Laser Doppler Velocimetry Technique Research Articles

Impact of blade shape on the aerodynamic performance and turbulent jet dynamics produced by a ducted rotor

A ducted rotor system was used to produce turbulent jets with a Reynolds number up to 5.97 × 105 and Mach number of 0.222 based on mean streamwise velocity. Three rotors with a diameter of 11.8 cm were manufactured and tested inside a duct with a 1 mm tip clearance at a speed up to 30 000 revolutions per minute (rpm). All rotor blades contain the same aspect ratio of 2.2, a National Advisory Committee for Aeronautics 2410 airfoil, and ideal pitch distribution. However, three different blade planform shapes were used including a rectangular shape with constant chord, trapezoidal shape with a taper ratio of 0.5, and elliptical shape where the trailing edge of the blade is expressed with an elliptical function. The rotor thrust and electric power were measured, and the thrust coefficient and figure of merit was computed. The flow-field produced by the ducted rotors was measured in the near-field using laser Doppler velocimetry techniques. The inflow velocity approximately 3 mm upstream of the rotor blade leading edge was acquired and its significance on blade aerodynamics and performance is analyzed. Time-averaged contours of cross-stream vorticity reveal intense hub and blade tip vortex structures, which are impacted by the shape of the blade, particularly in the blade tip region. Tip vorticity as well as streamwise turbulence intensity and turbulent kinetic energy in this region were mitigated for the rotors with trapezoidal and elliptical blades. However, the turbulent structure of the jet produced by all three rotor blade shapes showed similarity at a mere 2.8 rotor diameters downstream of the rotor. This finding emphasizes the importance of blade design on the near-field dynamics of ducted rotor flows for aircraft propulsion.

Mock-up conception for experimentally investigate the creep phenomenon caused by the fluid–structure interaction in a rod bundle

Pressurized water reactors (PWRs) are employed worldwide and continue to expand in capacity. They require thorough investigation, particularly concerning their safety and operational efficiency. To ensure these factors, comprehensive research into their various components and an understanding of the diverse phenomena they experience within a PWR are imperative. These phenomena can be of mechanical, thermal, hydraulic, or neutronic nature. Among these components, fuel assemblies (FAs) hold a main role in PWRs. The intricate interplay of these physical factors results in the modification of FAs geometry, specifically permanent elongation and lateral deformations referred to as irradiation creep. The earliest reported occurrence of these deformations dates back to 1994 in Ringhals reactors, where various FAs exhibited distinct deformations (Andersson et al., 2005). Given that these phenomena occur over a time span of months to years in metallic materials, conducting investigations within the confines of a typical laboratory observation period becomes impractical. Consequently, this project proposes an alternative experimental methodology to overcome this challenge, thus gaining a deeper understanding of the fluency phenomenology in FAs behavior. This methodology consists on the design of a reduced-scale test section, capable of replicating the fluid–structure interaction (FSI) responsible for creep, the creation of spacer grids through 3D printing technology, and selection of the appropriate material for the fuel rods (FRs), with an emphasis on macroscopic coupling effects, rather than focusing into the micro-structural response of the material. To experimentally observe the deformation on the FAs, cameras were used to capture images through the time during the test, to catch the displacement of the FRs. The first results showed the mock-up was able to reproduce the FSI causing the creep on the FAs, it was possible to capture the displacement evolution along time, and to observe different types of deformation, thus, it helps to understand the phenomenon. Further tests and investigations using laser doppler velocimetry (LDV) technique to analyze the flow will be held, to a better comprehension of these burden.

