Spatial Filtering Velocimetry Research Articles

Development of In-Line Measurement Techniques for Monitoring Powder Characteristics in a Multi-Stage Spray Drying Process

The integration of spray drying and agglomeration offers significant advantages, such us continuous production with lower energy consumption. However, it is a knife-edge process with a narrow operating window and limited degrees of freedom that decide between successful agglomeration and fluidized bed blockage due to excessive moisture. In this contribution, factors influencing the spray-through agglomeration process of skim milk powder as a model system were investigated via a design of experiments. Three in-line monitoring methods were applied and tested to observe the most important parameters in the agglomeration process—the product moisture and particle size distribution. Regarding the moisture content, a capacitive moisture sensor was calibrated with linear regression and a near-infrared sensor with partial least squares regression. Near-infrared spectroscopy was found to be the suitable method for determining the moisture content, while the capacitive moisture sensor mainly provides information on the bulk density, filling level, or fluidization state in the fluidized bed. Additionally, particle size distribution data were extracted from the spectral data using in-line data from a spatial filter velocimetry probe in the fluidized bed. This opens the potential to monitor both parameters in real time with a single non-invasive sensor.

Velocity field characterization of single-phase flows across a tube bundle through spatial filter velocimetry

This paper presents experimental vector velocity fields of external flows across a tube bundle to characterize the flow structure and elucidate the main mechanisms of turbulence generation. The experiments were conducted in a tube bundle test section composed of 20 rows of 4 tubes with 20 mm O.D. arranged in a normal triangular configuration with a transversal pitch per diameter ratio of 1.25. The experiments were conducted under single-phase flows with Reynolds numbers ranging from 210 to 19560, comprising transitional and turbulent flow regimes. The vector velocity fields were obtained through the Spatial Filter Velocimetry (SFV) technique, resulting in maximum spatial and temporal resolutions of 2.1 samples/mm and 49.6 kHz, respectively. The velocity measurements obtained through SFV enabled the analysis of the flow development, the vector velocity field, the flow turbulence, the velocity fluctuation along the time, and the effects of the mechanism of momentum transport on the pressure gradient. The obtained results indicate that the flow separation and the repeated intersection of opposite flows are the most relevant sources of turbulence. Moreover, the analysis of the terms of the RANS equations reveals that the convective terms are the most relevant terms for the pressure gradient.

Statistical Investigation of Rotary Fluidized Bed Agglomeration Process with Tangential Spray and In-Line Particle Size Measurement for PAT Process Control

A statistical design of experiments for a rotary fluidized bed agglomeration process is performed to improve both the knowledge of the process and the influence of the process parameters. Agglomerates of a pharmaceutical formulation are manufactured in a laboratory fluidized bed rotor apparatus with a tangential spray nozzle. Particle size is measured in-line over the entire agglomeration process with a spatial filter velocimetry probe installed directly in the process chamber and off-line with dynamic image analysis for comparison. The influence of the process parameters spray rate, spray pressure, rotor speed, and process air temperature on the fluidized bed is investigated using a central composite design. In-line measurement of particle size is possible over the entire rotor process. Spray pressure, spray rate, square of process air temperature, and some interactions proved to be statistically significant. Particle size measured with spatial filter velocimetry and dynamic image analysis indicates good agreement and a similar trend. The successful application of particle size measurement in a fluidized bed rotor agglomeration at a laboratory scale using spatial filter velocimetry to improve process control and reduce the risk of failed batches serves as the basis for transferring to a production scale.

Measurements of unconfined fresh concrete flow on a slope using spatial filtering velocimetry

Fluidity of fresh concrete is an important performance, and it can be evaluated by concrete flow process. Before the experiments, the theory of the lateral spread and accumulation were assumed. Then, the velocity and spread characteristics of concrete with different water content on an inclined plane were studied. Spatial filtering velocimetry (SFV) was used to measure the free-surface spreading evolution of concrete of a fixed volume slowly released onto a slope. The velocity gradients along the flow direction were calculated in the steady zone and the results showed that the velocity gradient was a reasonable indicator to assess concrete fluidity. Based on these analysis and results, the flow depth during the flow process was estimated too.

