Simultaneous Droplet Size and Gas-Phase Turbulence Measurements in a Spray Flow using Phase-Doppler Interferometry

A recently developed method to increase the sensitivity of a phase-Doppler interferometer (PDI) has been applied to an annular air flow interacting with a spray under isothermal conditions in order to demonstrate the applicability of the method to obtaining velocity and turbulence characteristics of the gas-phase in a two-phase flow. A conventional PDI system operated in the first order refraction mode cannot be configured to efficiently detect small seed particles in the presence of large droplets due to the limited dynamic range of the photodetectors. It is therefore difficult or impossible to obtain seed particle detection rates sufficient for turbulence measurements. Doping the spray with a very small quantity of dye preferentially attenuates the light intensity scattered by large droplets, thus allowing the PDI system to detect small seed particles without damaging the photodetectors when large particles are present in the flow. Application of this method to a two-phase flow produced by a pressure-swirl atomizer coaxially located within an annular air jet has resulted in profiles of axial mean and fluctuating velocities and shear stresses as well as integral time scales and turbulent energy spectra.     

Working Principle and Experimental Results for a Differential Phase-Doppler Technique

By replacing the two detectors of a standard phase-Doppler anemometer (PDA) with a charge coupled device (CCD) line scan sensor, the scattered light can be measured not only with high temporal but also with improved spatial resolution. Thereby, the quantity to be measured by PDA, the phase difference ΔΦ, can be determined as function of the elevation angle υ. This allows a statistical evaluation of the received signal and permits precise measurements of the size and velocity even of non-ideal solid particles with inhomogeneous composition, aspherical shape or rough surface. In this paper, the basis of data acquisition and evaluation is described. This is followed by experimental results for glass spheres with intact and defect surfaces and, for comparison, for water droplets. These results demonstrate the potential of this measuring device, described as a differential phase-Doppler anemometer (DPDA).     

Further Development and Application of a Tomographical Data Processing Method for Laser Diffraction Measurements in Sprays

Using a tomographical transformation, a data processing method is developed to extend the Malvern line-of-sight measurements based on laser diffraction theory into pointwise spatial distributions of various spray characteristics including droplet volume and number concentrations as well as all mean diameters of practical interest. The method has been applied to characterize the structures of sprays injected into still ambient air and annular air streams with various liquid and air flow rates. It is found that the various mean droplet diameters may have different tendencies of radial variations, exhibiting their respective importance in characterizing sprays, and that the air flow can significantly modify the spray structure along both the radial and axial directions and may cause the dilution or accumulation of droplets in certain regions.     

Mass Measurements in Nuclear Reactions

The present status of mass measurements from reactions producing nuclei at the driplines, including those unstable to nucleon or cluster emission, is discussed. The results of recent heavy ion and π-meson induced experiments on the study of the superheavy hydrogen isotopes (⁴H, ⁵H, ⁶H), helium (⁹He, ¹⁰He), lithium (¹⁰Li, ¹¹Li) and beryllium (¹³Be) are given. The possibilities of mass measurements in radioactive ion beam experiments are also considered. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ultra-Precise Mass Measurements Using the UW-PTMS

Based on the use of a single ion, isolated at the center of a cryogenically cooled Penning trap, an environment is produced which makes this mass spectrometer remarkably free of systematic errors. The most notable developments in our quest for an ultra-high accuracy instrument were (a) the compensation of the trapping potential, (b) the discovery that motional sidebands could manipulate radial energies, (c) the use of multiply-charged ions that could improve signal-to-noise, and (d) the use of an ultra-stable superconducting magnet/cryostat system with drift <0.010 ppb/h. The dominant systematic errors are associated with radial electric fields caused by image charges in the trap electrodes and with the rf-electrical drive field used to determine the harmonic axial resonance. To illustrate the potential of this improved spectrometer, the four-fold improved measurement of the proton's mass and the eight-fold improved measurement of oxygen's atomic mass will be described. This revised version was published online in July 2006 with corrections to the Cover Date.     

Deuterium and Impurity Flux Measurements in the Boundary Plasma of T-10

Time resolved measurements of deuterium and impurity fluxes in the boundary layer of T-10 tokamak were carried out using carbon strips as deposition probes. Analysing these probes by RBS and ERD deuterium impact energies of 25–40 eV could be estimated from the saturation behaviour of deuterium in carbon. The high impurity concentration level and it's time behaviour give indications for local impurity producing sources playing an important role for the impurity transport in the near wall plasma.     

Accuracy of Phase-Doppler Anemometry in the Presence of Flames

The objectives of the present study were to clarify the influence of flames on phase-Doppler anemometry (PDA) and to consider quantitatively the accuracy of measured sizes and velocities using a known-size polystyrene particle and a Bunsen burner placed in the optical path in PDA simulating the variation of refractive index in a combusting field. It was found that fluctuations of a flame had some influence on the measurement, especially on size, while the velocities obtained in these experiments showed little influence of the flame. Furthermore, a compensation procedure for the error was discussed by comparing the scattered data in size measurement with the displacement of incident laser beams. As a result, it was found that the displacement of the laser beams can be related to the degree of errors caused by the influence of a flame on the optical path in PDA.     

