Interferometric Particle Imaging Research Articles

Characterization of nasal spray aerosol fields using the extended interferometric particle imaging technique

Nasal-drug-delivery is an effective way to improve therapeutic effect. Droplet diameter and its distribution directly impact the deposition position and bioavailability of the drug in nasal passage. In this paper, the spatial distribution of the droplet size, location and refractive index of spray are explored with extended interferometric particle imaging technique. A generalized expression of the spatial spacing of interference fringes is derived theoretically. The fringe spacing for two counter-propagating beams is the same as that for a single beam along one of the two-beam directions at the sideward scattering region, which is verified by simulation and experiment. The polystyrene microsphere and the nasal spray of physiological saline and oxytocin are tested experimentally. The relative error of microsphere size is less than 0.3 %, the refractive index accuracy of spray can reach 10−4. The method presented herein is promising for many relevant applications, such as fuel spray and nasal spray.

Effect of cavitation treatment of coal-water slurries on a droplet average size in a jet

Relevance. Transition to environmentally friendly energy technologies, due to modern requirements for environmental protection, involves the search and creation of new energy sources, including fuels. One of the ways to meet these requirements and maintain the same level of energy production by thermal power plants is the transition to multicomponent fuels. The most promising and affordable boiler fuels from the point of view of energy, ecology and economy are coal-water slurries. In this regard, the study of the properties and characteristics of such fuels is relevant in many countries. Aim. Experimental studies of the effect of the coal-water fuel cavitation treatment duration on a droplet average size in a jet after spraying with a pneumatic nozzle and substantiation of the efficiency of such approach for practical application. Object. Experimental studies were carried out with coal-water slurries based on long-flame coal (D grade) with addition of 10 and 20 wt % by weight of pyrogenetic liquid. A slurry, consisting of just coal and water, without the addition of pyrogenetic liquid, was used as a reference sample. Method. The coal-water slurries were prepared in a rotary hydrodynamic cavitation generator. A pneumatic nozzle with external mixing was used to spray the coal-water slurries. The average size of fuel droplets after spraying was determined using the Interferometric Particle Imaging method. Results. Experiments on the preparation of coal-water slurries with pyrogenetic liquid showed an increase in the dynamic viscosity of the fuel. An increase in the duration of treatment of the slurries in a rotary hydrodynamic cavitation generator reduced the viscosity by 54%. The average size of droplets in the jet was reduced by 22%.

Uncertainty elimination in 2D shape reconstruction of irregular particles in Interferometric particle imaging

Interferometric Particle Imaging (IPI) technique is presently utilized in measuring irregular particle whose shape and size are indispensable parameters in various scientific fields, while orientation and size uncertainty are tough problems in IPI measurement. Herein, an effective method is proposed to eliminate aforementioned uncertainties. Based on Square Gradient function and multi-plane phase retrieval algorithm, our method eliminates conjugate solution in single-plane shape reconstruction thereby making the orientation of the reconstructed particle shape unique, while position search of focused image has significantly reduced the size error of reconstructed particle shape. Dual-detector IPI system is constructed to measure actual irregular particles whose shapes are successfully recovered from detected defocused speckles with an average shape similarity of 0.960 in Jaccard Index, and theoretical size error greatly decreases from 44.7% to 0.8% under the same system configuration. The proposed method is potential in further work such as real-time particle measurement and 3D shape reconstruction.

Liquid lens for adaptive interferometric particle imaging.

A liquid lens is used to realize an adaptive interferometric particle imaging system. The defocus parameter of the system can be changed instantaneously by adjusting the voltage applied to the lens. This enables adjusting the imaging conditions in real time. The setup is first tested on programmable rough particles generated by a digital micromirror device (DMD), and then with real glass particles under nanosecond pulse illumination.

Measurement of irregular particle size from the reconstructed shape images

A method for measuring the size of irregular particles is proposed. The smallest bounding rectangular box of the particle image can be acquired after obtaining interferometric out-of-focus image by using interferometric particle imaging technology and reconstructing particle shape through convolutional neural network. The number of image pixels of the particle can be obtained from the smallest bounding rectangular box. A new pixel size is defined by using the box counting method based on the analysis of the relationship between particle size and pixel size. The width and height of the particles are then obtained. The maximum relative errors in width and height are 1.47% and 1.16%, respectively. The results indicate that the proposed method can provide a research basis for the realization of three-dimensional size measurement of particles.