A new approach to the mechanisms of agglomeration in fluidized beds based on Spatial Filter Velocimetry measurements

Spatial Filter Velocimetry (SFV) is a technique that has been used for agglomeration processes during the past few years as it can monitor, control, and understand granulation and its implications in particle size distribution. This work has considered and aimed to analyze the evolution of the process as time goes on and in real-time and the influence of operating conditions on the process. A Plackett-Burman design was proposed with seven factors and three replicates at the central point condition, using microcrystalline cellulose (CMC) as the raw material and a maltodextrin solution as a liquid binder. Binder concentration, binder flow rate, powder initial moisture content, and fluidizing air temperature were significant at a 90% confidence level. A new approach was proposed for delimiting the stages of the fluidized bed agglomeration process, based on particle size classes that were obtained from the SFV probe data.

Characterization of the Velocity Field External to a Tube Bundle Using Spatial Filter Velocimetry Based on Variable Meshing Scheme

This paper presents results for the experimental vector velocity field obtained through spatial filter velocimetry in a triangular tube bundle with tubes of 20 mm O.D. and a transverse pitch of 25.2 mm. The experiments were conducted for single-phase water flows with Reynolds numbers ranging from 447 to 1842, and for air–water two-phase bubbly flow with liquid Reynolds number of 909 and gas Reynolds number of 42. The vector velocity field for each experimental condition was obtained using a variable meshing scheme to improve the spatial resolution in regions of low velocities. The results indicate that the variable meshing strategy is promising to increase the spatial resolution of the spatial filter velocimetry technique and to release from the constraint imposed by the uniform window sizes, especially for experimental data obtained with relatively low frame rates. Details of the flow structure of external flow across tube bundles, such as the near-wall velocity profiles, wake region and the effects of the gas buoyancy on vertical mean velocities are presented in this paper with high temporal and spatial resolution, which can be useful for validation of numerical models.

Improved spatial filtering velocimetry and its application in granular flow measurement**Project supported by the National Natural Science Foundation of China (Grant No. 11902190), the Construction Project of Shanghai Key Laboratory of Molecular Imaging (Grant No. 18DZ2260400), and the Fund from the Shanghai Municipal Education Commission, China (Class II Plateau Disciplinary Construction Program of Medical Technology of SUMHS, 2018-2020).

Spatial filtering velocimetry (SFV) has the advantages of simple structure, good stability, and wide applications. However, the traditional linear CCD-based SFV method requires an accurate angle between the direction of linear CCD and the direction of moving object, so it is not suitable for measuring a complex flow field or two-dimensional speed in a granular media. In this paper, a new extension of spatial filtering method (SFM) based on high speed array CCD camera is proposed as simple and effective technique for measuring two-dimensional speed field of granular media. In particular, we analyzed the resolution and range of array CCD-based SFV so that the reader can clarify the application scene of this method. This method has a particular advantage for using orthogonal measurement to avoid the angle measurement, which were problematic when using linear CCD to measure the movement. Finally, the end-wall effects of the granular flow in rotating drum is studied with different experimental conditions by using this improved technique.

Pressure and shear stress analysis in a normal triangular tube bundle based on experimental flow velocity field

This paper presents the experimental vector velocity field obtained through the spatial filter velocimetry technique in a normal triangular tube bundle test section with tubes of 20 mm O.D. and transverse pitch of 25.2 mm. The experiments were conducted for water flows and Reynolds numbers ranging from 447 to 1842. The pressure field was estimated based on the velocity results by solving the Poisson equation. The shear stress around the tubes was analyzed calculating the viscous and Reynolds stresses. The results for turbulence strength and flow vorticity were calculated and discussed. All the analyses were performed using a second-order finite difference scheme to estimate the partial derivatives. The results indicate that the spatial filter velocimetry technique provides accurate velocity data and is suitable to be applied to complex geometries. In addition, the obtained velocity fields show that the SFV technique is capable of capturing asymmetric flow distributions, which switch from time to time, indicating a suitable spatial and temporal resolution for the experimental conditions evaluated in the present study.