Effect of blade aspect ratio on the performance tradeoff between figure of merit and bending-torsion dynamics of wind turbines with synthetic jets

In this experimental study, two three-bladed rotors with a blade aspect ratio of 7.79 and 9.74 representing a 25% increase were tested. Each blade contains an S809 airfoil with zero pre-built twist and 20 high-performance synthetic jet actuators distributed along the span. The rotor was tested at four rotor speeds, Ω of 250, 500, 750, and 1,000 revolutions per minute (RPM) and three collective blade pitch angles, θc of 2, 5, and 8 degrees. Rotor thrust was measured using a high-capacity load cell, and blade bending and torsion was measured at four equally spaced radial locations on the blade defined by r/R= 0.24, 0.48, 0.72, and 0.96 using four onboard inertial measurement units. The spanwise flow over the suction surface of the blade was measured using laser Doppler velocimetry (LDV) techniques. The local Reynolds number produced with the test rotor speeds at the measurement locations ranges from 8.31 × 104≤Re∞≤ 9.49 × 105. It was found that rotor aerodynamic efficiency as quantified by the figure of merit is directly linked to blade aspect ratio and the magnitude of spanwise flow over the blade. The rotor with a higher blade aspect ratio produces less overall spanwise flow and is more aerodynamically efficient, however the blade also generates larger mean and fluctuating bending and torsion displacements, which are undesirable for aeroelastic stability. The use of synthetic jets on the blade mitigates the root mean square of the bending and pitch displacements above Ω= 250 RPM and θc= 2°. It was found that at Ω= 1,000 RPM, the blade structures undergo a second mode bending response indicating a condition of structural instability due to higher aerodynamic loading. At this rotor speed, flow control on the outboard of the blade reduces unsteady bending as quantified by arms up to a maximum of 36.5%, and unsteady torsion, θrms up to 22.9% compared to the baseline for the rotor with an aspect ratio of 9.74.

SARS-CoV-2 Spike Protein (RBD) Subunit Adsorption at Abiotic Surfaces and Corona Formation at Polymer Particles.

The adsorption kinetics of the SARS-CoV-2 spike protein subunit with the receptor binding domain at abiotic surfaces was investigated. A combination of sensitive methods was used such as atomic force microscopy yielding a molecular resolution, a quartz microbalance, and optical waveguide lightmode spectroscopy. The two latter methods yielded in situ information about the protein adsorption kinetics under flow conditions. It was established that at pH 3.5–4 the protein adsorbed on mica and silica surfaces in the form of compact quasi-spherical aggregates with an average size of 14 nm. The maximum coverage of the layers was equal to 3 and 1 mg m−2 at pH 4 and 7.4, respectively. The experimental data were successfully interpreted in terms of theoretical results derived from modeling. The experiments performed for flat substrates were complemented by investigations of the protein corona formation at polymer particles carried out using in situ laser Doppler velocimetry technique. In this way, the zeta potential of the protein layers was acquired as a function of the coverage. Applying the electrokinetic model, these primary data were converted to the dependence of the subunit zeta potential on pH. It was shown that a complete acid-base characteristic of the layer can be acquired only using nanomolar quantities of the protein.

METHODS OF ANALYSIS OF T-BURNER EXPERIMENTAL DATA

The measurement of response function for a given solid propellant is mostly done using a T-burner to address the issue of combustion instability in solid rocket motors. Once the experiment has been conducted, it becomes important to carefully analyse and reduce the data to the required response function using the measured pressure. Six different methods of analysing the experimental T-burner data are presented in this paper. An experiment conducted at 1 MPa pressure at 390 Hz frequency is utilized for this purpose. Detailed procedure is given to calculate the growth rate, decay rate and the response function for a self-excited test. These methods include Perry's method, Culick's method and exponential method with different combinations which is reported for the first time. Analyzing with different methods revealed that Culick's method is better and more consistent than the other methods. The response function of the given solid propellant calculated using this method for the self-excited tests of T-burner is in good qualitative agreement with the response measured using Laser Doppler Velocimetry technique.