Position and morphology detection of mixed particles based on IPI and YOLOv7

The acquisition of microphysical information, such as water or ice content in cloud fields, plays an important role in artificial precipitation and weather forecasting. Here, the position and morphology detection of mixed particles is realized by combining interferometric particle imaging (IPI) with YOLOv7. The simulative and experimental interferometric defocus images of mixed particles are obtained from the optical transfer matrix theory and the IPI system, respectively. The new network with stronger feature extraction capability based on YOLOv7 is proposed and named “RFBCA-YOLO,” which adds the coordinate attention (CA) module and employs the receptive field block (RFB) module. The position accuracy of RFBCA-YOLO is comparable to that of the erosion match algorithm, and the miss and false detections are reduced. Compared with the original YOLOv7 network in morphology detection, RFBCA-YOLO improves the mean average precision (mAP) and mAP0.5:0.95 by 2.0% and 1.3%, respectively, and the F1 score by 1.6%. The floating-point operations per second (FLOPs) and parameters are reduced by 2.4% and 8.7%, respectively.

3D trajectory, morphology and phase discrimination of burning Al/AP propellant particles with time-resolved astigmatic dual-beam interferometric particle imaging

This work implements astigmatic dual-beam interferometric particle imaging (ADIPI) in propellant combustion diagnostics to enable the measurement of the three-dimensional (3D) spatial position and particle morphology of opaque particles. The ADIPI allows the discrimination of different substances, such as metal droplets, flames, and pyrolysis residues. A general theoretical model based on the generalized Huygens-Fresnel integral and the ray transfer matrix model is developed to describe the identification of ADIPI signals for regular and irregular particles. An experimental system combining a 13 kHz time-resolved ADIPI with digital in-line holography (DIH) is built to enable simultaneous measurements of the propellant combustion field. The typical ADIPI signals presented by different substances in the combustion field are analyzed by comparing the experimental results of DIH. The time-resolved 3D trajectory reconstruction of burning particles and the measurement of irregular particle size and morphology are realized. Due to the effect of the flame, the average deviation of the depth locating of the particles is 1.4 mm with a standard deviation of 1.0 mm. The average deviation value of the depth position relative to the measured distance is 1%. In propellant combustion measurements, the motion of burning particles can be accurately determined, proving its feasibility and practicality.

Influence of cavitation treatment on the properties of coal-water slurries with pyrogenetic liquid and characteristics of their atomization by a pneumatic nozzle

Experimental studies were conducted to investigate the rheological properties and atomization characteristics of coal-water slurries sprayed by a pneumatic nozzle with addition of pyrogenetic liquid. The research object was coal-water slurries prepared on the basis of long-flame coal using a rotary hydrodynamic cavitation generator. The dynamic viscosity of samples was investigated using a Reotest-2 rotary viscometer. The droplet size of atomized slurries was determined by the interferometric particle imaging method. A pneumatic nozzle designed for spraying of coal-water slurry fuels was used. The calorific value of coal-water slurry compositions was estimated by a theoretical method using Mendeleev's equation for calculating the lower heating value of combustion of organic substances with a certain elemental composition. It was found that cavitation treatment of a two-component coal-water fuel for 90 s leads to a 48% decrease in its viscosity. It was shown that substitution of water with a similar amount of pyrogenic liquid (5 to 20%) leads to an increase in the viscosity of coal-water fuels. The cavitation treatment of such slurries reduces the viscosity of the respective three-component coal-water fuels by 27–45%. According to the results of static sedimentation studies, coal particles start to precipitate 24 h after the onset of cavitation treatment. The treatment of the slurries under consideration for 27 and 90 s in a rotary hydrodynamic cavitation generator was established to reduce the average droplet size in the jet after spraying with a pneumatic nozzle by 5.5% and 6.5%, respectively. The introduction of pyrogenetic liquid into the composition of coal-water fuels increases their calorific value by 6.9%. It can be concluded that the use of pyrogenetic liquid in the composition of coal-water slurry fuels followed by their treatment in a rotary hydrodynamic cavitation generator can solve the problem of low reactivity of coal-water slurries.

Particle Shape Recognition with Interferometric Particle Imaging Using a Convolutional Neural Network in Polar Coordinates

A convolutional neural network (CNN) was used to identify the morphology of rough particles from their interferometric images. The tested particles had the shapes of sticks, crosses, and dendrites as well as Y-like, L-like, and T-like shapes. A conversion of the interferometric images to polar coordinates enabled particle shape recognition despite the random orientations and random sizes of the particles. For the non-centrosymmetric particles (Y, L, and T), the CNN was not disturbed by the twin image problem, which would affect some classical reconstructions based on phase retrieval algorithms. A 100% recognition rate was obtained.