Mass Flux Schemes and Connection to Shock Instability

We analyze numerical mass fluxes with an emphasis on their capability for accurately capturing shock and contact discontinuities. The study of mass flux is useful because it is the term common to all conservation equations and the numerical diffusivity introduced in it bears a direct consequence to the prediction of contact (stationary and moving) discontinuities, which are considered to be the limiting case of the boundary layer. We examine several prominent numerical flux schemes and analyze the structure of numerical diffusivity. This leads to a detailed investigation into the cause of certain catastrophic breakdowns by some numerical flux schemes. In particular, we identify the dissipative terms that are responsible for shock instabilities, such as the odd–even decoupling and the so-called “carbuncle phenomenon”. As a result, we propose a conjecture stating the connection of the pressure difference term to these multidimensional shock instabilities and hence a cure to those difficulties. The validity of this conjecture has been confirmed by examining a wide class of upwind schemes. The conjecture is useful to the flux function development, for it indicates whether the flux scheme under consideration will be afflicted with these kinds of failings. Thus, a class of shock-stable schemes can be identified. Interestingly, a shock-stable scheme's self-correcting capability is demonstrated with respect to carbuncle-contaminated profiles for flows at both low supersonic and high Mach numbers.     

Droplet Size Distribution and Sphericity Measurements of Low‐Density Sprays Through Image Analysis

An image analysis technique has been developed in order to determine the drop size distributions of sprays produced by low‐velocity plain cylindrical jets. The particle sizing method is based on incoherent backlight images. Each drop is analyzed individually in the image. The two‐dimensional image resulting from the projection of the three‐dimensional object shape (the drop) on a screen (the video sensor surface) is modeled. The model, based on the point spread function formulation, has been developed to derive a relation between contrast and relative width of individual drops. This relation is used to extend the domain of validity of drop size in terms of size range, out of focus and image resolution. The shape parameter is determined for each drop image through morphological analysis. Spherical and non‐spherical droplets are then sorted on the basis of this parameter. Non‐spherical drops are regarded as non‐fully atomized liquid bulks or coalesced drops. Finally, the droplet size distribution of true spherical droplets is established for a low‐velocity plain cylindrical liquid jet.     

Size of the Detection Area of a Phase-Doppler Anemometer for reflecting and refracting particles

Measurements of particle size distributions in multi-phase flows with a phase-Doppler anemometer yield incorrect results if polydisperse particles are investigated. For weighting biased size distributions, different in situ methods, requiring the size of the detection area, are known, but all of these weighting procedures are restricted to very small measuring volumes if off-axis instrument configurations are considered. Moreover, the weighting functions have some disadvantages in the case of poor statistics in single size classes or the results are not suitable for determining the size of the detection area for particles which are larger than the beam waist. Therefore, the intention in this work was to measure the size of the detection area for different kinds of monodisperse particles, different instrument configurations and varied instrument sensitivities experimentally and to develop an improved weighting procedure that copes with the above difficulties. The application of the results obtained from the investigations with monodisperse particles to measured particle size distributions and volume flux densities of polydisperse water droplets in a spray cone of an atomizer confirms the applicability of this weighting procedure. It is still restricted to directed flows, perpendicular to the fringes.     

Mass Measurements at the Wright Nuclear Structure Laboratory

A program to measure masses along the astrophysical rp-process path in the A～60–80 region is underway at the Wright Nuclear Structure Laboratory, Yale University. The classic technique of end-point determinations for β⁺ spectra measured in coincidence with daughter γ-rays is used to determine Q _EC which, in turn, is used to calculate the mass. Several innovations have been incorporated to increase the sensitivity and selectivity of the method. Results of recent experiments are reported.     

Phase-Doppler Anemometry with the Dual Burst Technique for measurement of refractive index and absorption coefficient simultaneously with size and velocity

The principle of the dual burst technique (DBT) based on phase-Doppler anemometry (PDA) is proposed for simultaneous particle refractive index, size and velocity measurements. This technique used the trajectory effects in PDA systems to separate the two contributions of the different scattering processes. In the case of forward scattering and refracting particles, it is shown that from the phase of the reflected contribution, the particle diameter can be deduced, whereas from the refracted contribution the particle refractive index and velocity can be obtained. Furthermore, the intensity ratio of these two scattering processes can be used for absorption measurements. Simulations based on generalized Lorenz-Mie theory and experimental tests using monodispersed droplets of different refractive indices and absorption coefficients have validated this technique.     

Determining the Fast Neutron Flux Density and Transmutation Level Measurements in ADS by the Use of a Threshold Nuclear Reaction

Determining the Fast Neutron Flux Density and Transmutation Level Measurements in the ADS by the use of a Threshold Nuclear Reaction. The aim of the project was determining the fast neutron flux density by using data from the Quinta experiment (E+T RAW collaboration). The experimental assembly based on natural uranium was irradiated by a 660 MeV proton beam. To gain the knowledge about the neutron flux inside the experimental assembly, nuclear threshold reactions of (n, xn) type were used. The level of isotopes production are measured by the activation method using a gamma radiation HPGe detector. This paper describes the Quinta assembly, experimental results, calibration procedure and average high energy neutron calculation based on yttrium (Y-89) isotopes production. In the future, results and conclusions from an experiment like this could be useful to design accelerator-driven subcritical systems (ADS) or other 4th generation fast reactors. The investigation has been performed at the Laboratory of High Energy Physics, JINR.     