Acacia gum fluidized bed agglomeration: Use of inulin as a binder and process parameters analysis

AbstractThis work aimed to investigate the use of inulin as an alternative binder in fluidized bed agglomeration to improve both acacia gum functional and handling properties. Acacia gum was agglomerated in fluidized bed with inulin solution (18.0% wt/wt) at two different fluidizing air temperature (65 and 85°C) and binder feed rate (1.5 ml/min and 3.0 ml/min). The granule growth kinetics and system stability were monitored by a spatial filter velocimetry probe. The influence of process parameters on process yields and product characteristics: final particle size, wettability, and flowability were also evaluated. We observed an increase in particle size and the agglomerated particles showed a short wetting time, indicating that inulin can be successfully used as an alternative binder adding both nutritional and functional value to the acacia gum. Low binder feed rate provided better system stability and larger particle size.Practical ApplicationsThis paper presents inulin as an alternative binder for application in powder food agglomeration processes. The use of inulin has provided improved flowability and wetting properties. Moreover, the inulin may also add functional value to agglomerated foods. Besides, it was possible to monitor particle growth and process stability through a relatively new technique that measures the particle size, spatial filter velocimetry. In this way, it is possible to establish which conditions of temperature and binder feed rate are the most suitable for the agglomeration process.

In-line particle size measurement and process influences on rotary fluidized bed agglomeration

In-line particle size measurement with a spatial filter velocimetry probe for process control was already carried out successfully in conventional fluidized bed coating and agglomeration but has not yet been investigated in rotary fluidized bed agglomeration with a tangential spray for granulate and pellet manufacturing. In this project, a batch laboratory fluidized bed apparatus with a rotor insert and a tangential spray nozzle was used to investigate the feasibility of in-line particle size measurement with a spatial filter velocimetry probe and to detect critical process parameters.First, particle size and particle size distribution of a placebo mixture including small and large pellets were measured directly with the in-line probe in the rotary fluidized bed without spraying and without agglomeration. The volume density distribution shows bimodal curves, the peaks of which are related to the different ratio of pellets. Second, microcrystalline cellulose powder was agglomerated with a binder solution in the rotary fluidized bed by tangential spraying. At-line dynamic image analysis for the particle size measurement was used for comparison and showed similar results to the spatial filter velocimetry method. A Plackett-Burman screening design identified spray rate, atomizing air pressure, rotor disk velocity and batch size as critical process parameters by measuring particle size, particle size distribution and sphericity. The spatial filter velocimetry probe can be used in rotary fluidized bed agglomeration with tangential spray for process control.

Analysis of Particle Growth Kinetic of Pea Protein Isolate in Fluidized Bed by In-line Monitoring of Particle Size

Nowadays, there is a demand for products with good nutritional, technological and sensory characteristics. In this context, vegetable protein isolates, as pea protein, has been studied as a substitute to the soy protein, since it has higher levels of essential amino acids and vitamins. These powders are obtained commonly by spray drying that can modify the protein structure and that produces fine particles. So, to improve physicochemical properties, other processes, as agglomeration in fluidizing bed, could be used. The aim of this work was to study the influence of binder solutions characteristics on particle growth kinetics using an in-line particle size monitoring by spatial filter velocimetry. Two different acacia gum solutions (0.7 and 20.0 % w/w) were used as liquid binder. The operating conditions used were drying air temperature of 75 °C and binder flow rate of 3.0 mL/min. Atomization air pressure and atomization nozzle height were kept constant at 7.0 psi and 0.3 m, respectively. Fluid bed agglomeration was a useful method to produce instant pea protein concentrate powder under the operating conditions studied. This process produced larger particles, free-flow improved and shorter wetting time. The binder solution with higher concentration and more viscous provided a more pronounced particle growth and higher process yield. The in-line particle size monitoring was useful to observe the particle growth kinetics and the operating conditions influence on the growth kinetics and particle growth rate in fluidized bed agglomeration. It also was possible to observe that the particle growth rate oscillated during the process showing that the particle size growth results from a positive balance between agglomeration and break.

Snr-enhanced continuous spatial filtering velocimetry on a high-speed circuit breaker using linear cmos

An optical spatial filtering velocimeter that measures the velocity of a high-voltage circuit breaker is proposed. We examined the velocimeter theoretically and obtained the requirements for spatial filters (SFs), such as the transmission function. Theoretical analyses and experiments show that the sinusoidal transmission function spatial filter (STSF) provides a higher signal-to-noise ratio (SNR) and better accuracy than the traditional rectangular transmission function spatial filter (RTSF). Experiments show that spatial filtering velocimetry (SFV) with an STSF can yield better measurement results than those produced with an RTSF.

