Non-intrusive Diagnostic Tool Research Articles

Spectroscopic Diagnostics of Radiation Reabsorption in Dense He Arc Plasmas

Observing the light emission from plasmas spectroscopically allows for the determination of key plasma parameters like electron temperature, density and external field. This method, known as plasma spectroscopy, serves as a non-intrusive diagnostic tool to study plasma dynamics. However, overlooking the impact of radiation reabsorption in the typical analytic model may compromise the accuracy of observed plasma behavior. This study addresses the influence of radiation reabsorption on plasma spectroscopic diagnosis, focusing on linear divertor simulators and plasma spectrometers designed for high-density Large Helical Device (LHD) plasmas, where optical thickness cannot be disregarded. The discussion delves into understanding the effects of radiation reabsorption in these observations.

Investigating recent developments and applications of optical plasma spectroscopy: A review

Optical spectroscopy is a powerful, nonintrusive diagnostic tool that can provide unparalleled insight into fundamental plasma properties. Specifically, these techniques are widely employed to qualitatively and quantitatively characterize interactions of species within a discharge. This work is comprised of two parts: (1) a brief review of recent literature on the application of optical emission spectroscopy from the past decade, ranging from the study of atomic rare gas to more complex environmentally and technologically relevant plasma systems and (2) the presentation of new data that illustrate the power of optical spectroscopy techniques beyond simple species identification. Specifically, time-resolved optical emission spectroscopy was utilized to provide kinetic information about excited state species formation, ultimately lending mechanistic insights into a range of plasma processes. In addition, by combining optical emission and broadband absorption spectroscopies, rotational and vibrational temperatures for both excited and ground state species were determined. These data provide a thermodynamic base for enhanced understanding of the fundamental chemistry in plasma systems. The two platforms explored here were plasma-assisted catalysis systems containing NxOy species and fluorocarbon plasmas utilizing a range of precursors to evoke either etching or deposition, depending on the plasma conditions.

Experimental study of the process failure diagnosis in additive manufacturing based on acoustic emission

Currently additive manufacturing (AM) faces many challenges related to product quality, robustness, and reliability, which will hinder its industry-scale applications. Studies of the typical AM process failures and the corresponding effective sensor-based monitoring methods are needed to overcome these challenges. In this paper, a data-driven monitoring method for online AM process failure diagnosis based on acoustic emission (AE) is proposed, and its application to the fused filament fabrication (FFF) is demonstrated. Several typical FFF process failures are also investigated. Experimental study of a failed FFF printing process is benchmarked against the analysis of a normal printing process. AE signals from both normal and failed printing processes are recorded and processed. An unsupervised machine learning method, self-organizing map (SOM), is applied to formalize the diagnosis procedure of different failure modes. The experimental results show that it is feasible to use the proposed method to diagnose the typical process failures, including both detection and identification. This new method could serve as a non-intrusive diagnostic tool for FFF process monitoring, and has the potential to be applied to other AM processes.

Experiments on natural convection in water-cooled ribbed channels with different aspect ratios

Natural convection heat transfer in vertical ribbed channels, using water as working fluid, has been experimentally studied. The investigation encompassed a large range of the channel aspect ratio, defined as the ratio between channel spacing and channel height, while the wall-to-fluid temperature difference was kept fixed. The measurement of local heat transfer coefficient was facilitated by a non-intrusive diagnostic tool, the schlieren technique, whose use for the quantitative study of liquid flows is rarely documented in the literature. Results provided an insight into the nature of free convection heat transfer from ribbed channels, whose geometry is significant in such several engineering devices as electronic equipment. It was found that a general reduction of heat transfer performance, relative to that of a flat vertical surface or a smooth vertical channel, was induced by the presence of ribs, within the range of the parameters investigated. Local and heat transfer characteristics were sensitive to changes in interplate spacing for small channel aspect ratios. Experimental data, recast in dimensionless form, were in excellent agreement with those obtained by this author in a previous research performed for air-cooled channels, using the same experimental technique, the same geometric parameters of the ribbed surface, and a similar Rayleigh number.