Aeroelastic response of a propulsive rotor blade with synthetic jets

Understanding the aeroelastic response of a propulsive rotor blade is critical to implementing active flow control techniques to mitigate blade structural vibration. In this experimental study, the coupling between rotor blade aerodynamic loading and first flap mode bending and torsion is explored. The three-bladed rotor is 2.58 m in diameter, and contains a NACA 0012 airfoil with zero pre-built twist. Each blade contains 20 high-performance synthetic jet actuators distributed along the span and are activated with a constant mean jet velocity of 66.3 m/s. The rotor was tested at rotor speeds, Ω of 250, 500, 750, and 1000 revolutions per minute (RPM) and collective blade pitch angles, θc of 2, 5, and 8 degrees. Rotor thrust and torque were measured using a high-capacity load cell, and the flow near the blade tip was measured using laser Doppler velocimetry (LDV) techniques. Blade bending and torsion was measured at three equally spaced radial stations on the blade root, middle, tip regions defined by r/R= 0.32, 0.64, and 0.96 respectively using three onboard electronic accelerometers. Synthetic jets reduce the near-wall streamwise velocity deficit and turbulence intensity in the near wall flow, improving the sectional lift coefficient of the blade and delaying flow separation which results in marginally higher thrust and lower torque loading of up to 7.4% and 4.3 % respectively. At higher rotor speeds of 750 and 1000 RPM, there is a pronounced non-linear increase in bending and torsion along blade span. In the blade tip region, the streamwise flow undergoes a significant decrease in velocity and momentum, which contributes to instabilities in the boundary layer with early-stage unsteady flow separation at θc= 8°. This is correlated to a dramatic rise in the baseline power spectral density (PSD) at the blade’s natural frequency along with an increase in root mean square (rms) of bending acceleration and blade pitch angle, where the maximum values measured are arms= 0.74 g and θrms= 1.45°.

Direct velocity measurements in high-temperature non-ideal vapor flows

Direct velocity measurements in a non-ideal expanding flow of a high temperature organic vapor were performed for the first time using the laser Doppler velocimetry technique. To this purpose, a novel seeding system for insemination of high-temperature vapors was specifically conceived, designed, and implemented. Comparisons with indirectly measured velocity, namely inferred from pressure and temperature measurements, are also provided. Nozzle flows of hexamethyldisiloxane (MM, C_6H_{18}OSi_2) at temperature up to 220,^circ mathrm {C} and pressure up to 10 bar were taken as representative of non-ideal compressible-fluid flows. The relative high temperature, high pressure and the need of avoiding contamination pose strong constraints on the choice of both seeding system design and tracer particle, which is solid. A liquid suspension of tracer particles in hexamethyldisiloxane is injected through an atomizing nozzle in a high-temperature settling chamber ahead of the test section. The spray droplets evaporate, while the particles are entrained in the flow to be traced. Three different test cases are presented: a subsonic compressible nozzle flow with a large uniform region at Mach number 0.7, a high velocity gradient supersonic flow at Mach number 1.4 and a near-zero velocity gradient flow at Mach number 1.7. Temperature, pressure and direct velocity measurements are performed to characterize the flow. Measured velocity is compared with both computational fluid dynamics (CFD) calculations and velocity computed from pressure and temperature measurements. In both cases, the thermodynamic model applied was a state-of-the-art Helmoltz energy equation of state. A maximum velocity deviation of 6.6% was found for both CFD simulations and computed velocity.Graphical abstract

Air swirl effect on spray characteristics and droplet dispersion in a twin-jet crossflow airblast injector

Spray characterization in a novel twin-jet airblast injector is reported in this paper with the focus on the study of the effect of injector air swirl on droplet characteristics and dispersion behavior. The operational principle of the injector is based on achieving atomization of two liquid jets, injected in a radially opposite direction from a central hub by high-speed annular swirling cross-stream flow of air. Liquid jet atomization within model atomizers and the resulting spray study have not gained much attention in spite of its practical importance, for example, in lean premixed prevaporized combustors. In the present work, droplet size and three-component velocity measurements are measured in the above injector using the phase Doppler particle analyzer technique. Air velocity without liquid injection is also obtained using the laser Doppler velocimetry technique. For given inlet air and liquid mass flow rates, experiments are conducted in the absence and presence of annular air swirl corresponding to swirl number, S = 0 and 0.74, respectively. The addition of air swirl is found to dramatically affect the spray topology and also the measured spray characteristics as the droplet size reduces significantly downstream of the injector exit, which is explained. Droplet dispersion is studied by evaluating droplet size velocity correlation and also droplet Stokes number. The results not only provide insight into the physics behind improved atomization due to air swirl, but also demonstrate the ability of the novel injector to achieve atomization quality and high spray dispersion over a wide operating range.

