynamics in the plasma discharge for customize...

Biomass, as a renewable energy source, is available worldwide, is carbon neutral, and can be converted to various types of products depending on the market and on the specific applications. Among different technologies of biomass utilization, thermochemical conversion of biomass is the most efficient method with the shortest time scale of the proce...

Flame synthesis is a powerful and scalable method for generating nanoparticles for a wide range of applications. The chemical interaction of the flame and the precursor combined with the spatial and temporal temperature distribution determine the product properties. For controlled nanoparticle synthesis that can also be scaled to industrial product...