Agglomeration process of rice protein concentrate using glucomannan as binder: In-line monitoring of particle size

Rice protein has raised interest from food industry due to its singular nutritional value and nutraceutical properties. However, rice protein concentrate powder presents fine particles with moderate flowability and low wettability, limiting its use. The production of large and porous granules with both high wettability and flowability can be performed by agglomeration process. In this work, the fluid bed agglomeration using konjac glucomannan as binder agent was investigated as a potential method to improve the quality attributes of the RPC powder. The influence of binder concentration and binder feed rate on particle size and quality of the product was evaluated. In-line particle size was monitored by a spatial filter velocimetry probe. Agglomeration was successfully performed in a fluid bed, resulting in large granules with low moisture content, short wetting time and improvement of the flowability. In-line particle size data allowed a better understanding of the particles growth, which was influenced by the binder concentration and binder feed rate. The best operating condition was obtained using low binder concentration and low binder feed rate, since this condition provided an instant powder with very good flowability at the highest yield.

Spatial filtering velocimetry for surface velocity measurement of granular flow

In this study, we develop the spatial filtering velocimetry (SFV) technique to measure the velocity distribution of small spherical and irregular particle flows using a linear CCD camera. In addition, energy barycentre correction algorithm is used to enhance the measurement accuracy. A constantly running conveyor belt is used to test the accuracy of this SFV system. Furthermore, the velocity distributions of the spherical and irregular particle flows in a rotating drum are measured to demonstrate the usability of this method in a granular system. We further discuss the effect of the key system parameters on the results of the measurement, and the optimal thresholds of the parameters are given in this paper.

Fourier-based layout for grating function structure in spatial filtering velocimetry

Optical spatial filtering velocimetry (SFV) has been used for several decades for velocity measurements. Since the 1990s, charge-coupled device (CCD) line sensors have been used for the realization of spatial filtering systems by the inherent implementation of grating functions using a specialized clock regime. Another approach is the realization of optical SFV systems by utilizing array detectors (CCD or CMOS) with software-implemented grating functions, especially for two-dimensional velocity measurements.Choosing a suitable grating function for the observed scene can be an obstacle when using SFV, and relies on the experience of the user. With this in mind, this contribution presents an overview of how to assemble an optical spatial filtering system. After a general description of signal generation in spatial filtering systems, a straightforward approach to identifying matching harmonic grating functions by using Fourier analysis is presented. This approach has particular advantages for observed scenes with a periodically structured pattern, which were problematic when using SFV in connection with a fixed grating function. Matching periods of harmonic grating functions can be found as peaks in the spectral density distribution of the imaged scene. Once a matching grating function has been found, the signal processing can be made with SFV, which is simpler than calculating the cross-correlation of full frames and is suitable for real-time application. Criteria for the layout of an array-detector-based spatial filtering velocimeter are then discussed.

In-line particle size measurement and agglomeration detection of pellet fluidized bed coating by Spatial Filter Velocimetry

Particle size and particle size distribution are measured in-line in fluidized bed processes. Coating processes demand detection of the particle growth and the timely recognition of undesirable agglomeration for process intervention and process parameter change. The aim was the detection of agglomerates (large particles) in lots of small particles. Therefore spiking trials with pellets of microcrystalline cellulose were performed. The blends were fluidized in a fluidized bed apparatus and particle size was measured in-line by Spatial Filter Velocimetry method. Snapshots of volume density distribution and number density distribution at distinct moments of the process were registered, and finally the density distributions were averaged over the whole process time. Agglomeration was unequivocal detected by volume density distribution. In contrast the number density distribution was not suitable to detect low absolute numbers of large particles in the blends.In real fluidized bed coating processes with pellets and model substances, median particle size values x10,3; x50,3 and x90,3 were measured versus process time. Median values increase continuously with process time under optimized process conditions. Due to worst case conditions, caused by super-wetting of the fluidized bed, Agglomerates were generated and detected by a non-linear increase of the x90,3-time-plot (greater storage of large particles). Also snapshots of volume density distribution under worst case process conditions indicate clearly the formation of agglomerates. The in-line particle size measurement at fluidized bed coating is a useful Process Analytical Tool (PAT) in the process control.