Influence of upstream disturbances on performance of an LDV-based cryogenic flow meter standard – CFD modelling and preliminary measurements with air

Increasing trade of liquefied natural gas (LNG) imposes stringent requirements for accurate flow rate measurement of this high energy content fluid. To satisfy this demand, a flow meter has been developed by CEASAME Exadebit which is based on velocity measurement behind a contraction nozzle using Laser Doppler Velocimetry technique (LDV). For this instrument, a calibration factor is defined relating the measured velocity to the flow rate. This calibration factor depends on the Reynolds number and it can be sensitive to the velocity profile behind the nozzle outlet and to presence of upstream flow disturbances such as bends, valves, etc. when the meter is installed on-site. In this paper, CFD modelling, using OpenFoam software, was employed to analyse the sensitivity of the calibration factor to flow disturbances for two types of disturbing elements; a U-bend and half-plate orifice. The CFD model was validated by comparison with experimental data for the calibration factor and velocity profiles obtained from preliminary LDV measurements with air. Two measurement setups were considered where the velocity is measured either in one point at the nozzle axis or integrated along a line across the nozzle diameter. The results show that the considered disturbing elements cause deviations in the calibration factor in the order of tenths of percent and that the maximal sensitivity of the line-setup to these disturbances is approximately half of the maximal sensitivity of the point-setup. On the other hand, it was shown that the line-setup is more sensitive to the LDV positioning than the point-setup.

On the figure of merit and streamwise flow of a propulsive rotor with synthetic jets

Increasing the figure of merit of propulsive rotors for vertical takeoff and landing (VTOL) vehicles is critical to improving the hover efficiency and flight endurance of rotorcraft. In this paper, a new flow control scheme is proposed where 60 synthetic jet actuators are utilized on a large-scale propulsive rotor and the jets' velocity is increased from the blade root to the blade tip in order maintain constant levels of momentum coefficient per blade module. The three-bladed rotor measures 2.58 m in diameter and contains a NACA 0012 airfoil with zero blade twist distribution. The rotor was tested at speeds of 250, 500, 750 and 1,000 revolutions per minute (RPM) and blade pitch angles of 2, 5, and 8 degrees. Rotor thrust and power were measured using a high-capacity load cell and current sensor, and the streamwise flow was measured using phased-locked laser Doppler velocimetry (LDV) techniques at two measurement planes near the blade root and near the blade tip along the suction surface of the airfoil. Two flow control schemes were tested and compared; the new constant momentum coefficient (constant Cμ) and non-constant Cμ where the synthetic jet velocity is held constant throughout the rotor blade. When all 20 synthetic jets per blade are activated, it was found that constant Cμ improves low-speed rotor performance in terms of figure of merit, FM and thrust coefficient, CT at 250 RPM, while non-constant Cμ is marginally superior at higher rotor speeds. When both flow control schemes are applied for just the blade root module, an increase in performance compared to the baseline is observed at rotor speeds of 750 and 1000 RPM, however different values of FM and CT are achieved for each scheme. Near the blade tip the boundary layers undergo transition to turbulent flow combined with an increasing degree of adverse pressure gradient with rotor speed and blade pitch angle. Under these conditions where the normalized streamwise velocity profiles show significant velocity deficit in the near-wall flow, synthetic jets provide some momentum to delay separation as quantified by the boundary layer shape factor.