Optimization of the injection with a twin-fluid atomizer for suspension plasma spray process using three non-intrusive diagnostic tools

Suspension injection is a crucial point for suspension plasma spray, an emerging coating process. It must satisfy several requirements such as stability, reproducibility, high yield of suspension particles penetrating the plasma core. Indeed, the particles should follow a proper trajectory inside the plasma in order to be well treated and accelerated. Thus, the quality of the injection has a direct effect on the coating microstructure, therefore on the properties. This study focuses on the three-step characterization of a twin-fluid atomizer, without and within the plasma. While varying gas or suspension flow rates, the spray was firstly observed thanks to a shadowgraphy system. This system uses a short-pulsed diode laser in a back illumination configuration and a robust image processing software, allowing the detection of suspension droplets, even within a high emissive plasma. Secondly, droplet size measurements were performed via laser diffraction. Thirdly, droplet velocities were measured using a particle image velocimetry system. The combination of the results obtained by these techniques helped us to understand how gas and suspension flow rates impact on droplets size and velocity distributions and finally how one could select the best injection conditions. The injector characterization was completed by coating manufacturing and microstructure analysis.

Recovery Voltage Measurements of Oil-immersed Transformer

One of the methods currently being investigated as a possible non-intrusive diagnostic tool for condition monitoring of power transformer and cable is the recovery voltage measurement, which will be improving the ability to detect the content of water concentration and the ageing process in the insulation system and may thus be an indicator of insulation quality and its ageing status. The polarization phenomenon was studied using RVM with oil-paper samples. In order to interpret its mechanism, the Extended Debye model was introduced. With different circuit parameters, various simulation results were gotten. Furthermore, with the test samples of different ageing condition, measurements are accomplished in the lab. On the basis of this experiment as well as theoretical analysis, correlations between polarizations and ageing were analyzed.

Temperature mapping of reactive gas layer in thermal plasma chemical vapor deposition

Two-dimensional temperature maps of reactive gas layers were produced using pulsed laser Rayleigh scattering thermometry. The measurements were made in conditions of diamond film chemical vapor deposition (CVD) using a thermal inductively coupled plasma. In these conditions, the reactive gas layer is typically a few millimeters thick and the temperature drops across the layer from 4000 K at the free stream boundary to about 1200 K at the substrate. The reactive layer exhibits strong chemical nonequilibrium. Rayleigh scattering was induced using a pulsed laser sheet at 532 nm wavelength. The scattered radiation was detected and calibrated with an intensified charge coupled device camera. Temperature maps and axial profiles obtained under parametric variation of the gas flow conditions demonstrate how the technique can be employed to measure the reactive layer thickness and its radial distribution across the substrate. The results demonstrate that imaging Rayleigh scattering thermometry can be employed as a nonintrusive diagnostic tool to obtain useful experimental information pertinent to the gas phase chemistry in diamond CVD under conditions of extremely large temperature gradients.

Experimental and theoretical study on hollow-cone spray

A theoretical and experimental investigation has been conducted to study the two-phase turbulent structure in an isothermal hollow-cone spray. Mean and fluctuating velocity components, drop number density, as well as drop-size distribution were measured with a nonintrusive diagnostic tool, a two-component phase Doppler particle analyzer. Complete initial conditions required for theoretical calculations were also provided with measurements. Theoretical calculations were made with an Eulerian-Lagrangian formulism. Turbulent dispersion effects were numerically simulated using a Monte Carlo method. Turbulence modulation effects were also taken into account in the modeling. The well-defined experimental data were used to assess the accuracy of the resultant Eulerian-Lagrangian model. Comparisons showed that the theoretical predictions, based upon the Eulerian-Lagrangian model, yielded reasonable agreement with the experimental data. The improvements made by inclusion of the selected turbulence modulation model were insignificant in this work.