2D shape reconstruction of submillimetric irregular rough particles from speckle pattern in interferometric particle imaging measurement

Particle shape is a significant feature of irregular particles. The interferometric particle imaging (IPI) technique has been introduced to retrieve submillimetric irregular rough particle shapes, while inevitable experimental noises hinder the convergence of two-dimensional (2D) particle shapes from single speckle patterns. In this work, a hybrid input–output algorithm with shrink-wrap support and oversampling smoothness constraints is utilized to suppress the Poisson noise in IPI measurement and recover accurate 2D shapes of particles. Our method is tested in numerical simulations on ice crystal shapes and actual IPI measurements on four different types of irregular, rough particles. The shape similarity of the reconstructed 2D shape has reached an average Jaccard Index score of 0.927, and the relative deviation of the reconstructed size is within 7% for all 60 tested irregular particles at the maximum shot noise level of 7.4%. Furthermore, our method has obviously reduced the uncertainty in the 3D shape reconstruction of irregular, rough particles.

Upper Limit Analysis of Measurable Particle Size by Interferometric Particle Imaging Technology

Upper Limit Analysis of Measurable Particle Size by Interferometric Particle Imaging Technology

2D shape reconstruction of irregular particles with deep learning based on interferometric particle imaging.

Interferometric particle imaging (IPI) technology is widely used in the measurement of various particles. Obtaining particle shape information directly by IPI is challenging because of the complex relationship between the speckle distribution of interference-defocused speckle patterns and the shape of the corresponding irregular particles. Considering this challenge, we implement a deep learning method based on the convolutional neural network (CNN) to reconstruct defocused images of sand particles with sparse features. We also introduce the negative Pearson correlation coefficient as the loss function. To verify the feasibility of our method, we implemented it to reconstruct defocused images obtained from IPI experiments. Finally, compared with another common CNN-based structure, we confirmed that our network structure has good performance in the shape reconstruction of irregular particles.

Laser-Optical Shear-Flow Analysis across the Annular Gap of a Simplified Displacement Compressor Model

The present experimental feasibility study testifies the two flow measurement techniques Defocusing Particle Tracking Velocimetry (DPTV) and Interferometric Particle Imaging (IPI) for their applicability to measure the two-phase flow of thin (sub-millimeter) annular rotor-stator gaps such as occur across for the leakage flow e.g. in the housing gap of oil-injected rotary positive displacement compressors (RPDC). To provide unrestriced optical access to the annular gap and in turn eliminate secondary effects, a simplified displacement compressor model has been developed and fabricated from perspex. The proof-of-concept results of both experimental campaigns (DPTV & IPI) are discussed and avenues for future efforts towards a straight-forward and accurate applicability of either method are elaborated.

High-speed astigmatic dual-beam interferometric particle imaging for direct depth displacement and velocity measurement of metal droplet

High-speed astigmatic dual-beam interferometric particle imaging (HADIPI) is adopted to simultaneously measure the three-dimensional (3D) position, velocity and size of spherical metal droplets. We propose to infer the depth displacement of the droplet directly from the angle shift of the interference fringe. Angular cross power spectral density is used to detect the angular shifts of the interference fringe. The depth displacements and velocities can be further obtained from the obtained angular shifts. Proof-of-concept experiments are conducted on micron-sized gallium droplets, demonstrating that the 3D trajectories of the droplets can be accurately obtained, with depth displacement accuracy of tens of microns, improving accuracy in depth position measurement compared to the traditional Lagrangian framework. Different from traditional imaging methods, HADIPI can directly display the 3D movement of droplets, including in the depth direction. In the combustion measurements of the solid rocket motor, the motion state of metal droplets can be precisely determined, demonstrating the feasibility and practicality.

3D-Tracking of Sand Particles in a Wave Flume Using Interferometric Imaging

We report the 3D-tracking of irregular sand particles in a wave flume using a cylindrical interferometric particle imaging set-up. The longitudinal position of each particle is deduced from the ellipticity of its speckle-like interferometric image. The size of a particle is determined from the analysis of the 2D Fourier transform of its defocused image. It is further possible to identify some rotation of the particles. Simulations accurately confirm the experimental determination of the different parameters (3D position and size of each particle).

Accurate droplet depth displacement measurement with time-resolved astigmatic interferometric particle imaging.