Measurement of admittance and acoustic augmentation of burning rate of composite solid propellants using Laser Doppler Velocimetry

The present work involves the use of Laser Doppler Velocimetry (LDV) technique to measure the acoustic admittance of aluminized composite solid propellant (AP/HTPB/Al) by experimentally measuring the instantaneous velocities of the particles of solid propellant during burning while the acoustic pressure oscillations are being imposed. Both velocity fluctuations and pressure fluctuations are measured synchronously. The probe volume of the laser is maintained at a constant distance from the burning surface by using a linear actuator. Tests were conducted for two aluminized composite solid propellants at low frequency ranges (130-312 Hz) of the longitudinal acoustic modes and mean chamber pressures ranging from 1 to 4 MPa. A rotary valve is designed to acoustically excite the chamber to the required resonant frequency. It was found that admittance rises with frequency and peaks around 260 Hz and then falls. The use of linear actuator mechanism significantly improves the velocity data rate (number of data points). Maintaining the probe volume at 800 to 900 µm above the propellant surface is very crucial to determine the admittance accurately. Test results revealed that a good agreement between the steady state mean burning rates with the window bomb experiments is achieved. The measured mean burn rates under imposed acoustic pressure oscillations shows the augmentation up to 55%. The admittance measured for the metallized composite propellant using this technique and the comparison with T-burner shows good agreement. The comparison of responses with LDV and T-burner and the augmentation factor due to acoustic oscillations using LDV are reported for the first time.

Characteristics and analysis of a turbulent offset jet including the effect of density and offset height

This paper presents the results of measurements and numerical predictions of 3D turbulent offset jet flows. Mean velocity and turbulence characteristics of a rectangular offset jet with different offset heights and within variable densities are experimentally and numerically investigated in detail. Four jet gas exit densities, ρj = 1.2, 1.25, 1.3 and 1.4 Kg/m3, and four offset ratios, h/w = 8, 16, 25 and 33, are studied. The considered variation of the jet density is revealed at different Reynolds numbers and the velocity measurements are carried out using a Laser Doppler Velocimetry (LDV) technique. The handled configuration is numerically simulated by solving the Navier-Stokes equations with the finite volume method having a non-uniform grid system. Two different closure models are tested: the standard k–ε model and the Reynolds Stress Model (RSM). Results clearly revealed significant effects of the jet density and the offset height on the flow development in the early region. It is noted that the centerline velocity decay increases as the jet density and the offset height increase. It is also observed that the reattachment length of the jet decreases with the increase of the jet density. However, the reattachment length is found to increase with the increase of the offset height.

Experimental investigation of the flow field generated by idealized human foot tapping

In this work, Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) techniques were employed in order to experimentally investigate the flow field generated by a human foot-tapping during a footstep. Experiments were performed in a 56 × 56 × 56-cm sealed plexiglass tank. A rectangular plate that rotates downward with a controlled velocity was used to mimic the human foot-tapping motion. The PIV results show the formation of two counter-rotating vortices outside the plate as a result of the plate rotation movement. The LDV results show that the maximal velocity in the region under the plate increases with distance from the rotation axis and reaches a maximum at the bottom of the plate. In the outside region, maximal velocity decreases exponentially with distance from the plate. Using these two techniques, the velocity profiles in the vertical direction in front of the plate were compared, and, notably, good agreement was demonstrated between the two techniques.

Helicopter main rotor angular velocity analysis by laser Doppler velocimetry: simulation and experimental results.

In this paper, the three different motions of a helicopter blade are studied by the laser Doppler velocimetry (LDV) technique. Consequently, a calculation is performed by utilizing the Simulink simulation of Matlab software. All noises, including optical, electrical circuit, and experimental environment noises, are considered. Furthermore, the temporal and frequency behavior of the final signal are illustrated for uniform rotation of the helicopter blade. The results demonstrate that there is acceptable agreement between the frequencies calculated by the theoretical, simulation, and experimental analyses, which shows the capability of LDV in measurement of helicopter main rotor angular velocity.