Optical high-resolution analysis of rotational movement: testing circular spatial filter velocimetry (CSFV) with rotating biological cells

Circular spatial filtering velocimetry (CSFV) was tested during the microscopic registration of the individual rotations of baker’s yeast cells. Their frequency-dependent rotation (electrorotation; ER) was induced in rotating electric fields, which were generated in a glass chip chamber with four electrodes (600 μm tip-to-tip distance). The electrodes were driven with sinusoidal quadrature signals of 5 or 8 VPP with frequencies up to 3 MHz. The observed cell rotation was of the order of 1–100 s per revolution. At each measuring frequency, the independent rotations of up to 20 cells were simultaneously recorded with a high-speed camera. CSFV was software-implemented using circular spatial filters with harmonic gratings. ER was proportional to the phase shift between the values of the spatial filtering signal of consecutive frames. ER spectra obtained by CSFV from the rotation velocities at different ER-field frequencies agreed well with manual measurements and theoretical spectra. Oscillations in the rotation velocity of a single cell in the elliptically polarized field near an electrode, which were resolved by CSFV, could not be visually discerned. ER step responses after field-on were recorded at 2500 frames per second. Analysis proved the high temporal resolution of CSFV and revealed a largely linear torque-friction relation during the acceleration phase of ER. Future applications of CSFV will allow for the simple and cheap automated high-resolution analysis of rotational movements where mechanical detection has too low a resolution or is not possible, e.g. in polluted environments or for gas and fluid vortices, microscopic objects, etc.

Continuous Manufacturing of High Quality Pharmaceutical Cocrystals Integrated with Process Analytical Tools for In-Line Process Control

A continuous manufacturing process for pharmaceutical indomethacin–saccharine cocrystals was achieved by extrusion processing with high throughput. Down-stream milling and blending of the extrudates was followed by feeding the formulated cocrystals in a capsule-filling machine. By applying a quality by design approach, the process was optimized and scaled up to produce 3000 capsules/h of pharmaceutical cocrystals. Process analytical tools such as near infrared reflectance and spatial filter velocimetry probes were coupled at various process stages for in-line monitoring and quality control. Further physicochemical characterization of extruded batches confirmed the manufacturing of high quality cocrystals. A fully integrated continuous process starting from raw materials to produce a finished product was assembled with only six unit operations and a small footprint. The study is a paradigm of continuous manufacturing of pharmaceutical cocrystals.

Spatial filtering velocimetry for real-time measurements of speckle dynamics due to out-of-plane motion.

This paper describes an optical spatial filtering velocimetry technique that converts an expanding or contracting speckle pattern into a photocurrent. This photocurrent will have a quasi-sinusoidal dependency on this specific speckle motion. The spatial filter consists of a series of concentric rings. Each ring divides the incoming light into two radial-wise, almost even contributions and directs them by refraction toward two half-rings of photodetectors. The corresponding two photocurrents are balanced and provide a differential photocurrent. In this paper the optical spatial filtering velocimetry technique is used to demonstrate real-time measurements of speckle dynamics due to out-of-plane motion.

Selectivity and balance of spatial filtering velocimetry of objective speckles for measuring out-of-plane motion

We probe the dynamics of objective laser speckles as the axial distance between the object and the observation plane changes. With the purpose of measuring out-of-plane motion in real time, we apply optical spatial filtering velocimetry to the speckle dynamics. To achieve this, a rotationally symmetric spatial filter is designed. The spatial filter converts the speckle dynamics into a photocurrent with a quasi-sinusoidal response to the out-of-plane motion. Our contribution presents the technology, discusses the selectivity of the spatial filter and proposes two solutions to balance phase-stepped photocurrents. Specifically, we discuss how the selectivity of the spatial filter with regard to radial speckle motion is influenced by a concurrent in-plane speckle motion. The spatial filter is emulated with a CCD camera and is tested on speckle acquisitions obtained from a controlled setup. Experiments with the emulated filters illustrate the performance and potential applications of the technology.