Influence of Agglomerates of Conducting Spheres on the Response of a Phase-Doppler Anemometer

The influence of agglomerates of solid conducting spheres on the response of a phase-Doppler anemometer (PDA) is described for a two-sphere system by using a ray theory model. First- and second-order reflection and diffraction are considered for far-field calculations of the PDA phase difference. The numerical simulations are accompanied and supported by experimental results. Two-sphere systems of Sn63Pb37 alloy particles were captured inside an electrodynamic trap and investigated with a standard phase-Doppler system.     

Measurements of velocity using a lenticular grating

A new method is reported for measuring the velocity using a lenticular grating. The principle of the method is theoretically described on the basis of transmission-grating velocimetry. The theoretical studies are performed to estimate the deflection and collection characteristics of the light passing through the lenticular grating. The method is used to measure the velocity of a rotating random pattern. The experimental results show the usefulness of the method for measurements of the velocity.     

Local Elastic Measurements in Solids Using the Acoustic Transformer Technique

JETP Letters - The effect of transformation of focused ultrasound radiation into collimated beams of longitudinal and transverse waves in the volume of a hemispherical transformer after refraction...     

Measurements of the velocity gradient using a laser Doppler phenomenon

This paper reports on a method for measuring the velocity gradient using a laser Doppler phenomenon. The velocity gradient is determined from the velocity difference between two different points of the probing object and is actually obtained from the optical heterodyning of two differently Doppler-shifted scattered light fields from two points of the object having different velocities. The properties of output beat signals are theoretically investigated from their spectral broadening including the effect of the detecting aperture. The preliminary experiment was performed by using a rotating glass disk whose velocity is different from its center to the outside. The experimental results shows the usefulness of the present method for measurements of the velocity gradient.     

Magnetization-Grid Rotating-Frame Imaging Technique for Diffusion and Flow Measurements

A method for NMR imaging of magnetization patterns generated by a preparation radiofrequency pulse is reported. The technique is suitable for the simultaneous spatially and spectroscopically resolved acquisition of diffusion, flow, and spin-lattice relaxation data. The procedure is based on gradients of the RF amplitude B₁. A first preparation RF pulse produces a z-magnetization grid. After a certain evolution interval, the grid is imaged by a rotating-frame imaging technique using the same RF coil. Neither rotary nor Hahn echoes are intrinsic to the method. Transverse relaxation in the free-evolution intervals is irrelevant. High-power transmitters in combination with suitable probeheads normally produce RF pulses which are short relative to transverse relaxation in the presence of RF, so that spin-lattice relaxation is the only time-limiting factor. Gradients of the main magnetic field induced by variations of the magnetic susceptibility are uncritical. The proposed "real-space detection" method is compared with stimulated or rotary-echo "wave number encoding" procedures for diffusion experiments. It is shown that the imaging procedure presented not only makes visible the spatial (apart from the spectral) distribution of transport properties which otherwise are concealed in the wave-number encoded signal, but also renders the measuring procedure insensitive to inhomogeneities of the B₁ gradient, which needs neither to be constant nor to be uniformly oriented. Extremely inhomogeneous B₁ gradient distributions should even make single-scan diffusion experiments feasible. The magnetization-grid rotating-frame imaging procedure can be employed for the two-dimensional measurement and representation of the probability P(z₁, 0|z₂, t) that a particle is at a position z₁ at a time 0 and at a position z₂ at a time t.     

Precision Mass Measurements of Short-lived Nuclides at the Heavy-ion Storage Ring in Lanzhou

Recent commissioning of the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou enabled us to conduct high-precision mass measurements at the Institute of Modern Physics in Lanzhou (IMP). In the past few years, mass measurements were performed using the CSRe-based isochronous mass spectrometry employing the fragmentation of the energetic beams of 58Ni, 78Kr, 86Kr, and 112Sn projectiles. Masses of short-lived nuclides on both sides of the stability valley were addressed. Relative mass precision of down to 10−6 ~ 10−7 is routinely achieved. The mass values were used as an input for dedicated nuclear structure and astrophysics studies, providing for instance new insights into the rp-process of nucleosynthesis in X-ray bursts. In this contribution, we briefly review the so far conducted experiments and the main achieved results, as well as outline the plans for future experiments.     

Measurements of the thermodiffusion ratio in a binary solution using an acoustic resonator

The nonlinear acoustic resonator filled with a layered solution is studied. The possibility of its application to measure liquid parameters is shown. The proposed acoustic method is based on the dependence of the speed of sound in a solution on its concentration which varies due to thermal diffusion in the beam propagation region. An analysis of the relations describing the resonator transmittance showed that, having measured the steady-state and minimum resonator transmittances, the thermodiffusion ratio in a binary solution filling the resonator can be determined.