Experimental and numerical investigation on inspiration and expiration flows in a three-generation human lung airway model at two flow rates

The respiration flow pattern plays a key role in fluid flow, heat and mass transfer in human lung airway. To reveal the complex flow pattern within human lung multiple-generation airway, both the steady inspiration and expiration flows are comprehensively studied using laser Doppler velocimetry technique and computational fluid dynamics method for an idealized human tracheobronchial three-generation airway model at two flow rates, corresponding to an adult male breathing under light activity and moderate exercise conditions, respectively. The comparison of mainstream velocity between the measurements and simulations are generally good. Both of the inspiration and expiration flows are heavily influenced by the combination of geometrical bifurcating/merging, local wall curvature, limited generation length and multi-generation interaction. The mainstream flow is non-uniform and behaves as skewed, double-peaked and M-shaped patterns. The secondary flow is complex and characteristic of Dean-type two-vortex, four-vortex, six-vortex and eight-vortex patterns. This work is of scientific significance for a deep understanding of respiratory flow physics and of certain application values for clinical diagnosis and remedy of respiratory deceases.

Statistical Inference Method for Liner Impedance Eduction with a Shear Grazing Flow

This paper presents a statistical inference method for impedance eduction in a flow-duct facility. The acoustic impedance is recast into a random variable, and Bayes’s theorem is used to obtain the posterior probability density function of both its real and imaginary parts, thus expressing the knowledge/uncertainty one has on the impedance value, given a certain experimental data uncertainty. An evolutionary Markov chain Monte Carlo technique is selected to explore the probability space, and a surrogate model based on the method of snapshots is employed to speed up the calculations. The linearized Euler equations are solved using a two-dimensional discontinuous Galerkin scheme, accounting for the presence of a grazing flow. The inference process is first validated on published NASA Grazing Incidence Tube results, in which acoustic-pressure measurements on the wall opposite the liner are used as inputs. Then, the same procedure is applied to educe the impedance of a conventional single degree-of-freedom liner in the ONERA–The French Aerospace Lab B2A acoustic bench, in which a laser Doppler velocimetry (LDV) technique is used to measure the two components of the acoustic-velocity fields above the liner. The primary conclusion of the study is that the Bayesian inference method allows for consistent impedance eductions, as compared to a classical deterministic eduction approach, for both microphone and LDV measurements. Furthermore, it yields the credibility intervals of the identified impedance, which represent the uncertainty on the identified impedance values, given an uncertain measurement. The identified parameters are less correlated using an LDV-based inference than a microphone-based inference, which might be due to the more limited number of data.

Genotoxicity of Copper and Nickel Nanoparticles in Somatic Cells of Drosophila melanogaster.

Copper and nickel nanoparticles (Cu-NPs and Ni-NPs, respectively) are used in a variety of industrial applications, such as semiconductors, catalysts, sensors, and antimicrobial agents. Although studies on its potential genotoxicity already exist, few of them report in vivo data. In the present study we have used the wing-spot assay in Drosophila melanogaster to determine the genotoxic activity of Cu-NPs and Ni-NPs, and these data have been compared with those obtained with their microparticle forms (MPs). Additionally, a complete physical characterization of NPs using transmission electronic microscopy (TEM), dynamic light scattering (DLS), and laser Doppler velocimetry (LDV) techniques was also performed. Results obtained with Cu-NPs and Cu-MPs indicate that both failed to induce an increase in the frequency of mutant spots formation in the wings of the adults, suggesting a lack of genotoxicity in somatic cells of D. melanogaster. However, when Ni-NPs and Ni-MPs were evaluated, a significant increase of small single spots and total mutant spots was observed only for Ni-NPs (P<0.05) at the highest dose assessed. Thus, the genotoxicity of Ni-NPs seem to be related to their nanoscale size, because no genotoxic effects have been reported with their microparticles and ions. This study is the first assessing the in vivo genotoxic potential of Cu-NPs and Ni-NPs in the Drosophila model.