The astigmatic interferometric particle imaging (AIPI) model reveals that the fringe orientation shifts with droplet depth displacement, and their relationships are quantitatively formulated. The depth displacement is directly evaluated from the relative angular shift of the fringes with angular cross power spectral density, and this algorithm isolates the uncertainty of droplet depth position from depth displacement. Proof-of-concept experiments on micrometer-sized transparent droplets with a 5 kHz AIPI system demonstrates that droplet three-dimensional (3D) trajectories are accurately obtained with the accuracy of depth displacement up to tens of micrometers, improving an order of magnitude from hundreds of microns in a traditional Lagrangian framework by comparing droplet depth positions.

Quasi-hot spraying of coal-water slurries with pyrogenetic water additives

The relevance of the work is explained by the absence of the results of the heating effect of multicomponent coal-water slurries on rheological properties and characteristics of spraying in the literature.PURPOSE. Efficiency substantiation of thermal preparation of coal-water slurries based on pyrogenetic liquid by the results of experimental studies.METHODS. When solving this problem, the Brookfield RVDV-II+Pro rotary viscometer, general-purpose hydrometers, and the Interferometric Particle Imaging method were used.RESULTS. It was found that when water in coal-water fuel is replaced by a similar amount of pyrogenetic liquid (no more than 25%), the density of the slurry increases by 14% at a temperature of 293 K. Preheating of coal-water slurries to 363 K reduces the increase in the density value to 7%. The experimental results showed that the greatest influence of the thermal preparation of the studied slurries on their dynamic viscosity is characteristic of the temperature range from 293 to 333 K. At such temperatures, a decrease in the viscosity of the fuel is possible by 17-20%. Preheating of slurries before spraying in the temperature range from 293 to 333 K makes it possible to increase jet spraying angle by 21-29% in comparison with two-component coal-water fuel at a temperature of 293 K. Substitution of more than 25% by weight of water with pyrogenetic liquid in coal-water fuel is impractical for the studied grade of coal from the point of view of a significant increase in viscosity. Preheating coal-water fuel before spraying reduces the average droplet size by 5-9%.CONCLUSION. The efficiency of thermal preparation of coal-water slurries based on pyrogenetic liquid by the results of experimental studies of rheological properties and spraying characteristics was substantiated.

Beyond Fresnel’s approximation: Luneburg’s kernel to simulate the interferometric images of droplets or irregular rough particles

Interferometric particle imaging is generally interpreted in the framework of Fresnel conditions. We develop here a new formalism based on Luneburg’s kernel. It enables to predict the interferometric images of droplets or rough particles when Fresnel conditions are not respected. It is compared to previous experimental results, and then used to understand possible sources of noise when analyzing interferometric particle images.

Impacts of Micro-Deviations of Aperture on the Characteristics of Collision Atomization Field

As the final flow channel of the liquid rocket engine, the manufacturing of impinging atomization nozzles has become a critical link in the manufacture of impinging atomization components. At present, the high-precision machining of millimeter nozzles in large-scale production is quite difficult, which inevitably leads to the diversity of internal flow field and atomization field parameters. In this investigation, the influence of the diameter deviation of impinging nozzles on the atomization field is analyzed by experiment. The transparent nozzle is installed in a typical colliding atomizer. The ultra-precision measurement is carried out by the optical fiber measurement system and the flow field in the nozzle is visualized. The information of atomized droplets in the atomization field is assembled by the laser interferometric particle imaging technology (IPI). The experimental results indicate that the micro-deviations of the collision aperture have a profound influence on the cavitation state of the flow field in the nozzles and the atomization characteristics (droplet diameter and atomization cone angle) of the atomization field.

3D locating and sizing of volumetric metal droplets with astigmatic dual-beam interferometric particle imaging at panoramic scattering angle

This work goes insight into the feasibility of astigmatic dual-beam interferometric particle imaging (ADIPI) to enable the measurement of three-dimensional (3D) positions and sizes of spherical metal droplets at panoramic scattering angle. The ADIPI signal exists at arbitrary angle except the two laser beam axes, defined as backward scattering region, forward scattering region, and sideward scattering region according to the angle of light scattering. A generalized model for three types of scattering situation is derived and an algorithm based on the ellipse detection and two-dimensional (2D) Fourier transform is applied to locate the centroid of each pattern and extract the spatial frequency and the inclination angle of fringes. Experiments are designed and performed, showing that the results in both of the depth position and size measuring of the same droplets measured from different angles are essentially identical. The average deviation values of the depth positions both are 1% for forward-sideward situation and backward-sideward situation. For backward-forward situation, backward-sideward situation and forward-sideward situation, the average deviation values in size measuring are 6%, 13% and 9%, respectively. The flexibility of ADIPI, breaking the strict requirements for equipment arrangement, can be carried out over a wide range of angles, facilitating its great potential in metal droplet measurement.