The unsteady flow features behind a heliostat in a narrow channel at a high Reynolds number: Experiment and Large Eddy Simulation

Several heliostats are arranged on the field for concentrating beam solar radiation onto a receiver. The flow-induced dust deposition and vibration of heliostats will lead to failure of the receiver and the entire system in eventuality. Therefore, fluid flow analysis behind a heliostat model in a narrow channel of limited length is presented depicting a field-type condition. In this paper, experiment and Large Eddy Simulation (LES) are performed. Laser Doppler Velocimetry (LDV) technique is used for horizontal velocity measurement around a heliostat with 25° angle of inclination at a Reynolds number of 60,000 basing on the length of an inclined plate. The wall-resolved coarse, intermediate and fine grids are utilized for LES with dynamic- Smagorinsky–Lilly and subgrid-scale kinetic energy transport equation based models. Comparison between local instantaneous and statistical quantities, like horizontal velocity and its root-mean-square values are presented. The flow development in the wake region of heliostat model is described using the time-dependent and the statistical horizontal velocity. Based on the adopted LES approach the coherent structures are identified with the λci-criterion. The analysis of power spectral density and swirling strength isosurface reveal the responsible coherent structures in the inertial subrange for transport of energy to smaller structures. Interestingly, the presence of hairpin-type vortices is observed extending from the two sides of model heliostat using the λci-criterion. Further, instantaneous span-wise vorticity contour reveals their alignment with flow represented by streamlines. The provided insight to these flow features and their organization is expected to frame strategies for mitigating the unsteady flow-induced vibrations and dust depositions on heliostats.

Thermographic laser Doppler velocimetry using the phase-shifted luminescence of BAM:Eu2+ phosphor particles for thermometry.

Simultaneous point measurements of gas velocity and temperature were recently demonstrated using thermographic phosphors as tracer particles. There, continuous wave (CW) excitation was used and the spectral shift of the luminescence was detected with a two-colour intensity ratio method to determine the gas temperature. The conventional laser Doppler velocimetry (LDV) technique was employed for velocimetry. In this paper, an alternative approach to the gas temperature measurements is presented, which is instead based on the temperature-dependence of the luminescence lifetime. The phase-shift between the luminescence signal and time-modulated excitation light is evaluated for single BaMgAl10O17:Eu2+ phosphor particles as they cross the probe volume. Luminescence lifetimes evaluated in the time domain and frequency domain indicate that in these experiments, interferences from in-phase signals such as stray excitation laser light are negligible. The dependence of the phase-shift on flow temperature is characterised. In the temperature sensitive range above 700 K, precise gas temperature measurements can be obtained (8.6 K at 840 K) with this approach.

Toxicological assessment of tungsten oxide nanoparticles in rats after acute oral exposure.

Advances in and the rapid growth of the nanotechnology sector have escalated manufacture of nanoparticles (NPs), resulting in a significant increase in the probability of exposure of humans and wildlife to these materials. Many NPs have been found to exert genotoxicity. Therefore, genotoxicity studies are mandatory to assess the toxicity of NPs as a concern of succumbing to genetic diseases and cancers are universal. Tungsten oxide (WO3) NPs are being explored extensively in various fields. However, the toxicological data of WO3 NPs by oral route in mammals is limited. Hence, the goal of the current investigation was to evaluate the acute toxicity of WO3 NPs and microparticles (MPs) after single oral administration with 100, 500 and 1000mg/kg body weight doses in female Wistar rats. TEM, dynamic light scattering and laser Doppler velocimetry techniques were used to characterise the particles. The genotoxicity studies were conducted using comet, micronucleus and chromosomal aberration assays. Alterations in biochemical indices and metal distribution in various organs were also evaluated. The mean size of WO3 NPs and MPs by TEM was 53.2±1.91nm and 5.17±3.18μm, respectively. The results revealed a significant increase in DNA damage and micronuclei and chromosomal aberrations after exposure to 1000mg/kg dose of WO3 NPs. Significant alterations in aspartate transaminase, alanine transaminase, reduced glutathione, catalase and malondialdehyde levels in serum and liver were found only at the higher dose of WO3 NPs. Tungsten (W) biodistribution was observed in all the tissues in a dose-, time- and organ-dependent manner. In addition, the maximum concentration of W was found in the liver and the least in the brain was observed. The test substances were found to have a relatively low acute toxicity hazard. The data obtained gives preliminary information on the potential toxicity of WO3 NPs and MPs.